Microchemical and Morphological Studies of Effect of Light on Plants

Abstract

1. In plants with short exposures to light, there are usually low carbohydrate and low protein reserves with less total growth and less production of differentiated tissues than in longer intervals. 2. In plants with longer light duration, there is increase in carbohydrate reserves without proportionately increased use in elaboration of proteins and tissue production. 3. Nitrates are present in great amounts in all tomato plants except the control and gantry crane house specimens. They are low in amount in buckwheat in 17, 19, and 24-hour exposures. They are usually lowest in the gantry crane house with extra carbon dioxide. 4. The maximum development of the plant (considering height and differentiated tissue) occurs in the 12-hour tomato and the 17-hour buckwheat. 5. Injury is evident in the tomato in exposures of 17 hours or more, resulting in marked decrease in photosynthetic ability. 6. Continuous light tends to produce thinner leaves, with palisade layer shorter or lacking. 7. The effect of conditions in the gantry crane houses as regards leaf thickness is variable. 8. Thinner leaves usually show an increase in the number of stomata, except in continuous light in intensity used. 9. Root development in fibrous systems appears roughly comparable with that of the aerial parts. 10. In the storage roots of four o'clock, maximum development occurs in the gantry crane houses and continuous light, while maximum height of stem occurs in the 17-hour plant.