EFFECTS OF CORRELATION BETWEEN VEGETATIVE AND REPRODUCTIVE FUNCTIONS IN THE TOMATO (LYCOPERSICON ESCULENTUM MILL.)

Abstract

A statistical and chemically analytical study of the character and extent of correlation between vegetative and reproductive activities, specifically the effect of fruits on vegetative growth. Excepting 1 group, all plants were grown in sand cultures under 2 planes of nutrition as regards N supply. Each plant was trained to a uniaxial type of growth and all flowers were artificially pollinated. Flowers and fruit were removed at various stages of development. In every case a maximum crop of fruits had a conspicuous retarding effect on vegetative growth and development. This inhibition proceeded in approximately the following order (1) destruction in fecundity of blossoms; (2) decrease in size of floral clusters; (3) abscission of flower buds; (4) reduction and cessation of terminal growth of the stem; and (5) complete exhaustion and eventual death of all parts of the plant save the fruit. These symptoms appeared to be typical of a condition of N starvation of increasing severity. The rate of growth, as measured by increments of height, declines at the exact time and in inverse proportion to the amount of fruit set and developing. Removal of fruit before maturity led to complete recovery and renewal of vegetative growth. The rate of elongation of the central axis was then identical with that of non-fruiting deflorated plants. Stems, leaves, fruits, and roots of typical control and treated plants were analyzed for soluble, insoluble, nitrate, protein, and amino N; for total carbohydrates; and for starch, hemicellulose, dextrose, sucrose, also total reducing sugars. Results of chemical analyses and micro-chemical tests point to N in soluble form as an immediate limiting factor effecting these influences of correlation. The fruit diverts and monopolizes almost all the available N, accounting for the marked changes in development and in part at least for accumulation of carbohydrates. These effects are not neutralized by submitting the plants to a short daily exposure to light. They may be localized to 1/2 or part of a tomato plant. Suggestions are made as to the possible detailed mechanism of correlation between vegetative and reproductive functions.