On the Tovacco Plant as Affected by Climatic Factors : 1. ON the Change in Leaf Structure by LIght Intensities

Abstract

Studies on the leaf of tobacco affected by shading, which was grown under three sets of light intensities made of covering with Victoria Lawn cloth, were performed, three successive experiments being made during 1949 and 1950. Tobacco plants under observation showed marked effects upon their internal structures as well as other properties of leaves. The results are as follows. 1. The area of the leaf surface increased to a marked extent, viz. 30% and 80% for the ectively, compared with the control ones grown without covering. 2. The thickness of the leaves was remarkably reduced by shading. The leaves grown under stronger light had more palisade cells per unit of length, and longer palisade and spongy mesophyll than those in the poorer light. Mesophyll quotient (palisade/spongy)was found larger in the leaves under feeble illumination and smaller in those under stronger illumination. The epidermal cells of both the upper and lower sides of the leaves grown under feeble light were slightly reduced in dimention and their thickness. Measured volume of intercellular space in percent of the volume of whole leaf tissue showed was found to increase in the leaves under reduced illumination. The leaves under shading has smaller number of stomata per unit area, the size of stomata cells being larger, compared with those of the leaves under stronger light. 3. Leaves of the control plants without shading gave larger fresh and dry weight of substance per unit are, and also larger specific gravity of tissue powder in comparison with those grown under shaded conditions.