GROWTH-RESPONSES OF CUCUMBER-SEEDLINGS TO SULFUR-DIOXIDE FUMIGATION IN A TROPICAL ENVIRONMENT

Cucumber (Cucumus sativus) seedlings were grown from germination under intermittent sulphur dioxide (SO2) fumigation in naturally lit growth cabinets. Average cabinet temperature minima ranged from 12.7 to 14.1 degrees C, while maxima varied from 28.7 to 32.0 degrees C. Fumigatio n of SO2 for 8 h per day, 4 days per week, for 4 weeks at 0.1, 0.2 and 0.5 ppm reduced leaf area by 13.5, 46.7 and 45.1% and plant dry weigh t by 15.5, 55.4 and 58.6%, respectively. However, when plant growth wa s described as a function of accumulated degree days, no effect of 0.1 ppm SO2 was observed. Under 0.5 ppm SO2, specific leaf area was reduc ed and more assimilate was partitioned to the shoots at the expense of the roots. The application of these data to the assessment of possibl e crop losses in a tropical environment is discussed. (C) 1998 Elsevie r Science B.V. All rights reserved.