不同生长时期马缨杜鹃光合特性的变化及其主要影响因素

Variations of photosynthetic characteristics of Rhododendron delavayi in different growth phases and influencing factors

关键词:  马缨杜鹃, 光合作用, 温度, 相对湿度,影响因素

Key words:  Rhododendron delavayi, photosynthesis, temperature, relative humidity, influencing factors

摘要:

为了解高山杜鹃的光合能力在不同季节对环境因子适应的动态变化,该文以被广泛引种栽培的马缨杜鹃(Rhododendron delavayi)为材料,露天种植在2加仑塑料盆中,利用气体交换技术和叶绿素荧光技术测定了不同生长时期马缨杜鹃光合特性的动态变化,探讨不同生长阶段影响马缨杜鹃光合作用的主要生理生态因子。结果表明:在云南昆明地区,马缨杜鹃的生长与其光合变化重叠,光合特性的季节变化可准确反映其生长周期的变化。在5—7月的生长初期,马缨杜鹃的净光合速率(P_n)快速增加,气孔导度(G_s)是此阶段影响马缨杜鹃P_n的决定性因素,空气相对湿度(RH)则通过影响G_s和蒸腾速率(T_r)来对P_n产生较大的间接效应,可通过增加RH来激发光合潜能以促进生长; 在7—10月的生长盛期,RH高,G_s大,P_n较高且稳定,但受昆明地区独特气候的影响,该时期内较低的气温(AT)是影响该时期光合生理的重要因子,此阶段可通过增加AT来提高P_n以促进马缨杜鹃的快速生长; 在10月之后的生长后期,AT和RH快速下降,气孔关闭,光合系统Ⅱ的光能转化效率(F_v/F_m)和P_n逐渐降低,G_s和F_v/F_m是该阶段影响光合作用的主要因子。该研究结果可为马缨杜鹃的科学栽培及推广应用提供重要参考。

Abstract:

In order to understand the dynamic variations of photosynthetic capacity of Rhododendron to adapt to environmental factors in different seasons. Rhododendron delavayi, widely introduced and cultivated, was planted in a 2-gallon plastic basin in the open field. The dynamic variations of photosynthetic characteristics and influencing factors in different growth phases were investigated by the technique of gas exchange and chlorophyll fluorescence. The results were as follows: The growth cycle of R. delavayi were almost overlaps with photosynthetic variation at Kunming area. The variations of photosynthetic characteristics reflected the variations of growth cycle. In the net early growth period from May to July, the photosynthetic rate(P_n)increased rapidly, the stomatal conductance(G_s)was the decisive factor affecting P_n. The relative humidity of air(RH)had a significant indirect effect on P_n by affecting G_s and transpiration rate(T_r). The P_n and growth could be stimulated by increasing RH at this phase. In the peak growth period from July to October, the RH, P_n and G_s of R. delavayi were high and stable. However, lower air temperature(AT)in this phase was a unique climate character in Kunming area. Low AT became an important factor affecting photosynthetic capacity at this phase, and increasing AT could improve P_n and promote the growth of R. delavayi. In the late growth phase after October, AT and RH decreased rapidly, stomata closed gradually, the maximum quantum efficiency of photosynthetic system Ⅱ(F_v/F_m)and P_n were declined. G_s and F_v/F_m were the main factors affecting photosynthesis at this stage. Our results can provide important references for the scientific cultivation and popularization of R. delavayi.