外源SA和NO对NaCl胁迫下番茄幼苗生长、光合及离子分布的影响

以番茄(Lycopersicon esculentum Mill.)品种‘秦丰保冠’为试材,采用营养液培养法,研究单独和复配施用外源水杨酸(SA)、一氧化氮(NO)供体硝普钠(SNP)对100mmol/L NaCl胁迫下番茄幼苗生长、光合及离子分布的影响。结果表明:(1)单独和复配外施SA、SNP均能有效抑制NaCl胁迫下番茄幼苗叶片光合色素(Chla、Chlb、Chla+b和Car)含量、Chla/b值、净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)、瞬时水分利用效率(WUEt)、表观光能利用效率(LUEapp)和表观CO2利用效率(CUEapp)的下降及Car/Chla+b值和胞间CO2浓度(Ci)的升高,并以SA和SNP复配处理效果最明显。(2)NaCl胁迫下,外源SA、SNP单独和复配处理的番茄幼苗各器官(叶、茎和根)中Cl-、Na+含量和Na+/K+、Na+/Ca2+、Na+/Mg2+值显著降低,而K+、Ca2+和Mg2+的含量却不同程度提高,其中以SA和SNP复配处理效果最好。(3)单独和复配外施SA、SNP均能有效减轻NaCl胁迫对番茄幼苗生长的抑制作用,并促进各器官生物量的积累和壮苗的形成,且以SA和SNP复配处理效果更佳。研究表明,复配外施SA和SNP在诱导番茄幼苗提高抗(耐)盐能力方面具有协同增效作用。

Effects of exogenous salicylic acid and nitric oxide on growth, photosynthesis, and ion distribution in tomato seedlings under NaCl stress

Salicylic acid (SA) and nitric oxide (NO) are two biologically active signaling molecules in plants. Both of these molecules play important roles in various aspects of plant growth and development, including seed germination, root growth, leaf elongation, stomatal movement, and respiration. As signaling molecules, SA and NO also participate in signal transduction in the responses to biotic and abiotic stresses. Previous studies have shown that the signaling pathways of SA and NO do not exist in isolation, but "cross-talk" with each other, and they show synergistic interactions in many physiological and resistance reactions. Scientists inspired by the "cross-talk" and synergistic interactions have produced research on the synergistic induction of signaling pathways to improve plant resistance using exogenous SA and sodium nitroprusside (SNP), a NO donor. In the last decade, much research has been conducted on use of exogenous SA or SNP to improve the salt resistance of plants. However, most of these studies have focused on the ability of either SA or NO to induce resistance, and on the physiological and biochemical mechanisms by which these compounds induce resistance. Few studies have focused on synergistic induction of defense pathways using both SA and NO to improve plant resistance to salt stress. In our experiments, we evaluated the synergistic effects of SA and NO on the resistance of tomato (Lycopersicon esculentum Mill. cultivar "Qin Feng Bao Guan") seedlings to salt stress. We applied SA and SNP alone or in combination to tomato seedlings, and measured the growth, photosynthesis, and ion distribution in the tomato seedlings under salt stress (100 mmol/L NaCl) in a nutrient solution culture system. The main findings of our research are as follows: (1) Single or combined applications of SA and SNP reduced the decreases in the levels of photosynthetic pigments (chlorophyll a, chlorophyll b, chlorophyll a+b and Carotenoids), the ratio of chlorophyll a and chlorophyll b, net photosynthetic rate, transpiration rate, stomatal conductance, instantaneous water use efficiency, apparent light energy use efficiency, and apparent CO₂ use efficiency in tomato seedlings under salt stress. These treatments also reduced the increase in the intercellular CO₂ concentration and the value of Carotenoids/chlorophyll a+b in leaves of tomato seedlings under NaCl stress. The strongest effect was observed after applying a combination of SA and SNP. (2) Under NaCl stress, the Cl^- and Na⁺ contents and the Na⁺/K⁺, Na⁺/Ca²⁺, Na⁺/Mg²⁺ ratios in leaf, stem, and root tissues of tomato seedlings were lower in plants treated with SA, SNP, or SA + SNP than in untreated salt-stressed tomato seedlings. The K⁺, Ca²⁺,and Mg²⁺ contents of plant tissues were improved to different extents by SA, SNP, or SA + SNP applications, but the latter treatment had the strongest effect. (3) Single or combined applications of exogenous SA and SNP effectively reduced the negative effects of NaCl stress on tomato seedling growth and development, and promoted the accumulation of leaf, stem, and root biomass. The combined application of SA and SNP had the strongest effect. The results of our research show that a combined application of exogenous SA and SNP has a synergistic effect on improving the salt tolerance of tomato seedlings.