The relationship between salinity and drought tolerance in turfgrasses and woody species.

摘要

Both salinity and drought stresses induce osmotic stress. Thus, cross-tolerance responses and mechanisms may occur in plants. The overall objectives of this study were to determine morphological and physiological responses and mechanisms of turfgrasses and woody species under salinity and drought stress conditions, and determine the relationship between drought and salinity tolerance ability in those species.;Five turfgrass entries, 'Gazelle' and 'Matador' tall fescue (TF), 'Midnight' Kentucky bluegrass (KBG), PI368233 (Tolerant KBG), and PI372742 (Susceptible KBG), and three woody species, bigtooth maple (xeric-non saline), bigleaf maple (mesic-non saline) and Eucalyptus (mesic-saline) were compared.;For the drought study, water was withheld in Chapter 2 while the dry down treatment was based on daily evapotranspiration (ET) in Chapters 5 and 6. For the salinity study, NaCl and CaCl2 in turfgrasses at electrical conductivity (EC) of 1, 6, 12, 18, and 30 dS m-1 (Chapter 3) and woody species at EC of 1, 3, 6, 9, and 12 dS m-1 (Chapter 4).;Susceptible KBG was sensitive to salinity but equally drought tolerant as other turfgrasses entries. Salinity tolerant turfgrasses could lower their water potential (&psgr;leaf) and showed high K+:Na+ . Under drought stress, above ground tissues of all entries went brown when soil water content was beyond permanent wilting point, indicating an equal response to drought.;In woody species, Eucalyptus maintained acceptable visual appearance under salinity stress while bigtooth maple maintained this under drought stress. Bigleaf maple was susceptible to both drought and salinity. Under salinity stress, bigleaf maple showed signs of leaf injury at 3 dS m-1 while bigtooth maple showed at 6 dS m-1 but leaf injury did not occur in Eucalyptus even at 12 dS m-1, due to an ability to exclude salts at root level. Under drought stress, Eucalyptus and bigleaf maple showed anisohydric behaviors in which water uptake was maintained. In contrast, bigtooth maple stomata closed in order to conserve water along lead to maintaining acceptable visual appearance over drought periods. However, bigtooth maple was not growing but surviving while Eucalyptus and bigleaf maple kept growing until no water was available and faced fatal injury.