马尾松和红锥叶片解剖和光合对穿透雨减少的响应

The Response of Leaf Anatomical Structure and Photosynthetic Physiology of Pinus massoniana Lamb.and Castanopsis hystrix Miq.to Throughfall Reduction

[目的]探究8 a干旱胁迫条件下树木叶片光合生理特征与叶片解剖结构的响应及二者之间的关系。[方法]在南亚热带选取2种典型人工林(马尾松和红锥)设置林内穿透雨减少的模拟干旱实验,在穿透雨减少8 a后测定叶片气体交换参数、叶绿素荧光参数、叶片解剖特征以及叶片养分(N、P)含量。[结果](1)穿透雨减少后,马尾松针叶上、下表皮、叶片厚度以及气孔密度显著增加,而红锥仅叶片上表皮厚度显著增加,海绵组织厚度显著降低。(2)马尾松和红锥的气体交换参数(净光合速率P_(n)、气孔导度G_(s)、蒸腾速率T_(r))、叶绿素荧光参数(光系统Ⅱ最大光化学效率Fv/Fm、实际光化学效率ΦPSII,表观电子传递速率ETR)以及叶氮、磷含量在穿透雨减少8 a后均未发生显著变化。(3)与马尾松相比,红锥受到的气孔限制(L_(s))更大,水分利用效率(WUE)更高,尤其在干季更明显。[结论]马尾松和红锥应对干旱胁迫的策略存在差异,马尾松通过调节叶片解剖结构产生更具耐旱的针叶来应对干旱,红锥则更倾向通过调节气孔(L_(s))、提高水分利用效率(WUE)来适应干旱。

[Objective]To explore the response of leaf anatomy and leaf photosynthetic physiology to long-term drought and analyze the relationship between leaf anatomy and leaf photosynthetic physiology under long-term drought conditions.[Method]We conducted a manipulation drought experiment by reducing the throughfall in the forest and measured the leaf gas exchange,chlorophyll fluorescence,leaf nutrient(N,P)and leaf anatomy of the two typical tree species(Pinus massoniana Lamb.and Castanopsis hystrix Miq.)in subtropical China at the 8th year after the throughfall reduction treatment.[Results](1)Significant differences were observed in leaf anatomy between P.massoniana and C.hystrix in response to throughfall reduction;the upper and lower epidermis,leaf thickness and stomatal density of P.massoniana needles increased significantly.However,the thickness of the upper epidermis of the leaves of C.hystrix increased significantly,and the thickness of the spongy tissue decreased significantly.(2)No significant differences were observed in the gas exchange parameters(net photosynthetic rate Pn,stomatal conductance Gs,transpiration rate T_(r)),chlorophyll fluorescence parameters(photosystem Ⅱ maximum photochemical efficiency Fv/Fm,actual photochemical efficiencyΦPSII,apparent electron transfer rate ETR)and leaf nutrient contents of both species after 8 years of throughfall reduction.(3)Compared with P.massoniana,the stomatal limitation(L_(s))of the C.hystrix was larger and the water use efficiency(WUE)was higher,especially in the dry season.[Conclusion]There are differences in the strategies of P.massoniana and C.hystrix to cope with drought stress.P.massoniana responds to drought by adjusting leaf anatomy to produce xeromorphic needles,while C.hystrix is more inclined to adjust stomata(L_(s))and improve water use efficiency(WUE)to adapt to drought.