Plants need more than CO2 for photosynthesis. They also need a supply of water. Water deficit is the single most important factor limiting plant productivity in the field. Plants need to draw water through their system to assimilate carbon dioxide. Water Use Efficiency (WUE) is therefore very important to plants.
As soils dry, so water supply drops. In this situation, the roots sense the reduced water and send a signal by increasing abscisic acid (ABA) levels. “To explore the potential of poplar ABA receptors to engineer plants with enhanced WUE, we examined as a first step the effects of poplar ABA receptors in arabidopsis with the rationale to modify the sensitivity of arabidopsis to endogenous ABA,” said Papacek and colleagues in the Annals of Botany.
The team found that expressing ABA receptors in arabidopsis did increase water use efficiency, but there were some details that showed it wasn’t a simple matter. “While expression of poplar ABA receptors enhanced WUE and water productivity in arabidopsis, ectopic expression of endogenous ABA receptors provided even better WUE and growth performance in arabidopsis. Hence, we tend to favour the expression of ABA receptors in the homologous system and will pursue the ectopic expression of poplar ABA receptors for generating water-productive poplar lines,” the authors said.
The results show that while poplar is sensitive to drought, it may well be possible to increase drought-tolerance by using ABA receptors.