Gas exchanges in sugar apple (Annona squamosa L.) subjected to salinity stress and nitrogen fertilization

Abstract

Salinity is one of the modern agriculture major obstacles, causing several physiological disturbances in plants, adversely affecting its growth and development. Therefore, some techniques are required in order to alleviate the negative effects of salinity stress on plants, as for example an adequate nitrogen fertilization. The aim of this study was to assess the ecophysiological responses of sugar apple plants (Annona squamosa L.) submitted to different salinity levels and nitrogen fertilization doses. The experimental design was a randomized block in an incomplete factorial scheme, with five electrical conductivities of the irrigation water (ECw: 0.5, 1.01, 2.25, 3.49 and 4.0 dS m-1) and five nitrogen doses (0, 101, 350, 598.2 and 700 mg dm-3), with four replicates, generated from the Box Central Composite experimental design matrix. Through a daily course, it was observed variations in gas exchange, chlorophyll content and fluorescence parameters. The gas exchange, chlorophyll content and fluorescence parameters were measured on photosynthetically active leaves. There was significant interaction between the salinity levels (ECw) and nitrogen doses for the chlorophyll indexes. The electrical conductivity of the irrigation water caused significant negative effects on chlorophyll fluorescence. Therefore, it can be stated that the sugar apple plants ecophysiology varies through the day and that salinity affects its chlorophyll content and fluorescence.