Studies On Photosynthetic Characteristics Of Grape In Rain-shelter-cultivation

The photosynthetic characteristics of two grape frame system with Ruby Seedless and Red Globe were studied with LI-6400 portable photosynthesis system in protected cultivation. This test measured net photosynthetic rate and the daily variation of ecological factor. Responsive characteristics of Pn to photosynthetic active radiation (PAR) and CO2 concentration were also systematically studied. In order to investigate the change law of photosynthetic characteristics and find out the better frame system, the test compared the effect of photosynthesis in two kinds of frame system.The main results were as follows:1. The diurnal variation of Pn of Ruby Seedless and Red GlobeThe diurnal variation of net photosynthetic rates (Pn) of two kinds of grape presented a double-peak curve with a lower value of the second peak. The first peak occurred about 10:00 am, the second one occurred about 16:00 pm, decreased at noon, the first peak more than the second peak. It was indicated that the photosynthesis decline during midday time was principally influenced by stomatal conductance limitation.2. Response curve of Pn to PAR level of Ruby Seedless and Red GlobeThe PAR response curve followed a quadratic function in grape. Ruby Seedless in "T" and "V" type frame, light saturation points (LSP) at 1314.29-1450.00 (μmol·m-2·s-1) and 1421.43-1525.00 (μmol·m-2·s-1), light compensation points(LCP) at 13.40-41.33 (μmol·m-2·s-1) and 38.12-58.85 (μmol·m-2·s-1); appearance quantum yield (AQY) at 0.0285-0.0412 (mol·m-2s·-1) and 0.0369-0.0437(mol·m-2·s-1). Red Globe in "T" and "V" type frame, light saturation points (LSP) at 1466.67-1491.67 (μmol·m-2s·-1) and 1335.71-1387.50 (μmol·m-2·s-1), light compensation points (LCP) at 17.75-56.89 (μmol·m-2·s-1) and 24.64-60.76 (μmol·m-2·s-1); appearance quantum yield (AQY) at 0.0323-0.0378 (mol·m-2·s-1) and 0.0329-0.0443 (mol-m-2·s-1). Compared with "T" type frame, the leaves of Ruby Seedless in "V" type frame had lower LCP and higher LSP, which suggests that the leaves Ruby Seedless have much better efficiency of light utilization, and when the LSP was reached in the grape leaves, the higher P max and AQY means that the leaves have stronger capacity of making photosynthate. Compared with "T" type frame, the leaves of Red Globe in "V" type frame had higher AQY, which suggests that the leaves have stronger capacity of making photosynthate.3. Response curve of Pn to CO2 level of Ruby Seedless and Red GlobeResponse curve of CO2 was a quadratic equation in grape. Ruby Seedless in "T" and "V" type frame, CO2 saturation points (CSP) at 992.50-1082.50 (μmol·m-2·s-1) and 1025.00-1192.50(μmol·m-2·s-1); CO2 compensation points (CCP) at 46.38-67.36 (μmol·m-2·s-1) and 42.85-57.69 (μmol·m-2·s-1); carboxylation efficiency (CE) at 0.0358-0.0420 (mol·m-2·s-1) and 0.0323-0.0462 (mol·m-2·s-1). Red Globe in "T" and "V" type frame, light saturation points (LSP) at 965.00-1100.00(μmol·m-2·s-1) and 1035.00-1230.00 (μmol·m-2·s-1); compensation points (CCP) at 47.12-71.85 (μmol·m-2·s-1) and 44.56-66.79 (μmol·m-2·s-1); carboxylation efficiency (CE) at 0.0311-0.0386 (mol·m-2·s-1) and 0.0344-0.0468 (mol·m-2·s-1). Compared with "T" type frame, the leaves of Ruby Seedless and Red Globe in "V" type frame had lower CCP, higher CSP and CE, which indicates that the leaves Ruby Seedless and Red Globe have higher CO2 utilization ratio than that in "T" type frame.4. Comparison of photosynthetic characteristics of grape in two types frameThe comparison of photosynthetic characteristics of grape in two types frame shows "V" type frame's photosynthetic efficiency is better than "T" type frame's.