A Consideration of the Seasonal Trends in the Growth of the Fruit of Glasshouse Tomato Plants in Relation to Day-Length

Abstract

Seed of the Potentate variety of tomato was sown at weekly intervals for 56 weeks and weekly measurements of the diameters of every fruit were made to provide estimates of fruit volume production. Development of the plants could suitably be divided into the following periods : (a) from germination to the start of fruiting, (b) an initial lag in fruit volume production, (c) rapidly increasing production, (d) declining production and (e) arrested development, when fruit swelling virtually ceased.The duration of the period from germination to the start of fruiting was related to day-length.The condition of arrested fruit development occurred from approximately the shortest day to the vernal equinox in mature plants that had already attained a maximal rate of fruit volume production ; in juvenile plants it occurred, and was maintained, from approximately the autumnal equinox to the vernal equinox, i.e. when the duration of darkness exceeded that of the light. In both juvenile and mature plants the condition of arrested fruit development ceased when the duration of the light exceeded that of darkness, and a period of increasing fruit volume production ensued.The rate of fruit volume production during this period of rapid increase was related to day-length and the relation was curvilinear. It continued to increase as long as the days continued to lengthen. When the day-length began to decline so also did the rate of production and the relation with day- length was linear.