Project Results

Soil salinization is a major cause of plant stress, partly due to the physicochemical similarities between Na and K Na ions compete with K ions for their transport into root cells. However, the point of Na entry remains unidentified. Here, I have applied the Electrical Penetration Graph as a method for whole plant electrophysiology in order to test if (a) root exposure to NaCl induces depolarization waves that propagate
from root to shoot via the phloem, and if (b) the electrophysiological effects of root exposure to NaCl require expression of the potassium channels AKT1 and/or AKT2. The data suggest that AKT2 subunit containing K channels mediate NaCl-induced depolarization of root cells, and that this depolarization does not propagate to leaves via the phloem.

About This Project

Salt is dangerous to most plants, as it quickly disrupts their ionic homeostasis and their physiology. Most studies on plant adaptation to soil salinisation focus on the root, the part of the plant directly exposed to the salt. However, my recent recent work shows that application of salt to the roots induce long-distance electrical signals that quickly travel to the leaves via the phloem. These data open new questions regarding the role of systemic electrical signals in salt adaptation.

Ask the Scientists

What is the context of this research?

The root is the part of the plant that is affected first by salt, and its cells are known to react electrophysiologically to it. Wouldn't it be advantageous if the entire plant was informed about it? Would that increase its chance of survival in high salt conditions? My previous Experiment project showed that the roots of Azolla send fast electrical signals to the leaves via the phloem. And, the more concentrated the salt solution, the larger the electrical response in the leaves (project DOI: 10.18258/4845). These result pose a number of interesting questions: What is the role of these signals? How do they contribute to adapting the whole plant to high salt concentrations? In the future I intend to continue to investigate this phenomenon in the model angiosperm Arabidopsis thaliana.

What is the significance of this project?

Studying the physiological responses to salt only in the root is likely insufficient for understanding how plants adapt to salinisation as whole organisms. Soil salinisation is a current concern, as it affects over 20% of the agricultural land. Understanding the responses of plants to salt increase may be important to ensure the optimal growth of plants which will be necessary to feed an increasingly growing world population.

My research may change the way we think about the phloem and about plant physiology. A new concept of the phloem may emerge, one in which its electrical features figure prominently, and play fundamental roles in phloem function and in the function of other plant cells.

What are the goals of the project?

The main goal of this campaign is to gather enough funds to present these novel and potentially important data at a conference. I have gathered extensive data on the dose-dependent responses salt-induced systemic electrical signals in the aquatic fern Azolla filiculoides, and now I am performing similar experiments on Arabidopsis thaliana. The biophysical analyses of these data will be important for understanding how these electrical signals are incorporated into the full response of the plant to salt.

My goal in the long term is to find new genes that are necessary for the systemic salt-induced electrical signals. For this goal, I use cabbage aphids to record intracellularly from phloem cells of wild type and mutant Arabidopsis plants lacking expression of specific ion channel genes.