Use of growth retardants in wheat

Abstract

-In general, lodging has been controlled by restricting nitrogen fertilizer application and/or using short cultivars. Growth retardants can also be used to solve this problem.The objective of this study was to evaluate the effect of rates and application times of three growth retardants on Pioneiro wheat cultivar. The trial was carried out in Viçosa-MG, from May to September 2005, in a factorial and hierarchical scheme, in a randomized block design with four replications and a control treatment. The treatments consisted of 500, 1,000 and 1,500 g ha -1 of chlormequat; 62.5, 125 and 187.5 g ha -1 of trinexapacethyl and 40, 80 and 120 g ha -1 of paclobutrazol applied at growth stages 6 or 8, growth stage used on the scale of Feeks and Large, and a control treatment without growth retardant application. Only trinexapac-ethyl and chlormequat were efficient in reducing plant height; the effect of chlormequat and paclobutrazol on plant height was independent of the application time, but the trinexapac-ethyl at growth stage 8 produced shorter plant height than at stage 6. Increasing growth retardant rates produced shorter plant heights; chlormequat and paclobutrazol did not affect grain yield. However, the highest trinexapac-ethyl rates reduced wheat yield.

Selectivity of the plant growth regulators trinexapac-ethyl and sulfometuron-methyl to cultivated species

“…This has been used to reduce plant lodging (MAPA, 2011b;Espindula et al, 2009;Zagonel and Fernandes, 2007). This effect is explained by the trinexapac action on the synthesis of gibberellins, starting from the GA 12 aldehyde which, among other functions, is responsible for cell elongation (Caldas et al, 2009;Dalley and Richard Junior, 2010;Rademacher, 2000).…”

Rates of nitrogen and growth retardant trinexapac-ethyl on wheat

“…These results occurred because at lower N rates, the increase in retardant rates causes a decrease in leaf area and hence in the amount of photosynthates which compromises grain filling (ESPINDULA et al, 2009a). However, at higher N rates, the trinexapac-ethyl reduces lodging and increases the use of environmental resources, as a consequence of morphological changes in the canopy architecture of the plants (ZAGONEL & FERNANDES, 2007;ESPINDULA et al, 2009b).…”

“…practice changes structural and vital processes by altering the plant hormonal balance, aiming to increase production, improve quality or facilitate harvest (MATEUS et al, 2004). Among growth retardant, trinexapac-ethyl has been recently released in Brazil and studied in wheat (T. aestivum L.) (ESPINDULA et al, 2009b;ESPINDULA et al, 2010b;SOUZA, et al, 2010), rice (Oryza sativa L.) (ALVAREZ et al, 2007), soybean (Glycine max L.) (LINZMEYER JUNIOR et al, 2008), sugarcane (Saccharum sp L.) (LEITE et al, 2008, VIANA et al, 2008, among other crops. This compound is an acyl-cyclohexanedione derivative that inhibits 2-oxoglutarate-dependent dioxygenases in step 3 of gibberellin biosynthesis (SRIVASTAVA, 2002).…”

Growth retardants in wheat and its effect in physiological quality of seeds

“…These effects can change assimilate partition, improving seed filling and, consequently, the physiological quality of seeds (SAWAN et al, 2009). However, high doses of these products may promote excessive shoot reduction (ESPINDULA et al, 2009b) and spike retention (ZAGONEL & FERNANDES, 2007) Ciência Rural, v.40, n.6, jun, 2010. levels in wheat seeds (RADEMACHER, 2000) and act on other metabolic pathways (HECKMAN et al, 2002, HAJIHASHEMI et al, 2007 promoting effects still not clear on plant development. Thus, it is believed that the effect of retardants on plant growth and development can reflect changes in the physiological quality of wheat seeds.…”

“…This reduction in leaf area can reduce the plant photosynthetic area, while the reduction in stem mass can reduce the amount of reserves accumulated for translocation at seed filling (ESPINDULA et al, 2009b). On the other hand, growth retardants may cause morphological changes when reducing plant height, providing them with more suitable architecture for utilizing the environmental resources (ZAGONEL & FERNANDES, 2007).…”