A leucena é uma espécie florestal que proporciona forragem de boa qualidade e, pode ser utilizada como adubo verde, porém, suas sementes apresentam dormência causada pela impermeabilidade do tegumento à água, provocando redução na germinação, o que dificulta a produção de mudas. O objetivo deste trabalho foi avaliar a superação de dormência em sementes de leucena por métodos físicos e químicos. O delineamento experimental foi o inteiramente casualizado com quatro repetições composto por 20 sementes em cada tratamento. Utilizou-se como tratamentos químicos a imersão das sementes em ácido sulfúrico concentrado durante 1, 2, 4, 6, 8 e 10 minutos. Os tratamentos físicos usados foram o desponte (corte com estilete em lado oposto à micrópila), a escarificação com lixa d'agua nº 80 e a escarificação com lixa d’agua nº 100 (nestes dois últimos tratamentos lixou-se a semente em lado oposto à micrópila), tendo também o tratamento testemunha (sem intervenção). Avaliou-se o índice de velocidade de germinação, tempo médio de germinação, percentagem de germinação por um período de 10 dias após o semeio, altura de plântula, comprimento da raiz, diâmetro do caule, matéria fresca e seca da parte aérea e matéria fresca e seca da raiz. O método mais adequado para superar a dormência em sementes de leucena é o uso da escarificação com lixa d’água nº 100.

This study was conducted to evaluate the gas exchange, growth, and quality of passion fruit cultivars under irrigation with waters of different salinity levels. The experiment was conducted in a greenhouse, in Pombal-PB, Brazil, using a randomized block design in a 5 ? 2 factorial arrangement, with five levels of electrical conductivity of irrigation water (0.3, 1.1, 1.9, 2.7, and 3.5 dS m-1) and two passion fruit cultivars (BRS Sol do Cerrado and Guinezinho), with three plants per plot and four replicates. The reduction in transpiration, intercellular CO2 concentration and CO2 assimilation rate in passion fruit plants grown with saline water was related to factors of stomatal and non-stomatal origin. Gas exchange and growth of passion fruit cultivars were negatively affected by water salinity from 0.3 dS m-1 at 75 days after sowing. Despite the reduction in the growth of the passion fruit cultivars, irrigation with water of up to 3.5 dS m-1 could be used to obtain seedlings with acceptable quality. Based on the relative yield of total dry phytomass, the passion fruit cultivars BRS Sol do Cerrado and Guinezinho were classified as moderately sensitive to water salinity during the seedling phase.

Abiotic stresses are responsible for the loss of agricultural production in different regions, especially in semiarid regions, which have long periods of drought and high evapotranspiration, leading to the use of saline water as an alternative for the expansion of irrigated areas. In this context, the objective was to evaluate the physiological indices and the growth of the ‘Gigante Amarelo’ passion fruit as a function of the salinity of irrigation water and fertilization with silicon. A randomized block design was used in a 5 x 2 factorial scheme, whose treatments consisted of five electrical conductivities of irrigation water - ECw (0.3; 1.0; 1.7, 2.4 and 3.1 dS m-1) associated with two doses of silicion (150 and 300 g of silicon plant-1) with four repetitions. Salt stress causes changes in gas exchange, chlorophyll a and b synthesis and growth of ‘Gigante Amarelo’ passion fruit plants, 60 days after transplanting. Fertilization with silicon dose of 300 g plant-1 promotes increments in CO2 assimilation rate and instantaneous water use efficiency, being able to mitigate the deleterious effects of salinity. Passion fruit plants fertilized with silicon dose of 300 g plant-1 attained greater growth in stem diameter and relative growth rate in stem diameter, from 30 to 60 days after transplanting.