SALINITY-INDUCED CALLUS BROWNING AND RE-DIFFERENTIATION, ROOT FORMATION BY PLANTLETS AND ANATOMICAL STRUCTURES OF PLANTLET LEAVES IN TWO MALUS SPECIES

摘要

Among several abiotic stresses, drought or water scarcity is a major constraint for crop production in many parts of theworld. Six maize (Zea mays L.) cultivars; DTC, EV-77, EV-78, EV-79, Faisalabad mays, and 6621 were evaluated fordrought tolerance at germination and seedling stages. Distilled deionized water was used as control but uniform droughtstress was induced using 3, 6 and 9% of polyethylene glycol-6000 (PEG-6000) which correspond to osmotic potential of -0.0466, -0.0759 and -0.0876 MPa, respectively. PEG influenced the germination and growth of the cultivars in aconcentration dependent manner but the highest level of PEG induced more drastic decline for the various attributes studied.The cultivars showed significantly variable responses to different levels of PEG. The result of study clearly suggestedvariability of characters for drought tolerance among maize cultivars. Based on the pattern of variability for variousattributes, 3 groups of cultivars can be classified. The cultivar 6621 had a consistent degree of sensitivity to drought in termsthe reduction of various attributes studied. The second group includes DTC which showed a steady tolerance [(germinationpercentage (GP), energy of emergence (EG), germination rate (GR), root fresh and dry weight (RFW and RDW), shoot freshand dry weight (SFW and SDW), dry biomass tolerance index (DBTI) and seedling vigor index (SVI)] thus seemed toprovide some manifestation of drought tolerance. For the third group of cultivars, pattern of drought tolerance wasindependent for germination, growth and physiological indices as an incoherent variability of attributes was observed. Asimilar pattern of variability for a number of characters to simulated water stress in the cultivar DTC served as reliabledeterminants for drought tolerance in maize. To assess maintenance of degree of drought tolerance selected maize cultivars,a field experiment was also conducted. Kernel yield, 1000- kernel weight (g), number of kernel number/cob, kernelweight/cob (g) was maximally reduced in water stress sensitive cv. 6621 whereas it was maximal in drought tolerant cvDTC. Drought stress at the reproductive stage hindered the floral development and/or fertilization process and thus yieldreduction occurs. Overall, selection procedure for selecting drought tolerant maize cultivars was efficient at the germinationand seedling growth stages.