施氮和短时光辐射变化条件下毛竹幼苗光合限速因子分析

Limiting factors of photosynthesis of Phyllostachys edulis seedlings treated with nitrogen fertilized and change of short-term light irradiance

关键词:  毛竹, 氮处理, 光辐射变化, 光合限速因子, FvCB模型

Key words:  Phyllostachys edulis, nitrogen treatment, light irradiance change, limiting factors of photosynthesis, FvCB model

摘要:

为了解析施氮和短时光辐射变化下毛竹幼苗的光合限速因子,该文对毛竹幼苗进行施氮处理,并在不同光照辐射条件下(高光:1 200 μmol·m^-2·s^-1, 低光:200 μmol·m^-2·s^-1)测定其光响应曲线和CO₂响应曲线,并利用改进的FvCB模型研究了毛竹幼苗的光合特性。结果表明:(1)经过施氮处理的毛竹幼苗生物量显著高于对照,且光饱和最大净光合速率(P_Lmax)、表观羧化速率(CE)、最大羧化速率(V_cmax)和最大电子传递速率(J_max)均显著高于对照。(2)短时的高光照条件下,毛竹幼苗的CO₂饱和最大净光合速率(P_Cmax)、CE、叶肉细胞导度(g_m)、磷酸丙糖利用率(T_p)、CO₂饱和点(CSP)均显著大于低光照水平的植株。(3)施氮处理并未改变毛竹幼苗的g_m大小,而短时光辐射的降低则使得植株的g_m减少了60.31%。因此,氮素处理可以通过较高的V_cmax和J_max使得毛竹幼苗在光合作用过程中催化1,5-二磷酸核酮糖羧化酶/氧化酶(Rubisco)蛋白酶的数量和活性较高,促进了光合磷酸化和NADPH的合成,提高了1,5-二磷酸核酮糖(RuBP)的再生速率,促使毛竹幼苗能够充分进行光合碳同化,促进毛竹的高生长以及生物量积累。可以推断对未添加氮素的植株来说,Rubisco的含量、活性和RuBP的再生能力是其光合限速因子。综上所述,光照异质性影响了毛竹叶片内部的光合生理生化变化,光照强度的降低能够有效地调控g_m和T_p的变化,毛竹幼苗的光合作用主要受到g_m和T_p的限制。该研究表明,施氮和短时光辐射的改变影响了毛竹幼苗的光合作用和碳获取,同时对毛竹幼苗的生长和更新造成了影响。

Abstract:

In order to understand the limiting factors of photosynthesis of Phyllostachys edulis seedlings under nitrogen addition and change of short-term light irradiance. The light response curve and CO₂ response curve were measured under different short-term light irradiance conditions(high light:1 200 μmol·m^-2·s^-1, low light:200 μmol·m^-2·s^-1), and an improved FvCB model was used to study the photosynthetic characteristics of P. edulis seedlings with nitrogen fertilized. The results were as follows:(1)Biomass of P. edulis seedlings treated with nitrogen fertilized was significantly higher than that of control, and light saturated maximum net photosynthetic rate(P_Lmax), carboxylation efficiency(CE), maximum carboxylation rate(V_cmax)and maximum electron transport rate(J_max)were significantly higher than those of control.(2)CO₂ saturated maximum net photosynthetic rate(P_Cmax), CE, mesophyll conductance(g_m), triose phosphate utilization rate(T_p)and carbon dioxide saturation point(CSP)of P. edulis seedlings under high light level were significantly higher than those of low light level.(3)g_m has no differences after nitrogen fertilized, but it reduced 60.31% while the decrease of short-term light irradiance. In conclusion, P. edulis seedlings with nitrogen treatment increased the quantity and activity of ribulose-1, 5-bisphosphate carboxylase/oxygenase(Rubisco)protease in photosynthesis process, promoted photosynthetic phosphorylation and NADPH synthesis, and improved the reqeneration rate of ribulose-1, 5-bisphosphate(RuBP)through higher V_cmax and J_max, in order to fully assimilate photosynthetic carbon, promote the high growth and biomass accumulation. Therefore, it could be inferred that the content and activity of Rubisco and regeneration capacity of RuBP were the limiting factors of the photosynthesis rate, for the control P. edulis seedlings with no nitrogen. To sum up, light heterogeneity affect the photosynthetic physiological and biochemical changes inside the leaves of P. edulis, the decreasing of light intensity effectively regulate the changes of g_m and T_p, indicating that the photosynthesis of P. edulis seedlings are mainly limited by g_m and T_p. The research shows that nitrogen fertilized and the change of short-term light irradiance affect the photosynthesis and carbon acquisition of P. edulis seedlings, and also affect its growth and regeneration.