Retention of mobile water during dehydration in the desiccation‐tolerant grass Eragrostis nindensis

Abstract

Leaf tensile strength was measured for the drought‐tolerant grass Eragrostis curvula and the desiccation‐tolerant grass E. nindensis when fully hydrated, partially dehydrated, naturally air‐dried, and flash‐dried. Leaf tensile strength increased in intact, air‐dried leaves of E. curvula but not for similarly treated leaves of E. nindensis. Examination of leaf cross‐sections by light microscopy and histochemical staining for lignins failed to show any significant structural differences between the two species in the hydrated state. When leaves were flash‐dried, the tensile strength of E. curvula remained unchanged from leaves dried naturally, while there was a marked increase in the tensile strength of flash‐dried leaves of E. nindensis. Proton NMR indicated that the desiccation‐tolerant E. nindensis retained mobile water when leaf relative water content was less than 20% if dried naturally but not if flash‐dried, whereas no mobile water was detected in leaves of E. curvula when dried either naturally or with flash‐drying to below 20% relative water content. This behaviour suggests a fundamental difference in strategy for surviving water loss in vegetative tissues between desiccation‐tolerant species and drought‐tolerant species.