Studies evaluating simultaneous effects of more than one environmental factor on germination are rather scarce. Population dynamics of plant species would be understood better provided these effects are known. A study was undertaken to investigate the interactive effects of temperature with matric and osmotic potential on germination characteristics of three dryland species, Danthonia caespitosa Gaudich, Atriplex nummularia Lindl. and A. vesicaria Hew. ex Benth. Matric potentials were simulated by aqueous solutions of polyethylene glycol (mol. wt. 20,000) and their effects were compared with those of osmotic potential created by sodium chloride solutions. The rate and total germination of all the species declined with decreasing water potential. The germination rates increased with increasing temperature but final germinations were highest at intermediate temperatures (20 to 25 C). All species germinated better at low water potentials in the vicinity of the optimum temperatures. Interactive effects of temperature with both types of water potential were highly significant for all species. In general, osmotic effects were qualitatively similar to those of matric potential, although asmotic inhibition of germination was reduced at low temperatures. Both Atriplex had reasonable germination at extreme temperatures (5 C, 40 C) while D. caespitosa did not germinate at all. At low water potential (—15 bars) A. nummularia germinated in the range of 15 to 40 C, D. caespitosa germinated only at 25 C while A. vesicaria had poor germination at all temperatures. The order of species with respect to their capability to germinate against environmental stress was A. nummularia > A. vesicaria > D. caespitosa. It follows that because of capability of Atriplex spp. to withstand extreme temerature and water potential, germination is possible following rains during summer as well as winter, however Danthonia is likely to germinate only during spring and autumn.
No takes yet. Share an insight, caveat, or question.
Мукунд Шарма (1976) studied this question.