Lucas León Peralta Ogorek:
|
Climate change is increasing the frequency and intensity of flooding and drought events, leading to great human and economic losses, particularly in crop production and food security. A root trait called the barrier to radial oxygen loss (ROL) allows rice plants to grow in flooded soils as it retains oxygen in the root tissue so that it can be used for respiration and root elongation. However, this trait might provide additional protective aspects. It was therefore tested whether the ROL barrier could prevent hydrogen sulphide intrusion and radial water loss.
In addition, it was assessed whether low concentrations of hydrogen sulphide and a low water potential in the growth solution could induce the formation of the ROL barrier. The protective traits of the ROL barrier were also tested, along with other root acclimations to soil flooding, under conditions of water deficit, as rice paddies experience both high and low soil water content conditions. The work in this thesis revealed that the ROL barrier greatly restricts hydrogen sulphide intrusion and radial water loss. Moreover, the restricted hydrogen sulphide diffusion resulted in a lower toxic effect on root respiration. Low concentrations of hydrogen sulphide induced an ROL barrier formation and gene expression results indicated that more lignin- than suberin-related genes were upregulated in roots exposed both to hydrogen sulphide and in stagnant conditions (which mimic soil flooding). Since the ROL barrier restricts radial water loss, roots acclimated to soil flooding might have relative advantages compared to plants growing in aerated soils if a condition of water deficit follows.
Indeed, plants from stagnant conditions survived sudden changes to very low water potentials in the root medium (which mimics water-deficit conditions) while plants from aerated conditions (which mimics well-watered and drained soils) did not. In addition, low water potentials induced an ROL barrier with a similar tightness to radial water loss as the barrier induced in stagnant conditions.
To conclude, this thesis highlighted protective aspects of the ROL barrier under two contrasting water content conditions. In addition, new signaling cues for the induction of the ROL barrier were discovered, which can be useful to further improve the understanding the ROL barrier induction pathways with the purpose of breeding more stress tolerant rice cultivars.