低温胁迫对白及光合作用及叶绿素荧光参数的影响

为了研究白及对低温胁迫的生理响应,以一年生白及为试材,分别进行22、18、14、10℃4个低温处理,之后再置于26℃进行恢复培养,分别于处理0、7、14、21、28 d和恢复培养的3、7 d测定叶片光合速率和叶绿素荧光动力学参数。结果表明,14和10℃处理下,白及叶片净光合速率(Pn)、气孔导度(Gs)和蒸腾速率(Tr)显著下降,胞间二氧化碳浓度(Ci)呈现先下降后上升的趋势,在14 d时Ci最低;叶绿素荧光参数F_o上升,F_v/F_m、Y(Ⅱ)、qP和ETR大幅度下降,植株不能恢复生长。说明10℃和14℃对白及叶片PSⅡ光合系统造成严重损害,导致植株不能正常生长。18和22℃处理下,Pn、Gs、Tr和Ci均缓慢下降,说明气孔因素是导致Pn下降的主要因素,其中18℃处理条件下F_o小幅度上升,而F_v/F_m、Y(Ⅱ)、qP和ETR有小幅度下降,说明PSⅡ光合系统受到轻微损伤,22℃处理7 d时,Y(Ⅱ)、qP和ETR有轻微下降,F_o轻微上升,之后无显著变化,而F_v/F_m一直处于正常范围之内,说明7 d后白及可以适应22℃的温度环境,且Fo、Y(Ⅱ)、qP和ETR的变化均在正常范围之内,未对白及的光合系统造成伤害。研究结果表明,10、14℃严重抑制了白及的生长和光合作用;18℃处理下,白及的生长形态未受到影响,但光合作用受到轻度抑制;22℃对白及的生长和光合作用不造成影响。

Effects of Low Temperature Stress on the Photosynthetic Characteristics and Chlorophyll Fluorescence Parameters of Bletilla striata

In order to study the physiological responses to low temperature stress in Bletilla striata, one-year-old B Striata plants were treated by four different low temperatures of 22, 18, 14 and 10 ℃, respectively. The low temperature treatment was conducted during the subsequent 0, 7, 14 and 28 days, whereas the plant recovery treated for 3 and 7 days. Samples from the all above treatments were used to measure the photosynthetic characteristics and chlorophyll fluorescence parameters. The net photosynthetic rate (Pn), stomatal conductance (Gs) and transpiration rate (Tr) of the leaves decreased significantly under 14 and 10 ℃ treatment while the intercellular carbon dioxide concentration (Ci) decreased at first and then increased with the lowest value at 14 d. The chlorophyll fluorescence parameter F_o increased and the other three indexes including F_v/F_m, Y(II), qP and ETR decreased significantly, respectively. These findings indicted that the PSⅡ photosynthetic system of B. Striata was damaged by 10 and 14 ℃ temperature treatments, and further to affect the plant growth. The Pn, Gs, Tr and Ci values decreased slowly under 18 and 22 ℃ treatments, indicating that the decrease of Pn value was leaded by the stomatal factors. Moreover the index F_o increased slightly but F_v/F_m, Y(II), qP and ETR decreased slightly, suggesting that the PSⅡ photosynthetic system was damaged slightly. Finally, the changes of Y(II), qP, ETR, F_o, F_v/F_m were not obvious under the 22 ℃ treatment, indicating the photosynthetic system was not damaged by the low temperature treatment. These findings suggested that the growth and photosynthesis of B. striata were severely inhibited by 10 ℃ and 14 ℃ low temperature treatments, and the plant morphology was not affected by the 18 ℃ treatment, but the photosynthesis was inhibited.