1162. Make a Stethoscope for Plant Stress Diagnosis (Takaragawa’s Newsletter vol. 2)

JIRCAS publishes a booklet called Koho JIRCAS in Japanese, which is also available on our website (https://www.jircas.go.jp/ja/publication/jircas). The following article is an excerpt from the latest issue of the newsletter. For more detailed information, please refer to the main text.

Unlike animals, plants rarely move and have no voice. Appearance (greenness, wilting, etc.) is very important to ensure that the plant is living a healthy life. However, a plant that shows stress in its appearance is as damaged as an animal that is badly injured or seriously ill. Often, they are actually under stress even if it is not apparent on the outside. If we can understand the health of plants before they are seriously damaged, we may be able to take steps to improve plant growth and crop yields. I would like to create a “stethoscope” to listen to the plants. The stethoscope could also be useful in breeding to select stress-tolerant lines and varieties. Since we do not know where the plant's heart is, I would like to focus on plant “breathing”.

Plant breathing is called gas exchange, and photosynthesis, which takes place through the stomata on the leaf surface, is the minimal process of growth. In photosynthesis, stomata open when exposed to sunlight, absorbing carbon dioxide and releasing oxygen and water vapor at the same time. The rate of carbon dioxide absorption (or oxygen release) is called the photosynthetic rate, and the rate of water vapor release is called the transpiration rate. How much carbon dioxide is obtained for growth with how little water loss is evaluated by an index called water use efficiency, which is photosynthetic rate divided by transpiration rate, and is said to represent the ability to grow under conditions of low soil moisture. This indicator is usually measured with expensive equipment due to its high performance, but I am searching for alternative simple evaluation indicators (morphological characteristics such as stomatal density, metabolite concentration, etc.) and developing inexpensive methods to measure them. These indicators, also called “traits” or “phenotypes” in technical terms, will be clarified in future research to see if they can be used as a stethoscope to assess plant health and stress tolerance. Thus, the fundamental work that precedes breeding, such as searching the genetic resource population for physiological traits related to yield improvement and developing evaluation techniques to genetically endow new traits, is referred to as “trait development”.

I have focused on the diversity of traits in existing cultivars and have conducted crop ecology research on risk diversification through the use of multiple cultivars and mixed planting of different cultivars with the aim of effectively utilizing the diversity of cultivars, which have both advantages and disadvantages. I have been working on “trait (diversity) utilization”, and now, as a member of JIRCAS, I am working on “trait development”. From such experiences, I intend to establish a “trait development and utilization science” that combines these two concepts (trait development + trait diversity utilization). In order to foster this new field, I am actively interacting with researchers from different fields, such as breeding, ecology, molecular genetics, engineering, horticulture, and sociology, to gain a broad and multifaceted viewpoint.