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

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.