On the fruiting of sunflower.

Abstract

In sunflower plants, the fertilized flowers develope generally into matured grains, but when the migration of nutriment into the fruits is not enough, some of them are blasted at the early stage of seed-formation (blasted grains). Some of the unfertile lowers are blasted immediately (sterile grains), but another vigorous flowers develope into parthenocarpic grains. Therefore, the fruiting ability will be able to be indicated with the relation between the number of fertilized grains and the number of flowers (fertilizing percentage), the rate of the blasted grains to fertilized grains in number (blasted percentage), the relation between the number of parthenocarpic grains and the one of unfertile grains (parthenocarpic percentage), and the average weight of the matured grains. (1) The flower disk was divided into outer, middle and inner parts, and the fruiting ability of each part was compared respectively. The tubular flowers on the outer part opened earlier and were more vigorous than those of the middle or inner part, therefore the unfertile percentage and the brasting percentage were lowest at the outer part and highest at the inner part. On the contrary, the parthenocarpic percentage was highest at the outer part and lowest at the inner part. The average weight of the matured grains was generally lightest at the inner part. (2) When some of the tubular flowers on the outer part were picked off at the flowering time, the remaining flowers became vigorous and the fruiting ability of those was invigorated, and the average weight of matured grains became heavy, then these influences were more remarkable in the inner flowers. (3) There was no remarkable difference in the growth habit of the sunflower plants at Nobeyama highland and Tokyo. Nevertheless, the blasted grains were considerably numerous and the average weight of the matured grains was smaller at highland. These may be due to the low temperature at the maturing stage in highland.