Diurnal Variations of Photosynthesis and Transpiration of Pennisetum centrasiaticum Tzvel and Their Relationships with Meteorological Factors

[Objective] The aim was to study the effects of meteorological factors on photosynthetic physiological characteristics of Pennisetum centrasiaticum Tzvel.[Method] With healthy leaves from good p.centrasiaticum plants as the materials,their vivo detection was conducted with Li-6400 portable photosynthesis system to study the diurnal variations of their photosynthetic rate and transpiration rate and their relationships with meteorological factors.[Result] P.centrasiaticum were C4 plants and they had no midday depression of photosynthesis.The diurnal variations of photosynthetic rate and transpiration rate of P.centrasiaticum were all single peak curve,and the highest value of photosynthetic rate appeared at 12:00 am and that of transpiration rate appeared at 14:00 pm.The net photosynthetic rate of P.centrasiaticum had very significant positive correlation with light intensity,but it had no obvious correlation with relative humidity,temperature and leaf temperature.The transpiration rate of P.centrasiaticum had significant positive correlation with temperature and leaf temperature,and it had very significant positive correlation with intensity,but it had significant negative correlation with relative humidity.[Conclusion] The optimum irrigation time for P.centrasiaticum was 10:00 am and 18:00 pm in 1 d.