The seeds of cucumbers which began growth on Earth orbit indicated a role of white of CsPIN1 which “feels” gravitation and directs effect of hormones of growth.
Already for a long time it is known that plants are capable “feel” the direction of action of forces of an attraction and as appropriate to distribute a gradient of auxins – vegetable hormones of growth and development. But better to understand how these processes are implemented at the cellular level, the Japanese scientists investigated growth of seeds of a cucumber onboard the ISS, in the conditions of a microgravity.
Hideyuki Takahashi and his colleagues chose cucumbers as they as representatives of family of pumpkin (Cucurbitaceae), at early stages of development form the special “hooks” located between the growing root and a stalk. They allow a plant to gain a foothold in the soil and facilitate punching of a sprout through a dense seed cover, and the direction of their growth is defined by gravitation. If the seed is placed truly (vertically, the necessary party up), then “hooks” grow horizontally at the surface of soil. If the seed lies horizontally, growth of “hook” from the top party is suppressed with gravitation. And on the ISS it grows anyway.
In new work of Takakhasi and his coauthors used such plants delivered with the ISS, having studied behavior of white of CsPIN1 which activity is regulated by gravitation, and having for the first time shown that it can serve as “a transfer link” between gravitation and hormonal reaction of a plant which is shown also in the direction of growth of “hooks”. Scientists write about it in article published by the Nature Microgravity magazine.
Having placed seeds of cucumbers in specially developed containers, scientists sent them into orbit again. One group of plants developed here in usual conditions of a microgravity, and the second – at not too bystry centrifugation which imitated weak (1g) gravitation. The experiment continued only two hours then the astronauts who began growth seeds fixed in complex solution on the basis of alcohol and returned to Earth.
Here Takakhasi compared a condition of those and other plants to colleagues, having painted over their fabrics on existence of CsPIN1 and having found out an arrangement of this white in cages. It turned out that under the influence of gravitation of CsPIN1 moves to a transitional zone between a back and a hypocotyl (intermediate area between a root and a stalk). According to scientists, it forces cages to form the transport channel on which hormones of growth can move from one part of a plant to another and operate its development according to gravitation.