Effects of hypergravity on growth and cell wall properties of cress hypocotyls

Abstract

Elongation growth of etiolated hypocotyls of cress (Lepidium sativum L.) was suppressed when they were exposed to basipetal hypergravity at 35 x g and above. Acceleration at 135 x g caused a decrease in the mechanical extensibility and an increase in the minimum stress-relaxation time of the cell wall. Such changes in the mechanical properties of the cell wall were prominent in the lower regions of hypocotyls. The amounts of cell wall polysaccharides per unit length of hypocotyls increased under the hypergravity condition and, in particular, the increase in the amount of cellulose in the lower regions was conspicuous. Hypergravity did not influence the neutral sugar composition of either the pectin or the hemicellulose fraction. The amount of lignin was also increased by hypergravity treatment, although the level was low. The data suggest that hypergravity modifies the metabolism of cell wall components and thus makes the cell wall thick and rigid, thereby inhibiting elongation growth of cress hypocotyls. These changes may contribute to the plants' ability to sustain their structures against hypergravity.

Shoot circumnutation and winding movements require gravisensing cells

“…In addition to gravitropism, gravity affects how plants build their bodies, anchor themselves, and elevate their apical meristems to higher positions. For example, plants synthesize tough cell walls to withstand gravitational forces (1,2), and cucurbitaceous plants develop a peg that functions to pull the seed coat out only on the gravistimulated side of the region between the root and hypocotyl (3,4). The graviresponse also participates in the regulation of apical dominance (5).…”

Reverse Genetic Approach to Exploring Genes Responsible for Cell-Wall Dynamics in Supporting Tissues of Arabidopsis thaliana under Microgravity Conditions

“…In contrast, in microgravity experiments, plants which are grown under reduced gravity or microgravity conditions are compared to those grown in 1G conditions. Very high gravity conditions, such as 300G, can inhibit shoot growth and stimulate cell wall stiffening (Waldron et al, 1990;Hoson et al, 1996). In contrast, microgravity conditions have been shown to exert the opposite effect on the mechanical properties of the cell wall.…”

Development of the anti-gravitational system in land plants and its implication for the interaction between plants and other organisms

“…Hypergravity treatment inhibits elongation growth and decreases the cell wall extensibility in stem organs of various plants (Hoson et al 1996, Soga et al 1999a. Plant organs grown under hypergravity conditions also had thicker cell walls and a higher molecular mass of the hemicellulosic polysaccharides such as xyloglucans and (163)(164)-‚-glucans (Soga et al 1999a, b).…”