钙对盐胁迫下西瓜光合特性和果实品质的影响

Effects of Supplemental Calcium on the Photosynthetic Characteristics and Fruit Quality of Watermelon Under Salt Stress

采用营养液水培方式,以小型西瓜(Citrullus lanatus Mansfeld)品种‘秀丽’为试材,研究了营养液增补Ca2+对盐胁迫(100mmol·L-1NaCl)下西瓜幼苗光合特性,叶绿素荧光,花粉萌发,果实品质的影响。结果表明,当营养液中Ca2+浓度由4mmol·L-1升高到6mmol·L-1时:①显著提高盐胁迫植株叶片的气孔导度(Gs)、胞间二氧化碳浓度(Ci)、净光合速率(Pn)、PSⅡ的最大光化学量子产量(Fv/Fm)、PSⅡ的实际光化学效率(ΦPSII)、相对电子传递速率(rETR)、光化学猝灭系数(qP)和非光化学猝灭系数(qN),降低气孔限制值(Ls)和光抑制(1-qP/qN);②显著提高盐胁迫果实质量及果实中抗坏血酸、可溶性固形物、可溶性总糖、可溶性蛋白质和游离氨基酸的含量,降低有机酸的含量;同时降低果实中Na+含量,提高果实中Ca2+、Mg2+、Fe、Cu、Mn含量;③明显促进盐胁迫花粉萌发和花粉管伸长。表明Ca2+可有效降低盐胁迫对光合作用的气孔限制,缓解盐胁迫对光合器官的伤害,使叶片保持较高的光合性能;促进盐胁迫下西瓜的生殖生长,有利于果实的生长发育及矿质营养平衡,进而改善果实品质。因此,Ca2+可通过调节光合代谢和生殖代谢来提高西瓜植株的耐盐性。

The objective of the study was to investigate the effects of calcium concentration on photosynthesis, chlorophyll fluorescence, pollen germination and fruit quality of watermelon under salt stress. Mini-watermelon（ Citrullus lanatus Mansfeld） cultivar ＇ Xiuli＇ was used to carry out the experiment by supplementing exogenous calcium to nutrient solution containing 100 mmol · L^-l NaC1. The results showed that the stomatal conductance （Gs）, intercellular carbon dioxide concentration （Ci）, net photosynthesis rate（Pn ）, P S II photochemical quantum yield（Fv/Fm）, P S II actual photochemical efficiency （ qh, sa）, relative electron transport rate （rETR）, photochemical quenching （qe）, non-photochemical quenching（qN）were significantly increased when calcium concentration in salty nutrient solution increased from 4 to 6 mmol. L-1 and stomatal limitation （Ls）, photoinhibition （ 1 - qP/qN） were decreased in salt-stressed seedlings. Fruit weight and the contents of ascorbic acid, soluble solids, soluble sugar, soluble protein and free amino acid in salt-stressed fruit flesh were remarkably increased by supplemental calcium from 4 to 6 mmol ~ L-1. However, organic acid content was decreased. The contents of Ca2＋, Mg2＋, Fe, Cu, and Mn were increased but Na＋ was reduced in salt-stressed fruit flesh. Besides, supplemental calcium obviously promoted pollen germination and pollen tube elongation. These results indicated that supplemental calcium could effectively reduce the salt-induced stomatal limitation of photosynthesis and alleviate salt stress damage on photosynthetic apparatus. This was conducive to maintain photosynthetic performance and promote growth of salt-stressed watermelon. Meanwhile, the reproductive growth and mineral nutrition balance in fruit were improved. It could be concluded that supplemental calcium enhanced the tolerance of watermelon plants to salt stress by regulating photosynthetic and reproductive metabolisms of plants under salt stress.