Question

What are the major benefits of gravitropism for a germinating seedling?

Short answer

Helps seedling to grow upward to receive light.

Step-by-step solution

Step-1 Introduction

The movement of plants that takes place in response to gravity is termed gravitropism. Mainly two types of gravitropism are seen such as positive gravitropism and negative gravitropism. The shoot system develops against gravity therefore known as negative gravitropism. Similarly, positive gravitropism is the elongation of roots into the soil in response to gravity.

Step-2  Explanation 

Positive gravitropism allows the root to grow into the soil which ensures the anchorage and absorption of water. Settling of amyloplast at the bottom of the cell responding to gravity causes the root elongation. When amyloplast interacts with the Endoplasmic Reticulum (ER), it releases calcium ions. Indole-3-acetic acids (IAA) are transported to the bottom. Higher IAA concentration inhibits excess cell elongation at the bottom part and the shoot system grows normally.

Step-3  Final answer

In contrast, IAA accumulation at the lower part of the stem helps in the elongation of cells and the stem grows normally. Seedlings grow upward to receive lights which is helpful for photosynthesis.