The weight of a body is diffrent plants
Answers
1. The problem of the relationship between the size of the plant body and the size of the organs it produces has been studied by various workers, who find that in most cases there is a small but significant correlation between these characters. 2. In a series of bean plants, the coefficients of correlation were determined between plant size, as measured by dry weight of shoot, dry weight of fruit, number of leaves, number of pods and number of seeds; and the average dry weight per plant of leaf, pod and seed. A positive and significant correlation, though usually a small one, was found in each case. 3. An examination of the curve of means for organ size on plant size shows that in each case the curve rises steeply at first and then flattens out. In other words, an increase in the size of the plant is accompanied by an increase in the size of its organs if we consider comparatively small plants only; but after a certain size is reached, any further increase in plant size is not followed by increase in organ size. Separate correlations between plant size and organ size made for small plants (those below the point where the curve flattens) and for large ones (those above it) showed a very decided correlation in the former and practically none at all in the latter. 4. These facts suggested that the size of an organ may not be correlated with body size at all, but rather with the size of the axial growing point from which it develops. In support of this idea attention is called to the fact that during the early stages of a plant's growth there is up to a certain point a progressive and parallel increase in the size of the plant and in the size of the primary meristems of its axes; but that after this point is reached meristem size remains constant and further increase in body size is not accompanied by any increase at all in that of the growing point. 5. Favorable material to test this hypothesis directly was afforded by twigs and leaves of Acer saccharum. The correlation between the blade volume of a given leaf pair and the cross-sectional area of the pith of the internode below (used as an index to the size of the growing point from which the leaves had developed) was found to be high (+ .807 ± .024). 6. It is therefore concluded that the size of a plant organ (leaf, fruit or seed) is dependent not upon the body size of the plant on which it is borne, but rather upon the size of the growing point from which it developed.
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