Effect of Leaf Shape and Plant Population on Rate of Fruiting Position Appearance in Cotton 1

Rate of appearance of fruiting positions in cotton (Gossypium hirsutum L.) is an important component of earliness. The objective of this research was to evaluate the influence of leaf type (size) and population density rate of fruiting position appearance along branches of individual plants. Normal, okra, and superokra leaf cotton plants were grown in rows 51 cm apart in irrigated basins at 11.2 and 18.5 plants/m² in 1973, and 10.0 and 20.0 plants/m² in 1974. Fruiting positions reaching anthesis were tagged daily. Rate of appearance was determined by observing the number of days between successive fruiting branches (sympodial plastochron) and the number of days between first fruiting positions of successive fruiting branches (monopodial plastochron). Plants grown in high population densities generally had larger sympodial and monopodial plastochrons (longer time intervals between appearance of fruiting positions) than plants in the low population. Okra and superokra plants had smaller monopodial plastochron and larger ratios of sympodial to monopodial plastochrons than normal leaf plants. Sympodial plastochron, increased from early to mid-season and then declined. Monopodial plastochrons increased from early season to plateau values at mid-season. The seasonal changes in plasto-chrons did not appear to be related to changes in temperature. This study shows that both leaf type and population density affect rate of fruiting position appearance and earliness in cotton but changes in temperature found in fields may have little effect on plastochrons.