Growth Response of Various Perennial Grasses to Increasing Salinity

ABSTRACT

Although the effect of salinity on plant growth has been the focus of a substantive research effort, much of this research has failed adequately to separate the various growth-limiting aspects of salinity; thus, the results are confounded by multiple factors. Eight perennial grass species were grown in a sand-culture system dominated by sodium chloride (NaCl) [electrical conductivities (ECs) between 1.4 and 38 dS m⁻¹], with sufficient calcium (Ca) added to each treatment to ensure that Na-induced Ca deficiency did not reduce growth. Of the eight perennial grass species examined, Chloris gayana cv. ‘Pioneer’ (Rhodes grass) was the most salt-tolerant species, while Chrysopogon zizanioides cv. ‘Monto’ (vetiver) was of only moderate tolerance. However, observed salinity tolerances tended to be lower than those expected from published values based on the threshold-salinity (bent-stick) model. This discrepancy may be due in part to differences in the evapotranspirational demand between studies; i.e., an increase in demand accelerates the accumulation of sodium (Na) in the shoots and hence decreases apparent salinity tolerance. It was also observed that the use of a non-saline growth period (to allow seed germination and establishment) results in the overestimation of vegetative salinity tolerance if not taken into consideration. This situation is particularly true for species of low salt tolerance, due to their comparatively rapid growth in the non-saline medium compared with growth at full salinity.

Keywords:

• osmotic adjustment
• salinity tolerance
• vetiver

ACKNOWLEDGMENTS

The authors wish to acknowledge the statistical advice of Rosemary Kopittke. The assistance of Michael Geyer with the sample preparation and analysis was also gratefully received.

Notes

^aNote that the basal nutrient solution contains 4100 μM Ca.

^aNo significant interaction between salinity and time of harvest; where the P value is < 0.05, there were significant differences between harvests for all salinities.

^bSignificant interaction between salinity level and the time of harvest; there were significant differences between harvests for some but not all salinities.

^c Russell (1976).

^d Troung et al. (2002).

^a Jones et al. (1991) and Reuter and Robinson (1997).