不同供水条件下冬小麦叶与非叶绿色 器官光合日变化特征

为揭示小麦叶片与非叶绿色器官的光合活性在一日中的变化特性及其在器官间的差异性,探讨群体及不同器官光合日变化对不同供水条件的响应特征,在田间设置生育期不灌水(I0)、灌2水(I2,拔节水＋开花水)和灌4水(I4,起身水+孕穗水+开花水+灌浆水)3个处理,于灌浆期测定了群体光合与呼吸速率的日变化, 旗叶片、叶鞘、穗、穗下节间各器官光合速率、蒸腾速率、气孔导度及叶绿素荧光参数的日变化。结果表明,灌浆期小麦穗和穗下节间光合速率日变化呈单峰曲线,而旗叶叶片与旗叶鞘光合速率均呈双峰型,表现出不同程度的午休。随着灌水次数减少,各器官光合速率降低,叶片对严重水分亏缺的反应大于各非叶器官。器官光合速率的日变化与F_v/F_m变化相一致,而与气孔导度日变化有较大差异。各器官上午的累积光合量均高于下午,上午光合量占日总光合量的比例为51％-62％,随着灌水次数减少而增大。不同灌水处理群体光合速率、呼吸速率日变化均未出现午休现象。春季浇2水处理与春浇4水处理相比,灌浆期群体光合速率及日光合积累量没有显著差异。综合研究认为,小麦叶与非叶器官光合性能及其日变化特征有较大不同,非叶光合对水分亏缺的敏感性低于叶片,生育期浇2水可以获得与浇4水相似的群体日光合积累量。

Photosynthetic diurnal variation characteristics of leaf and non-leaf organs in winter wheat under different irrigation regimes

The wheat in northern China is subject to drought stress, which leads to decreases in both the leaf photosynthetic capability and grain yield, at the grain filling stage. The green leaves and non-leaf organs, such as spike, stem and sheath, play very important roles in wheat photosynthesis. The diurnal photosynthetic variation (DPV) can determine the response of wheat to the environment. However, most of the research on DPV is focused on the leaf blade. Very little research have concerned DPV and midday depression of green non-leaf organs in wheat. The purpose of this study was to determine the DPV characteristics of green leaf blade and non-leaf organs in wheat, so as to investigate the response characteristics and responses of DPV of wheat canopy and green non-leaf organs to different irrigation regimes, and detect differences in diurnal photosynthesis accumulation among the green organs. A field experiment was conducted with three irrigation treatments in the growth period of wheat. The diurnal variations of the canopy photosynthetic and respiration rates and the net photosynthetic rate, respiration rate, stomatal conductance and chlorophyll fluorescence parameters in flag leaf blade, leaf sheath, ear and peduncle were measured at the grain filling stage. The diurnal variations of the net photosynthetic rate in the ear and the peduncle showed a single-peak curve, while those in the flag leaf blade and the leaf sheath were a double-peak curve, i.e., a midday depression occurred at around 12 pm, at the grain filling stage. The net photosynthetic rate decreased in all the investigated organs with decrease of the irrigation time. Under serious drought conditions, the leaf photosynthetic rate and diurnal photosynthetic accumulation decreased significantly, but those of the non-leaf organs were not affected so much as those of the leaf blade. The diurnal variation of net photosynthetic rate in all the investigated organs was coincident with that of the F_v/F_m and differed slightly from that of stomatal conductance. The photosynthetic accumulation of all the investigated organs was higher in the morning than in the afternoon with the morning photosynthetic accumulation occupying 51% to 62% of the diurnal photosynthetic accumulation. The photosynthetic accumulation in the morning was increased with the reduction in irrigation times. No midday depression was found in the canopy photosynthetic rate and canopy respiration rate under different irrigation treatments. In addition, no significant difference was observed in canopy photosynthetic rate and diurnal photosynthetic accumulation amount between the two times and the four times irrigation. There were significant differences in photosynthetic performance and the diurnal variation characteristics between wheat leaf blade and non-leaf organs. The net photosynthetic rate in leaf blade was more sensitive to water deficit than that in the non-leaf organs. Light water deficit did not affect canopy photosynthetic rate significantly. The canopy photosynthetic rate was less affected than the net photosynthetic rate of the leaf blade by serious water deficit. Two times irrigation in the growth period of wheat achieved a similar canopy diurnal photosynthetic accumulation amount to that of the four times irrigation. The combination of cultivars with higher water usage efficiency, limited rates of irrigation and nitrogen fertilizer, and higher planting density with more non-leaf organs were the best choice to achieve high grain yield for wheat in northern China.