Studies of the tolerance of Atriplex species. 1. Environmental characteristics and plant response of A. vesicaria, A. nummularia and A. semibaccata

Abstract

The effect of climate on the growth of three species of Atriplex viz., A. vesicaria Heward, A. nummdaria Lindl., and A. semibaccata R. Br., was measured for two years in the Riverine plains area of Australia. A single harvest of Kochia georgii R. Br, was also made. Plant life in the area is exposed to the stresses of wide diurnal and seasonal extremes of temperature and humidity and to low rainfall, with high actual evaporation and evapotranspiration rates during the summer. The plants also grow in soils that are highly saline with an unfavourable ratio of sodium to potassium contents. Despite these adverse conditions for plant growth the Atriplex species and Kochia georgii were well adapted and had high leaf weight ratios. The species were summer growers. A. semibaccata was dormant in the winter, but the other Atriplex species remained green and healthy, although they grew very little during the winter. The ratios of leaf to stem weights and the leaf water content showed seasonal fluctuations in the Atriplex species, but these were modified in accord with previous rainfall and evaporation rates. The remarkable capacity of Atriplex species to remain leafy and viable, under such adverse conditions, as were observed, is a major factor contributing to its pastoral importance in these inland areas.