Periodic Reporting for period 2 - HALO (Understanding Halophytes for an Agriculture Worth its Salt)
Berichtszeitraum: 2018-12-01 bis 2019-11-30
The main objective of the HALO project is to elucidate the complementary morphological, physiological and anatomical characteristics that enable dicotyledonous halophyte to be successful on saline soils, including their unique ability to sequester cytotoxic Na and Cl ions in specialised external structures called salt bladders. This will reveal the fine print of one of the most interesting mechanisms evolved by plants over the course of evolution not only to deal with NaCl toxicity but also use it to thrive in these otherwise hostile NaCl-rich environments, opening up novel and previously unexplored breeding targets to improve salt tolerance in crops.
1. Dissect the physiological and molecular modification occurring in halophytes under saline conditions underlying their ability to thrive in saline environments;
2. Identify (electrophysiological and molecular characterisation) the transporters involved in ion transport in stalk cells within the epidermal bladder cells.
For objective 1 the response of four accessions of the halophyte quinoa with contrasting salt tolerance and epidermal bladder cell (EBC) density were evaluated to determined why accessions with a high density in EBC (thus elevated sequestration of cytotoxic ions) fail to achieve high salt tolerance compared with two accessions that have low EBC density. To elucidate possible mechanism(s) underlying this enhanced tolerance in accessions with low EBC density, different physiological and electrophysiological parameters were evaluated after long and short-term treatment with NaCl. The combined data indicate that additional tolerance mechanisms operate in roots rather than shoots in salt tolerant accessions. This in turn results in an improved responses to NaCl and ROS stress, which improves root functionality following salt stress and ultimately results in improved leaf stomatal regulation and enhanced salt tolerance.
For objective 2, ion fluxes and membrane potentials were measured in stalk cells in petioles of leaves of control and salt grown quinoa plants using non-invasive microelectrode ion flux measuring MIFE technique. Subsequent pharmacological experiments using a range of channel blockers and metabolic inhibitors revealed the most likely transporters involved in Na, Cl and K loading via the stalk cells in EBC.
Halophytes’ ability to thrive in saline soils has increasing potential in a world where most known agricultural crop are salt-sensitive glycophytes and where changes in climate and land use will increase resources salinisation. Indeed, halophytes could represent the “silver bullet” approach for maintaining food supply over the coming years as they could play an important role as crops in their own right and also as models for generating salt tolerance in traditional crops. Overall, this will enable farmers to use currently unproductive lands and saline waters to increase agricultural outputs while limiting the global diversions of “good” resources to agriculture, which is critical for the state of the environment and for the civil society at large.