. Biological effects of radiation; mechanism and measurement of radiation, applications in biology, photochemical reactions, effects of radiant energy on organisms and organic products. Radiation; Biology. SOME INFRA-RED EFFECTS ON GREEN PLANTS 847 excess energy received in this region is of special interest. Johnston (14) observed that plants grown in chambers where infra-red radiation was present were found to be more economical in their use of water than those grown with visible only. This indicates that plants lose less water under infra-red than under visible radiation. In order to obtain
. Biological effects of radiation; mechanism and measurement of radiation, applications in biology, photochemical reactions, effects of radiant energy on organisms and organic products. Radiation; Biology. SOME INFRA-RED EFFECTS ON GREEN PLANTS 847 excess energy received in this region is of special interest. Johnston (14) observed that plants grown in chambers where infra-red radiation was present were found to be more economical in their use of water than those grown with visible only. This indicates that plants lose less water under infra-red than under visible radiation. In order to obtain more data on transpiration as related to both infra-red and visible energy a study was made by Arthur and Stewart (3) of water losses from tobacco plants grown under various conditions of temperature, humidity, and radiation intensity with both the visible plus infra-red and infra-red regions only. In this work 1000- or 1500-watt tungsten-filament lamps were used and standard air-conditioning machin- ery served to control temperature and humidity. Coming's heat- transmitting glass was used to absorb the entire visible region. Plants were potted in metal con- tainers and were sealed in with a paraffin mixture so that all water loss was through the leaf and stem surfaces of the plant. Using the lamp without a filter (visible and infra-red) within a temperature range of 73° to 78°F., it was found that doubling the total energy increases the rate of water loss by This was found to be inde- pendent of humidity within a range of 50 to 88 per cent relative. At an energy level of ^./min. the loss at this temperature was almost twice as great under infra-red plus visible conditions as under infra-red alone. At a higher energy level ( to gm. cal.) and at the same temperature the loss under visible plus infra-red was times that under infra-red alone. When the temperature was increased to the range 98° to 100°F., the infra-red rate of loss increased
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