山东小麦品种更替过程中光合特性的演变

Evolution in Photosynthetic Characteristics of Wheat Cultivars Widely Planted in Shandong Province Since 1950s

【目的】探讨山东小麦品种更替过程中光合性能的演变规律,为今后小麦育种提供指导。【方法】选用山东省建国以来8次品种更替过程中的8个主要推广品种,在大田试验条件下测定了生育后期旗叶的叶绿素含量、光合参数和叶绿素荧光参数,成熟时生物学产量、籽粒产量和收获指数(Harvest index,HI)。【结果】山东小麦品种更替过程中,籽粒产量和HI呈正相关性,但生物学产量并没有显著增加。旗叶叶绿素含量、净光合速率(net photosynthetic rate,Pn)、气孔导度(stomatal conductance,Gs)、羧化效率(carboxylation efficiency,CE)、光系统Ⅱ(photosystemⅡ,PSⅡ)实际光化学效率(photochemical efficiency,ΦPSⅡ)和呼吸速率(respiratory rate,R)在开花期到花后10 d达到最大值,然后开始下降,1980年以后选育的品种下降的速率低于1980年以前的品种;生育后期小麦旗叶Pn的下降是由非气孔因素引起的,Pn的初期下降并不是由叶绿素含量的变化直接引起,在此过程中,光合暗反应的羧化酶起了重要作用;灌浆中后期Pn的进一步降低与叶绿素含量、ΦPSⅡ、非光化学淬灭(non-photochemical quenching,NPQ)等密切相关。品种更替过程中,叶绿素含量、Pn、Gs、CE、ΦPSⅡ等指标呈升高的趋势,叶片功能期延长,光合性能得到明显改善,这可能是籽粒产量提高的重要生理基础。但品种更替中呼吸速率呈升高的趋势,影响了同化产物的积累,不利于籽粒产量的提高。【结论】山东小麦品种更替过程中,叶片的光合能力提高,高光合持续期延长,HI和光能利用效率增加,综合性能的改善是品种更替过程中产量不断提高的生理基础。山东小麦品种HI仍有进一步改良的空间,但不能完全依赖株高的降低,必须综合考虑光能利用的各个环节,小麦高光效育种才有可能取得较大的突破。

[Objective] The evolution in photosynthetic characteristics of historical wheat cultivars was investigated in order to understand the main yield-limiting factors and guide future breeding strategies for improving light use efficiency. [ Method ] Changes in grain yield, harvest index （HI） and photosynthetic parameters of eight landmark wheat cultivars widely planted in Shandong province in different years since 1950s were investigated in the fields. [Result] The grain yield and HI showed a significant linear improvement in Shandong province with the cultivars changed, however, the biomass did not increase obviously. The chlorophyll content （Chl a and Chl b）, net photosynthetic rate （Pn）, stomatal conductance （Gs）, carboxylation efficiency （CE）, photochemical efficiency （ФPSII） of photosystem II （PS II）, and respiratory rate （R） of flag leaves from all historical cultivars reached their maximal values between flowering date and 10 days after anthesis （DAA）, then declined gradually, and the reduced rate of varieties after 1980 was less than the varieties before 1980. The intercellular CO2 concentration （Ci） and the non-photochemical quenching （NPQ） increased persistently after the flag leaves were full expanded. The decrease of Pn was not caused by stomatal factors. The carboxylase activity of ribulose bisphosphate carboxylase oxygenase （Rubisco） was crucial for the earlier reduction of Pn after flowering rather than chlorophyll content, while the chlorophyll degradation, ФPSII and NPQ played important roles in further reduction at the late duration of grain filling. The photosynthetic characteristics improved with the cultivar evolution derived from both the increase in chlorophyll content, Pn, Gs, CE and ФPSII and their longer duration, and which may be the physiological basis of the grain yield improvement. However, the respiratory rate also enhanced with the cultivar change and which was disadvantage to yield increase. [ Conclusion ] Improved photosynthetic characteristics and lengthened duration played important roles in genetic gain in grain yield of Shandong wheat. The HI of Shandong wheat can be improved further, while it should be independent of plant height reduction. The future breeding for yield increase through improving light use efficiency should take all steps involved in photosynthesis as a whole.