Morphological and physiological responses and drought resistance enhancement of ornamental shrubs by trinexapac-ethyl application

Abstract

Irrigation water shortage and restricted water access is considered as one of the major constrains on the development of the horticultural crops industry, hence developing water-wise cultivation strategies in horticultural crops became vital. In this study we aimed to evaluate the morphological and physiological effects of trinexapac-ethyl (TE) foliar sprays and/or four irrigation levels of 100, 70, 50, and 25% of container capacity on the ornamental shrubs of Spirea nipponica, Pittosporum eugenioides, and Viburnum nadum to simulate restricted water access conditions. Deficit irrigation levels significantly reduced leaf number and area, plant dry weight, root dry weight, plant height, photosynthetic rate, stomatal conductance, transpiration rate, leaf midday water potential and relative water content and the evapotranspiration rate in the three species. Compared with untreated plants, under well-watering conditions, there were reduction in root dry weight following TE sprays but these sprays had no effect on root dry weight in S. nipponica. Also, TE sprays during water stress conditions significantly enhanced shrubs tolerance to the imposed drought by improving morphological and physiological parameters in the three species in a proportional manner. The biweekly applications of 0.2Lha−1 in S. nipponica and 0.3Lha−1 in P. eugenioides, and V. nadum were sufficient for enhancing stress tolerance and maintaining quality under moderate drought conditions. The favorable effects of TE on ornamental shrubs stress responses could be linked to the maintenance of the photosynthetic rate, stomatal closure, suppressing vertical growth and adjustment of water potential.