Morpho-physiological adaptation of Jatropha curcas L. to salinity stress

Abstract

The aim of the current study is to assess the growth response, biochemical changes, photosynthetic pigments content and gas exchanges of physic nut (Jatropha curcas) grown under natural saline conditions. The experiment was arranged in a completely randomized design based on the following soil electrical conductivities: 0.29 dS.m -1 (control), 1.76 dS.m -1 (moderate salt concentration), 2.61 dS.m -1 (high salt concentration), 3.79 dS.m -1 (very high salt concentration). Physic nut plants were kept under saline conditions for 19 days in greenhouse. Plant growth analyses were performed on a weekly basis. Plant biomass allocation was quantified at the end of the experiment. Leaf gas exchange, stomatal conductance, Fv/Fm and quantum yield were quantified 102 days after planting. Photosynthetic pigments, amino acids, proline and carbohydrates in fresh leaf tissue were also quantified. The leaf antioxidant enzymes catalase (CAT) and ascorbate peroxidase (APX) were quantified. Although there was no alteration in biomass allocation, the initial growth of J. curcas was gradually reduced by increasing salt concentration, which was observed through reduced plant height, stem diameter, and total number of leaves. Soil electrical conductivity 3.79 dS.m -1 was lethal to seedlings. Seedlings exposed to salt stress had their photosynthesis, stomatal conductance, transpiration and effective photochemical efficiency reduced, and their catalase and ascorbate peroxidase enzyme activity increased. Amino acids, proline and carbohydrate concentrations increased due to salt stress, whereas there was decrease in the chlorophyll content. J. curcas is sensitive to soil salinity at electrical conductivity levels higher than 1.76 dS.m -1 . To some extent, salinity effects can be relieved by osmolyte accumulation and by greater antioxidant activity; however, these factors were not sufficient to keep plant growth within normal rates.

Photosynthetic performance in Eucalyptus clones cultivated in saline soil

“…Bhargava et al (2014) and Sixto et al (2016), in working with Eucalyptus under salt stress, observed that the salinity promoted the reduction of gas exchange in plants. In a similar way, studies done with Anacardium occidental (Bezerra et al, 2003), Ricinus communis L. (Pinheiro et al, 2008), and Jatropha curcas L. (Cavalcante et al, 2018) cultivated in saline soil have also confirmed that gas exchanges are negatively affected by salinity, as observed among Eucalyptus clones.…”

“…Reductions in gas exchange, caused by salt stress, contributed to reduction in biomass production, which can be confirmed by the correlations of gs, A and A/Ci with the TDM, in the largest salt concentrations. Indeed, biomass production is reduced as a consequence of less CO 2 assimilation, as has been verified also in Eucalyptus plants (Sixto et al 2016) and in Jatropha curcas L. (Cavalcante et al 2018) under salt stress.…”

“…In a study with barley cultivars under saline conditions, the Fv/Fm ratio decreased with increasing salinity, with lower intensity in the more tolerant cultivar (Kalaji et al, 2011), also found in Jatropha curcas in which soil salinity reduced Fv/Fm, especially in the hottest hours of the day (Cavalcante et al, 2018). In this sense, the maximum photochemical efficiency of PSII is quite efficient as an indicator of disturbances in the photosynthetic apparatus caused by soil salinity (Kalaji et al, 2011;Cavalcante et al, 2018), since low values of Fv/Fm are considered a stress sensitivity response (Sá et al, 2018).…”

“…In different Eucalyptus genotypes cultivated in saline solutions presenting an electrical conductivity (EC) of 7 dS m -1 to 14 dS m -1 , decrease in photosynthesis, stomatal conductance, and biomass production were found (Sixto et al 2016), while higher salt concentrations (EC 20 dS m -1 to 40 dS m -1 ) were lethal to the plants (Bhargava et al, 2014). Other studies involving different species such as Ricinus communis L. (Pinheiro et al, 2008) and Jatropha curcas L. (Cavalcante et al, 2018) also found reductions due to salinity of stomatal conductance, photosynthesis, photosynthetic pigments, maximum photochemical efficiency of photosystem II, and total dry matter.…”

Germination and morphophysiology of passion fruit seedlings under salt water irrigation1

“…Passion fruit is highly sensitive to salinity (Dias et al 2011), which affects the plant photosynthetic apparatus. This effect can be interpreted by the maximum quantum efficiency of the photosystem II, through the Fv/Fm ratio, or by damage to photosynthetic pigments, assessed via the chlorophyll content (SPAD) index (Freire et al 2014), thus decreasing seedling growth and dry weight yield (Bezerra et al 2016, Cavalcante et al 2018.…”