Effects of temperature and moisture stress on germination and seedling growth of four tropical species

Abstract

Two controlled environment experiments and one field experiment were conducted to study the effects of temperature and moisture stress on germination, emergence and seedling growth of Zea mays, Echinochloa utilis, E. frumentacea and Pennisetum americanum. When night/day temperatures ranging from 5/10¦C to 25/30¦C were imposed, none of the species germinated at 5/10¦C within 14 d. At 10/15¦C or above, at least 50% of seed of all species germinated in 14 d although germination of P. americanum was more depressed by 10/15¦C than the other three species. In the second experiment, seed were exposed to a range of osmotic potentials (0 to - 1.5 MPa) at night/day temperatures of 10/15, 15/20 and 20/25¦C. Decreasing osmotic potentials had only small effects on germination at 15/20 or 20/25¦C but had marked effects on all species at 10/15¦C. The field experiment treatments comprised a number of sowing dates and irrigation treatments to give a range of soil temperatures and moisture potentials. Considerable differences between Z. mays and the other three species were recorded; more Z. mays seedlings emerged and their weights and root lengths three weeks after sowing were greater than those of the other three species by a factor of 10. Reasons for these differences ire discussed.