31
Growth and Physiological Adaptations of Grasses
to Salinity Stress
Kenneth B. Marcum*
The University of Arizona, Tucson, Arizona
623I. INTRODUCTION
Degradation of arable lands is a major constraint to agriculture worldwide, with soil salinization, partic-
ularly in irrigated areas, playing a major role [1]. Nearly 10% of the earth’s total land surface, or 954 Mha,
is covered with salt-affected soil [2], of which from 60 to over 100 Mha is currently salt-affected as a re-
sult of human activity [3,4]. In addition, the extent of soil salinization is continually increasing. Ten to 20
Mha of irrigated agricultural lands deteriorate to zero productivity each year because of salt buildup [5,6].
Much of this land, although now too saline for conventional agriculture, is currently, or has the potential
to be, utilized for growing salt-tolerant or halophytic forage species, of which the Poaceae (grasses) play
a prominent role [7].
Critical water shortages are occuring in urban areas, resulting in restrictions on the use of potable wa-
ter for irrigation of landscaped areas. For example, in a number of western U.S. states, laws have been
passed that require the use of sewage effluent or other secondary, saline water sources for the irrigation
of turfgrass landscapes [8,9].
The Poaceae, represented by over 7500 species, inhabit the earth in greater numbers and have greater
range of climatic adaptation than any other plant family [10,11]. Therefore, it is not surprising that grasses
show extreme range in salinity tolerance, from salt sensitive to extremely salt tolerant (halophytic).
Grasses range in classification through salt sensitive, e.g., annual bluegrass (Poa annuaL.); moderately
salt sensitive, e.g., meadow foxtail (Alopecurus pratensisL.); moderately salt tolerant, e.g., dallisgrass
(Paspalum dilatatumPoir.); and salt tolerant, e.g., bermudagrass [Cynodon dactylon(L.) Pers.] [12–14].
Other grasses are recognized as true halophytes, e.g., cordgrasses (Spartinasp.), coastal dropseed
[Sporobolus virginicus(L.) Kunth], and saltgrasses (Distichlis spicataL.) [15,16].
The goal of this chapter is to investigate the range of salinity tolerance and physiological adaptations
to salinity present in grasses utilized for forage, grazing, soil stabilization, or turf. This chapter will de-
scribe the responses to salinity of three grass species representing the full range of salt tolerance present
in the Poaceae. Data from a study that compared three grass species will be presented: salt-sensitive buf-
falograss [Buchloë dactyloides(Nutt.) Engelm.], salt-tolerant bermudagrass, and halophytic desert salt-
grass [Distichlis spicatavar.stricta(Torr.) Beetle] [17]. Response differences highlighting important
physiological mechanisms of salt tolerance will be discussed and results cross-referenced to other
studies.
*Current affiliation:University of Hawaii at Mano’a, Honolulu, Hawaii.