Abstract
Abstract: The objective of this work was to assess the morphophysiological characteristics and the ionic imbalance in the substrate, roots, and leaves of young oil palm (Elaeis guineensis) plants under different levels of saline stress, following a substrate salinization protocol in which the level of salt was known. Bifid oil palm plants were subjected to different NaCl rates (0.0, 0.5, 1.0, 1.5, and 2.0 g NaCl per 100 g substrate on a dry basis), and their morphophysiological responses were evaluated for a period of 12-14 days. This protocol generated different levels of stress due to the gradients of electrical conductivity and water potential in the saturation extract of the substrate, according to the added NaCl. Based on the rates of real evapotranspiration and leaf gas exchange, the osmotic effect of the salt reflected negatively on leaf temperature, on the chlorophyll content index, and on the chlorophyll fluorescence variables. The increase in Na and Cl levels in the saturation extract culminated with the increasing availability of Ca, K, and Mg in the solution and their accumulation in the leaves. However, the plants poorly absorbed Na and Cl. The obtained results are indicative that, for a better characterization of the osmotic and ionic phases of salinity stress, it is necessary to reduce the applied level of salinity stress and to increase the evaluation period.
Highlights
Oil palm (Elaeis guineensis Jacq.), a monocotyledon crop originated from the eastern part of the African continent, is a highly important commercial source of vegetable oil (Bakoumé et al, 2015)
The values obtained for both variables were proportional to the salt rate added to the substrate, implying that oil palm plants subjected to the same rate were exposed to the same levels of electrical conductivity (EC) and ψw throughout the experiments
Fo; the latter variable suffered a drop at the maximum salt rate of 2.0 g and on the fourteenth day of stress. These results suggest that, with chlorophyll degradation, which occurred in the young oil palm plants due to saline stress, the chloroplasts lost part of the antenna structure responsible for capturing light energy
Summary
Oil palm (Elaeis guineensis Jacq.), a monocotyledon crop originated from the eastern part of the African continent, is a highly important commercial source of vegetable oil (Bakoumé et al, 2015). In the 2017/2018 harvest season, it once again ranked first among the crops used for vegetable oil production, totalizing 70 million tons or 37% of all consumed vegetable oil worldwide (Statista, 2018). Of the approximately 200,000 ha cultivated with the species, only about 60% were harvested that year (Diagnóstico..., 2018; IBGE, 2019) This is considered a small area to meet the demands for palm oil in Brazil, which are increasing every year due to the government programs that encourage the use of the biodiesel derived from the crop to fuel the national fleet of trucks and buses (Programa de Produção Sustentável de Óleo de Palma no Brasil, 2010; Carvalho, 2015)
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