Effect of Temperature and Methyl Parathion on Vegetative Development and Fruiting of the Cotton Plant1

Abstract

AbstractIn the northern areas of the Cotton Belt, suboptimum temperatures are rather common during the very early stages of growth and during the latter stages of boll development of cotton (Gossypium hirsutum). The effects of low temperature on boll development have been well defined, but little is known of the early season effects on plant fruiting and development. Thus, the purpose of this research was to determine how temperature influences early fruiting and vegetative development in cotton and to what extent the action of a chemical known to effect fruiting may be modified by temperature. Two diverse cotton cultivars, ‘Gregg 35’ and ‘Deltapine 16,’ were grown in field growth chambers under night temperature regimes of 10, 15, 20, and 25 C from the day of seedling emergence until frost. Methyl parathion was sprayed on half the plants of each cultivar at 10, 12, and 13 days after planting to assess the temperature chemical interaction. The observed effects, in the order of their magnitude were temperature > cultivar > chemical. Temperature‐cuitivar and temperature‐chemical effects were apparent in some cases. Earliness of fruiting as measured by days from emergence to first square, and bloom was most timely at 20 and 25 C. As temperature decreased below 20 C, however, there was a marked increase in both days to first square and days to first bloom. Nodal positions of first squares and blooms were essentially the same at 15 and 20 C, but either a reduction to 10 C or an increase to 25 C resulted in a significantly higher nodal position of these forms. The total number of limbs per plant was relatively constant across cultivars and treatments, but the ratio changed between vegetative and fruiting limbs. At 10 and 25 C the number of vegetative limbs increased at the expense of fruiting limbs. Number of bolls per plant and seed cotton yield were drastically retarded at 10 C for both cultivars. Maximum boll production was achieved at 15 C for Gregg and 20 C for Deltapine. Maximum yields were attained for both cuitivars at 20 and 25 C.