Leaf gas exchange and water relations of the woody desiccation-tolerant Paraboea rufescens during dehydration and rehydration

Abstract

Desiccation-tolerant (DT) plants can withstand dehydration to less than 0.1 g H ₂O g ⁻¹ dry weight. The mechanism for whole-plant recovery from severe dehydration is still not clear, especially for woody DT plants. In the present study, we evaluated the desiccation tolerance and mechanism of recovery for a potentially new woody resurrection plant Paraboea rufescens (Gesneriaceae). We monitored the leaf water status, leaf gas exchange, chlorophyll fluorescence and root pressure of potted P. rufescens during dehydration and rehydration, and we investigated the water content and chlorophyll fluorescence of P. rufescens leaves in the field during the dry season. After re-watering from a severely dehydrated state, leaf maximum quantum yield of photosystem II of P. rufescens quickly recovered to well-watered levels. Leaf water status and leaf hydraulic conductance quickly recovered to well-watered levels after re-watering, while leaf gas exchange traits also trended to recovery, but at a slower rate. The maximum root pressure in rehydrated P. rufescens was more than twice in well-watered plants. Our study identified P. rufescens as a new DT woody plant. The whole-plant recovery of P. rufescens from extreme dehydration is potentially associated with an increase of root pressure after rehydration. These findings provide insights into the mechanisms of recovery of DT plants from dehydration.

Abstract

Desiccation-tolerant (DT) plants can survive in extremely dry environments and withstand dehydration to less than 0.1 g H ₂O g ⁻¹dry mass, and after rehydration the DT plants will regain normal function. This study provides the first evidence that Paraboea rufescens, a small shrub from Gesneriaceae, is a DT plant. After re-watering from a severely dehydrated state, leaf water status and leaf physiological function of P. rufescenscan quickly recover to the well-watered levels. This study also shows that root pressure is an important driving force for whole-plant recovery in P. rufescensfrom severe desiccation.