Jatropha curcas L. (Euphorbiaceae) is a species grown in tropicalcountries and used for biodiesel production. Morphophysiological traits were analyzed to assess the genetic diversity in nine genotypes of J. curcas under deficit water. Seeds of plants from different populations, collected in diferente brazilian regions, were grown under two water regimes (100% and 50% tank capacity). Multivariate analysis was used to characterize genetic diversity. The UPGMA dendrogram built from the genetic distance group indicated the segregation of genotypes into five groups for growth traits and six groups for physiological traits. Then, an principal components analysis was carried out, to evaluate the pattern of character variations and then segregate the characteristics that could distinguish parental genotypes for use in plant breeding. Results showed 65.50% and 56.02% for the two first principal components of growth and physiological traits, respectively. Total root area was the most determining trait for genetic dissimilarity (18.9%) and group formation, followed by plant height (17.9%) and number of leaves (17.6%). On the other hand, stomatal conductance (gs) (24.9%) and guaiacol peroxidase (GPX) (20.9%) were the most determining physiological traits. The analysis of morphophysiological traits indicated CNPAE-298 and 299 as the most distant genotypes among the plant groups. Under water-limited conditions, total root area, plant height, gs and GPX were the most efficient traits to explain genetic dissimilarity among the genotypes, and for this reason they should be referred as a priority for further studies on genotypes selection in this species.

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Background and Aims Water restriction significantly affects the growth and survival of young plants following transplantation. Although silicon (Si) is not typically considered essential for plants, it can help mitigate abiotic stresses. We hypothesized that Si application in plants, depending on how it is applied, can improve the tolerance to water restriction. The objective was to investigate how applying Si to the leaves and roots of young Eucalyptus urophylla plants can mitigate water restriction effects. Methods A greenhouse experiment was conducted with one factor consisting of three Si application methods (via root substrate, foliar spray, and a combination of both) and a control group with no Si; the other factor involved well-watered and water-deficit irrigation regimes, based on 90% and 30% pot capacity, respectively. Results Silicon application improved the plant’s tolerance to water restriction by maintaining stable cell turgor and increasing intrinsic water use efficiency. Silicon also helped to reduce stomatal conductance and water losses through transpiration, which prevented a decline in CO2 assimilation and promoted osmoregulation. It also prevented a decrease in chlorophyll content and attenuated oxidative stress, by increasing superoxide dismutase and guaiacol peroxidase activity, which contributed to preventing an increase in lipid peroxidation and electrolyte leakage. The effectiveness of Si supply was higher when applied through the roots or a combination of roots and leaves compared to foliar spray alone. Conclusion These findings suggest that Si application can be a useful strategy for improving plant tolerance to water restriction, particularly when applied through the roots.

This study aimed to evaluate the effect of cattle manure on young plants of Khaya senegalensis submitted to different irrigation intervals. A greenhouse experiment was carried out during 2017 cold season, based in a 5x3 factorial arrangement – cattle manure fertilizing with 0, 10, 20, 30 and 40% doses, and 3-day, 6-day and 12-day irrigation intervals. Water potential, relative water content (RWC), water consumption (WC), water use efficiency (WUE), chlorophyll content estimation (SPAD index), plant height, stem diameter, plant total dry mass and free amino acid and proline content were measured. Irrigation intervals had no significant effect on physiological traits and plant water relationships, except for WUE, which was higher under 12-day irrigation interval. This was assumed as an indication of non-occurrence of water stress, even under the longest irrigation interval. Cattle manure, in turn, played a significant effect on these traits, except for water potential, irrespective of irrigation intervals. Increasing cattle manure doses improved RWC (just doses up to 20%), reduced WC and increased WUE, SPAD index, and both free amino acid and proline contents. On the other hand, growth-related parameters were not affected by cattle manure, but a significant effect of irrigation intervals was observed. Both plant height and total dry mass were lower under 3-day and 6-day irrigation intervals. We suspect a possibly low evapotranspiration, given the relatively low temperatures of that season (14-16 ºC), which may have reduced the demand for irrigation in the experimental period. Thus, soil moisture under the shorter irrigation intervals may have increased until reach to a close to saturation level, limiting the amount of soil oxygen and hampers nutrient uptake.