Interaction of Hormone and Photoperiod in an Early Variety of Rice

Abstract

THE interaction of hormone and photoperiod has been studied in cocklebur1–5, Biloxi soybean5 and Orchad grass6. In the present investigation the effect of the hormones in relation to photoperiodism has been studied in an early variety of rice, N136, which has been found to be intermediate in its photoperiodic behaviour7. Graded seeds of this pure strain were soaked on December 10, 1956, with 500 p.p.m. of the three plant-growth substances, β-indolylacetic acid (IAA), α-naphthylacetic acid (NAA) and 2,3,5-tri-iodobenzoic acid (TIBA), for 72 hr., a treatment which was found to be effective in earlier studies8,9. The grains were next thoroughly washed in water and sown in earthenware pots containing a mixture of loamy garden soil and cow-dung manure. The pots were divided into two series. In series 1 the plants simply grew after the initial hormone seed-treatment. In series 2 the plants also received an 8-hr, photoperiod (6 a.m.–2 p.m.) from the twenty-first day until panicle emergence. Two other series of unsoaked seeds were used. In series 3 the plants were given the short photoperiod as in series 2. In series 4, plants remained as untreated controls. The results are shown in Tables 1 and 2.