ATPase Activities and Membrane Fine Structure of Rhizodermal Cells from Sorghum and Spartina Roots Grown Under Mild Salt Stress

Abstract

The study aims at correlations between ultrastructure of rhizodermal membranes and ATPase activities of two gramineous C 4-species effected by salinization of the growth medium.Comparative investigations were done with drought-resistant Sorghum and drought-sensitive, salt tolerant Spartina plants grown under steady-state conditions without or with 40 mol m -3 NaCI. Both species sustained this treatment and showed marked influences of salt on growth but not on root respiration. Generally, the intramembraneous particle (IMP) frequencies, found on freeze-fracture replicates of rhizodermal plasmic fracture faces of the plasmalemma (PPF) and tonoplast (TPF), were higher in Sorghum than in Spartina. NaCI leads in both species to an increase of the rhizodermal IMPfrequency in the TPF (-150 %) and PPF (-120 %).points out that salt-effected increases of ATPase activities of Sorghum roots were -4 times higher than the increases of IMP frequencies on rhizodermal membranes; in Spartina this effect is less intense.It is concluded that a salty environment leads to a higher ATPase activity per IMP in both species. The stronger reaction of Sorghum is explainable by the increase in K+/Na+ selectivity of the plasma membrane under salt stress. This is not the case for Spartina because the roots of this species include salt which subsequently is sequestered by the salt glands ofthe leaves. Abbreviations and SymbolsThe activities of T-and P-ATPase were determined for membrane vesicles from crude extracts and from isolated protoplasts of roots, respectively; the results from both preparations were the same. The vanadate-sensitive tissue ATPase activities increased under salt stress -5 times in Sorghum and -2 times in Spartina whilst the nitrate and azide-sensitive tissue ATPase activities increased -6 times only in Sorghum.

Effect of salinity on growth and accumulation of organic and inorganic solutes in the leguminous plantsAlhagi pseudoalhagiandVigna radiata

“…Stelzer (1984) showed that the P concentration in the mitochondria of maize root cells decreased by salinity. Koyro et al (1993) reported that the halophyte Spartina townsendii minimized energy demand, while the glycophyte Sorghum species required more metabolic energy for osmotic adjustment. It is possible that the P concentration limits the ATPase activity under salinity (Gronwald et al 1990) which may account for the difference in salt tolerance between Alhagi pseudoalhagi and Vigna radiata.…”

Effects of Exogenous Glycinebetaine on Growth and Ultrastructure of Salt-Stressed Rice Seedlings (Oryza sativaL.)

“…K-deficiency and NaCl-salinity in salt-sensitive Sorghum species also lead to an increase in the number of mitochondria as well as an increase in the number of microbodies (Hecht-Buchholz et al, 1971;Hecht-Buchholz, 1983;Walker and Taiz, 1988). The salt-induced activation of F-ATPase in Sorghum roots corresponds to the increase in the number of mitochondria in the root tip cells and, therefore, may supply additional energy for osmotic adaptation and for selective uptake and transport processes (Koyro et al, 1993). Koyro and co-workers discussed the high-energy requirement of salt-stressed plants, explaining it as the consequences of the very selective uptake of K over N a.…”

Guard cell cation channels are involved in Na+–induced stomatal closure in a halophyte

“…Indeed, Na ϩ is known to block several types of inward and outward K ϩ channels in plant and animal cells (French and Wells, 1977;Harvey and Ten Eick, 1989;Kourie and Goldsmith, 1992;Tester, 1988;Thiel and Blatt, 1991). Moreover, several studies in halophytic and non-halophytic species mention NaCl-induced regulation of activity or expression of some ion transport systems, including plasma membrane and tonoplast H ϩ -ATPases (Kirsch et al, 1996;Koyro et al, 1993;Niu et al, 1993;Niu et al, 1996;Tsiantis et al, 1996), Na ϩ /H ϩ antiporters of both membranes (Barkla et al, 1995;Wilson and Shannon, 1995), and a non-selective cation channel of the root tonoplast (Maathuis and Prins, 1990).…”