潮汐对秋茄叶表型塑造及叶经济谱的影响

Effects of Tides on Leaf Phenotypic Modeling and Leaf Economics Spectrum of Kandelia obovata

【目的】明确秋茄叶表型及叶经济谱对自然潮汐生境的响应特征,以期掌握秋茄在周期性浸淹下的适应机制。【方法】对福州市罗源湾秋茄成熟林满潮线上及线下叶片进行研究,以上层未受淹叶片为对照,测定上、下层叶表型性状,并对各性状间关系及叶经济谱进行分析。【结果】与满潮线上层叶片相比,满潮线下层叶片干质量、叶柄长及叶干物质含量较小(P<0.01),叶形指数较小(P<0.05),比叶面积较大(P<0.01);在叶片气孔特性中,满潮线下层叶片气孔长度、宽度、面积、周长、开度、开口长度、开口面积、开口周长均大于上层,而气孔密度则小于上层(P<0.01);满潮线下层叶片的净光合速率、蒸腾速率及气孔导度较小,而胞间CO2浓度较大(P<0.01),羧化速率较小(P<0.01),水分利用效率在满潮线上、下层叶片中差别不显著。满潮线上层秋茄叶片气孔特性与光合功能之间相关性比下层高,而满潮线下层叶气孔特性与叶形态性状相关性高于上层。【结论】秋茄满潮线上、下层的叶表型差异明显,下层叶片气孔功能适应性较强,但光合功能受到一定限制。上层叶气孔特性与光合功能具有协同进化表现,而下层叶气孔特性与叶形态性状存在趋同适应。满潮线上、下层秋茄叶为适应自然潮汐生境,存在明显生存策略选择。叶经济谱表现为:满潮线下层叶片总体上向“缓慢投资-收益型”一端偏移,具有较小的叶干物质含量、气孔密度,较低的净光合速率及较大的比叶面积、气孔面积和气孔开度,以适应周期性低光、缺氧的淹水极端环境;上层叶片则向“快速投资-收益型”一端偏移以应对海岸带大风、海浪拍打等特殊生境。

【Objective】The aim of this study was to investigate the responses of leaf phenotype and leaf economics spectrum of Kandelia obovata under natural tidal habitat in order to examine the adaptation mechanism of K.obovata under periodic tidal inundation.【Method】The leaves above and under high tide line of mature forest of K.obovata in Luoyuan Bay in Fuzhou City of Fujian Province were measured,with those above the high tide line without tidal inundation used as control group,to study phenotype characteristics of the leaves and the relationships among each leaf characteristics and the leaf economics spectrum.【Result】Compared with the leaves above the high tide line,dry weight,petiole length and dry matter content of the leaves under the high tide line were significantly smaller(P<0.01),the leaf shape index was significantly smaller(P<0.05)and the specific leaf area was significantly larger(P<0.01).Among the stomatal characteristics,stomatal length,width,area,circumference,aperture,opening length,opening area and opening circumference of the leaves under the high tide line were significantly larger than those of the leaves above the high tide line(P<0.01),but the stomatal density was significantly smaller(P<0.01).Net photosynthetic rate,transpiration rate and stomatal conductance of the leaves under the high tide line were significantly lower,while the CO2 concentration was significantly higher(P<0.01).Carboxylation rate of the leaves under the high tide line was significantly smaller(P<0.01),and water use efficiency was not significantly different between the leaves above and under the high tide line.The correlation between the stomatal characteristics and the photosynthetic function of the leaves above the high tide line was higher than that of the leaves under the high tide line,while the correlation between the stomatal characteristics and the foliar morphological traits of the leaves under the high tide line was higher than that of the leaves above the high tide line.【Conclusion】Our results demonstrated that the phenotypic difference between the leaves above and under the high tide line was obvious,and the stomatal function of the leaves under the high tide line had strong adaptability,but the photosynthetic function was limited.The stomatal characteristics and the photosynthetical function of the leaves above the high tide line showed synergistic evolution,while the stomatal characteristics and the foliar morphological traits of the leaves under the high tide line indicated adaptive convergence.In order to adapt to the natural tidal habitat,there were obvious survival strategies in the leaves above and under the high tide line of Kandelia obovata.The results of the leaf economics spectrum indicated that the leaves under the high tide line generally shifted toward the“slow investment-return”end,with smaller dry matter content and stomatal density,lower net photosynthetic rate and larger specific leaf area,stomatal area and stomatal opening,so as to adapt to the extreme tidal inundation environment of low light and hypoxia.The leaves above the high tide line shifted toward the“fast investment-return”end to cope with special habitats such as strong winds and waves.