Estresse salino in vitro e silício nas características fisiológicas de physalis

Abstract

This study aimed at evaluating the effect of salt stress NaCl-induced and silicon (Si) application as mitigating element of stress on the physiological characteristics of physalis. Furthermore, we also evaluated the effect of Si in physalis grown in greenhouse. Studies carried out on in vitro conditions began with a preliminary study about the sensitivity of physalis to salinity and thus, two types of explants were cultured on MS medium with increasing concentrations of NaCl (0, 0.5, 1.0, 1.5 and 2.0%). After 30 days, we evaluated growth and esterase expression of plants. We continued with salt stress studies, but with Si on culture medium. For this, nodal segments were innoculated in MS medium with salt (0.5 and 1.0% NaCl) with different Si concentrations (0, 0.5 and 1.0 g L-1). Growth, photosynthetic pigments content, gas exchange, electrolyte leakage, leaf anatomy, isozyme expression, proline content, CO2 content and biological activity were evaluated after 30 days. In the preliminary study, it was observed that the number of buds and shoot length decreased and esterase enzyme increased its expression with increasing NaCl concentration. All growth variables and the contents of photosynthetic pigments as well as photosynthesis and electrolyte leakage were impaired with increased salt level. The DNA content was not affected by any of the factors. There was a reduction in stomatal density and greater thickness of the leaf blade with increase of NaCl percentage. All enzymes tended to increase its expression with increasing salt concentration. The proline and CO2 levels increased and biological activity of the leaves was higher with increase in salt concentration. The Si was significantly effective only in mitigating the damage to pigments and anatomical variables, as well as in superoxide dismutase, esterase and malate dehydrogenase enzymes and respiratory rate (CO2 content). To conduct the study in the greenhouse, we carried out the application of Si (0.0, 1.0, 2.0, 3.0 and 4.0 g kg substrate-1) and after 60 days we evaluated the amount leaf Si, estimation of chlorophyll content via SPAD index, gas exchange, lignin content and expression of polyphenoloxidase. The results of greenhouse experiment showed that the application of different Si doses did not affect the leaf Si content, but there was a higher content of element in the old leaves. Consequently, the measured physiological characteristics suffered no effect. Physalis presents a Si non-accumulator species behavior.