CHANGES OF BAMBOO LEAVE’S PN AT DIFFERENT POSITION IN THE CANOPY

In order to learn the photosynthetic productivity of the bamboo canopy, an 18 meter iron tower has been established in Miao Shan Wu Maozhu (Phyllostachys pubescens) stand for measuring the changes of Pn at different position of the canopy by IRGA made in England. Then we measure and calculate the light transmissity, the changes of the leave's increase and decrease of the canopy, the leaf area index and the distribution of leaf area at different position in the canopy. The results are as follows:1.There are litters being collected in the whole year, but the first and second peak values occur in April to May and November to December respectively. The maximum LAI of the experimental area is 8.02, but those in the upper, middle and low tiers of the canopy are 1.38, 4.36, 2.28 respectively.2.The light transmissivities in the canopies different tiers as mentioned in result 1 are 50%, 20% and 4-5% respectively.3.The light compensation point of bamboo leaves is about 50μmolm-2S-1, and the light saturation point of the various tiers of the canopy shows different values, i.e. the upper about 1000μmolm-2S-1, the mid about 400-600 μmolm-2S-1, and the low about 200-400μmolm-2S-1.4.The value of Pn of leaves at the upper part of the canopy is higher. It is about 15 μmolm-2S-1 under a proper environment. A noontime snooze will take place at a high temperature and a low moisture. So usually, the curve of daily changes of Pn is a double peaked curve. Due to the low transmissivity at the mid and low part of the canopy, the density of photon is less, and the Pn within a day often shows a negative value.