Microchemical and Morphological Studies of Effect of Light on Plants

Abstract

Studies were made of the microchemical and morphological variations resulting from illumination of 5, 7, 12, 17, 19, and 24 hours'' duration, and an increased CO2 supply, especially in tomato and buckwheat. Two intensities of artificial light were used, the one supplementing daylight, the other serving as the sole source of light. The maximum development of the plant, considering height and differentiated tissue, occurred in the 12-hour tomato and in the 17-hour buckwheat. The shorter exposures to light tended to produce low carbohydrate and low protein reserves with less total growth and less differentiated tissue. The longer durations tended to increase the carbohydrate reserves without a proportionately increased use in the elaboration of proteins and in tissue production. In a study of the effect of these light intervals in a number of cultivated plants, it was found that continuous light tended to produce thinner leaves; daylight supplemented by 6 hours of artificial light produced varying results in different species. Thinner leaves, except in continuous light, showed an increase in the number of stomata. Effects on stem anatomy are also recorded. The amount of development in fibrous root systems appeared roughly comparable with that of the aerial parts of the same plants, but no such coordination appeared in the storage roots of the four o''clock.