Tissue weight and water content in a tetracotyledonous mutant of Phaseolus vulgaris

Abstract

In 1915 studies of the tissues of normal and variant bean seedlings were begun in an effort to explain the differential mortality with respect to morphological characters demonstrated in an earlier experiment. 1

In a first paper 2 it was demonstrated that teratological seedlings show a lower capacity for the development of primordial leaf tissue than do normal individuals of the same strain grown under conditions as nearly as possible identical. In these first experiments the conclusions were based upon the green weight of primordial leaves.

In a second study, tissue weight determinations were based on the trifoliate leaves of the third node as well as on the primordial leaves of the second node. 3 In these two investigations we attempted to determine to what extent morphologically aberrant seedlings differ from the normal seedlings of the race to which they belong in their physiological characters in so far as these can be measured by the capacity for the production of tissue. The results indicated that teratological seedlings show a lower capacity for tissue production as measured both by green weight and dry weight in primordial and first compound leaves than do their normal controls.

In a subsequent series of investigations we have instituted comparisons between the highly abnormal seedlings of a tetracotyledonous race of Phaseolus 1 and the normal seedlings of the parental race from which it originated.

The tetracotyledonous race is characterized by a modal number of four cotyledons and four primordial leaves but both of these characters are highly variable.

Classifying the tetracotyledonous plants according to number of primordial leaves, we have the mean green weight and the mean dry weight of primordial leaf tissue in teratological and normal seedlings shown in the accompanying table.

The data are given as average weights per plant and per leaf.