Leaf Production and Growth Rates of Exotic Cottons1

Abstract

AbstractAn understanding of the growth and development of diverse nonflowering photoperiodic (long‐night) exotic cottons (Gossypium hirsutum L.) differing in traits associated with drought tolerance is needed before this material can be fully utilized in genetic selection programs. Therefore, glasshouse studies were conducted in 1980 to relate previously observed differences in dry matter production to differences in leaf morphology and development. Ten exotic and two commercial cotton lines were investigated at Lubbock; three of the exotic cottons were also grown in another study at Lubbock and at Temple, TX. Plants were grown in a commercial growing medium in the Lubbock experiments and in an Amarillo fine sandy loam soil (fine‐loamy, mixed, thermic, Aridic Paleustalfs) in the Temple experiment. The number of mainstem nodes was counted in the first experiment at Lubbock; in the second experiment the number of mainstem leaves was counted and harvested for dry weight, and total leaf number, total number of nodes, and total leaf area were recorded at 30,44,58,72, and 86 days after planting. Similar measurements were made at 44 and 56 days after planting at Temple. Leaf initiation rates varied significantly, from 0.35 to 0.29 leaves per day, among the exotic cottons in the first experiment, and significant differences occurred between the two locations. The development of leaf area, total dry matter accumulation, rate of dry matter production per unit leaf area, leaf size and total leaf number differed significantly among strains that had similar leaf initiation rates. Observed differences between greenhouse and field‐grown plants at Lubbock indicated a strong environmental influence on the relationships between the growth parameters. Leaf area was directly correlated with dry matter production for all strains. The development of and increase in leaf area, however, was strain‐specific and depended on either increased leaf numbers or increased leaf size.