青海祁连棱果沙棘自然杂交带三种沙棘光合特性日变化分析.

Hybrid zone is a natural laboratory for studying speciation and evolution. In order to explore the ecophysio-logical adaptability of three species of seabuchthorn(Hippophae), we measured the relevant environmental factors and diurnal changes in photosynthetic characteristics of female and male plants of the three Hippophae species in Qilian County of Qinghai Province in July. The results were as follows:(1)The diurnal variation of photosynthesis between female and male plants of the same species was basically consistent, and there are differences in the diurnal variation of photosynthetic characteristics of the threeHippophae species. Diurnal changes of net photosynthetic rate(Pn)in H. rhamnoides ssp. sinensis showed a significant bimodal curve, with peak values at 10:00 and 14:00, and the highest value was(19.53±5.35)μmol·m-2·s-1 when photosynthetically active radiation(PAR)and air temperature(Ta). Although the diurnal changes of Pn in H. goniocarpa and H. neurocarpa ssp. neurocarpa were all nearly bimodal curve, the higher values at 8:00 and 16:00, and the highest values were(13.43±3.43)and(15.27±2.43)μmol·m-2·s-1, repectively when PAR and Ta were lower.(2)Water use efficiency(WUE)of the three species of Hippophae was consistent with the change of Pn, but H. rhamnoides ssp. sinensis had a higher WUE, which peaked at 10:00 and 14:00, and the highest value was(6.7±0.95)μmol·mmol-1. The peak values of H. goniocarpa and H. neurocarpa ssp. neurocarpa were 8:00 and 16:00, and the highest values were(4.03±1.08)and(4.93±0.86)μmol·mmol-1, respectively.(3)The diurnal changes of transpiration rate(Tr), stomatal conductance(Gs), intercellular CO2 concentration(Ci)and stomatal limiting value(Ls)of the three species of Hippophae were similar. Gs decreased uniformly after 10:00 among them, and there were different degrees of stomatal closure at around 12:00, which was one of the causes of leaf photosynthetic depression in midday. In diurnal changes of photosynthesis, H. rhamnoides ssp. sinensis was significantly different from others, H. goniocarpa showed similar change trend with H. neurocarpa ssp. neurocarpa, and its Pn and WUE may be affected by environmental factors such as Ta, PAR and air relative humidity(RH). [ABSTRACT FROM AUTHOR]