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Plants exhibit directional growth in response to gravity (known as gravitropism). Generally, roots grow towards gravity (positive gravitropism), and shoots grow in the opposite direction of gravity (negative gravitropism). The gravity-sensing region in the root is located at the root tip (Chavarrķa-Krauser et al., 2008). Gravity sensing begins with the biosynthesis and accumulation of a highly dense form of starch in the amyloplasts (known as statoliths) of the columella cells of the root cap. These specialized columella cells (known as statocytes) act as a primary site of gravity sensing. The statoliths sediment in the direction of gravity that triggers the downstream signaling pathway, leading to the formation of asymmetrical auxin gradient and differential gene expression, eventually resulting in differential growth response and bending of root (Sack, 1991; Blancaflor et al., 1998). However, the root?s specific angle is determined by gravitropic and anti-gravitropic offset mechanisms to facilitate the optimum absorption of water and nutrients from the soil to achieve maximum plant growth in a given environment.
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