科研之友
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摘要
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.
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