Abstract
Salt marsh grasses are adapted to thrive under saline conditions by various combinations of traits. Some researchers suggested that salt excreting grasses would differ from non-excreting ones in these traits. However, little is known about the differential responses between these plant types. Here, we compared the growth and physiology of salt excreting and non-excreting grasses. Differences were found between the two grass types in leaf water content, accumulation of organic compounds and Na
+
distribution which appeared to be linked with salt excretion. Additional studies on a number of halophytic grasses could help to identify key traits for salt resistance.
The combination of traits that makes a plant successful under saline conditions varies with the type of plant and its interaction with the environmental conditions. Knowledge about the contribution of these traits towards salt resistance in grasses has great potential for improving the salt resistance of conventional crops. We attempted to identify differential adaptive response patterns of salt-excreting versus non-excreting grasses. More specifically, we studied the growth, osmotic, ionic and nutrient (carbon/nitrogen) relations of two salt-excreting (
Aeluropus lagopoides
and
Sporobolus tremulus
) and two non-excreting (
Paspalum paspalodes
and
Paspalidium geminatum
) perennial C
4
grasses under non-saline and saline (0, 200 and 400 mM NaCl) conditions. Growth and relative growth rate decreased under saline conditions in the order
P. geminatum
>
S. tremulus
=
A. lagopoides
>
P. paspalodes
. The root-to-shoot biomass allocation was unaffected in salt-excreting grasses, increased in
P. paspalodes
but decreased in
P. geminatum
. Salt-excreting grasses had a higher shoot/root Na
+
ratio than non-excreting grasses. K
+
, Ca
2+
and Mg
2+
homoeostasis remained undisturbed among test grasses possibly through improved ion selectivity with rising substrate salinity. Salt-excreting grasses increased leaf succulence, decreased
ψ
s
and xylem pressure potential, and accumulated proline and glycinebetaine with increasing salinity. Higher salt resistance of
P. paspalodes
could be attributed to lower Na
+
uptake, higher nitrogen-use efficiency and higher water-use efficiency among the test species. However,
P. geminatum
was unable to cope with salt-induced physiological drought. More information is required to adequately document the differential strategies of salt resistance in salt-excreting and non-excreting grasses.