Physiological responses of Triplaris gardneriana Wedd. seedlings (Polygonaceae) under intermittent drought

Abstract

Triplaris gardneriana Wedd is a deciduous riparian tree occurring in areas with different climatic conditions in Brazil, from the rainforest to the tropical dry forest. An increase in global temperature and drought events can change the growth pattern and establishment of the species. To evaluate the effects of intermittent drought on the growth of T. gardneriana seedlings, an experiment was performed using seedlings with one month old subjected to three water treatments (daily irrigation as control, and intermittent drought through cycles of water suppression of seven (S7) and 14 days-intervals (S14) between watering. Growth, biomass production and partitioning, relative water content (RWC), the accumulation of organic solutes, protoplasmic integrity and phenotypic plasticity index (PPI) were evaluated for a better understanding about its drought tolerance level. Intermittent drought severely affected plants growth in S14 plants, showing lower plant height, number of leaves, leaf area, and dry biomass. RWC was reduced, while carbohydrates and proline contents increased in response to drought stress. Protoplasmic damage increased electrolyte leakage in plants subjected to severe stress. However, T. garderiana demonstrated moderate tolerance to water deficit. The plastic changes observed were more physiological than morphological.  Therefore, T. gardneriana seems to be a moderately tolerant species to intermittent drought.