糖槭光合速率和气孔导度对光合有效辐射的响应

Response of Photosynthetic Rate and Stomatal Conductance to Photosynthetically Active Radiation of Sugar Maple

树木生长主要靠叶片光合作用积累有机物质,光合速率和气孔导度是反映树木光合作用的重要因素,探明三者之间的相关性对掌握树木生理作用具有重要意义。本文报道了加拿大糖槭(Acer saccharum Marsh.)在不同光照时间条件下光合速率和气孔导度的变化规律。在不同的光照时间条件下,将光合有效辐射(PAR)在0~1 200μmol/(m^2·s)范围内进行高—低—高的改变,利用CIRAS-2型便携式光合作用仪测定糖槭叶片光合速率(Pn)和气孔导度(Gs)的变化,建立PAR-Pn和PAR-Gs响应曲线,并对三者的相关性进行了分析。测定结果显示,在其他环境因子不变的情况下,温度为25~27℃时,糖槭叶片光合速率达到最高[4.3μmol/(m^2·s)]。从PAR-Pn响应曲线可以看出,光照时间为5 min以上时,光合速率达到稳定;光合有效辐射为900μmol/(m^2·s)以上时,光合速率达到最大值。从PAR-Gs响应曲线可以看出,光照时间少于2 min时,气孔对外界光照变化尚未做出有效反应,气孔导度呈现不规律的变化;当光照时间为5 min以上时,气孔有足够的时间对光照变化做出响应,气孔导度随着光合有效辐射的变化呈现双峰曲线,在光合有效辐射为600μmol/(m^2·s)时达到最大值[218 mmol/(m^2·s)]。光合速率和气孔导度与光合有效辐射呈正相关。

The growth of trees mainly relies on the photosynthesis of leaves accumulating organic matter. Photosynthetic rate and stomatal conductance are the most important factors reflecting the photosynthesis of trees. It is important to understand the physiological action of trees by making the correlation among them clear. This paper reported the change regulation of photosynthetic rate and stomatal conductance of Acer saccharum under different photoperiod conditions. The changes of photosynthetic rate（Pn） and stomatal conductance（Gs） were measured using CIRAS-2 photosynthesis equipment according to changing the photosynthetically active radiation（PAR） at the range of 0-1 200 μmol/（m^2·s） under different photoperiod conditions. We established the PAR-Pn and PAR-Gs response curves and analyzed the correlation between the three numerical values. The results showed that the photosynthetic rate of sugar maple was 4.3 μmol/（m^2·s） at 25-27 ℃ when other factors remain unchanged. The photosynthetic rate was stable when the light time was above 5 minutes. Furthermore, the photosynthetic rate was a maximum of4.3 μmol/（m^2·s） when the photosynthetically active radiation reached 900 μmol/（m^2·s）. From the changes of photosynthetically active radiation and photosynthetic rate,the stomata had not make an effective response to the external light and showed irregular changes when the light time was less than 2 minutes. The stomata had enough time to respond to the changes of light and showed bi-modal curve with the change of photosynthetically active radiation when the light time was more than 5 minutes.The stomatal conductance reached the maximum value of 218 μmol/（m^2·s）,when the photosynthetically active radiation was 600 μmol/（m^2·s）. The photosynthetic rate and stomatal conductance were positively related to photosynthetically active radiation.