Journal of Applied Botany and Food Quality 95, 17 - 22 (2022), DOI:10.5073/JABFQ.2022.095.003 University of Alicante, Spain Only low saline conditions benefited yield and quality of iceplant grown in pot culture M.C. Rodríguez-Hernández*, I. Garmendia (Submitted: November 3, 2021; Accepted: January 10, 2022) * Corresponding author Summary Mesembryanthemum crystallinum L. or iceplant is an annual facul- tative halophyte adapted to extreme environmental conditions, as salinity. This characteristic has special importance in the Mediterra- nean region, where the drought conditions entail the most important problems of soil and water salinity. Furthermore, there is current- ly a great gastronomic interest for this plant due to its soft texture, fresh and salty taste, high content of water and beneficial compounds for health. Therefore, the objective of this work was to establish the optimal salt growth conditions for pot cultivation of iceplant in greenhouse. Thus, the effect of different salinity levels (0, 100, 200 and 300 mM NaCl) under controlled conditions was evaluated. Severe salinity treatments reduced crop production. However, results showed that the 100 mM NaCl treatment benefited plant growth. This treatment showed greater leaf fresh weight and area, pigment content and maintained its root and shoot biomass similar to control values. In addition, compared to control plants, salinity increased the spe- cific leaf area and leaf relative water content, reduced leaf starch and K concentrations. Therefore, results confirm that iceplant pot culture can be strategically perform under low salinity conditions with an enhancement or maintenance of crop yield and quality. Keywords: Mesembryanthemum crystallinum, salinity, growth, production. Introduction It is known that soil salinity can reduce crop, horticulture and forage production in arid and semiarid regions. Salt may arise naturally in the subsoil or be introduced by brackish irrigation waters. In any case, salinity is becoming more extensive as a result of land clear- ing and unsustainable irrigation practices and through pressures for bringing marginal land into production (Munns and GillihaM, 2015). Hence, intensified use of halotolerant crop plants will be necessary, even in Europe. In this context, commercial use of halophytes as fresh food is nowa- days very limited. Several facultative halophytic members of Aizoa- ceae are used as special crop plants since many years (herppich et al., 2008). Per example, an old, but rare salad green is the com- mon iceplant or glacier lettuce, Mesembryanthemum crystallinum (VoGel, 1996). This species is an annual facultative halophyte with a crassulacean acid metabolism (CAM), which is induced by saline stress, among others. It is an ephemeral or pseudo-biennial prostrate white flowering herbaceous weedy plant with simple, ovate, succu- lent leaves and stems which are densely covered with bladder cells. These cells give the plant a glistening appearance (adaMs et al., 1998). It is native from South and East Africa (Winter, 1978) and is introduced in Western Australia and in the Mediterranean amongs others (Winter and sMith, 1996). With its succulent, mellow, slightly salty tasting leaves and young shoots, this species is a delicious cool flavored salad green. In Eu- rope it is also known as a quickly cooked tender vegetable (herppich et al., 2008). On the other hand, M. crystallinum was classified as a highly functional food according to the work of aGarie et al. (2009), due to high concentration of polyols that is increased under condi- tions of saline and water stress. The high salt tolerance and content in bioactive compounds and its excellent capacity for phytoremedia- tion, makes the ice plant an important candidate for use as human food and medical care, and in the decontamination of polluted sites (loconsole et al., 2019). The effects of environmental stress factors have frequently been stu- died in M. crystallinum, as salt stress (aGarie et al., 2009; otsuka et al., 2021). But more studies are needed to determine the optimum conditions in pot cultivation of M. crystallinum to obtain maximum yield and market introduction, to boost the use of this wild edible plant. Therefore, the objective of this work was to establish the non detrimental saline growth conditions for the cultivation of glacier lettuce in greenhouse. To this end, the effect of different irrigation salinity levels on edible leaf production and quality were evaluated. Materials and methods Plant material and growth conditions Seeds of Mesembryanthemum crystallinum L. were collected from wild plants of Alicante (SE Spain), disinfected with 0.5% NaClO during 2 h and pre-hydrated with aerated, deionised water for 22 h. Then, they were germinated in vermiculite hydrated with deionised water and mantained in a growth chamber with an air temperature (T) of 24 °C day/night (D/N) and relative humidity (RH) of 70% D/N (thoMas et al., 1998). Light conditions of the chamber were 16 h light-8 h dark cycle with a photosynthetically active radiation of 400 μmol m-2s-1 supplied by a combination of fluorescent tubes (Philips TLD 36W/83 Germany and Silvana F36W/GRO, USA). After 20 days, seedlings were transferred to a greenhouse under semi-controlled conditions of T D/N: 25/18 °C; RH D/N: 60/80% and received natural daylight (mean photosynthetic photon flux rate of 400 μmol m-2 s-1) (aGarie et al., 2007). Then, seedlings were transplanted to 1 L plastic pots with vermiculite watered weekly with 500 ml of Hoagland solution. After 55 days of transplantation, plants were divided into 4 homogeneous groups of 6. Four saline treatments were compared: control (0 mM), 100 mM, 200 mM and 300 mM of NaCl. To avoid an osmotic shock, the concentration of NaCl was increased gradually during the first week to reach the desired NaCl concentration and maintained for one additional week. After 15 days of salinity conditions, plants were harvested and the different deter- minations were performed. At the end of the experiment, the elec- trical conductivity (EC) of the substrate from non-saline container and the pots cultivated under 100, 200 and 300 mM of NaCl was 1.80, 13.67, 19.08, 25.01 dS m-1, respectively. Growth parameters Plant dry weight (DW) was determined after drying fresh matter at 80 °C in an oven until constant weight. In addition, shoot and root length were measured. Leaf area was measured by the app “Easy 18 M.C. Rodríguez-Hernández, I. Garmendia Leaf Area Free” (easlon and BlooM, 2014) and specific leaf area (SLA) was calculated as the ratio of the leaf area and the dry weight of leaves. Water status The leaf relative water content (RWC) was calculated according to Weatherley’s method (1950), using the following formula RWC (%): (FW-DW) / (TW-DW) × 100, being FW: fresh weight, TW: turgid weight, and DW: dry weight of the tissue, respectively. Foliar succu- lence was measured according to atzori et al. (2017) by the ratio of the FW of the leaves and the foliar area. Midday water potential (Ψ) of the root was measured by a Scholander pressure chamber (SKPM 1450/40, Skye Instruments Ltd., United Kingdom). All the determi- nations were performed in expanded young leaves collected at noon. Biochemical analysis These analyses were performed on the youngest full-mature leaves harvested at midday, frozen in liquid nitrogen and stored at -20 °C for later quantifications. The concentration of foliar photosynthetic pigments was determined according to sesták et al. (1971). The samples (20 mg FW) were included in 5 ml of 96% ethanol at 80 °C for 10 minutes to extract the pigments. The absorbance of the extracts was spectrophotometrically measured and the equations reported by lichtenthaler (1987) were used to calculate the concentration of chlorophylls and carotenoids. Starch, total soluble sugars (TSS) and proline in leaves were quan- tified in potassium phosphate buffer (KPB) (50 mM, pH = 7.5) ex- tracts of fresh tissue (0.1 g). These extracts were filtered through four layers of cheesecloth and centrifuged at 28710 g for 15 min at 4 °C. The pellet was used for starch determinations (JarVis and Walker 1993). The supernatant was collected and stored at 4 °C for TSS and proline determinations. Total soluble sugars were analysed spectro- photometrically with the anthrone reagent (YeMM and Willis, 1954). Free proline was estimated by spectrophotometric analysis at 515 nm of the ninhydrine reaction (iriGoYen et al., 1992). Mineral analysis Leaf samples (0.5 g DW) were dry-ashed and dissolved in HCl ac- cording to duque (1971). Magnesium, potassium, phosphorus, calcium, sodium, manganese, zinc and iron concentrations were de- termined using a Perkin Elmer Optima 4300 inductively coupled plasma optical emission spectroscopy (ICP-OES) (Perkin Elmer, USA). The operating parameters of the ICP-OES were: radio fre- quency power 1300 W, nebulizer flow 0.85 L min-1, nebulizer pres- sure 30 psi, auxiliary gas flow 0.2 L min-1, sample introduction 1 ml min-1 and three replicates per sample. Total carbon and nitrogen were quantified after combustion (950 °C) of leaf DW with pure oxygen y an elemental analyzer provided with a thermal conductivity detector (TruSpec CN, Leco, USA). Statistics The results were analyzed with one-way analysis of variance (ANOVA) by the statistical program SPSS v.26 (IBM Corp., USA). The means ± standard deviation (SD) were calculated and, when the F ratio was significant (p<0.05), least significant differences were evaluated by the Duncan test. Significance levels were set at 5%. Results Growth parameters showed significant differences regarding to the salt treatment (Tab. 1). Plants grown with 100 mM of NaCl main- tained high shoot and root biomass, if we compare with the rest of saline treatments. In addition, iceplant subjected to 100 mM of NaCl enhanced significantly leaf area (Tab. 1) and leaf fresh weight (Fig. 1). Values of SLA also increased in plants cultivated with sa- linity conditions comparing with control ones (Tab. 1). The results of shoot height and root length showed that there were no differences between salinity levels. With reference to leaf water status, plants grown under salinity over 100 mM NaCl had greater RWC than control plants (Tab. 2). How- ever, the highest leaf succulence was observed in control plants. In relation to root water potential, this parameter did not show a clear trend, with higher values in 100 and 300 mM NaCl treatments in comparison with controls. Biochemical analysis (Tab. 3) performed on the leaves of iceplant displayed differences between treatments. In relation to the photo- synthetic pigments, plants cultivated with 100 mM NaCl increased levels of both chlorophylls and carotenoids concentration. More- over, although amounts of starch declined in leaves of iceplant due to salt stress, TSS concentration only reduced in treatments of 100 and 300 mM of NaCl. Levels of proline increased in plants subjected to saline conditions over 100 mM. Tab. 1: Growth parameters in iceplant subjected to different salt conditions. Treatment Shoot DW Leaf DW Root DW Leaf area SLA Shoot height Root length [NaCl] mM (g plant-1) (g plant-1) (g plant-1) (cm2) (cm2 g-1) (cm) (cm) 0-Control 1.95 ± 0.40 ab 1.38 ± 0.29 a 0.91 ± 0.20 ab 139.12 ± 20.00 c 96.47 ± 12.95 b 15.87 ± 2.84 a 38.20 ± 6.14 a 100 2.12 ± 0.35 a 1.45 ± 0.41 a 1.08 ± 0.32 a 243.34 ± 16.47 a 178.97 ± 53.94 a 15.48 ± 3.79 a 35.00 ± 2.24 a 200 1.60 ± 0.19 bc 1.22 ± 0.16 a 0.64 ± 0.11 b 172.63 ± 18.38 b 146.43 ± 15.72 a 16.00 ± 3.24 a 34.58 ± 8.38 a 300 1.46 ± 0.27 c 1.15 ± 0.31 a 0.66 ± 0.21 b 183.10 ± 32.22 b 163.20 ± 28.15 a 15.75 ± 3.42 a 32.25 ± 8.64 a Means (n=6) ± SD were compared with Duncan test. Within each column, values followed by a common letter are not significantly different (p≤0.05). DW: dry weight. Fig. 1: Leaf fresh weight (FW) in iceplant subjected to different salt con- ditions. Means (n=6) ± SD were compared with Duncan test. Bars followed by a common letter are not significantly different (p≤0.05). 9 Low saline conditions benefited iceplant grown 19 The effect of salinity in leaf mineral concentration of iceplant was also assessed (Tab. 4 and 5). Despite leaf concentration of C and N was similar between treatments, plants grown with 300 mM NaCl had significantly greater concentrations of Mg and Ca compared to the rest of treatments (Tab. 4). On the other hand, the amount of K was lower as salt concentration increased over 100 mM and there were no differences between treatments in the amount of P. With respect to the micronutrients (Tab. 5), Mn concentration had not a clear trend related to the effect of salinity and there were no dif- ferences between treatments in the amount of Zn. Iceplant that re- ceived 100 and 200 mM NaCl showed the highest values of Fe, and as expected, the accumulation of Na was higher as the severity of salt stress increased. Discussion High salinity is a critical problem in crop production that results in reduced plant growth and a significant reduction in productivi- ty (tsukaGoshi et al., 2015). Mesembryanthemum crystallinum (iceplant) is an halophyte that can survive in high salinity soils and switches from C3 photosynthesis to CAM under high salinity and drought stress (adaMs et al., 1998). We have observed that irrigation with 100 mM of NaCl produced an improvement in growth, with important effect on parameters affecting edible parts of the crop, such as the leaf area or leaf fresh weight. In addition, the application of higher concentration of salt generated growth reduction. These results are in accordance with the study of Winter (1973), in which the maximum growth of iceplant was obtained with a concentration of 100 mM NaCl. rodríGuez-hernández and GarMendia (2021) showed that a moderate concentration of salinity (100 mM NaCl) improved the accumulation of nutraceuticals and the production of edible leaves while high saline conditions were detrimental to the plant’s growth. atzori et al. (2017) also described the increase of leaf biomass and area in plants subjected to moderate salinity. In this regard, it should be noted that most halophytes as iceplant require saline conditions to attain optimal growth. According to FloWers et al. (1986) M. crystallinum shows optimal growth within 50-250 mM NaCl. Thus, in this study it was confirmed that M. crys- tallinum irrigated with 100 mM NaCl for two weeks had the highest leaf FW and leaf area. Similarly, he et al. (2021) recently showed that 100 mM NaCl had the highest shoot FW and largest leaf area compared with those grown at 0 and 250 mM NaCl for 15 days. This Tab. 2: Relative water content (RWC), succulence and root water potential (Ψ) in iceplant subjected to different salt conditions. Treatment RWC Succulence Root ψ [NaCl] mM (%) (g FW cm-2) (MPa) 0-Control 88.59 ± 5.39 b 0.73 ± 0.15 a -0.27 ± 0.08 b 100 94.22 ± 8.59 ab 0.57 ± 0.06 b -0.10 ± 0.01 a 200 97.67 ± 2.38 a 0.53 ± 0.07 b -0.25 ± 0.05 b 300 99.12 ± 1.73 a 0.48 ± 0.04 b -0.15 ± 0.08 a Means (n=6) ± SD were compared with Duncan test. Within each column, values followed by a common letter are not significantly different (p≤0.05). FW: fresh weight. Tab. 3: Leaf photosynthetic pigment concentration and leaf concentration of starch, total soluble sugars (TSS) and proline in iceplant subjected to different salt conditions. Treatment Chlorophylls Carotenoids Starch TSS Proline [NaCl] mM (mg g-1 DW) (mg g-1 DW) (mg g-1 DW) (mg g-1 DW) (mmol g-1 DW) 0-Control 32.30 ± 7.49 b 5.35 ± 1.10 ab 309.01 ± 90.18 a 189.85 ± 52.17 a 43.66 ± 12.77 c 100 41.60 ± 7.20 a 6.47 ± 1.76 a 84.83 ± 34.52 b 119.70 ± 27.76 b 41.39 ± 11.72 c 200 29.79 ± 3.56 b 4.22 ± 0.64 bc 37.53 ± 13.05 bc 193.60 ± 56.79 a 101.37 ± 30.41 b 300 29.27 ± 7.94 b 3.17 ± 0.88 c 20.06 ± 9.80 c 94.40 ± 25.99 b 203.87 ± 47.56 a Means (n=6) ± SD were compared with Duncan test. Within each column, values followed by a common letter are not significantly different (p≤0.05). DW: dry weight. Tab. 4: Foliar concentrations of macronutrients in iceplant subjected to different salt conditions. Treatment C N Mg K P Ca [NaCl] mM (mg g-1 DW) (mg g-1 DW) (mg g-1 DW) (mg g-1 DW) (mg g-1 DW) (mg g-1 DW) 0-Control 431.17 ± 119.95 a 56.39 ± 15.78 a 18.49 ± 3.49 b 43.78 ± 6.29 a 2.70 ± 0.83 a 7.55 ± 1.11 b 100 370.33 ± 57.40 a 45.19 ± 7.31 a 17.98 ± 3.60 b 31.82 ± 4.66 b 2.55 ± 0.66 a 7.98 ± 1.78 b 200 395.40 ± 46.25 a 50.29 ± 4.97 a 22.62 ± 4.86 b 30.69 ± 5.55 b 2.35 ± 0.35 a 8.71 ± 2.24 b 300 362.67 ± 40.93 a 46.41 ± 3.55 a 28.16 ± 3.31 a 33.87 ± 6.80 b 2.45 ± 0.49 a 16.02 ± 2.62 a Means (n=6) ± SD were compared with Duncan test. Within each column, values followed by a common letter are not significantly different (p≤0.05). DW: dry weight. Tab. 5: Foliar concentrations of micronutrients and sodium in iceplant subjected to different salt conditions. Treatment Mn Zn Fe Na [NaCl] mM (μg g-1 DW) (μg g-1 DW) (μg g-1 DW) (mg g-1 DW) 0-Control 483.07 ± 66.04 a 67.06 ± 1.79 a 1666.48 ± 474.77 b 3.41 ± 1.02 c 100 320.47 ± 37.30 b 65.60 ± 5.52 a 2305.05 ± 494.23 a 24.01 ± 7.72 b 200 432.41 ± 63.97 a 70.92 ± 7.34 a 1976.63 ± 454.53 a 30.63 ± 4.38 ab 300 349.84 ± 39.88 b 70.54 ± 8.64 a 900.32 ± 375.47 c 37.18 ± 11.07 a Means (n=6) ± SD were compared with Duncan test. Within each column, values followed by a common letter are not significantly different (p≤0.05). DW: dry weight. 20 M.C. Rodríguez-Hernández, I. Garmendia good performance of the iceplant under low salinity conditions, indi- cates its potential for saline agriculture. Furthermore, an increase in SLA was observed in our plants sub- jected to saline stress related to the enhancement of leaf area. It can be suggested that the ice plant leaf area was not reduced by salinity because another feature helped in regulating the leaf ion concentra- tion: the epidermal bladder cells, which function as peripheral salt and water reservoirs (luttGe et al., 1978; aGarie et al., 2007). In addition, it is worth mentioning that the saline treatment applied last- ed two weeks. In this short term effect of salinity, concentrations over 100 mM NaCl resulted to be detrimental for iceplant growth under pot culture. According to aGarie et al. (2007), iceplant subjected to 100 mM NaCl for 3 weeks gained a higher dry matter than the same treatment for a week and even at 2 weeks. Moreover, only much higher saline treatments (800 mM) showed a decrease in dry biomass as the exposure time increased to 3 weeks. Therefore, a longer term treatment of salt stress in iceplant pot culture seems to led to similar results. The increase in RWC of plants irrigated with NaCl can be explained by the adaptive mechanisms to the saline stress that M. crystallinum performs, since the bladder cells accumulate water, in addition to salts, to improve ionic and osmotic stress (aGarie et al., 2007) and the induction of CAM metabolism causes the plant to lose less water related to stomatal closure during the day. Due to these adaptations it was expected that the iceplant had greater succulence in salinity treated plants. However, since succulence is calculated as the ratio of fresh leaf weight to the leaf area, the maintenance of high leaf area in saline conditions would explain the decrease in succulence according to our data. On the other hand, the expected response of the root water potential was to decrease with the increase of salinity levels, but our results differed. Root Ψ in controls was lower than in the 100 and 300 mM NaCl treatments. Because M. crystallinum is a crass plant, the manipulation and determination of Ψ could have hindered using the pressure chamber, which would indicate a pos- sible inaccuracy of these measurements (herppich and herppich, 1997; Busso, 2008). In relation to photosynthetic pigments, total leaf chlorophyll con- centration was higher in the plants treated with 100 mM NaCl. Ac- cording to herppich et al. (2008), the increase in chlorophyll can be explained by a general physiological stimulation in response to sa- linity. Furthermore, the similar values of chlorophylls in treatments with high salinity levels in relation to the control indicated that in the halophyte M. crystallinum, salinity did not destroy chloroplasts or increase the activity of the chlorophyllase enzyme, which affects the synthesis of chlorophylls (arGentel et al., 2006). The concen- tration of carotenoids was maintained as controls in the treatment of 100 mM NaCl, with significant lower values as saline conditions increased. These results did not coincide with those obtained by atzori et al. (2017), where the concentration of carotenoids in- creased with the increase in salinity. However, redondo-GóMez et al. (2010) in Arthrocnemum macrostachyum halophilic plant, de- scribed a progressive decrease in the concentration of carotenoids in salinity treatments above 100 mM. Carotenoids have a membrane stabilizing role (MorGan, 2004) and are related to the VAZ or xanthophyll cycle. This cycle dissipates energy in the form of heat, protects chloroplasts against photoxidation caused, for example, by saline stress. Therefore, similar or increased concentration of photo- synthetic pigments in plants subjected to a low salt stress of 100 mM comparing with controls, could presume an increase of the photo- synthetic capacity together with greater amount of energy in thermal dissipation over photochemistry (atzori et al., 2017). Salinity did not influence negativelly the leaf concentration of C, N, P and Zn. As expected, salinity treatments increased the foliar concentration of Na in iceplant, demonstrating that M. crystallinum acts as a sequestrant of salts, due to the presence of bladder cells (aGarie et al., 2007). Ca and Mg increased with salinity, reaching the maximum concentration of these minerals with 300 mM NaCl. atzori et al. (2017) studied the effect of different levels of salinity on Mesembryanthemum and found that none of the salinity treat- ments negatively affected the biomass production of glacier lettuce and Ca leaf concentration increased with increasing salinity. Fur- thermore, the increase in salinity lengthened the vegetative stage, obtaining an additional month of harvest compared to the non-saline treatment. The significant increase of Ca and Mg concentrations may represent an interesting nutritional improvement achievable in sali- nity conditions. Calcium is among the main mineral elements lack- ing in the diet of over two-thirds of the world’s population (White and BroadleY, 2009). On the other hand, Ca and Mg are antagonists of Na, so in plants not adapted to salinity a decrease in Ca or Mg concentrations would be expected, due to a displacement by Na from the cell membrane binding sites (dodd et al., 2010). But, according to Bressan et al. (1998), in iceplant, the increase in Ca, as Mg, is a cause of adaptation to salinity, since it has a protective effect on membranes under salinity conditions. In relation to the concentration of K, it decreased with salinity, because Na competes by the binding sites in the transport system that mediates the taking of K (niu et al., 1995). Our results are in the same line of the study by atzori et al. (2017), where Na was higher in iceplant irrigated with salt than in the controls, as well as Ca and Mg, while K decreased with increasing salinity. Additionaly, starch leaf concentration of glacier lettuce decreased as salinity increased. Similarly, adaMs et al. (1992) and paraMonoVa et al. (2004), observed the diminishing of starch content in iceplant grown with NaCl, probably caused by starch degradation under stress conditions. Also, the levels of TSS were lower in salt treatments than in control, in accordance with atzori et al. (2017). Nevertheless, plants irrigated with 200 mM presented similar values of sugars as the control treatment, while the starch concentration was lower. On the other hand, proline is part of the osmolytes that act in the osmotic adjustment (huanG et al., 2000; zoBaYed et al., 2007). Our results showed that proline increased with the amount of salinity in order to retain water in the cells (cVikroVá et al., 2013), that probably allowed the increase of RWC in plants subjected to saline conditions. Conclusions The analysed growth parameters showed that iceplant is a crop suit- able for irrigation with saline water, wich is important in Mediter- ranean region. Thus, the implementation of the pot cultivation of M. crystallinum would represent an alternative to the current prob- lem of salinization of arable land and irrigation water, since most traditional crops are sensitive to salinity. Furthermore, in this work it has been described that iceplant irrigated with 100 mM NaCl dur- ing 2 weeks increased important growth parameters as leaf area and its fresh weight. These parameters are especially important in crop yield. Also, this treatment of salinity turned out to be the only one capable of maintaining both the shoot and root biomass at values similar to those of the control, while higher salinity conditions were detrimental to growth. On the other hand, aspects highly valued by the consumer in this plant, such as the relative water content and its salty flavor, were enhanced with salinity. Despite the halophilic na- ture of iceplant, salinity treatments for two weeks over 100 mM were not very suitable for edible fresh leaf production under pot culture. Acknowledgements The authors wish to thank to Susana Carrión and Mar Benavent for their help with biomass analysis and laboratory determinations. Conflicts of interest No potential conflict of interest was reported by the authors. Low saline conditions benefited iceplant grown 21 Funding This work was financed by the Valencian Community − Spain (GV/2018/068). References adaMs, p., nelson, d., YaMada, s., chMara, W., Jensen, r.G., Bonhert, h.J., GriFFiths, h., 1998: Growth and development of Mesembryanthe- mum crystallinum (Aizoaceae). New Phytol. 138, 171-190. DOI: 10.1046/j.1469-8137.1998.00111.x adaMs, p., thoMas, G.c., Vernon, d.M., Bohnert, h.J., Jensen, r.G., 1992: Distinct cellular and organismic responses to salt stress. Plant Cell Physiol. 38, 1215-1223. DOI: 10.1093/oxfordjournals.pcp.a078376 aGarie, s., kaWaGuchi, a., kodera, a., sunaGaWa, h., 2009: Potential of the common ice plant, Mesembryanthemum crystallinum as a new High-functional food as evaluated by polyol accumulation. Plant Prod. Sci. 12, 37-46. DOI: 10.1626/pps.12.37 aGarie, s., shiModa, t., shiMizu, Y., BauMann, k., sunaGaWa, h., kondo, a., ueno, o., nakahara, t., nose, a., cushMan, J., 2007: Salt tole- rance, salt accumulation, and ionic homeostasis in an epidermal bladder- cell-less mutant of the common ice plant Mesembryanthemum crystalli- num. J. Exp. Bot. 58, 1957-1967. DOI: 10.1093/jxb/erm057 arGentel, l., González, l.M., áVila, c., aGuilera, r., 2006: Compor- tamiento del contenido relativo de agua y la concentración de pigmentos fotosintéticos de variedades de trigo cultivadas en condiciones de salini- dad. Cult trop. 27, 49-53. atzori, G., de Vo,s a.c., Van riJsselBerGue, M., ViGnolini, p., rozeMa, J., Mancuso, s., Van BodeGoM, p.M., 2017: Effects of increased sea- water salinity irrigation on growth and quality of the edible halophyte Mesembryanthemum crystallinum L. under field conditions. Agr. Water Manage. 187, 37-46. DOI: 10.1016/j.agwat.2017.03.020 Bressan, r.a., haseGaWa, p.M., pardo, J.M., 1998: Plants use calcium to resolve salt stress. Trends Plant Sci. 3, 411-412. cVikroVá, M., GeMperloVá, l., MartincoVá, o., VankoVá, r., 2013: Effect of drought and combined drought and heat stress on polyamine metabolism in proline-over-producing tobacco plants. Plant Physiol. Biochem. 73, 7-15. DOI: 10.1016/j.plaphy.2013.08.005 dodd, k., GuppY, c., lockWood, p., rochester, i., 2010: The effect of sodicity on cotton: plant response to solutions containing high sodium concentrations. Plant Soil. 330, 239-249. DOI: 10.1007/s11104-009-0196-6 duque, F., 1971: Joint determination of phosphorus, potassium, calcium, iron, manganese, copper and zinc in plants. An. Edafol. Agrobiol. 30, 207-229. easlon, h.M., BlooM, a.J., 2014: Easy Leaf Area: Automated digital image analysis for rapid and accurate measurement of leaf area. Appl. Plant Sci. 2, 1400033. DOI: 10.3732/apps.1400033 FloWers, t.J., haJiBaGheri, M.a., clipson, n.J.W., 1986: Halophytes. Q. Rev. Biol. 61, 313-337. he, J., koh, d.J.q., qin, l., 2021: LED spectral quality and NaCl salinity interact to affect growth, photosynthesis and phytochemical production of Mesembryanthemum crystallinum. Func. Plant Biol. DOI: 10.1071/FP20375 herppich, W.B., huYskens-keil, s., schreiner, M., 2008: Effects of saline irrigation on growth, physiology and quality of Mesembryanthemum crystallinum L., a rare vegetable crop. J. Appl. Bot. Food Qual. 82, 47-54. huanG, J., hirJi, r., adaM, l., rozWadoWski, k.l., haMMerlindl, J.k., keller, W.a., selVaraJ, G., 2000: Genetic engineering of glycine- betaine production toward enhancing stress tolerance in plants: meta- bolic limitations. Plant Physiol. 122, 747-756. DOI: 10.1104/pp.122.3.747 iriGoYen, J.J., eMerich, d.W., sanchez-diaz, M., 1992: Water stress in- duced changes in concentrations of proline and total soluble sugars in nodulated alfalfa (Medicago sativa) plants. Physiol Plant. 84, 55-60. DOI: 10.1111/j.1399-3054.1992.tb08764.x JarVis, s.c., Walker, F.r.l., 1993: Simultaneous, rapid, pectrophotometric, determination of total starch, amylose and amylopectin. J. Sci. Food Agric. 63, 53-57. DOI: 10.1002/jsfa.2740630109 lichtenthaler, h.k., 1987: Chlorophylls and carotenoids: pigments of photosynthetic biomembranes. Methods Enzymol. 148, 350-382. DOI: 10.1016/0076-6879(87)48036-1 loconsole, d., Murillo-aMador, B., cristiano, G., de lucia, B., 2019: Halophyte common ice plants: A future solution to arable land salini- zation. Sustainability 11, 6076. DOI: 10.3390/su11216076 luttGe, u., Fischer, e., steudle, e., 1978: Membrane potentials and salt distribution in epidermal bladders and photosynthetic tissue of Mesem- bryanthemum crystallinum L. Plant Cell Environ. 1, 121-129. DOI: 10.1111/j.1365-3040.1978.tb00753.x MorGan, J.M., 2004: Osmoregulation as a selection criterion for drought tolerance in wheat. Aust. J. Agric. Res. 34, 607-614. Munns, r., GillihaM, M., 2015: Salinity tolerance of crops – what is the cost? New Phytol. 208, 668-673. DOI: 10.1111/nph.13519 niu, X., Bressan, r.a., haseGaWa, p.M., pardo, J.M., 1995: Ion homeo- stasis in NaCl stress environments. Plant Physiol. 109, 735-742. DOI: 10.1104/pp.109.3.735 otsuka, M., kato, h., YaMada, s., nakaYaMa, t., sakaoka, s., MorikaMi, a., tsukaGoshi, h., 2021: Root system architecture analysis in Mesem- bryanthemum crystallinum (ice plant) seedlings reveals characteristic root halotropic response. Biol. Open. 10, bio052142. DOI: 10.1242/bio.052142 paraMonoVa, n.V., sheVYakoVa, n.i., kuznetsoV, V.l.V., 2004: Ultra- structure of chloroplasts and their storage inclusions in the prima- ry leaves of Mesembryanthemum crystallinum affected by putrescine and NaCl. Russ. J. Plant Physiol. 51, 86-96. Translated from Fiziologiya Rastenii 51, 99-109. DOI: 10.1023/B:RUPP.0000011307.95130.8f redondo-GóMez, s., Mateos-naranJo, e., FiGueroa, M.e., daVY, a.J., 2010: Salt stimulation of growth and photosynthesis in an extreme halo- phyte, Arthrocnemum macrostachyum. Plant Biol. 12, 79-87. DOI: 10.1111/j.1438-8677.2009.00207.x rodríGuez-hernández, M.c., GarMendia, i., 2021: Optimum growth and quality of the edible ice plant under saline conditions. J. Sci. Food Agric. DOI: 10.1002/jsfa.11608 sesták, z., càtskY, J., JarVis, p., 1971: Plant Photosynthetic Production: Manual of Methods 1st ed. Editorial Dr. W. Junk Publishers. thoMas, J., Malick, F., endreszl, c., daVies, e., MurraY, k., 1998: Dis- tinct responses to copper stress in the halophyte Mesembryanthemum crystallinum. Physiol. Plant 102, 360-368. DOI: 10.1034/j.1399-3054.1998.1020304.x tsukaGoshi, h., suzuki, t., nishikaWa, k., aGarie, s., ishiGuro, s., hiGashiYaMa, t., 2015: RNA-Seq analysis of the response of the halo- phyte, Mesembryanthemum crystallinum (Ice Plant) to high salinity. PLoS ONE. 10, e0118339. DOI: 10.1371/journal.pone.0118339 VoGel, G., 1996: Handbuch des speziellen Gemüsebaues; 99. Spargel, 778-814. Verlag Eugen Ulmer, Stuttgart, Germany. WeatherleY, p.e., 1950: Studies in the water relations of the cotton plant. I. The field measurements of water deficits in leaves. New Phytol. 49, 81-87. DOI: 10.1111/j.1469-8137.1950.tb05146.x White, p.J., BroadleY, M.r., 2009: Biofortification of crops with seven mineral elements often lacking in human diets-iron, zinc, copper, cal- cium, magnesium, selenium and iodine. New Phytol. 182, 49-84. DOI: 10.1111/j.1469-8137.2008.02738. Winter, k., 1973: CO2-Fixierungsreaktionen bei der Salzpflanze Mesem- bryanthemum crystallinum unter variierten Außenbedingungen. Planta. 114, 75-85. DOI: 10.1007/BF00390286 Winter, k., 1978: Phosphoenolpyruvate carboxylase from Mesembryanthe- mum crystallinum: its isolation and inactivation in vitro. J. Exp. Bot. 29, 539-546. DOI: 10.1093/jxb/29.3.539 Winter, k., sMith, J.a.c., 1996: Crassulacean acid metabolism: Biochem- istry, ecophysiology and evolution. 1st ed. Editorial Springer-Verlag, 235. YeMM, e.W., Willis, a.J., 1954: The estimation of carbohydrates in plant extracts by anthrone. Biochem. J. 57, 508-514. DOI: 10.1042/bj0570508 http://dx.doi.org/10.1046/j.1469-8137.1998.00111.x http://dx.doi.org/10.1093/oxfordjournals.pcp.a078376 http://dx.doi.org/10.1626/pps.12.37 http://dx.doi.org/10.1093/jxb/erm057 http://dx.doi.org/10.1016/j.agwat.2017.03.020 http://dx.doi.org/10.1016/j.plaphy.2013.08.005 http://dx.doi.org/10.1007/s11104-009-0196-6 http://dx.doi.org/10.3732/apps.1400033 http://dx.doi.org/10.1071/FP20375 http://dx.doi.org/10.1104/pp.122.3.747 http://dx.doi.org/10.1111/j.1399-3054.1992.tb08764.x http://dx.doi.org/10.1002/jsfa.2740630109 http://dx.doi.org/10.1016/0076-6879(87)48036-1 http://dx.doi.org/10.3390/su11216076 http://dx.doi.org/10.1111/j.1365-3040.1978.tb00753.x http://dx.doi.org/10.1111/nph.13519 http://dx.doi.org/10.1104/pp.109.3.735 http://dx.doi.org/10.1242/bio.052142 http://dx.doi.org/10.1023/B:RUPP.0000011307.95130.8f http://dx.doi.org/10.1111/j.1438-8677.2009.00207.x http://dx.doi.org/10.1002/jsfa.11608 http://dx.doi.org/10.1034/j.1399-3054.1998.1020304.x http://dx.doi.org/10.1371/journal.pone.0118339 http://dx.doi.org/10.1111/j.1469-8137.1950.tb05146.x http://dx.doi.org/10.1111/j.1469-8137.2008.02738 http://dx.doi.org/10.1007/BF00390286 http://dx.doi.org/10.1093/jxb/29.3.539 http://dx.doi.org/10.1042/bj0570508 22 M.C. Rodríguez-Hernández, I. Garmendia zoBaYed, s.M.a., aFreen, F., kozai, t., 2007: Phytochemical and phy- siological changes in the leaves of St. John’s wort plants under a water stress condition. Environ. Exp. Bot. 59, 109-116. DOI: 10.1016/j.envexpbot.2005.10.002 ORCID M.C. Rodríguez https://orcid.org/0000-0001-6896-8067 Idoia Garmendia https://orcid.org/0000-0002-8673-6515 Address of the corresponding author: M.C. Rodríguez-Hernández, Department of Earth and Environmental Sciences, University of Alicante, Alicante, PO Box 99, 03080 Spain. E-mail: maricarmen.rodriguez@ua.es © The Author(s) 2022. This is an Open Access article distributed under the terms of the Creative Commons Attribution 4.0 International License (https://creative- commons.org/licenses/by/4.0/deed.en). http://dx.doi.org/10.1016/j.envexpbot.2005.10.002 https://orcid.org/0000-0001-6896-8067 https://orcid.org/0000-0002-8673-6515