SPH -JHS Coverpage December 2019 Number 2 149 J. Hortl. Sci. Vol. 14(2) : 149-154, 2019 Original Research Paper Effect of Calcium Nitrate and Potassium Nitrate Priming on Seed Germination and Seedling Vigour of Papaya (Carica papaya L.) Maneesha S.R. and Priya Devi S. ICAR-Central Coastal Agricultural Research Institute, Ela, Goa - 403 402 Email: Maneesha.sr@icar.gov.in ABSTRACT The effect of seed priming with calcium nitrate Ca(NO3)2 and potassium nitrate (KNO3) on germination and seedling vigour were studied in papaya varieties. Open pollinated local (gauty) papaya seeds were soaked in Ca(NO3)2and KNO3 solutions (10000 ppm, 15000 ppm and 20000 ppm) up to 24 hours and germination percentage and seedling characteristics were recorded. The least number of days taken for seed germination (4.33 days), the highest germination percentage (82.56 % ), the highest shoot length (14.31 cm) the highest fresh biomass (1.36 g) and dry biomass (0.174 g) were recorded in 10000 ppm Ca(NO3)2treatment. Further, seeds of papaya varieties viz., Arka Surya, Arka Prabhat and Madhu bindhu were treated with 5000 ppm, 10000 ppm and 15000 ppm Ca(NO3)2 and observed that Arka Prabhat seeds treated with 10000 ppm Ca(NO3)2had taken the least number of days for germination (4.75 days) and also the highest shoot length (25.2 cm). The results of the experiment proved the significant effect of calcium ions over potassium ions on papaya seed germination and seedling vigour. Keywords: Calcium nitrate, Papaya, Potassium nitrate, Seed germination and Seedling vigour. INTRODUCTION Papaya is one of the important tropical fruit crops cultivated in India. It is a highly nutritious with high amount of vitamin A (258 µg), vitamin C (60.90 mg) and folic acid (37 µg). It also contain dietary fibers (1.7 g), calcium (20 mg), iron (0.25 mg), magnesium (21 mg), phosphorus (10 mg), potassium (182 mg), protein (0.47g) and fat (0.26 g) (USDA, 2019). Papaya is mostly consumed as a fresh fruit and raw fruits are used as vegetable. Processed products like tutty fruity, jam and squash are prepared from papaya. Papain (vegetable pepsin) is a digestive enzyme extracted from mature unripe papaya, which is widely used in meat and leather industry as a tenderizing agent. The medicinal properties of papaya plant are also well exploited by pharmaceutical and cosmetic industries. Total area under papaya cultivation in India is 0.146 million hectare with a production of 6.096 million tonnes and productivity of 41.8 tonnes per hectare (Indiastat, 2019). Commercially, papaya plant is propagated by seeds sown in protrays, poly bags or raised beds in nursery. The seedlings are transplanted to the main field after 45 days maturity in the nursery. Earliness in seed germination and seedling growth at the nursery stage are the indicators of the vigour of the plant. Poor germination percentage, low seedling vigour and diseases like damping off and viral diseases are major problems faced by papaya growers in nursery stage. Stored papaya seeds germinate faster than the fresh seeds, but long storage period causes asynchronous and slow germination with low germination percentage (Andred et al., 2008). Seed germination is affected by internal factors like seed maturity, age of seeds, moisture condition of the seeds (Ellis et al., 1991), nutritional and health status of the mother plant and inhibitors present in the sarcotesta and seed coat (Reyes et al., 1980 and Chow and Lin, 1991). The external factors like storage conditions and duration of storage, pH and nutritional conditions of the growing media and biotic and abiotic stress factors also influence papaya seed germination. Heat shock induced stimulation of germination in pre-dried and re- imbibed papaya seed were reported by Webster et al. , (2016) T hey a lso r epor ted the effect of 150 J. Hortl. Sci. Vol. 14(2) : 149-154, 2019 Maneesha and Priya Devi exogenous a pplica tion of gibber ellic a cid to r epla ce the hea t shock stimulation. Seed treatments with chemicals or growth hormones are usually practiced in papaya for early and uniform seed germination and better seedling growth. Pre-sowing treatment of papaya seeds in 2.0- 3.0 mM GA3 solution improves germination in papaya (Pandit et al., 2001). According to Marcos Filho (2015) osmopriming with chemical agents such as polyethylene glycol (PEG), calcium nitrate, and potassium nitrate activate germination of seeds by forming a water potential equilibrium between seeds and the solution by osmosis. External nitrogenous compounds ca n substitute costly pla nt growth substances, which are difficult to dissolve. Calcium nitrate and potassium nitrate are cheap and familiar chemicals with strong dissolving capacity. These cations can imbibe water fast and change the water potential of the seeds. Calcium nitrate pretreatment removed dormancy and enhanced germination in Brachiaria seeds (Silva et al., 2017). The priming of tomato seeds with CaCl2 and KNO3 solution was efficient to improve the seedling growth under salinity conditions (Ebrahimi et al., 2014). Batista et al. (2015) reported that the priming with KNO3 and Ca (NO3)2 resulted in greater growth of pepper (C. frutescens) seedlings.T he effectiveness of seed treatments varies with varieties in papaya (Rodriguez et al., 2019). T her efore, this exper iment wa s constituted to study the effects of calcium and potassium ions on seed germination and seedling vigour of different papaya varieties. MATERIALS AND METHODS Effect of Ca(NO 3)2 and KNO 3 on s eed germination and plant biomass of local papaya var. Gauty In Goa and adjoining areas, an open pollinated tall papaya variety (Gauty) is commonly grown in the back yards. The tree will bear profusely with small round fruits with sweet yellow flesh. This local variety shows comparatively good field tolerance to Papaya Ring Spot Virus (PRSV) and other viral diseases. For this experiment, seeds were collected from the well- ripened fruits and washed thoroughly in tap water to remove the sarcotesta (mucilaginous coat surrounding the seed). The seeds were shade dried and stored in butter paper covers under room temperature. The seeds were treated with three different concentrations (10000 ppm, 15000 ppm and 20000 ppm) of Calcium Nitrate (Ca(NO3)2) and Potassium Nitrate (KNO3 ). The treatment solutions were prepared on the same day of treatment application using distilled water. Fifty seeds were counted and soaked in the treatment solution for 24 hours. The next day the solutions were dra ined a nd the seeds wer e sown in the black polythene nursery bags (20 cm x 10 cm) with drainage holes. The experimental design was completely randomized design with three replications. Obser va tions on da ys ta ken for ger mina tion, germination percentage, shoot length, root length, fresh weight of leaves, dry weight of leaves; leaf area, fresh biomass and dry biomass were recorded on 15 days after germination. Chlorophyll was extracted using 80 % acetone and chlorophyll a, chlorophyll b, total chlorophyll and chlorophyll a/b ratio were estimated using spectrophotometer as per the method suggested by Arnon (1949). Specific leaf weight and specific leaf area were calculated by the standard formula given below. Specific leaf Area (SLA) = Leaf area/ Leaf dry weight Specific Leaf Weight (SLW) = Leaf dry weight/ Leaf area Effect of Ca(NO3)2 on seed germination and seedling characteristics of important commercial varieties In this experiment, three varieties of papaya viz., Arka Surya, Arka Prabhat and Madhu bindu seeds were treated with three different concentrations of calcium nitrate (5000 ppm, 10000 ppm and 15000 ppm). Exper imenta l design wa s fa ctoria l completely randomized design (FCRD) with three replications. All other experimental procedures and observations were same as that of previous experiment. The data of both the experiments were analyzed in ANOVA at 0.05 probabilities using the statistical software WASP 2.0 of ICAR-CCARI, Goa. RESULTS AND DISCUSSION Effect of Ca(NO3)2and KNO3 on seed germination and plant biomass of local papaya var. Gauty The effect of Ca(NO3)2and KNO3 at different levels (10000 ppm, 15000 ppm and 20000 ppm) to the seeds 151 Effect of Calcium Nitrate and Potassium Nitrate Priming of Papaya (Carica papaya L.) of local (Gauty) papaya showed that, there is a significant influence of seed treatment on papaya seed germination. The least number of days taken for germination (4.33 days)) and the highest germination percentage (82.56 %), shoot length (14.31 cm), fresh biomass (1.36 g) and dry biomass (0.174 g) were recorded in 10000 ppm Ca(NO3)2treatment. Number of leaves, fresh weight and dry weight of the leaves and leaf area showed non- significant difference between the treatments (Table 1). Effect of calcium ions on papaya seed germination was studied earlier by Bautista-Calles et al. (2008) and reported that, seeds treated for 4 days in 10"5 M calcium chloride solution increased seed germination up to 262 % and seedlings generated from treated seeds accumulated more biomass than the control seedlings. According to Salles et al. (2019), calcium nitrate enhanced the germination of eggplants in adverse environmental conditions. Chlorophyll is the pigment molecule responsible for the light absorption and photosynthesis. The concentration of chlorophyll content in the leaves is an indication of the photosynthetic capacity and the productivity of the plant. Total chlor ophyll content of the leaves, chlorophyll a, chlorophyll b and the chlorophyll a/ b r a tio ha d no significant differ ence a mong the treatments (Fig. 1). Specific leaf area and specific leaf weight are parameters, which indirectly show the efficiency of photosynthesis. The partitioning of dry matter to leaf area is an important determinant of plant growth rate during early phases of development J. Hortl. Sci. Vol. 14(2) : 149-154, 2019 Table 1: Effect of calcium and potassium nitrate on germination and seedling vigour of local (gauty) papaya variety D ays Ge r m i - N u mb e r S h o o t Fresh leaf Dry leaf L eaf Fr es h Dry Treat men ts taken for n a t i o n o f l e n g t h we i g h t we i g h t ar e a b i o m as s b i o m as s g e rmin a t i o n % l e av e s ( cm ) ( m g ) ( m g ) (cm2 ) (g ) (g) 10000 ppm 4.33a 87.80a 4.93 14.31a 109.41 14.00 14.00 1.36a 0.17a Ca(NO3)2 15000 pm 6.00ab 57.27ab 4.92 11.67b 136.31 16.33 12.93 0.88b 0.12b Ca(NO3)2 20000 ppm 7.00abc 66.03b 3.87 12.11abc 89.10 14.66 10.31 0.77bc 0.09c Ca(NO3)2 10000 ppm KNO3 8.00 bc 43.59b 4.33 10.92abc 98.33 14.67 11.25 0.67c 0.05c 15000 ppm KNO3 7.67 c 48.72b 4.23 9.31bc 90.00 19.67 10.54 0.53b 0.09c 20000 ppm KNO3 7.33 d 48.72b 4.22 13.26ab 101.83 17.00 12.27 1.01c 0.12b Control 8.33e 43.59b 4.13 10.42bc 90.46 13.33 10.42 0.42c 0.04c CD (0.05) 0.76 27.42 NS 3.08 NS NS NS 0.41 0.05 Fig. 1: Effect of calcium nitrate and potassium nitrate on physiological parameters of local (gauty) papaya variety 152 (Potter and Jones, 1977; Nelson, 1988).Specific leaf weight (leaf weight/leaf area) has been positively correlated with photosynthesis per unit of leaf area for genotypes of many species (Nelson, 1988). However, in this experiment, the results showed that, the seed treatments have no significant role in the photosynthetic efficiency of the plants. Effect of Ca(NO 3)2 on seed germination and seedling characteristics of important commercial varieties Three varieties of papaya (Arka Surya, Arka Prabhat and Madhu bindhu) were treated with CaNO3 at different levels (5000 ppm, 10000 ppm and 15000 ppm) along with control. Among the three varieties, Arka Prabhat treated with 10000 ppm Ca(NO3)2 r ecor ded the lowest number of da ys ta ken for germination (4.75 days) and the highest shoot length (25.2 cm). Fresh weight of the leaves, dry weight of the leaves, leaf area and specific leaf weight were also estimated (Table 2). The experiment proved the significant effect of calcium ions in the papaya seed germination at low concentration. The interaction effect of the three varieties with the three different concentration of calcium nitrate treatment showed that, Arka Prabhat treated with 5000 ppm and 10000 ppm calcium Nitrate had taken the least number of days for germination. The highest germination percentage was recorded in Arka Prabhat treated with 5000 ppm calcium nitrate (87.85%). Shoot length, fresh weight of the leaves, dry weight of the leaves, leaf area and specific leaf weight was J. Hortl. Sci. Vol. 14(2) : 149-154, 2019 Maneesha and Priya Devi Table 2: Effect of Ca(NO3)2 on seed germination and seedling vigour of papaya varieties Days taken Ge r m i - N u mb e r S h o o t Fr es h Dry L eaf S pe ci fi c Treat men ts for n a t i o n o f l e n g t h b i o m as s b i o m as s ar e a leaf area g e r m i n at i o n % l e av e s (cm) (g ) (g ) (mm2 ) (mm2 /g ) V1 (Arka Surya) 5.50 70.40 6.50 20.49 0.37 0.18 3388.13 1949.16 V2 (Arka Prabhat) 4.75 70.40 5.90 20.95 0.51 0.30 4682.75 1668.22 V3(Madhu bindhu) 6.50 78.99 6.25 18.63 0.47 0.26 3936.00 1504.51 CD (0.05) 0.62 12.40 0.82 2.77 0.10 0.04 902.20 421.61 C1 (5000 ppm Ca(NO3)2) 5.33 85.77 6.67 21.75 0.44 0.24 4188.50 1933.09 C2 (10000 ppm Ca(NO3)2) 5.50 72.92 6.33 22.37 0.42 0.22 3871.33 1783.47 C3 (20000 ppm Ca(NO3)2) 5.50 71.88 6.33 21.12 0.53 0.26 4415.50 1718.51 C4(Control) 6.00 62.50 5.50 14.85 0.42 0.27 3533.83 1394.12 CD (0.05) 0.72 14.31 0.95 3.20 0.12 0.05 1041.77 486.84 V1 C1 4.50 84.73 7.00 20.90 0.30 0.12 3110.00 2574.64 V1C2 5.50 68.75 6.00 20.95 0.43 0.21 4159.00 2031.32 V1C3 6.00 65.63 6.50 24.20 0.48 0.23 4042.00 1756.80 V1C4 6 .00 62.50 6.50 15.90 0.27 0.15 2241.50 1433.90 V2C1 5.00 87.85 6.50 24.95 0.50 0.29 5760.50 1981.77 V2C2 4.50 65.63 6.00 25.20 0.43 0.21 4140.00 1960.28 V2C3 4.50 65.63 6.00 20.45 0.63 0.30 4892.00 1738.45 V2C4 5.00 62.50 5.00 13.20 0.48 0.40 3938.50 992.36 V3C1 6.50 84.73 6.50 19.40 0.51 0.30 3695.00 1242.87 V3C2 6.50 84.38 7.00 20.95 0.40 0.25 3315.00 1358.81 V3C3 6.00 84.38 6.50 18.70 0.49 0.25 4312.50 1660.28 V3C4 7.00 62.50 5.00 15.45 0.49 0.25 4421.50 1756.09 CD (0.05) 1.24 24.79 1.64 5.539 0.21 0.09 1804.39 843.22 153 J. 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