Amounts and Kinds of Sugars in the Nectars of Cotton (Gossypium spp.) and the Time of Their Secretion1,2

Abstract

AbstractNectar of cotton (Gossypium spp.) attracts many beneficial as well as harmful insects. Variations in the amount or quality of this nectar influences the number of these insect visitors. This paper deals with the amount, source on the plant, time of exudation, and sugar content of nectar produced by G. barbadense L. and G. hirsutum L. in Arizona. The nectar was collected in micropipets and the percentage of various sugars determined by gas liquid chromatography (GLC).Leaf nectar on different plants, species, and dates varied from 0.70 to 19.00 µl/plant, sub‐bracteal nectar from 0.25 to 4.58 µl/flower, circumbracteal nectar from 0.22 to 2.00 µl/flower and floral nectar from 0.96 to 20.23 µl/flower. The concentration of fructose and glucose was greater than sucrose in the nectar from all sources. The volume of flower nectar in G. barbadense was five times that of G. hirsutum. The greatest amount of sugar in leaf nectar of G. barbadense was present at 0800 hours; in G. hirsutum at 1,100 hours. Fields of G. barbadense plants produced from 0.6 to 3.8 liters of nectar/ha/day. Some leaf nectar was secreted during the night.