Art05_Thevs.indd Journal of Applied Botany and Food Quality 85, 159 - 167 (2012) 1 Institute of Botany and Landscape Ecology, University of Greifswald, Germany 2 Faculty of Science and Technology, Free University of Bozen-Bolzano, Italy 3 Faculty of Textile and Clothing Technology, Niederrhein University of Applied Sciences, Mönchengladbach, Germany 4 Institute of Resource and Environmental Sciences, Xinjiang University, China 5 Republican Research Center of Forestry and Ornamental Garndening, Uzbekistan Apocynum venetum L. and Apocynum pictum Schrenk (Apocynaceae) as multi-functional and multi-service plant species in Central Asia: a review on biology, ecology, and utilization N. Thevs1, S. Zerbe2, Y. Kyosev3, A. Rozi1, B. Tang1, N. Abdusalih4, Z. Novitskiy5 (Received March 20, 2012) Summary During the second half of the 20th century cotton was strongly promoted along the rivers of Central Asia. The irrigation agriculture resulted in wide spread soil salinization and severe water shortages within the river systems. Most prominent example is the desiccation of the Aral Sea. The natural vegetation along the rivers of Central Asia is adapted to periods of water shortage, is very productive, and contains plant species with valuable utilization opportunities. We reviewed the literature about Apocynum venetum L. and A. pictum Schrenk, two plant species of those riparian ecosystems, which are used as fi bre and medicinal plants. A. venetum and A. pictum yield fi bres, which can be used as textiles, though the fi bres best are blended with cotton and/or chemical fi bres. Though, the fi bre extraction process needs more research attention. Furthermore, the literature shows that Apocynum leafs are used to produce anti- hypertonic tea and medicine. Both species grow under the arid climate of Central Asia without irrigation, because they exploit groundwater. Furthermore, both species can withstand higher soil salinization levels than cotton. Both species can be used and provide an income to local people under conditions, which are unfavourable to grow crops under irrigation. Such conditions are unreliable water supply for irrigation systems and/or saline soils. 1. Introduction Central Asia, which stretches from the Caspian Sea over Kazakhstan, Turkmenistan, and Uzbekistan to Northwest China (i.e. Xinjiang, Gansu, Qonghai, Inner Mongolia, Ningxia, Shanxi, and Shaanxi), and Mongolia, is largely covered by steppes, semi-deserts, and de- serts. There, the most productive ecosystems are part of the riparian vegetation along the rivers (THOMAS et al., 2006; THEVS et al., 2007; 2011). But, vast areas of those productive ecosystems have been degraded due to enlarging the area for irrigation agriculture in Central Asia. Furthermore, river runoffs have dropped and fi elds have become subject to severe soil salinization. In the Aral Sea Basin, i.e. along the Amu Darya and the Syr Darya, planting of cotton was strongly promoted from the 1960ies onward. As a consequence the Aral Sea has nearly vanished (GLANTZ, 1999). In the Tarim Basin, the oases area was enlarged from the 1950ies onward leading to the complete desiccation of the Lakes Lop Nor and Taitema, the former end-lakes of the Kenqi and Tarim River, respectively (SONG et al., 2000). In both basins, the lower reaches of the rivers turned into episodic river courses or fell dry completely. Under those conditions, the natural riparian vegetation and the irrigation agriculture, especially along the lower reaches, suffered and suffers water shortage leading to ecological degradation and economic losses, respectively (HOPPE, 1992; SPOOR, 1993; GLANTZ, 1999; TRESHKIN, 2001; ZHU et al., 2006; THEVS et al., 2007; WESTERMANN et al., 2008). Along with the enlargement of irrigation area and periods of water shortage, soil salinization has become a major concern Fig. 1: A. venetum stand, fl ood plain of the Ulungush River, Aleghak, Altay Prefecture, Xinjiang, China (Photo: N. Thevs, Sept. 2008). for farmers in the area (KUZMINA and TRESHKIN, 1997; FORKUSTA, 2006; IBRAKHIMOV et al., 2007). In Xinjiang, Gansu, and Inner Mongolia, there are attempts to reduce the area under irrigation and shift the land use to perennial plants, which are adapted to the local environmental conditions, e.g. fruit trees, fodder plants, or medicinal plants (GAO et al., 2006). The two species Apocynum venetum L. and Apocynum pictum Schrenk (Fig. 1 and 2) are promising candidates for a sustainable land use away from irrigation. The genus Apocynum comprises nine species, which are distributed in temperate regions of North America, Europe, and Asia. The two species Apocynum venetum and Apocynum pictum occur in Central Asia (ROYAL BOTANIC GARDENS, 2012). A. venetum and A. pictum are perennial plants with rhizomes, while the stems die yearly, i.e. life form geophytes according to (RAUNKIAER, 1934). New stems grow out of the roots every spring (PAVLOV, 1942). A. venetum and A. pictum are adapted to survive even under the extreme arid climate of the Tarim Basin or Aral Sea Basin with less than 50 mm mean annual precipitation by exploiting the ground- water to cover their water demand. Thus, these two species are phreatophytes (GRIES et al., 2003; CHEN et al., 2006; THOMAS et al., 2006). Consequently, A. venetum and A. pictum provide utilization options without irrigation. The two species offer opportunities as fi bre and medicinal plants. In this paper, we present a comprehensive review on the two species Apocynum venetum and Apocynum pictum, focusing on biology, phytogeography, ecology, planting techniques, and utilization. We will draw conclusions on the utilization potential of these two species and point out open research questions. The term Apocynum is used, when we refer to both species A. venetum and A. pictum 160 N. Thevs, S. Zerbe, Y. Kyosev, A. Rozi, B. Tang, N. Abdusalih, Z. Novitskiy 2. Biology of A. venetum and A. pictum 2.1 Taxonomy, nomenclature, and morphology The genus Apocynum belongs to the family Apocynaceae, order Gentiales, class Dicotyledonae. Today, only the two Apocynum species A. venetum (Fig. 1) and A. pictum (Fig. 2) are distributed in Central Asia (ROYAL BOTANIC GARDENS, 2012) and thus reviewed in this paper. A. venetum furthermore is split into several sup-species, from which A. venetum subsp. lancifolium Russanov and A. venetum subsp. scabrum Russanov are distributed in Central Asia. The synonyms for the two Apocynum species and two sub-species of A. venetum are given in Tab. 1 for Central Asia. In the Russian literature, today’s sub-species A. venetum subsp. lancifolium and scabrum are considered as species next to A. venetum (PAVLOV, 1942; ROMANOVICH, 1951). Furthermore, A. sibiricum is a synonym of today’s A. venetum subsp. lancifolium (PROZOROVSKII, 1932). In our review, we will only refer to the species names A. venetum and A. pictum. If there appears uncertainty regarding the species names, we use Apocynum. A detailed history of the Apocynum taxonomical classifi cation is provided by ZHANG et al. (2006a). In the Russian literature, Kendyr (Кендыр) is used as trivial name for Apocynum (BERLJAND, 1950; ROMANOVICH et al., 1951). In China, the trivial names Luobuma, translated into English as Lop Kendyr (or Lop Kendyr), is used for the genus Apocynum, while Luobuhongma ( ) and Luobubaima ( ) refer to A. venetum and A. pictum, respectively (ZHANG et al., 2006a; b). A. venetum is taller and bigger than A. pictum. The former can grow as tall as 4 m, while the latter only reaches 2 m. In open vegetation, i.e. grassland, A. venetum usually grows 2 m high and each plant branches into 5-10 stems, but as an understory plant in Central Asian fl oodplain forests it grows up to 4 m and hardly branches off (PROZOROVSKII, 1932; BERLJAND, 1950; ROMANOVICH et al., 1951; ZHANG et al., 2006a; b). The most obvious feature to distinguish the two species is that A. venetum has opposite leafs, while A. pictum has alternate leafs (FLORA OF CHINA, 2011). The further morphological characteristics of the two Apocynum species are given in Tab. 2. The root system consists of vertical and horizontal roots and rhizomes. The vertical roots connect to the groundwater and thus secure the water supply of the plant. Each autumn, buds start to grow at the upper part of the vertical rhizome, from which the new stems emerge in the following spring. Nutrients are stored in the upper part of the vertical rhizome and in the entire horizontal rhizome. The horizontal rhizomes carry dormant buds (2-3 per cm), from which vertical roots and root suckers grow, when the horizontal rhizome has been cut off its mother plant. The horizontal roots of an Apocynum plant can extend up to 5-6 m (BERLJAND, 1950; ROMANOVICH et al., 1951). There are whitish to yellowish mycorrhiza knots on the roots of Apocynum (BERLJAND, 1950). Vascular arbuscular mycorrhiza was described for the plant order Gentiales, including Apocynaceae (ZHANG et al., 2003). 2.2 Life history The stems emerge from the rhizomes in March to April. Flowering season is from June to August followed by fruit season from September to October (ZHANG et al., 2005). The stems show the fastest length growth before onset of the fl owering period. During Fig. 2: A. pictum stand, fl ood plain of the Layi River, i.e. a river branch of the Tarim River, Qongaral, Korla, Xinjiang, China (Photo: N. Thevs, Sept. 2008). Tab. 1: Subspecies and synonyms of A. venetum and Apocynum pictum with their distribution (ROYAL BOTANIC GARDENS, 2012). Species / sub-species Synonym Apocynum venetum L. Homotypic synonyms: Trachomitum venetum (L.) Woodson Apocynum venetum subsp. lancifolium Russanov Homotypic synonyms: (distribution: Siberia to China) Apocynum lancifolium Russanov, Trachomitum lancifolium (Russanov) Pobed. Heterotypic synonyms: Nerium sibiricum Medik., Apocynum compressum Moench, Nerium antidysentericum Lepech., Apocynum sibiricum Pall. ex Roem. & Schult, Apocynum venetum var. microphyllum Bég. & Beloserky, Trachomitum venetum var. microphyllum (Bég. & Beloserky) Woodson Apocynum venetum subsp. scabrum Russanov Homotypic Synonyms: (distribution: Asia to Pakistan) Apocynum scabrum Russanov, Trachomitum scabrum (Russanov) Pobed., Trachomitum venetum subsp. scabrum (Russanov) Rech.f. Heterotypic Synonyms: Apocynum venetum var. turkestanicum Bég. & Belosersky Apocynum pictum Schrenk. Homotypic synonyms: (distribution: Central Asia to Mongolia) Poacynum pictum (Schrenk.) Bail. Heterotypic Synonyms: Apocynum hendersonii Hook, Apocynum grandifl orum Danguy, Poacynum hendersonii (Hook) Woodson while Luobuhongma ( ) and Luobubaima ( ) refer while Luobuhongma ( ) and Luobubaima ( ) refer Apocynum review 161 and after the fl owering period, the length growth ceases (BERLJAND, 1950). Apocynum plants reach an age of 30 years (PROZOROVSKII, 1932). Apocynum is not very prone to pests and illnesses (TANG, 2008). 3. Phytogeography and phytosociology A. venetum is distributed over a vast area in Eurasia, i.e. from Southeast Europe over Turkey, Iran, Turkmenistan, Uzbekistan, Kazakhstan, and Southern Sibiria to Mongolia, Northern China, and Japan. In Central Asia, A. venetum is distributed in the fl oodplains and valleys along the rivers, e.g. Amu Darya, Pandzh, Vakhsh, Syr Darya, Chu, Talas, Ili, Irtysh, Tarim with its tributaries, and Heihe (ROMANOVICH et al., 1951). In Central Asia, only the sub- species A. venetum subsp. lancifolium and scabrum (Tab. 1) occur. In Kazakhstan, i.e. Syr Darya and Chu river basins, A. venetum subsp. lancifolium is found, while the sub-species A. venetum subsp. scabrum is recorded in the Amu Darya Basin (PAVLOV, 1942; BERLJAND, 1950). A. pictum’s distribution is restricted to southern Kazakhstan, the Ili Basin, Xinjiang, Gansu, and Inner Mongolia (PAVLOV, 1942). Both species are part of the riparian vegetation along the rivers and streams in the drylands of Central Asia. So, they are distributed along perennial and episodic river courses, on alluvial plains, and at desert margins (PAVLOV, 1942; ZHANG et al., 2003; 2005). In China, the two Apocynum species are mainly recorded in Xinjiang, Qinghai (Caidam Basin), Gansu, Inner Mongolia, Shanxi, Shaanxi, Hebei, Jilin, and Heilongjiang. Within this area A. venetum occurs in the semi-arid, semi-humid, and humid part, i.e. with an annual mean precipitation of more than 250 mm. In contrast, A. pictum is restricted to the arid climate, i.e. with an annual precipitation of less than 250 mm (ZHANG, 2002; ZHANG et al., 2006a; b). Only in the Caidam Basin with a mean annual precipitation of less than 200 mm, but at an elevation of higher than 2,600 m, A. venetum is dominant over A. pictum (TIE and LIU, 2006; TANG, 2008). Within Xinjiang, A. pictum is restricted to the more arid parts, e.g. the Tarim Basin and the southern rim of the Zhungar Basin, while A. venetum occurs in the less arid northern part of the Zhungar Basin and the foothills of the Altay Mountains, as shown in Fig. 1 (ZHANG, 2002; ZHANG et al., 2006a; b). All over China, the area of Apocynum vegetation, natural or artifi cial, amounts to 1,330,000 ha (TANG, 2008). One third to half of this area is located in Xinjiang, i.e. approximately 600,000 ha (ZHANG et al., 2003). In the Caidam Basin, 91,000 ha of natural Apocynum vegetation is recorded (TANG, 2008). Within this area, Apocynum is often accompanied by Nitraria spec. L. and Phragmites australis Trin. ex Staud. The areas stated here for China as well as for Xinjiang and the Caidam Basin do not represent Apocynum dominated or even single species vegetation, but they may represent the area within which Apocynum is distributed as accompanying species or dominant species (HONG et al., 2002). This is further illustrated by the distribution of Apocynum in Aksu Prefecture, Xinjiang (ZHANG et al., 2003): Apocynum is distributed along the Tarim River as grassland on higher river terraces and in a mosaic with Tugai forests. In Aksu Prefecture, the area of Apocynum vegetation is 50,600 ha comprising reed and A. venetum with 17,100 ha, A. pictum with 800 ha, A. venetum and Glycyrrhiza L. with 1,600 ha, Tamarix ramosissima Ledeb. and A. venetum with 4,400 ha, Tamarix ramosissima and A. venetum and Alhagi spec. Gagnebin with 11,900 ha, Tamarix ramosissima, A. pictum, and Alhagi spec. with 3,600 ha, and Populus euphratica Oliv. and A. venetum with 11,200 ha. 4. Ecology of A. venetum and A. pictum 4.1 Climate adaptation The above-ground parts of A. venetum do not withstand frost and die off under frost. However under a snow cover, the root can withstand strong frost up to -30 °C. The seedlings do not withstand frost at all (BERLJAND, 1950; ROMANOVICH et al., 1951). 4.2 Soil conditions: water and salt Apocynum is adapted to arid climate or dry periods as being a phreatophyte (BERLJAND, 1950). The most productive sites of A. venetum are found on a groundwater not deeper than 3 m with salt contents between 1 g/l and 10 g/l (BERLJAND, 1950; ZHANG, 2002). Along the lower reaches of the Tarim River, which had been dry from the 1970ies to 2000 (SONG et al., 2000), A. pictum is mainly found on groundwater levels of 4-6 m below surface, with a maximum groundwater depth of 8 m (HAO et al., 2008). A. venetum in contrast, is restricted to groundwater levels not deeper than 4 m below surface (ZHANG, 2002). Within its distribution area, Apocynum forms island-like mono- species stands or dominates stands, but mostly occurs as accom- panying species in various plant communities (PROZOROVSKII, 1932; HONG et al., 2002; ZHANG, 2002). Thus, it often growths together with Phragmites australis, Glycyrrhiza infl ata, Alhagi sparsifolia, and Tamarix shrubs (ZHANG, 2002; HONG et al., 2002; CHEN et al., 2006), with halophytes on salinized soils (ROMANOVICH et al., 1951), or as understory in fl oodplain forests, e.g. built up by Populus euphratica (PROZOROVSKII, 1932). A. pictum bears deeper groundwater levels than Phragmites australis (THEVS et al., 2008a), similar groundwater levels as Glycyrrhiza infl ata (CHEN et al., 2006), Tab. 2: Morphological characteristics of A. venetum and A. pictum (FLORA OF CHINA, 2011). Apocynum venetum Apocynum pictum Stem Up to 4 m tall, glabrous except for infl orescences; branches and Up to 2 m tall, branchlets pubescent when young, soon glabrous branchlets whitish gray, terete, fi nely striate Leaves Usually opposite; petiole 3-6 mm; leaf blade narrowly elliptic Usually alternate; petiole 2-5 mm, rarely shorter; leaf blade oblong to narrowly ovate, 1-8 x 0.5-2.2 cm, base rounded or cuneate, to ovate, 1.5-4 x 0.2-2.3 cm, closely denticulate, granulose margin denticulate, apex acute or obtuse, mucronate Flowers Sepals narrowly elliptic or narrowly ovate, ca. 1.5 mm; corolla Sepals ovate or triangular, 1.5-4 mm; corolla pink or purplish red, purplish red or pink; tube campanulate, 6-8 mm, granulose; often with distinct darker markings; tube basin-shaped, 2.5-7 mm; lobes 3-4 mm; disc fl eshy, 5-lobed; lobes rounded, base adnate lobes broadly triangular, 2.5-4 mm; corona inserted at base of to ovary corolla tube, lobes broadly triangular, apex long acuminate Fruits Follicles slender, 8-20 cm x 2-3 mm Follicles slender, pendulous, 10-30 cm x 3-4 mm Seeds Ovoid or ellipsoid, 2-3 mm, coma 1.5-2.5 cm Narrowly ovoid, 2.5-3 mm; coma 1.5-2.5 cm 162 N. Thevs, S. Zerbe, Y. Kyosev, A. Rozi, B. Tang, N. Abdusalih, Z. Novitskiy but cannot exploit the groundwater as deep as Populus euphratica, Tamarix ramossissima, or Alhagi sparsifolia (CHEN et al., 2006; FAN et al., 2006). Next to the ability to use groundwater, the stems and branches and leafs are covered with a wax layer, which reduces evaporation (ROMANOVICH et al., 1951). Apocynum can withstand periods of submergence. However, prolonged submergence or water logged soil inhibits its growth (BERLJAND, 1950). Under such conditions, the majority of the roots is concentrated at the upper boundary of the reduced gleyic horizon, in order to avoid prolonged anoxic conditions (PROZOROVSKII, 1932). Apocynum is most productive on sandy (ROMANOVICH et al., 1951) and silty (PROZOROVSKII, 1932), well drained soils (BERLJAND, 1950). It cannot grow on clayey soils (PROZOROVSKII, 1932). The topsoil under Apocynum stands often is salinized, reaching salt contents of up to 20 %. However, 30 cm below surface the salt content drops to only 1 % and less (ZHANG et al., 2003). This shows that Apocynum can grow on sites with a pronounced surface salinization, as long as the subsoil and the groundwater are not strongly salinized. Under such conditions, fl ooding is harmful for Apocynum, because the fl ood leaches salt into the subsoil, where it damages the roots. A. pictum has a stronger ability to bear salinization than A. venetum (ZHANG, 2002). Apocynum seedlings do not tolerate salt. Older plants with deeper roots reach non- or low-saline soil layers so that they can withstand saline top soils, as resulted from irrigation or natural soil salinization (BERLJAND, 1950; ZHANG, 2002). The adult Apocynum plants tolerate salt better than cotton (BERLJAND, 1950). 4.3 Plant nutrient status Apocynum needs considerable amounts of nutrients from the soil, because it grows rather fast. From the second half of the summer onward, Apocynum stores nutrients in its root system (BERLJAND, 1950). The net primary production of vegetation dominated by Apocynum in the Tarim Basin amounts to 0.93 t/ha (HONG et al., 2002). In A. venetum leaves from Xinjiang, the contents of the nutrients K, Ca, and Mg are 8.1 mg/g, 1.13 mg/g, and 5.01 mg/g, respectively. The Na content is 6.2 mg/g (FAN et al., 2006). 5. Reproduction and planting techniques 5.1 Natural reproduction and germination Under natural conditions, Apocynum predominantly recruits vege- tatively through root suckers. Seed germination and successful seedling establishment rarely occurs (ROMANOVICH et al., 1951). The seeds require moist, non-saline, well drained sandy to loamy sediments (ROMANOVICH et al., 1951). Such sites only can be found along river banks after fl ood events. After germination, the seedlings grow slowly above ground, but invest strongly into the root system which is typical for phreatophytes. The seeds germinate easily, but the establishment of the seedlings by accessing a continuous connection to the groundwater poses a bottleneck for the generative recruitment (PROZOROVSKII, 1932; TANG, 2008). Thus, the re- cruitment of Apocynum is similar to that of Populus euphratica Oliv. (THEVS et al., 2008b; WIEHLE et al., 2009). The fruits are 12-20 cm long and have a diameter of 3-4 mm. When ripe, they turn brown. Each fruit contains 100-150 seeds. The seeds are 2.5 mm long with a diameter of 0.5 mm. The 1,000-grain weight of Apocynum venetum ranges from 350 mg to 1,000 mg in the former Soviet Union (ROMANOVICH et al., 1951). In Shaanxi, i.e. the more humid part of the Apocynum distribution area in China the 1,000- grain weight of A. venetum is 500-600 mg (HU et al., 1988). In the more arid regions of the distribution area, i.e. Xinjiang and southern part of Central Asia, the seeds of Apocynum are less than 1 mm long. There, the 1,000-grain weight of A. venetum ranges from 332 mg (BAI et al., 2005) to 469 mg (BERLJAND, 1950). The 1,000-grain weight of A. pictum was measured as 264 mg (BAI et al., 2005). The seeds carry pappus-like hair. The light weight and the hair enable an anemochorous dispersion (BERLJAND, 1950; BAI et al., 2005). The seeds lose their germination ability rapidly. However, when stored at dry conditions, i.e. moisture content of 3-6 %, in air-sealed containers, 60 % of seed samples retained germination ability even after 8 years. When the moisture content exceeds 8 %, the seeds lose their germination ability within two years. Under non-sealed conditions, the seeds also lose their germination ability within 2-3 years, even under a moisture content of 4 %. It is not necessary to store the seeds under dark conditions (HU et al., 1988). Those results were obtained from seeds from Shaanxi, which ripened under moist and hot conditions and therefore did not develop a very hard shell. A. venetum requires at least 10 °C for its germination. Frost then kills saplings (PROZOROVSKII, 1932; BERLJAND, 1950). The infl uence of NaCl solution on the germination of A. venetum and A. pictum is shown in Tab. 3 (HE et al., 1997; CHEN et al., 2007). When the NaCl concentration was increased from 0.2 % to 0.4 %, the length growth of the A. venetum seedlings, measured after 38 days, decreased signifi cantly from 5.7 cm to 2.7 cm. With increasing NaCl concentration, the length growth dropped further to 0.5 cm under 2 % NaCl concentration. In germination experiments, the fi rst seed- lings of A. venetum appear after three days, while most seedlings appear after 7 days and all seeds have germinated after 28 days. Under salt concentrations around 2 %, the germination rate of A. pictum is double as high as that of A. venetum (Tab. 3), corresponding with the higher ability of A. pictum to withstand salinized soil conditions than A. venetum (CHEN et al., 2007). 5.2 Cultivation and planting techniques There are two reproduction methods for cultivation, i.e. seed propagation and vegetative propagation from root or plant parts (BERLJAND, 1950; ZHANG et al., 2005). Direct seeding is the most labour saving method to cultivate Apocynum. But, better results are obtained, if Apocynum seeds are sown in a nursery and the saplings are transplanted after the second year (BERLJAND, 1950; TANG, 2008). The most suitable seeding time is mid April to May, Tab. 3: Germination rate of Apocynum venetum and A. pictum under different NaCl concentrations. Sources: (CHEN et al., 2007)1 and (HE et al., 1997)2, - = no data. NaCl concen- Germination rate [%] tration [%] A. venetum1 A. venetum2 A. pictum2 0 86.0 - - 0.2 87.5 - - 0.4 96.0 91.3 - 0.6 100.0 91.3 - 0.8 87.5 - - 0.9 - 85.7 - 1 82.5 - - 1.6 78.0 - - < 1.8 - - 89.3 - 96.7 2 44.0 - - 2.1 - - 86.7 2.5 8.6 0 - 3 - - 0 Apocynum review 163 in order to avoid spring frosts (ROMANOVICH et al., 1951; TANG, 2008). During the fi rst year, 7-15 times irrigation with a total amount of 10,000 m³/ha to 12,000 m³/ha of water is needed for A. venetum. Fields on which A. venetum is sown should have a groundwater level not deeper than 2 m. On the other hand, the soil must be well drained, in order to avoid wet conditions (ROMANOVICH et al., 1951). Apocynum germinated from seeds grows 30-40 cm high until the end of the vegetation season of the fi rst year. The root system grows faster than the above ground part. After the fi rst vegetation season, the roots reach 70-75 cm deep into the soil. In the second year, the sprouts grow out of the soil in March. At the end of the second vegetation season, Apocynum reaches a height of 100 cm. These stems start to yield fi bres. Fruits are formed only after the second year. In the fourth year, the stems reach a height of 2 m. In the third year and afterwards, the stems can be harvested before the onset of the fl owering time. The horizontal roots penetrate the whole plantation area in the third year. The root system of A. venetum reaches a groundwater level of 1.5 m during the second year. In the third year, the roots reach a groundwater level of 2 m (BERLJAND, 1950). For the establishment of Apocynum plantations root parts can be used, too. The roots can be taken from wild Apocynum stands, though over-exploitation must be avoided. Root pieces of 10-15 cm length are planted 10 cm deep into the soil. The work load is high, because 60,000 to 70,000 root pieces, i.e. 1-2 t are needed per hectare. The planting time can start a bit earlier than seeding time, i.e. end of March, but spring frosts also hamper root sprouting. During the fi rst and second year, irrigation is necessary under the arid climate of Central Asia. Water has to be applied 5-6 times per year, which sums up to 4,000 m³ to 5,600 m³ water per year. If root pieces have been planted instead of seeds, the plant development is faster. At the end of the fi rst vegetation season, the stems grow as high as 40-50 cm. At the end of the third year, the stems reach a height of 2 m (BERLJAND, 1950). Insect pests do not pose a problem in the Apocynum cultivation, but the fungus Septaria leaf spot damages Apocynum under moist and rainy conditions (ZHANG et al., 2005). As the most important pests on Apocynum the fungus Fusarium spec. and the snail Septaria spec. are considered. 6. Utilization of A. venetum and A. pictum A. venetum and A. pictum are used as medicinal plant and as fi bre plant. The leaves, harvested in June/July, serve as raw material for tea and drugs, while the stems, harvested in summer or autumn, serve as raw material for the fi bre extraction. Furthermore, Apocynum as part of the natural riparian vegetation is grazed (ZHANG et al., 2003). In an experimental scale natural rubber was extracted from A. venetum. But due to its poor quality, this utilization was given up rapidly (PAVLOV, 1942). In this paper, we will focus on the utilization of Apocynum as fi bre plant and as medicinal plant. The fi bres of Apocynum are bast fi bres (Fig. 3), like hemp or fl ax (ROMANOVICH et al., 1951). The fi bre bundles of Apocynum are stronger, i.e. 30-40 fi bres, than the bundles of fl ax, i.e. 10-30 fi bres (PAVLOV, 1942). The strong bast fi bres obtained from the inner bark are used in making cloth, strings, sails, fi shing nests, and high- quality paper (ZHANG et al., 2006b). Next to the fi bres from the stem, A. venetum yields a fl oss fi bre from the seeds (ZHANG et al., 2006b). The fi bre quality from both Apocynum species reviewed here are similar (HE et al., 1997). The cultivation of A. venetum for fi bre production started as early as 1930 in the former USSR. Just after World War II, there were plans in the USSR to set aside large areas for the cultivation of A. venetum as fi bre plant. In China, Apocynum fi bres are used for textiles, mainly for underwear. In China, A. venetum grows as high as 3.6 m. In the Caidam Basin the above ground biomass fresh weights was measured with 1798 kg/ha and 1964 kg/ha for A. pictum (TANG, 2008). From a plantation near Tashkent, an average yield of 5-6 t/ha with a stem density of 300,000 plants per hectare was reported (PAVLOV, 1942). The annual demand for Apocynum fi bres of whole China has been estimated at 50,000 kg over the past years. This demand is covered by the Apocynum stands in China. In contrast to that, the demand for leaves as raw material for tea and medicine cannot be covered (TANG, 2008). In the fi rst year after planting, A. venetum can be harvested once during that year. Afterwards, it can be harvested twice, i.e. in June before or at the beginning of the fl owering period and a second time in September (ZHANG et al., 2005). In contrast, (BERLJAND, 1950) states that Apocynum can be harvested after 2-3 years. Only after 10 years, the productivity and yields decrease (PAVLOV, 1942). 6.1 Fibre extraction and fi bre content After harvest, the stems are dried on the fi eld and roasted. Then, the bark and woody parts have to be removed mechanically from the fi bres (BERLJAND, 1950). In a second step, the pectin, cellulose, and lignin, in which the fi bre cells are embedded has to be digested (degumming), in order to yield the pure fi bres (WANG et al., 2007). Chemical degumming (WANG et al., 2007) and biological (bacterial) degumming (can be applied to extract Apocynum fi bres. The fi bre properties do not vary between the two degumming methods (WANG et al., 2007), though bacterial degumming avoids pollution and thus is regarded superior to chemical degumming (BAO et al., 2002). The fi bres can be extracted better from A. venetum compared to A. pictum, because the internodes of A. venetum are longer as the leaves and branches are opposite. But, the fi bre extraction and the dying of Apocynum is more diffi cult than cotton (LIU and ZHOU, 2002). The bark amounts for 20-22 % of the stem weight for A. venetum Fig. 3: Cross section of an A. venetum stem, a) pith, b) xylem, c) fi bre bundle, d) epidermis 164 N. Thevs, S. Zerbe, Y. Kyosev, A. Rozi, B. Tang, N. Abdusalih, Z. Novitskiy (ROMANOVICH et al., 1951). The fi bre content of dry stems of A. venetum ranges from 10.2 % (ZHANG et al., 2006b) to 17 % (BERLJAND, 1950). A. pictum has lower fi bre contents, i.e. 7.6 % as shown in Tab. 4 (ZHANG et al., 2006b). The longest fi bres were found in the upper part of the lower half of the stem. The fi bre length correlates with the stem height (ZHANG et al., 2006b). The stem heights of A. venetum growing as understory in a fl oodplain forest and growing on an open site are 379.4 cm and 192.8 cm, respectively (ZHANG et al., 2006b). 6.2 Fibre properties The Apocynum fi bres resemble cotton but are stronger than cotton. In the cross-section the Apocynum fi bres are round, elongated, or even triangular. The fi bres yield a pure white yarn, which is very similar to fl ax yarn. Apocynum fi bres have small openings, which increase the turnover of air into the fi bre and keep the fi bre dry (HAN, 2006; LI and LI, 2006). Compared to cotton, Apocynum textiles keep warmer, have a higher aeration, and absorb a higher proportion of UV light (WEI, 2004). The properties of Apocynum fi bres are given in Tab. 5. In Tab. 6 and 7, the Apocynum fi bre properties are compared with Ramie and Flax as two other bast fi bre plants and with cotton. However, between the Apocynum fi bres and cotton there are considerable differences. The modulus of all Apocynum fi bre from the three treatments is higher than 300 cN/dtex, while that of cotton is only 96 cN/dtex. Thus, textiles from Apocynum might be less soft than from cotton. Furthermore, the work of rupture of the Apocynum fi bres with 11.82-13.72 µJ/dtex is lower than the corresponding value of cotton being 16.77 µJ/dtex. Apocynum fi bres thus might be less durable than cotton fi bres (WANG et al., 2007). Still, the Apocynum fi bres extracted through the three degumming methods all can be readily processed in normal textile machinery and are suitable for blending with other commonly used fi bres (WANG et al., 2007). Though, the low breaking elongation, the variance in fi bre length, and the smooth surface of the Apocynum fi bres may lead to diffi culties during the spinning process (PAVLOV, 1942; LIU and ZHOU, 2002). Therefore, Apocynum fi bres usually are blended with cotton or chemical fi bres (WEI, 2004). The blend ratio usually is 65 % cotton and 35 % Apocynum (ZHANG et al., 2001). The chemical composition of Apocynum is little different from other hemp fi bre. The pectin content of Apocynum is 13.14 % .The water soluble content is 17.22 % It is the highest ranking among the hemp fi bre. The lignin content of is 12.14 %, higher than ramie, fl ax, abaca and sisal. The cellulose content ranges from 40.82 %, which is the lowest of all hemps, to 72 %, i.e. the same as fl ax fi bre (LI and LI, 2006). 6.3 Hygiene and medicinal effects of Apocynum fi bres Apocynum fi bres show an anti-microbial effect. The inhibition rates of Apocynum fi bre on Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Candida albicans is 47.7 %, 69.0 %, 56.6 %, and 40.1 %, respectively, compared to cotton fi bres. Under an electron microscope, it was visible that the cell walls of the bacteria were destructed upon contact to the Apocynum fi bres (LÜ et al., 2006). This can be attributed to the fi nding that the stem cells of Apocynum contain tanning agents, which makes the fi bres resistant against microbial decomposition (ROMANOVICH et al., 1951). Tab. 4: Stem height, bast and fi bre contents, and fi bre lengths (mean and standard deviation) of A. venetum and A. pictum in Xinjiang (ZHANG et al., 2006b). The asterix indicates signifi cant differences between the two means at p <= 0.05, calculated with t-test. Plant parameter Apocynum venetum Apocynum pictum Mean ± standard deviation Stem height [cm] 244.1 ± 78.0 112.0 ± 22.2 * Bast content of stem [%] 22.4 ± 4.4 23.7 ± 4.7 Bast content of branches [%] 19.6 ± 3.5 27.3 ± 5.0 * Percentage of stem bark 66.0 ± 17.1 47.0 ± 10.2 * from total bark [%] Fibre content [%] 10.2 ± 2.9 7.6 ± 1.9 * Fibre length of stem [mm] 36.3 ± 8.4 29.4 ± 8.0 * Fibre length of branches [mm] 20.2 ± 5.9 20.8 ± 5.4 Tab. 5: Fibre properties of Apocynum fi bres. Fibre parameter Size of parameter Fibre length [mm] 15-25, max. 70 (PROZOROVSKII, 1932) 50-55, min. 5, max. 120 (PAVLOV, 1942) 20-25, min. 10, max. 40 (LI and LI, 2006) Average 26 (ZHANG et al., 2001) Diameter [µm] 45 (PAVLOV, 1942) Fineness [dtex] 4.15 (XU, 2005) 3-4 (LI and LI, 2006) 4.7 (ZHANG et al., 2001) Strength [cN/dtex] 3.7-4.4 (LI and LI, 2006) 3-7 (ZHANG et al., 2001) Tab. 6: Comparison of fi bre properties between Apocynum and the bast fi bres Ramie and Flax Specifi cations Apocynum Ramie Flax Source Fibre length [mm] 20-25 50-120 15-20 (XU, 2005) Fibre diameter [µm] 14-15 20-45 12-17 (XU, 2005) Fineness [dtex]1 3 4.5 2 (LI and LI, 2006) Strength (dry) 3-7 6.5 6.3 (LI and LI, 2006) [cN/dtex] Breaking elongation 2.5 2.3 1.8 (LI and LI, 2006) (dry) [%] Divergence rate [%] 100 100 88 (LI and LI, 2006) 1 The unit tex is equivalent to 1 g/km. Thus, an Apocynum fi bre of 3 dtex has a weight of 0.3 g per 1 km fi bre length. Tab. 7: Comparison of fi bre properties of Apocynum venetum (three extraction treatments) and cotton (WANG et al., 2007) Fibre Machine bast Hand bast Machine bast Cotton parameter pealing + pealing + pealing + chemical chemical bacterial degumming degumming degumming Modulus 318.9 383.7 394.5 96.6 (cN/dtex) Breaking 4.06 3.58 3.26 10.69 elongation (%) Work of rupture 12.36 13.72 11.82 16.77 (µJ/dtex) Apocynum review 165 6.4 Medicinal applications of A. venetum and A. pictum Tea from A. venetum and A. pictum is used as a traditional Chinese medicine, which mainly is consumed in Northwest China. Anti- hypertensive and anti-hyperlipidemic effects are attributed to Apocynum tea (MA and CHEN, 1999). In 1977, Apocynum was listed as Chinese medicine in China (ZHANG, 2004). A. venetum leaves are rich in ash elements and minerals, such as Ca, Fe, and Na, but differ from green tea leaves in that they contain no caffeine (YOKOZAWA et al., 2002). The leaves of A. venetum and A. pictum have a high fl avonoid content (SAKUSHIMA et al., 1978; KAMATA et al., 2008). Aqueous A. venetum extracts showed an anti-hypertensive effect on hypertensive rats. This anti-hypertensive effect was observed after treatment with aqueous extracts from roasted and non-roasted leaves (KIM et al., 2000). The anti-hypertensive effect was mainly attributed to an improved kidney function, i.e. increased excretions of urine volume and urine electrolytes. Such a diuretic effect of aqueous A. venetum extracts had been reported before (QING et al., 1988). Furthermore, a vascular relaxation effect after treatment of rat aortas with an A. venetum extract in an in vitro experiment was found. This vascular relaxation effect plays a role regarding the anti-hypertensive effects of Apocynum tea (KWAN et al., 2005). Apocynum extract caused vasodilation on tissues (TAGAWA et al., 2004). Aqueous A. venetum extracts decreased the serum total cholesterol and LDL-cholesterol levels and the atherogenic index, as well as the hepatic total cholesterol level in an experiment with hyper- cholesteraemic rats, but they increased the HDL cholesterol level. The decrease of cholesterol values was stronger when using roasted Apocynum leaves to prepare the extract (KIM et al., 1998). The leaves yield up to 5 % gum, which is used for making rubber, and a medicine used as a sedative and to treat hypertension (ZHANG et al., 2006a). An extract of A. venetum leaves reduced signifi cantly the immobility of rats in an forced swimming test. Therefore, it was concluded that such an A. venetum extract shows antidepressant activity in the forced swimming test. (BUTTERWECK et al., 2001; BUTTERWECK et al., 2003; ZHOU et al., 2007). Furthermore, A. venetum extracts contain anti-oxidants. The anti- oxidative effect was attributed to condensed tannin compounds. The radical scavenging activity of A. venetum extracts was determined to be similar to Gingko biloba L. Thus, A. venetum extracts may serve as protective reagents against the oxidative stress in nerve cells due to lipid peroxidation (CAO et al., 2003; YOKOZAWA and NAKAGAWA, 2004; SHIRAI et al., 2005). 7. Conclusions The literature reviewed shows that A. venetum and A. pictum yield fi bres, which can be used as textiles, though the fi bres best are blended with cotton and/or chemical fi bres. Such yarns have good aeration and warming properties due to the hollow structure of the Apocynum fi bres and are mostly used to produce underwear. Furthermore, the literature shows that Apocynum leafs are used to produce anti-hypertonic tea and medicine. Both species yield fi bres and leafs on considerable areas under the arid climate of Central Asia without irrigation, because they use the groundwater. Furthermore, both species can withstand higher soil salinization levels than cotton. A. pictum can withstand more saline and more arid conditions than A. venetum. Both species can be used and provide an income to local people under conditions, which are unfavorable to grow crops under irrigation. Such conditions are un- reliable water supply for irrigation systems and/or saline soils. Though, a number of research questions still are open. The area, from which Apocynum currently could be harvested, and the potential annual yields of fi bres and leafs are unknown. Furthermore, the water consumption and water use effi ciency must be measured, in order to make sure that Apocynum utilization does not consume more water than current utilizations. Currently, in China mostly natural Apocynum stands are harvested. These stands are not fertilized. Therefore the nutrient exports due to Apocynum harvest and possible stand degradations must be investigated. The current used degumming methods require longer process time (bacterial degumming), are not very environment friendly and require water resources, which are usually not available in the cultivation regions. Therefore, more effi cient and environmental friendly degumming method need to be investigated. The fi bres demonstrate technological properties similar to the other cellulosic fi bres (fl ax, cotton), but with signifi cantly lower braking elongation and larger length variations. These two features disturb the classical spinning process of pure apocynum yarns and are one of the reasons the apocynum fi bres to be blended with cotton. The development of an adjusted spinning process and equipment for apocynum fi bres can allow the production of yarns with higher apocynum content, which can extend the application areas for textiles. Due to its high strength, it has to be investigated if the fi bres are suitable for other than clothing applications, as for instance for natural fi bre composites. In such case the fi bres can be used directly without or after only partial degumming procedure, which will reduce their price as well. Acknowledgements We thank the Bauer-Hollmann Foundation and the Helene and Rudolf Glaser Foundation for funding personal costs within the Junior Research Group Adaptation Strategies to Climate Change and Sustainable Land Use in Central Asia (Turkmenistan and Xinjiang, China). Furthermore, we thank the Robert-Bosch-Foundation, the Federal Ministry for Education and Research, Germany, and the German Academic Exchange Service (DAAD) for funding travel costs to China and Uzbekistan, respectively. References BAI, L., LUO, M.B., CHUAN, L.C., WANG, S.L., A, M.N., 2005: Short Report on planting techniques of Apocynum venetum. Chinese Wild Plant Resources 24, 65-68. 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