Formação de mudas enxertadas de gravioleira em condições de salinidade.

Abstract

The experiment was conducted under greenhouse conditions at EMBRAPA -Agroindustria Tropical, located in the municipality of Pacajus - CE, during the period of January to July, 2001. The effects of diferent concentrations of salt in the irrigation water - ECw (0.5, 1.5, 2.5, 3.5, 4.5 and 5.5 dS m"1) on the production of grafted seedlings of soursop (Annona muricata L.) in tubete, from gerrnination to transplanting stage. A completely radomized block design, was utilized with four replications. The irrigation waters were prepared with NaCl, CaCb- 2H20 and MgCb.óFfeO salts, mamtaining the equivalent proportion of 7:2:1 among Na:Ca:Mg, respectively. The variables appraised were: gerrnination (number of days, percentage of plants emerged and emergency speed), growth of rootstock (leaf number, plant height, stem diameter, green and dry weights of the aerial parts, roots and total, leaf area, root aerial parts ratio, leaf area ratio, absolute growth rate ratio, relative growth rate, net assimilation rate, water content of the leaf and the stem, number of graftable plants). Evaluation were also performed 25 and 50 days after grafting and some variables cited previously relative to growth and development of the graft plant were studied. In the gerrnination of the soursop, the leveis of ECw did not affect the percentage of gerrnination, the emergency speed was reduced and the period of gerrnination was prolonged. In the phase of formation of rootstock and graft, the increase in the salinity above 0.5 dS m"1, affected the growth and development of the plants, with growth of the aerial parts more affected than that of the root system. The water content of the leaf 80 days after emergence (DAE) was not affected with increase in the ECw, while the water content of the stem linearily increased with water salinity. The absolute growth rate (AGR) and relative growth net (RGR) of soursop 40 and 80 DAE decreased with increase in the water salinity and more drastic effects occured above ECw 2.5 dS m"1 for the AGR and 3.5 dS m*1 for the RGR The net assimilation rate (NAR) during the same time decreased with increase in the ECw. The number of graftable rootstocks were affected significantly with increasing salt concentration in the water and at highest concentration the decrease was 81.64 %, and the number of living grafts decreased significantly increased above ECw 1.22 dS m'1 of and time of salinity exposition of the plants, occurring death of ali plants submitted to the water salinity above 3.5 dS m"1. The increase in the ECw increased the water content of leaf 50 days after the grafting were as, the water content of stem did not vary. The mean consumption of water during the formation of seedlings decreased with the increase in the salinity of irrigation water.