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

Diurnal changes of photosynthetic characteristics of three species of Qinghai Qilian Hippophae in hybrid zone

关键词:  杂交带, 沙棘属, 光合日变化, 水分利用效率

Key words:  hybrid zone, Hippophae, diurnal change of photosynthesis, water use efficiency(WUE)

摘要:

杂交带是研究物种形成及进化的天然实验室。为探究棱果沙棘自然杂交带三种沙棘的生理生态适应性,该研究在光照充足的7月中旬分别测定了该区域三种沙棘雌、雄株的光合特性及相关环境因子的日变化。结果表明:(1)同种沙棘雌、雄株间光合日变化规律基本一致,不同沙棘光合特性的日变化规律存在较大差异。中国沙棘(Hippophae rhamnoides ssp. sinensis)净光合速率(P_n)日变化呈明显的双峰曲线,峰值出现在光合有效辐射(PAR)和空气温度(T_a)相对较高的10:00和14:00,最高达到(19.53±5.35)μmol·m^-2·s^-1; 棱果沙棘(Hippophae goniocarpa)和肋果沙棘(H. neurocarpa ssp. neurocarpa)P_n日变化均呈近双峰曲线,在PAR和T_a相对较低的8:00和16:00有较高的值,最高值分别为(13.43±3.43)和(15.27±2.43)μmol·m^-2·s^-1。(2)三种沙棘水分利用效率(WUE)与P_n的日变化规律一致,但中国沙棘具有最高的WUE,达到(6.72±0.95)μmol·mmol^-1,棱果沙棘和肋果沙棘的WUE日变化最高分别为(4.03±1.08)和(4.93±0.86)μmol·mmol^-1。(3)三种沙棘蒸腾速率(T_r)、气孔导度(G_s)、胞间二氧化碳浓度(C_i)和气孔限制值(L_s)的日变化规律相似,其中G_s均在10:00后一致下降,在12:00左右均出现不同程度的气孔关闭现象,这是其发生光合午休的主要原因之一。杂交带三种沙棘光合特性日变化差异主要表现在中国沙棘和其他两种沙棘之间,而杂交种棱果沙棘与亲本种肋果沙棘的变化规律基本一致,其P_n与WUE可能受到了T_a、PAR和空气相对湿度(RH)等环境因子的影响。

Abstract:

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(P_n)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(T_a). Although the diurnal changes of P_n 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 T_a were lower.(2)Water use efficiency(WUE)of the three species of Hippophae was consistent with the change of P_n, 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(T_r), stomatal conductance(G_s), intercellular CO₂ concentration(C_i)and stomatal limiting value(L_s)of the three species of Hippophae were similar. G_s 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 P_n and WUE may be affected by environmental factors such as T_a, PAR and air relative humidity(RH).