亚热带六种常见榕属植物日间呼吸特征

植物呼吸作用是生态系统碳循环的一个关键过程。陆地植被每年通过光合作用固定的碳有一半被呼吸作用释放，而释放的这部分又有大约一半来自叶片呼吸。植物不仅在夜晚进行呼吸作用(R_d, Dark respiration),白天也在呼吸，即日间呼吸(R_L, Light respiration)。有研究表明光照条件下植物叶片呼吸低于黑暗环境下叶片呼吸速率，通常受到的光照抑制程度为30%—40%左右。但在实际研究中，经常忽视植物叶片日间呼吸的光抑制，进而大幅高估生态系统呼吸，从而使得生态系统总初级生产力(Gross primary productivity, GPP)被高估，因此有必要对植物的日间呼吸特性进行研究。以中国南方亚热带六种常见榕属植物(垂叶榕、高山榕、黄金榕、菩提树、细叶榕、小叶榕)为研究对象，测量其叶片的日间呼吸速率(R_L, Kok方法)、暗呼吸速率(R_d)、比叶重(LMA)、叶片氮含量(N)、磷含量(P)、最大光合速率(A)、1800及80μmol m^-2 s^-1

Light respiration characteristics of six Ficus species in subtropics

Plant respiration plays a vital role in the carbon cycle of ecosystems. Approximately, half of the carbon assimilated via photosynthesis in terrestrial vegetation anually is released through respiration,with leaf respiration contributing significantly. Leaf respiration occurs not only at night (Dark respiration, R_d), but also during the day (Light respiration, R_L). Studies reveal that under light condition, leaf respiration is lower compared to dark environments, indicating that light inhibition of approximately 30%-40%. Regrettably, recent research often neglects this light inhibition, leading to an overestimation of ecosystem respiration and gross primary productivity (GPP). Thus, a comprehensive exploration of leaf day respiration becomes imperative. In this study, we conducted a study focusing on six prevalent Ficus species native to southern China''s subtropical region (Ficus benjamina L., Ficus altissima B., Ficus microcarpa cv Golden Leaves, Ficus religiosa L., Ficus microcarpa L., Ficus concinna L.). We measured light respiration rate(R_L,Kok method) and dark respiration rate (R_d), along with leaf traits such as leaf dry mass per unit area (LMA), leaf nitrogen content (N), leaf phosphorus content(P), Rubisco enzyme oxygenation (V_o80) and carboxylation rate (V_c80) at 80 μmol photons m^-2 s^-1 PPFD, and Rubisco enzyme oxygenation (V_o1800) and carboxylation rate (V_c1800) at 1800 μmol photons m^-2 s^-1 PPFD. Employing Pearson correlation analysis,we examined the relationship between R_L and other leaf traits, subsequently utilizing stepwise regression analysis to establish an R_L correlation prediction model. The results indicated that R_L for the six Ficus species was lower than R_d, exhibiting an average inhibition of 38.4% and ranging from 24.1%-61.2%, and there was inter-specific variation in R_L and light inhibition of respiration rate. R_L exhibited significant positive correlations with R_d, A, N, V_o80, V_c80, V_o1800 and V_c1800, and exhibited significant negative correlation with LMA and not statistical correlation with P. The Stepwise regression analysis showed a model incorporating R_d, N and V_c80, which explained 96.5% of R_L variation (R_L=6.686+0.555R_d+0.375N+0.072V_c80). Similarly, V_c80 and N explained 74.5% of R_L variation (R_L/R_d =0.13+0.06V_c80+0.019N)_. R_L and R_L/R_d are affected by leaf N and Rubisco enzyme carboxylation rate (V_c), which may be caused by the intricate interplay between photosynthesis and respiration. This study culminated in the establishment of a prediction model for leaf respiration in subtropical Ficus species, providing a deeper understanding of the mechanisms behind light inhibition of respiration. The insights gained will contribute to a more accurate assessment of the leaf carbon cycle and GPP.