Abstract
ABSTRACT High salt concentration in water are common in Brazilian semirad region, being important to research alternatives for use this waters on crop, like use of tolerant genotypes to salinity. Thus, in order to evaluate the saline stress perception of citrus rootstocks varieties crop from gas exchange and fluorescence analysis, an experiment was realized in greenhouse at the Center for Science and Technology Agrifood, CCTA, of Federal University of Campina Grande, UFCG, Pombal, PB, Brazil. It was studied in a randomized block design with factorial scheme (2x4), two salinity levels (0.3 and 4.0 dSm-1) and four varieties of citrus rootstocks [1 -common Sunki mandarin (TSKC), 2 - Florida Rough lemon (LRF), 3 -Santa Cruz Rangpur lime (LCRSTC) and 4-Volkamer lemon (LVK)], with three replications. The citrus rootstocks varieties grown on hydroponic system and at 90 days after sowing the plants were evaluated by gas exchange and PSII fluorescence at 0, 24 and 48 hours after application of treatments to determine the times for the physiological establishment of salt stress. The first 48h under saline conditions promoted changes in gas exchange and PSII fluorescence in varieties TSKC, LRF and LCRSTC indicating the begin of physiological stress; the common ‘Sunki’ mandarin and the ‘Florida Rough’ lemon are the more sensitive genotypes to saline stress, in order hand the ‘Santa Cruz Rangpur’ lime and ‘Volkamer’ lemon are the genotypes more tolerant.
Highlights
Brazil is a world reference in the production of fresh fruits, especially the orange-’Doce ‘[Citrus sinensis (L.) Osbeck] and lime-sour’ Tahiti ‘(C
The two factors that were studied corresponded to two water salinity levels [0.3 and 4.0 dS m-1] and four genotypes, represented by varieties recommended as rootstock citrus [1 ‘Sunki’ Common tangerine (TSKC) (Citrus sunki (Hayata) hort ex Tanaka.); 2 ‘Rough Florida’ lemon (LRF) (C. jambhiri Lush.); 3 ‘Rangpur Santa Cruz’ (LCRSTC) (Citrus limonia Osbeck), and 4- ‘Volkameriano’ lemon (LVK)
Studying gas exchange through the unfolding of the factors in all variables measured at 24 and 48 h (Table 2), it was found, regardless of the concentration of salts in solution, higher average values in the ‘Rough Florida’ lemon tree especially with respect to the stomatal conductance, transpiration (E) and net photosynthesis (A) did not differ statistically, from the ‘Rangpur Santa Cruz’ and the ‘Volkameriano’ lemon, implying greater physiological potential observed in these lemons compared with the common ‘Sunki’ tangerine
Summary
Brazil is a world reference in the production of fresh fruits, especially the orange-’Doce ‘[Citrus sinensis (L.) Osbeck] and lime-sour’ Tahiti ‘(C. Salt stress is one of the main limiting factors to growth and to the productivity of citrus in the Northeast, due to the reduction in water availability to plants, and due to the lower osmotic potential of the soil solution, which implies increased energy expenditure for absorption of water and nutrients (Leonardo et al, 2003) These effects vary among species and genotypes of the same species and between plant developmental stages (Ayers; Westcot., 1999; Fernandes et al, 2011), making it possible to identify genetic materials tolerant to this factor, enabling the expansion of new agricultural frontiers. The objective was to study the gas exchange and chlorophyll a fluorescence in citrus genotypes, during the initial phase of submission to salt stress in order to identify physiological changes that are indicative of possible tolerance
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