水稻产量形成对盐-旱复合胁迫的响应与生理机制

Response of rice yield formation to combined salinity-drought stress and its physiological mechanism

以江苏沿海地区广泛种植的常规粳稻南粳9108和淮稻5号为试材,设计盆栽试验,在0.3%土壤含盐量下,于拔节期至抽穗期设置干旱胁迫(土壤水势-25 kPa),并以无盐、无干旱胁迫为对照,研究水稻产量形成对盐-旱复合胁迫的响应特征。结果表明:与对照相比,单一盐胁迫、单一干旱胁迫和盐-旱复合胁迫下水稻产量(两品种平均)分别下降114.8%、39.6%和154.2%。盐-旱复合胁迫下水稻产量(两品种平均),较单一盐胁迫和单一干旱胁迫分别显著下降18.6%和82.2%。与单一盐胁迫和单一干旱胁迫相比,盐-旱复合胁迫下水稻产量降低主要为每穗粒数、结实率和千粒重的显著下降。与对照相比,单一盐胁迫、单一干旱胁迫和盐-旱复合胁迫均显著降低植株抽穗期和成熟期干物重、拔节后20 d和抽穗后20 d叶片净光合速率与叶绿素(a+b)含量,收获指数有所增加。盐-旱复合胁迫下植株抽穗期和成熟期干物重、拔节后20 d和抽穗后20 d叶片净光合速率与叶绿素(a+b)含量均显著低于单一盐胁迫和单一干旱胁迫;收获指数则呈相反趋势。单一盐胁迫、单一干旱胁迫和盐-旱复合胁迫下水稻拔节后20 d和抽穗后20 d叶片超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)活性均显著低于对照;叶片丙二醛(MDA)和过氧化氢(H_(2)O_(2))含量则呈相反趋势。与单一盐胁迫和单一干旱胁迫相比,盐-旱复合胁迫下拔节后20 d和抽穗后20 d叶片SOD、CAT和APX活性显著下降,MDA和H_(2)O_(2)含量则显著增加。这说明,与单一盐胁迫和单一干旱胁迫相比,盐-旱复合胁迫显著抑制水稻植株光合性能,从而影响光合同化物的积累与分配,最终导致库容量与充实效率以及水稻产量的显著下降。盐-旱复合胁迫造成水稻产量的降幅显著高于单一盐胁迫和单一干旱胁迫,其对水稻产量的抑制效应具有叠加效应。

This research was designed as a pot experiment with conventional japonica rice Nanjing 9108 and Huaidao 5, which are widely planted in the coastal saline areas of Jiangsu. The experiment was conducted at 0.3% soil salt concentration, and set drought stress(soil water potential-25 kPa) from jointing to heading with salinity-and drought-free as control(CK). This study was conducted to identify response characteristics of rice yield formation to combined salinity and drought stress of the two varieties. Under single salinity stress, single drought stress, and combined salinity-drought stress, rice average yield of the two varieties decreased by 114.8%, 39.6%, and 154.2% compared to the control, respectively. The average yield of the two varieties under combined salinity-drought stress was significantly lower than that under single salinity stress and single drought stress, with a decrease of 18.6% and 82.2% respectively. Compared with single salinity stress and single drought stress, the decrease in rice yield under combined salinity-drought stress was mainly due to a significant decrease in spikelets per panicle, filled-grain percentage, and 1000-grain weight. Compared with the control, single salinity stress, single drought stress, and combined salinity-drought stress significantly reduced the dry matter weight of plants at heading and maturity stages, as well as the net photosynthetic rate and chlorophyll(a+b) content of leaves at 20 days after jointing and 20 days after heading, and increased the rice harvest index. Under combined salinity-drought stress, dry matter weight at heading and maturity, and the net photosynthetic rate and chlorophyll(a+b) content of leaves at 20 days after jointing and 20 days after heading of plants were significantly lower than those under single salinity stress and single drought stress;the harvest index showed the opposite trend. Under single salinity stress, single drought stress, and combined salinity-drought stress, the activities of superoxide dismutase(SOD), catalase(CAT), and ascorbate peroxidase(APX) enzymes in rice leaves at 20 days after jointing and 20 days after heading were significantly lower than those of the control;the content of malondialdehyde(MDA) and hydrogen peroxide(H_(2)O_(2)) in leaves showed an opposite trend. Compared with single salinity stress and single drought stress, the activities of SOD, CAT, and APX enzymes in leaves at 20 days after jointing and 20 days after heading significantly decreased under combined salinity-drought stress, while the content of MDA and H_(2)O_(2) in leaves significantly increased. This study demonstrated that compared to single salinity stress and single drought stress, combined salinity-drought stress significantly inhibited the photosynthetic performance of rice plants, thereby affecting the accumulation and allocation of photosynthetic assimilates, ultimately leading to a significant decrease in sink size and sink-filling efficiency, and rice yield. The decrease in rice yield caused by combined salinity-drought stress was significantly higher than that caused by single salinity stress and single drought stress, and its inhibitory effect on rice yield had a superimposed effect.