Abstract

Peanut (Arachis hypogaea L.) cultivars differ in growth habit and potential for vegetative and reproductive growth modification with plant growth regulators (PGRs). Cultivars differing in growth habit were studied in light, dark, and field environments in 1982 and 1983 to assess the effects of two PGRs on apparent assimilate partitioning, and on vegetative and reproductive growth. The cultivars used were Dixie Runner (indeterminate spreading type), Florunner (somewhat determinate spreading type), and Pronto (bunch type). The PGR foliar spray treatments were gibberellic acid (GA), a growth stimulant, and daminozide (DA) (Kylar), a growth retardant. The field-study treatments included Dixie Runner and Florunner, and GA and DA in one and two applications, beginning at pod initiation. Gibberellic acid (0.01 or 0.1 g L⁻¹) increased stem petiole elongation in the light, dark, and field environments. Dixie Runner in most comparisons was slightly less responsive to GA than was Florunner. Daminozide (0.5 g L⁻¹) retarded main-stem, cotyledonary-branch, and petiole elongation in both cultivars in light and dark environments. Response to a mixture (l:l,v/v) of GA and DA was similar to the water control in most comparisons. Darkness stimulated greater stem elongation than did GA; the two effects were additive. Daminozide decreased leaf area and shoot/root ratio, and increased chlorophyll concentration on a leaf-area basis. Effects of PGR treatments were similar for Dixie Runner and Florunner. It is concluded that cultivars diverse in growth habit respond similarly to GA and DA, and modification of vegetative growth by PGRs to alter assimilate partitioning and fruiting appears problematic.

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