Estresse salino no desenvolvimento de copo-de-leite

Abstract

Soil salinity is a problem in agricultural production, especially floriculture, being caused mainly by excessive use of fertilizers and use of inadequate water quality, mainly in crops grown in greenhouses. Salt stress inhibits plant growth by restricting the availability of water, causing morphological, structural, metabolic and physiological changes. This experiment aimed to evaluate the growth responses, ecophysiological, biochemical and anatomical in the early development of calla lily plants (Zantedeschia aethiopica (L.) Spreng) subjected to salt stress by NaCl. Rhizomes were cultivated in plastic trays with coconut fiber substrate and the treatments were 0; 25; 50; 75 and 100 mM NaCl manually applied through irrigation to induce salt stress, and evaluations carried out after 60 and 90 days. Were evaluated the growth parameters, photosynthesis, stomatal conductance, transpiration rate, relative chlorophyll content, amino acids, total protein, total soluble sugars, reducing sugars, non-reducing sugars and starch in addition to the anatomical features of leaves and roots. After 60 and 90 days was observed decrease in plant height. The number of tillers and leaves, main root length, fresh and dry weight of shoot and root system, water content of the root system, the relationship between the shoot/root system also reduced after 90 days of imposition of salt stress, causing a greater allocation of dry matter in the roots. The photosynthetic rate, stomatal conductance, transpiration rate and relative chlorophyll content after 60 days reduced with increasing concentration of NaCl. However, after 90 days, the photosynthetic rate was unchanged, with increased stomatal conductance, the transpiration rate, besides the chlorophyll content of plants exposed to 75 mM NaCl as compared to the control treatment. The salt stress caused higher accumulation of total amino acids in the leaves in 50 mM NaCl, however, this concentration the total amino acids levels decreased in the roots. In the shoot, there was an increase in the levels of total protein and carbohydrates and roots increased carbohydrate content. Analyzing the anatomical characteristics it was reducing the polar diameter, equatorial and the relationship between DP/DE of the stomata, however, there was an increase in stomatal density due to increas ed salinity. In general, higher concentrations of NaCl affected the development of calla lily in all parameters, indicating that this species is susceptible to salt stress.