Growth and photosynthetic responses of Gallesia integrifolia (Spreng.) Harms and Schinus terebinthifolius Raddi seedlings in dense shade
Growth and photosynthetic responses of Gallesia integrifolia (Spreng.) Harms and Schinus terebinthifolius Raddi seedlings in dense shade
复制标题
DOI：
10.1007/s10457-008-9190-x
复制
发表时间：
2009-09-01
影响因子：
2.2
通讯作者：
Lavinsky, Alyne O.
中科院分区：
文献类型：
--
作者：
Feijo, Natalia S. A.;Mielke, Marcelo S.;Lavinsky, Alyne O.
我们分析了生长和光合行为的Gallesia integrifolia（'pau-d' alho '）和Schinus terebinthifolius（' aroeirinha '）在树荫下，寻求获得生理生态信息，这些物种的幼苗在以前建立的可可农林复合系统。考虑到可可树的阴影下的光照强度在5%和10%日光之间变化，5个月大的幼苗暴露于四个辐照度水平（25%、17%、10%和5%日光）92天。随着遮荫程度的增加，两种植物的单位叶面积叶重、单株叶面积、相对生长率和净同化率均呈下降趋势，叶面积比呈上升趋势。在25%和5%光照下，光饱和净光合速率（P（nmax））的平均值分别为12.8和8.0 μ molCO_2·m ~（-2）·s ~（-1）。integrifolia和17.9和7.4 μ molCO_2 m ~（-2）s ~（-1）。石杉基于光合光子通量密度的测量和光合饱和辐照度（Is）的估计值，我们得出结论，在所有的阴影条件下，这两个物种的叶片是次优的光条件下达到P（nmax）。尽管P（nmax）值最低，但G的RGR和NAR显著高于G。integrifolia在所有辐照水平。生长速率的差异可以用高的LA、LAR和叶质量比（LMR）以及低的Is、光合补偿辐射和暗呼吸速率来解释。全缘叶即使在G. integrifolia表现出更高的能力，在密集的遮荫条件下，我们认为，这两个物种在25%以下的光照环境中的遮荫诱导的胁迫条件下。从实用的角度来看，可以得出结论，这两个物种的幼苗应该在大树倒下后形成的光隙中引入，或者在可可树种植的地方使用大的植物间距。
We analyzed the growth and photosynthetic behavior of Gallesia integrifolia ('pau-d'alho') and Schinus terebinthifolius ('aroeirinha') under shade, seeking to obtain ecophysiological information for introducing seedlings of those species in previously established cacao agroforestry systems. Considering that light intensity under the shade of cacao trees varied between 5 and 10% daylight, 5 months old seedlings were exposed to four irradiance levels (25, 17, 10 and 5% daylight) for 92 days. With shade increase both species displayed trends of decrease leaf mass per unit leaf area, leaf area per plant (LA), relative growth rate (RGR) and net assimilation rate (NAR), and increase leaf area ratio (LAR). The mean values of light-saturated net photosynthetic rate (P (nmax)) in 25 and 5% daylight were 12.8 and 8.0 mu mol CO2 m(-2) s(-1) for G. integrifolia and 17.9 and 7.4 mu mol CO2 m(-2) s(-1), respectively, for S. terebinthifolius. Based on the measurements of photosynthetic photon flux density and estimated values of photosynthetic saturated irradiance (Is) we concluded that, in all shaded conditions, the leaves of both species were under sub optimal light conditions to reach P (nmax). In spite of the lowest P (nmax) values, RGR and NAR were significantly higher for G. integrifolia in all irradiance levels. Differences in growth rates can be explained by the higher values of LA, LAR and leaf mass ratio (LMR), as well as by the lower values of Is, photosynthetic compensation irradiance and dark respiration rates observed for G. integrifolia. Even though seedlings of G. integrifolia presented higher capacity to adapt under conditions of dense shade, we concluded that both species were under stress conditions induced by shade in light environments below 25% daylight. On a practical point of view it is possible to conclude that seedlings of both species should be introduced in light gaps, formed after the fall of big trees, or in places in which cacao trees are cultivated using large plant spacing.