Morphophysiological changes by mepiquat chloride application in Eucalyptus clones

Abstract

First study of mepiquat chloride as a growth regulator in Eucalyptus. Application of mepiquat chloride in Eucalyptus clones at planting may promote drought resistance. The reduction of available areas has pushed Eucalyptus away to marginal areas with low water availability. Management practices such as the application of growth retardants may have potential to modify plant morphological and physiological features, increasing their drought tolerance. Trying to understand the drought tolerance mechanisms of Eucalyptus clones, the objective of this work was to evaluate the effects of different mepiquat chloride (MC) concentrations to Eucalyptus clones on morphological and physiological changes. Commercial clones of E. grandis × E. urophylla hybrid were planted in 20 L pots in a complete randomized block design with eight replications and four treatments. The treatments consisted of three concentrations of MC: 250, 500 and 1000 mg L−1 of MC. The control treatment consisted of a non-MC application (0 mg L−1 of MC). Evaluations of morphological and physiological parameters were carried out for 35 days after the MC application. Results indicated morphophysiological changes after the MC application. Eucalyptus clones increased root dry mass (RDM), total dry mass (TDM), number of leaves and secondary branches, and decreased height. MC application modified the physiological plant system improving intrinsic water use efficiency (WUEi) and SPAD index, and decreasing transpiration rates (E) and stomatal conductance (gs). RDM, TDM, E, WUEi and SPAD index improved when 250 and 500 mg L−1 MC concentration were applied. Our results suggest that MC application may promote drought resistance to Eucalyptus clones.