Substituição parcial de K por Na reduz o estresse por seca e incrementa a eficiência de uso de água em mudas de espécies de Eucalyptus

• Processo: 21/00463-7
• Modalidade de apoio: Auxílio à Pesquisa - Publicações científicas - Artigo
• Data de Início da vigência: 01 de fevereiro de 2021
• Data de Término da vigência: 31 de julho de 2021
• Área do conhecimento: Ciências Agrárias - Agronomia - Ciência do Solo
• Pesquisador responsável: José Lavres Junior
• Beneficiário: José Lavres Junior
• Instituição Sede: Centro de Energia Nuclear na Agricultura (CENA). Universidade de São Paulo (USP). Piracicaba , SP, Brasil
• Palavra(s)-Chave do Pesquisador: drought | photosynthesis | sodium application | stable carbon isotope | water consumption | water use efficiency | Fisiologia nutricional de plantas

Resumo

Eucalyptus, the most widely planted tree genus worldwide, is frequently cultivated in soils with low water and nutrient availability.Sodium (Na) can substitute some physiological functions of potassium (K), directly influencing the plants' water status. However, the extent to which K can be replaced by Na in drought conditions remains poorly understood. A greenhouse experiment was conducted with three Eucalyptus genotypes under two water conditions (well-watered and water-stressed) and five combination rates of K and Na, representing a20 substitution of 0/100, 25/75, 50/50, 75/25, and 100/0 (% of Na/% of K), to investigate growth and photosynthesis-related parameters. This study focused on the positive effects of Na supply, since depending on levels applied, the Na supply may induce plants to salinity stress (>100 mM of NaCl). Plants supplied with low to intermediate K replacement by Na reduced the critical level of K without showing symptoms of K deficiency and providing higher total dry matter (TDM) than those Eucalyptus seedlings supplied only with K in both water conditions. Those plants supplied with low to intermediate K replacement by Na had improved CO2 assimilation (A), stomatal density (Std), K use efficiency (UEK), and water use efficiency (WUE), in addition to reduced leaf water potential (¨w) and maintained leaf turgidity, with stomata partially closed, indicated by the higher values of leaf carbon isotope composition (´13 26 C 0). Meanwhile, combination rates higher than 50% of K replacement by Na led to K deficient plants, characterized by lower values of TDM, ´13C, WUE, leaf K concentration, and higher leaf Na concentration. There was positive evidence of partial replacement of K by Na in Eucalyptus seedlings, meanwhile the ideal percentage of substitution increased according to the drought tolerance of the species (E. saligna < E. urophylla < E. camaldulensis). (AU)