EFFECT OF TEMPERATURE, LIGHT, SALINITY, DROUGHT STRESS AND SEEDING DEPTH ON GERMINATION OF Cucumis melo var. agrestis

For understanding of seed germination, the ecology of weeds can assist in predicting their potential distribution and in developing their effective management strategies. In this experiment, the effects of various environmental factors on seed germination of Cucumis melo var. (agrestis) were investigated under laboratory and greenhouse conditions during 2009, in the department of Agronomy, University of Agriculture, Faisalabad, Pakistan. The treatments comprised of different temperature regimes (25, 30, 35, 40 and 45°C); salinity levels (0, 25, 50, 75, 100, 125 and 150 mM of NaCl); osmotic stress (0, -0.2, -0.4 and -0.6 MPa) and seed sowing soil depths (0, 1, 2, 4 and 6 cm). Results revealed non-significant effects of temperatures on germination and germination time whereas significant effects on seed germination index (8.39) at 25°C. Seed germination at 25 mM to 100 mM salinity was statistically similar to control treatments; whereas, the 150 mM salinity showed maximum reduction in seed germination and seed germination time, and minimum in seed germination index. The -0.4 MPa osmotic potential had reduced the seed germination of C. melo up to 25% and seed germination of C. melo was completely inhibited at -0.8 Mpa osmotic potential. Osmotic stress at -0.6 MP showed maximum reduction in seed germination and minimum in seed germination time and the germination index. Seedling emergence was 57.50 to 62.50% at seeding depths of 0 to 1cm but decreased as the soil depth increased. Maximum MGT and GI was recorded when seeds were planted at 1.0 cm soil depth. Below and above this depth, the seeds showed decrease in emergence. Seed germination of C. melo was delayed in respect of time to start germination and time to 50% germination (except in drought osmotic stress and soil sowing depth) with increased temperature, salinity, osmotic stress and sowing depth.