摘要
受太阳活动的影响,树冠不同方位以及内外部的叶片接受到的光照存在差异,造成温度、湿度等小气候因子也存在差异。叶片的形态解剖结构和生理特性等会对外界环境条件的改变发生响应。为了更好地了解树木生长的局部小环境条件差异对树木生长的影响,该文选择国槐(Sophora japonica)、悬铃木(Platanus orientalis)、银杏(Ginkgo biloba)、榕树(Ficus mi-crocarpa)和黄葛榕(F.lacor)5种冠幅较大的树种,通过测定树冠内外部及4个方位上的比叶重(leaf mass per area,LMA)、叶绿素a(chlorophyll a,Chl a)、叶绿素b(chlorophyll b,Chl b)及类胡萝卜素(carotenoid,Car)的含量及碳稳定同位素比率(carbon isotope ratio,δ13C)等指标,研究叶片形态、生理指标等随树冠开度的变化以及方位差异。结果表明,叶片LMA和δ13C均随树冠开度增加而增大,光合色素含量则相反;叶片LMA和δ13C的方位变化则是南向>西向>北向>东向,与叶片所接受到的光强变化规律一致,而光合色素含量的方位差异较复杂、且因树种而异,总的来说,以受光最弱的东向含量最高。上述结果表明,树冠外围和南向、西向的叶片由于接受到的光能较多、温度高、相对湿度小等,其叶片会增大单位面积的重量、减小气孔开度和光合色素含量,从而减少对光能的吸收,也使光合作用降低、δ13C增大,而不同方位光照对光合色素含量的影响机制较为复杂,这些都表明了叶片对周围小气候的形态和生理上的适应。
Aims Light, temperature and humidity conditions differ among individual leaves and may influence leaf morphology, anatomy, stomatal conductance, chlorophyll content and distribution and leaf photosynthetic processes. Our objective was to determine the influence of local microenvironment on structure and biophysical characteristics of leaves through research on changes of leaf morphology and biophysical indices along the lateral distribution of leaves within tree crowns and with orientation differences.Methods We selected five tree species with wide crowns （Sophorajaponica, Platanus orientalis, Ginkgo biloba, Fieus microcarpa and F. lacor） and measured leaf photosynthetic pigments （including chlorophyll a, chlorophyll b and carotenoids）, leaf mass per area （LMA） and carbon isotope ratio （δ^13C） along the horizontal distance from the sample point to the tree trunk and with different orientations in each tree species. Pigment content was measured by colorimetry, LMA as the ratio of leaf dry mass to fresh area and δ^13C with a mass spectrograph. Important findings Leaf δ^13C and LMA increased and photosynthetic pigment decreased with horizontal distance from the sample point to the trunk. Leaf δ^13C and LMA also differed by orientation, with southward leaves having the highest values, followed by westward leaves, and eastward leaves having the lowest values. Photosynthetic pigments had a more complex relation with orientation, although chlorophyll a, chlorophyll b, total chlorophyll content, chlorophyll a to b ratio and carotenoids were the highest in eastward leaves. These results suggest that southward, westward and leaves on the outside of the crown have increased LMA, reduced stomatal aperture and photosynthetic pigment content and, as a result, decreased photosynthesis and increased δ^13C values in response to stronger irradiance, higher temperature and lower humidity. Therefore, local microenvironmental differences within an individual tree greatly influence leaf morphological and biophysical characteristics.
出处
《植物生态学报》
CAS
CSCD
北大核心
2010年第2期134-143,共10页
Chinese Journal of Plant Ecology
关键词
δ~13C
类胡萝卜素
叶绿素
开度
比叶重
方位
carbon isotope ratio, carotenoid, chlorophyll, lateral spread of crown, leaf mass per area, orientation
