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Temperature and mepiquat chloride effects on cotton canopy architecture

Reddy, V.R., Baker, D.N., Hodges, H.F.
Agronomy journal 1990 v.82 no.2 pp. 190-195
height, plant characteristics, Gossypium hirsutum, growth retardation, temperature, leaf area, density, canopy, stem elongation, mepiquat
Cotton, (Gossypium hirsutum L.) when grown in a fertile, wellwatered, and suitable environment, produces excessive vegetative growth. Such luxuriant growth causes several production problems. A plant growth regulator, mepiquat chloride (1,1-dimethylpiperidinium cloride; BASF Wyandotte Corp, Parsippany, NJ) has been found to reduce vegetative growth, but the crop responses to it appears to be temperature sensitive. An experiment was conducted to determine the crop responses to temperature in naturally lighted, temperature- and CO2-controlled plant growth chambers. The experiment was conducted at five temperatures and measurements were made of several plant parameters. A preliminary experiment showed that mepiquat chloride (MC) caused a dramatic reduction in plant height and number of main-stem nodes. A more detailed study showed that the impact of MC on main-stem elongation was temperature dependent, with the greatest effect occurring at 35/25 degrees C day/night temperatures. The application of MC also caused a reduction in mainstem, vegetative-branch and fruiting-branch node formation. Leaf area was reduced on plants treated with MC at each of the temperatures. Specific leaf area (m2 kg-1) was also reduced on leaves from various positions on the plants. It appears that MC affects more than one physiological process. The primary effects were reduction in stem elongation, node formation, and leaf expansion. The reduced stem growth and leaf area development also caused greater leaf densities-probably a secondary or tertiary effect.