HIGHLIGHTS
Irrigation water salinity alters gas exchange and biosynthesis of photosynthetic pigments in po-megranate.
The reduction in CO2 assimilation in pomegranate plants under salt stress is related to non-stomatal factors.
Increasing nitrogen doses increase electrolyte leakage in pomegranate seedlings.
Key words:
Punica granatum L.; photosynthesis; mineral fertilization
ABSTRACT
The semi-arid region of northeastern Brazil is characterized by scarce and irregular rainfall; in addition, the waters available for irrigation commonly contain high concentrations of salts, causing osmotic and/or ionic effects on plants. Thus, it is important to identify species adapted to the conditions of scarcity and lower quality of irrigation waters. In this context, the objective of this study was to evaluate the physiological changes of pomegranate when subjected to irrigation with saline waters and different nitrogen doses under greenhouse conditions. The study was carried out using a randomized block design in a 5 × 5 factorial arrangement, whose treatments consisted of five values of electrical conductivity of irrigation water - ECw (0.3; 1.8; 3.3; 4.8 and 6.3 dS m-1) and five nitrogen doses (50, 75; 100; 125 and 150% of the recommended dose for pot experiments), with four replicates. Water salinity from 0.3 dS m-1 reduced the CO2 assimilation rate, chlorophyll b concentration and total dry mass of pomegranate seedlings. However, stomatal conductance and leaf transpiration were not influenced by electrical conductivity of up to 4.0 and 3.6 dS m-1, respectively. The increase in intercellular CO2 concentration in pomegranate is related to factors of non-stomatal origin. Nitrogen doses did not attenuate the deleterious effects of salt stress on gas exchange, chlorophyll a concentrations and electrolyte leakage of pomegranate seedlings.
Key words:
Punica granatum L.; photosynthesis; mineral fertilization
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ns, *, ** - Not significant, significant at p ≤ 0.05 and at p ≤ 0.01 by F test, respectively
ns, *, ** - Not significant, significant at p ≤ 0.05 and at p ≤ 0.01 by F test, respectively; 
*, ** - Significant at p ≤ 0.05 and at p ≤ 0.01 by F test, respectively