Produção de mudas enxertadas de cajueiro anão precoce, usando águas de diferentes salinidades.

Abstract

The present study was conducted under greenhouse conditions in the Experimental Field of Pacajus (EFP) belonging to EMBRAPA Tropical Agroindustria, located in the municipal of Pacajus - CE, during the period of January to May, 2001, having as objective to study the effects of water salinity in different genotypes of cashew {Anacardium occidenlcde L.) in the germination phase and initial development of the rootstock and after grafting. The treatments consisted of six levels electrical conductivity of irrigation water - ECw (0.5, 1.5, 2.5, 3.5, 4.5 e 5.5 and dS m"1) tested in two clones of precocious dwarf cashew (CCP06 and CCP1001) recommended as rootstock. As graft, the clone (CCP76) was used because of its good productivity and acceptance in the market. The experiment was carried out in randomized block design, in 6x2 factorial scheme, with four repetitions, totaling 48 units each formed of 54 plants. The irrigation waters were prepared using NaCi, CaCL^FL-O and MgCl2.6H20, keeping equivalent ratio 7:2:1 among Na:Ca:Mg, respectively. The plants were appraised 25 and 40 days after seeding (DAS); the variables evaluated in the rootstock were: days for germination; percentage of emerged plantlings; growth indices (leaf number, plant height, stem diameter, leaf area, green weight of the aerial parts, dry weight of the roots and of the aerial plants and total) and physiologic indices (absolute growth rate, relative growth rate, net assimilation rate, ratio of leaf area and root / aerial parts). The salinity levels of the irrigation water did not affect the germination percentage significantly but prolonged the duration of germination phase. Same variables were also appraised 45 and 60 days after grafting (DAG), in the graft in addition to water content of the leaf and the stem 60 DAG. The salinity of irrigation water did not affect the percentage of emerged plantlings significantly but it delayed the germination phase. The increase in salinity of irrigation water induced significant reduction in the vegetative growth in both rootstocks, the number of leaves, plant height, stem diameter, leaf area, green weight of the aerial parts, dry weights of aerial parts, roots and total; the effect of salinity was more severe on the aerial parts than on the root system. With the increment of the salinity there was significant increase in the root/aerial parts ratio and decrease in absolute growth rate. The growth of the rootstock CCP06 presented greater tolerance to the salinity in terms of development of the diameter, plant height and in the number of grafted plants when compared to the rootstock CCP1001. The increase of ECw influenced significantly in the percentage of living plantling after graftings, though it did not vary with rootstocks. ECw above 2.5 dS m"1 caused the death of all plantlings of the grafted plants permiting to conclude that the grafting of CCP76 on the rootstock under the conditions of the present study, has greater susceptibility to water salinity above electrical conductivity of 2.5 dS m"1. The variables electrical conductivity of drained water (ECd), leaching fraction (LF), concentration factor (CF) and consumption of water (Cw), these were influenced with the increment of the conductivity of irrigation water, occuring increase of ECd and of LF, while CF had an inverse relationship with LF. The consumption of water was found to decrease with the increase of ECw in both the rootstocks in a similar way.