功能叶早衰突变体水稻后期自然衰老的生理特性研究

生育后期功能叶早衰已成为限制杂交水稻产量和品质发挥的重要因素。为探究生育后期功能叶早衰生理特性的变化,以生育后期功能叶早衰的突变体(ospls2)和野生型水稻浙恢7954为材料,对其生育后期上部3片功能叶的叶绿素含量、叶绿素荧光、活性氧(ROS)、抗氧化保护酶系统和可溶性糖进行比较分析。结果表明,突变体ospls2功能叶叶绿素含量、叶绿素a/b值和PSⅡ最大光化学效率(F_v/F_m)均随着生育后期叶片的衰老明显降低,且明显低于相同叶位的野生型,初始荧光(F₀)表现则相反;在水稻生育后期,突变体ospls2功能叶的超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和抗坏血酸过氧化物酶(APX)活性均明显低于野生型,且随着叶片的衰老明显降低。其中,CAT活性的降低时间晚于APX,表明在水稻生育后期叶片自然衰老过程中,突变体ospls2功能叶H₂O₂含量早期上升主要与APX活性降低有关,而后期的升高则与CAT活性的降低有关。POD活性在水稻叶片自然衰老过程中可能与ROS合成有关,而并未起到抗氧化保护酶的功能。本研究为水稻生育后期耐早衰品种的选育提供了理论依据。

Physiological Characteristics of Top Three Functional Leaves for a Senilism Rice Mutant

The premature senescence of functional leaves at the late growth stage has become an important constraint factor for yield and quality improvement of hybrid rice. In order to investigate its physiological characteristics, two rice genotypes, the functional leaves premature senescence mutant (ospls2) and its wild type (Zhehui 7954), were used to compare the differences in the chlorophyll content, chlorophyll fluorescence, reactive oxygen species, antioxidant protective enzyme system, and soluble sugar content in the top three functional leaves during the late growth stage. The results showed that the total chlorophyll content, chlorophyll a/b and PSⅡ maximum photochemical efficiency (F_v/F_m) in ospls2 mutant decreased significantly with the senescence of the functional leaves during late growing stage, and were notably lower than those in the wild type. However, the Fluorescence (F₀) had an opposite trend. Compared with the wild type, ospls2 mutant exhibited dramatically lower activities of SOD, CAT and APX in the functional leaves, and these enzymes were decreased significantly with the process of leaf senescence. Furthermore, the decreasing of CAT activity occurred later than APX, indicating that the early and late increase in the content of H₂O₂was mainly due to the decreased activity of APX and CAT, respectively. In addition, POD may play a role in catalyzing ROS production, and not as antioxidant enzymes. The results will provide an insight into the breeding of the early-senescence-resistant rice at the late growth stage.