湛江5种红树林树种光合作用特性及光合固碳能力研究

Characteristics of photosynthesis and photosynthetic carbon fixation capacity of five mangrovetree species in Zhanjiang City

关键词:  红树林  光合日变化  光合固碳  通径分析

Key words:  mangrove trees  diurnal course of photosynthesis  photosynthetic carbon fixation  path analysis

摘要:

应用Li-6400便携式光合作用测定系统,对湛江市特呈岛5种红树林树种的净光合速率日变化和光合作用—光响应曲线进行了测定,探讨了各树种的光合作用特性以及主要影响因子并评估其固碳能力大小。结果表明:在自然光照条件下,秋茄和红海榄叶片净光合速率(Pn)的日变化曲线呈单峰型,白骨壤、木榄和桐花树为双峰型,光合“午休”现象明显,而且峰值分别出现在10:00和14:00左右。其中,白骨壤和木榄的光合午休主要由气孔限制因素引起,桐花树主要由非气孔限制因素引起。通径分析表明,光合有效辐射(PAR)是影响白骨壤和桐花树叶片Pn的主要决策因子,而叶面大气蒸汽压亏缺(VPD)是主要限制因子; 影响秋茄和红海榄叶片Pn的主要决策因子是气孔导度(Gs),主要限制因子是叶温(T_l); 影响木榄叶片Pn的主要决策因子是气孔导度(Gs)。基于叶片净光合作用速率的各树种日净固碳量存在显著性差异(P<0.01),秋茄的日净固碳量最大(13.83 g·m^-2·d^-1),其次为白骨壤和桐花树(9.48和8.24 g·m^-2·d^-1),木榄和红海榄的较小(6.72和6.30 g·m^-2·d^-1)。5种红树林树种的光补偿点(LCP)介于28.3～137.0 μmol·m^-2·s^-1之间,显示了阳生植物的特性。光饱和点(LSP)介于169.3～1189.3 μmol·m^-2·s^-1之间,桐花树最大,红海榄最小。5种红树林树种的表观量子效率(AQY)存在极显著差异(P<0.01),白骨壤最高为0.064 mol·mol^-1,木榄最低,仅为0.005 mol·mol^-1。5种红树林植物叶片的光响应参数与日净固碳量的关联度大小顺序为最大净光合速率(P_max)、LSP-LCP、AQY、LSP、LCP。

Abstract:

The photosynthetic characteristics of five mangrove tree species in Techeng Island of Zhanjiang City were measured by Li-6400 photosynthetic measurement system to explore the factors on diurnal course of photosynthesis and evaluate their photosynthetic carbon fixation capacity. The results showed that daily variation of net photosynthetic rate in leaves of Kandelia candel and Rhizophora stylosa presented a single-peak curve, however, Avicennia marina, Bruguiera gymnorhiza and Aegiceras corniculatum presented a double-peak curve and an obvious “midday depression” phenomenon occurred, with the peak values at 10:00 am and 14:00 pm. Among them, midday-depression of photosynthesis in Avicennia marina and Bruguiera gymnorhiza was affected by stomatal limitation,however, Aegiceras corniculatum was affected by non-stomatal limitation. By path analysis, photosynthetic active radiation(PAR)was the decision factors and vapor pressure deficit(VPD)was the main limiting factors which affecting the characteristic of net photosynthetic rate( Pn)of Avicennia marina and Aegiceras corniculatum. In contrast to the situation of Avicennia marina and Aegiceras corniculatum, leaf temperature(T_l)was the main limiting factor and stomatal conductance(Gs)was the decision factor which affected Pn of Rhizophora stylosa and Kandelia candel. Gs was also the decision factors which affected Pn of Bruguiera gymnorhiza. The daily net carbon fixation amount was significant different among the five mangrove trees based on the leaf net photosynthesis rate, of which Kandelia candel was the highest(13.83 g·m^-2·d^-1), followed by Avicennia marina and Aegiceras corniculatum (9.48 and 8.24 g·m^-2·d^-1, respectively), the lowest was Bruguiera gymnorhiza and Rhizophora stylosa(6.72 and 6.30 g·m^-2·d^-1, respectively). The light compensation point(LCP)values of five mangrove trees ranged from 28.3 to 37.0 μmol·m^-2·s^-1 which showed the typical properties of sun plants. The light saturation point(LSP)values range between 169.3 and 1 189.3 μmol·m^-2·s^-1 of which Aegiceras corniculatum was the largest but Rhizophora stylosa is minimal. There were significant differences among the five mangrove tree plants of apparent quantum yield(AQY)(P<0.01), of which Avicennia marina was up to 0.064 mol·mol^-1 while Bruguiera gymnorhiza was the lowest 0.005 mol·mol^-1. The magnitude on grey correlation degree between light response parameters and daily net photosynthetic carbon fixation in leaves of mangrove tree species was the maximum net photosynthetic rate(P_max), LSP-LCP, AQY, LSP and LCP.