Partitioning of Biomass in Well‐Watered and Water‐Stressed Cotton Plants Treated with Mepiquat Chloride

Abstract

Most of the research investigating the effect of mepiquat chloride (1,1‐dimethylpiperidinium chloride) on the growth of cotton (Gossypium hirsutum L.) has been limited to well‐irrigated plants and has been focused primarily on the growth of aboveground organs. This study was conducted to evaluate the effect of mepiquat chloride (MC) on the partitioning of biomass in whole cotton plants grown in controlled‐environment test chambers under well‐irrigated and water‐deficient conditions. Single plants of ‘Stoneville 825’ were transferred from a nursery room into test chambers when they reached a leaf area of ≈500 cm2 and were then exposed to the following treatments: (i) sprayed at a recommended rate for commercial crops with 12 ± 1 mL plant−1 of a MC solution (27.3 mg L−1 a.i.) and maintained well irrigated, (ii) not sprayed with MC and maintained well irrigated, (iii) sprayed with MC and not irrigated, and (iv) not sprayed with MC and not irrigated. Durations of experiments varied from 11 to 14 d. Tests were replicated four times. Environmental conditions in the test chambers were typical of sunny and humid summer days in central Texas. Leaf area was measured daily during the tests. At the end of each test, the plants were harvested and separated into various categories of plant organs, oven‐dried and weighed. Water deficits inhibited the accumulation of plant biomass through inhibition of leaf lamina, petiole, and branch growth. The MC, on the other hand, did not affect the accumulation of biomass on a whole‐plant basis, but did affect biomass partitioning by inhibiting growth of branches and stem and by promoting growth of fine roots; MC also inhibited expansion of leaves and extension of stem internodes and petioles, which led to the development of a more compact canopy structure. These effects of MC on biomass partitioning and size of plant organs may result in decreased plant photosynthesis rates, but also may induce a water‐conservative behavior.