This study aimed to evaluate the effects of potassium fertilization on Myracrodruon urundeuva, Libidibia ferrea and Mimosa tenuiflora seedlings submitted to a short period of water deficit. Three doses of K (0, 150 and 300 mg dm-3 KCl) and three water regimes (without water deficit, moderate water deficit and severe water deficit) were evaluated. The plants were kept in black plastic bags containing soil from the Caatinga and, 30 days after the beginning of the water regimes, the relative water content (RWC), transpiration (E), stomatal conductance (gs) and photosynthesis (A) were evaluated. High moisture content in the soil was unfavorable to plants, promoting reduction in RWC and gas exchange. The water deficit increase E, gs and A, but the intensity of these responses was variable between species. The water deficit favored L. ferrea, with elevated RWC and reduced alterations in gas exchange, demonstrating its greater tolerance in relation to the others species evaluated, however it was the species most benefited by K. The supply of 300 mg dm-3 of KCl positively influenced the water status and gas exchange of the studied species with an increase in the water deficit. We suggest the development of research subjecting the plants to a longer period of time, in order to establish a better relationship between potassium and the increased tolerance of these plants to water deficit.
Este estudo teve como objetivo verificar os efeitos da baixa disponibilidade de água às plantas jovens de pereiro e o papel da adubação potássica na atenuação desses efeitos. Os tratamentos foram dispostos em delineamento inteiramente casualizado (DIC), distribuídos em esquema fatorial 3 x 3 sendo três níveis de água [100%cp (capacidade de pote) (controle), 50%cp (déficit moderado) e 25%cp (déficit severo)] e quatro doses de potássio (0, 50, 100 e 150 mg dm3 K), com quatro repetições. Foram avaliadas a condutância estomática (Gs), taxa de transpiração (E), fotossíntese (A), eficiência intrínseca no uso da água (A/Gs) e eficiência de carboxilação (A/Ci). Os parâmetros avaliados foram afetados negativamente pelo déficit hídrico, mas influenciados positivamente pelo potássio, com aumentos nos valores à medida que se aumentou a quantidade de KCl. As plantas mantidas em solo com umidade de 50%cp, apresentaram os melhores resultados, constituindo-se em uma possibilidade de economia de água durante a fase de produção das mudas de pereiro. Recomenda-se a adubação com 100 mg dm3 K e manutenção do substrato com 50%cp de umidade, por proporcionar maiores condutância estomática, taxa fotossintética e eficiência de carboxilação.
This work aimed to evaluate the physiological behavior and growth of jurema-preta seedlings under salinity conditions. The experiment was conducted at the Forestry Nursery of the Academic Unit of Forestry Engineering/UFCG, with the plants kept in 'Leonard' pots. The salinity treatments were distributed in a completely randomized design, with five levels of electrical conductivity (EC) of the nutrient solution (0.5; 2.0; 3.5; 5.0 and 6.5 dS m-1) and four repetitions. The salinization of the solution was achieved by adding a mixture of NaCl, CaCl2.2H2O and MgCl2.6H2O salts. There was a progressive decrease in plant height, stem diameter, relative growth rate, relative water content, stomatal conductance, transpiration rate, photosynthesis rate in the dry mass production of the plants as the EC of the solution increased. Transpiration was less sensitive to salinity than stomatal conductance and seedling photosynthesis. Among the growth parameters, the roots were the most affected by salinity.
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