荒漠河岸林胡杨光合参数变化特征及影响因子研究

Study on the Variation Characteristics of Photosynthetic Parameters and Environmental Influencing Factors of Populus Euphratica in Desert Riparian Forest

光合作用是绿色植物形成初级生产力的基础,在植物生长过程中起着非常重要的作用。光合作用能力的大小不仅与植物自身种类的差异有关,而且外界环境对植物光合作用的影响也十分重要。本研究通过测量额济纳旗荒漠河岸林胡杨在自然条件下生长的光合生理参数、气象环境因子,并分析其变化特征及影响因素,以期揭示胡杨光合作用的限制因素以及弄清干旱荒漠地区的抗旱机理。研究结果表明:(1)胡杨的净光合速率日变化呈先增加后降低趋势,造成这种变化的主要原因是从早上开始净光合辐射逐渐增强,光合速率也随之增加,而到14:00(北京时,下同)之后光合有效辐射和大气温度逐渐降低导致胡杨同化能力逐渐减弱;(2)6月、7月和8月的11:00-13:00均出现了明显的光合午休现象,且同时气孔限制值在6月、7月和8月都为先增加后降低的变化趋势,导致胡杨光合午休的原因是气孔导度下降,胞间CO2浓度降低,属于光合作用的气孔限制;(3)胡杨的气孔导度呈周期性波动的变化规律,其中6月和7月的波动周期大致为1 h,8月的波动周期为2 h,9月的波动周期为4 h;(4)胡杨的蒸腾速率与气孔导度相对应而呈同步的周期波动,目的是有助于提高胡杨的水分利用效率,使胡杨能够安全地度过极其炎热干燥的夏季。

Photosynthesis is the basis of primary productivity of green plants and plays an important role in plant growth.The net photosynthetic rate is not only related to the difference of plant species,but also the influence of external environment.In this study,photosynthetic physiological parameters and meteorological environmental factors of Populus euphratica in desert riparian forest of Ejina Banner were measured under the field conditions,and their variation characteristics and influencing factors were analyzed in order to reveal the limiting factors of photosynthesis of Populus euphratica and understand the drought resistance mechanism in arid desert areas.The results showed that:(1)The diurnal variation of net photosynthetic rate of Populus euphratica showed a trend of increasing first and then decreasing.The main reasons for this change was that net photosynthetic radiation increased gradually from the morning and photosynthetic rate increased accordingly.The decrease of photosynthetic rate after 14:00(Beijing time,the same after)is due to the gradual decrease of photosynthetic active radiation and atmospheric temperature.(2)The midday depression of photosynthesis appeared between 11:00 and 13:00 in June,July and August,and the stomatal limitation value increased first and then decreased in June,July and August.The reason for the midday depression of photosynthesis in Populus euphratica is the decrease of stomatal conductance and intercellular CO2 concentration,which belongs to the stomatal limitation of photosynthesis.(3)The variation of stomatal conductance of Populus euphratica showed a periodic fluctuation pattern,in which the fluctuation period in June and July was approximately 1 hour,that in August was 2 hours,and that in September was 4 hours.(4)The transpiration rate of Populus euphratica corresponds to stomatal conductance and fluctuates periodically,its purpose is to help improve water use efficiency of Populus euphratica and to enable Populus euphratica to pass through the extremely hot and dry summer safely.