不同遮阴强度对赤松幼苗生长和光合特性影响

Effects of different light stress on growth and photosynthetic characteristics of Pinus densiflora saplings

在5个不同遮阴强度试验区（全光处理、遮阴强度80%、遮阴强度60%、遮阴强度40%、遮阴强度20%，分别记为对照、Ⅰ区、Ⅱ区、Ⅲ区、Ⅳ区）内栽植赤松幼苗，测定生物量、苗高和地径生长量、光合特性，分析植株构型变化，研究不同遮阴处理对赤松生长和光合的影响。结果表明：对照区地径最大，3年总生长量48.8cm，高于其他处理区18.06%～34.43%。总生物量依次为对照区＞Ⅳ区＞Ⅲ区＞Ⅱ区＞Ⅰ区。对照区一级侧枝最多，Ⅰ区最少。Ⅱ区和Ⅲ区平均枝长较长，Ⅰ区枝长最短。净光合速率日变化，对照区呈“双峰”曲线，且对照区光合速率平均值最大，其他处理区都呈“单峰”曲线。蒸腾速率日变化与净光合速率日变化趋势一致。可见，全光条件对赤松幼苗生长有利，而适当遮阴（遮阴强度低于20%）不影响赤松生长。

An experiment was conducted to study the effects of five levels shade on growth and photosynthetic characteristics of Pinus densiflora saplings,which are Ⅰ(80% shade)、Ⅱ(60% shade)、Ⅲ(40% shade)、Ⅳ(20% shade),comparing with ck(full light). Through growth and biomass measurement of Pinus densiflora saplings, and the changes of the architecture and photosynthetic characteristics show that ground diameter of ck is maximum, and the increment of ck is 48.8cm in three years,18.06%～34.43% higher than others. With the increase of shade ratio,the total biomass reduced in turn. The primary lateral branch mumber of ck are most, Ⅰare least. The average branch length of Ⅱ and Ⅲ is longer than others,and the branch of Ⅰis the shortest. The daily change of photosynthetic rate in ck is double peak curve,Meanwhile,the average photosynthetic rate is maximum,but the others are single peak curve.Transpiration rate variations is in accord with photosynthetic rate. Obviously,full light is conducive to Pinus densiflora saplings growth,but proper shade(20% below)has no effect.