Morphophysiological and biochemical changes in seedlings of Enterolobium contortisiliquum (VELL.) morong. under abiotic stresses

Abstract

Among the native species of the Caatinga,Enterolobium contortisiliquum(Vell.) Morong stands out as a fast-growing tree species with multiple purposes such as medicinal application, recovery of degraded areas, boat manufacturing, furniture and crates in general. The objective of this study was to evaluate the morphophysiological and biochemical changes in E. contortisiliquumseedlings subjected to abiotic stresses. The experience was carried out at the Academic Unit Specialized in Agrarian Sciences (UAECIA), belonging to the Federal University of Rio Grande do Norte (UFRN), Macaíba,RN -Brazil, in the first half of 2019.Water stress was established by watering suspensions of 0, 4, 8, 12 and 16 days, while salt stress was simulated at the following electrical conductivities of irrigation water (ECw): 0.3 (control), 2, 4, 6 and 8 dS.m-1. Prior tosowing, the pre-germination treatment of dormancy overcoming was performed with a sandpaper, removing part of the seed coat in the region opposite to the hilum. Substrate consisted of the mixture of common earth and aged bovine manure (1:1). The evaluated variables for water and salt stresses were: plant height, number of leaves, leaf area, stem diameter, root length, Dickson quality index, ratio between height and shoot dry mass, shoot dry mass, root dry mass and total dry mass, as well as biochemical tests (total free amino acids, proline, total soluble sugars and starch).The four-day period of water stress promotes E. contortisiliquumseedlings with better drought tolerance capacity. Osmotically active solutes act positively to minimize thedamage caused by increased water stress, whose mechanisms may be the main determinants used by plants under this condition. The gradual increase in irrigation water salinity was detrimental to the growth and dry mass accumulation of E. contortisiliquumplants, with a sharp decrease from the threshold of 2 dS.m-1. The biochemical mechanism of tolerance to salt stress was the increase of amino acids, proline and total sugars, concomitantly with the consumption of starch reserves