遮阴对濒危植物风吹楠幼苗叶形态和光合参数的影响

Effect of shading on leaf morphology and photosynthetic parameters in endangered Horsfieldia glabra seedlings

探讨风吹楠(Horsfieldia glabra)在不同遮阴条件下的适应能力,为风吹楠野生资源保护和利用提供理论依据。选取生长在3个不同自然遮阴环境——无遮阴(正常光照)、中午前遮阴和下午15:00点前遮阴的风吹楠同一家系一年生实生苗作为试验材料,测定苗木的生长量、生物量分配、叶片形态及光合生理参数等23个指标。结果表明:(1) 3种处理下风吹楠幼苗生长、生物量分配及光合生理参数等各指标差异均达到显著或极显著水平; 12个叶片性状除长/宽、形状因子及脉左宽/叶宽等3个指标差异不显著外,其余均达到显著或极显著水平。(2)遮阴处理下苗木生长矮小,其叶片、侧枝和主干各部分的生物量比正常光照减小了几倍到几十倍,说明遮阴影响了风吹楠干物质积累,影响苗木的正常生长。但3种处理地上各部分生物量分配规律基本相同,表现为叶片>主干>侧枝;随着光照时长的缩短,植株地上部分生物量主要分配在叶片上。(3)遮阴处理使风吹楠苗木叶片变小变薄,叶脉更紧密,叶片数成倍减少,组织含水量变大。(4)遮阴处理风吹楠叶片叶绿素含量显著高于正常光照,且主要表现在叶绿素a显著增多;遮阴处理使风吹楠的最大净光合速率(Pmax)、表观量子效率(AQY)、光饱和点(LSP)、净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)和瞬时水分利用效率(WUEi)均显著降低;胞间CO2浓度(Ci)高于正常光照;光补偿点(LCP)和暗呼吸速率(Rd)也相应地发生改变,但变化规律不一致。从光合日变化结果来看,强光照高温下风吹楠并未发生明显光抑制现象,也未出现"午休现象"。总之,遮阴对风吹楠幼苗生长、叶片形态、光合生理等影响较大,光照充足的环境才适合其正常生长,而遮阴程度较大时风吹楠苗木生长严重受阻。

Research on the adaptability of Horsfieldia glabra under different shading environments can providetheoretical basis for the protection and utilization of H. glabra resources. One-year-old seedlings of H. glabrafrom a same family grown under three different natural shading environments, no shading(normal lighting),shading before noon and shading before 15:00, as the test materials. Twenty three indexes were measured, in-cluding seedling growth, biomass allocation, leaf morphology and photosynthetic physiological parameters, etc.The results show:(1) under three treatments, the seedling growth, biomass allocation, photosynthetic physio-logical parameter were significantly different, and most of the 12 leaf traits were also significantly different ex-cepted for the ratio of length to width, leaf shape factor and the ratio of the leaf width on the left of main vein toleaf width.(2) Under shading treatment, the seedlings were stunted and the biomasses of leaves, lateral branch-es and stems were reduced by several times to dozens of times than those in normal environment, indicatingshading treatment seriously affected the accumulation of dry matter and the normal growth of H. glabra seed-lings. However, the distribution pattern of overground biomass was similar under the three shading environ-ments, with an order as leaf > stem > lateral branch. As the lighting time shortened, the overground biomasswas mainly allocated to leaves.(3) Shading treatment led to smaller and thinner leaves, more intensive leafveins, fewer leaves and increased content of tissue water.(4) The chlorophyll content of H. glabra in shadingenvironment was significantly higher than that in normal lighting environment, especially the chlorophyll a.Under shading treatment, the maximal net photosynthetic rate(Pmax), apparent quantum yield(AQY), light satu-ration point(LSP), net photosynthetic rate(Pn), transpiration rate(Tr), stomatal conductance(Gs) and instanta-neous water use efficiency(WUEi) were all significantly decreased, while the intercellular CO2 concentration(Ci) was increased. The light compensation point(LCP) and dark respiration rate(Rd) changed inconsistently.According to the diurnal variation of photosynthesis, there was no light suppression and 'siesta phenomenon'observed in H. glabra under strong light and high temperature. In conclusion, shading has significant effects onseedling growth, leaf morphology and photosynthesis physiology. H. glabra is more suitably grown in sufficientlighting environment, and heavy shading could seriously hinder its regular growth.