Studies on the carbon dioxide environment for plant growth. I

Abstract

The present study was undertaken to determine the effect of atmospheric CO2 concentrations on the growth, flowering and fruit setting of eggplant.Cultivar of eggplant, “Senryo”, grown in polyvinyl plastic growth chambers were treated with CO2 at 4 levels of concentrations, 200, 300 (normal air), 900 and 3, 000ppm, for 8 hours daily from April 1 to June 30, 1964. Above normal CO2 concentrations were obtained by regulation of the flow rate of air and CO2 from cylinder at inlet to the chambers. The chamber used for below normal CO2 was sealed off and air in the chamber was recirculated through the air conditioner and maintained about 200ppm.1) Differences in growth and appearance of the plants grown under the normal and the above normal levels of CO2 were apparent within 20 days. At the end of treatment, marked increases in fresh and dry weights, number of leaves and leaf area were observed as the CO2 concentrations increased, but there was little effect on plant height. In the 3, 000ppm chamber, fresh and dry weight yields of plant were increased about 1.5-1.6 times as compared to that in the 300ppm chamber. Similarly, leaf area in the 3, 000ppm chamber was about 1.2 times as compared to that in the 300ppm chamber, and this consisted of both expansion in leaf size and increase in number of leaves per plant. Moreover, CO2 enrichment enhanced net assimilation rate. NAR in the 3, 000ppm chamber doubled as compared with that in the 300ppm chamber. This was a similar result to that. obtained with swiss chard in a previous report.2) As CO2 concentrations increased, number of flowers increased, while the ratio of the abnormal short or moderate styled flower to the normal long styled flower decreased. Similarly, percentage of fruit set per flower opened and the total yield of fruit increased. Fresh and dry weight yields of fruit in the 3, 000ppm chamber were 2, 271g and 135.9g, respectively, compared to 734.5g and 58.1 g in the 300ppm chamber.3) Content of chlorophyll, nitrogen, phosphorus and potassium in leaves were not significantly affected by CO2 concentrations, while their amounts per plant increased as the CO2 concentrations were raised.