Native auxin (endogenous) is transported in the plant

Options

A. From the shoot tip in the downward direction
B. From the root tip in the upward direction
C. Through vascular systems in plants
D. By a special transport system in the root

Answer

### Step-by-Step Solution:

1. **Understanding Auxins**: Auxins are a class of plant hormones that play a crucial role in regulating plant growth and development. They are primarily responsible for cell elongation, apical dominance, and the formation of roots.

2. **Source of Native Auxin**: The primary source of native auxin in plants is the shoot tip. This region contains meristematic cells, which are actively dividing and responsible for the majority of new cell formation.

3. **Direction of Transport**: Native auxin is transported from the shoot tip downwards. This downward transport is essential for promoting growth in the shoot, allowing the plant to increase in height and size.

4. **Role of the Vascular System**: While the vascular system (xylem and phloem) is involved in the transport of water, nutrients, and sugars, it does not play a significant role in the transport of hormones like auxins. Instead, auxins move through a specialized transport mechanism.

5. **Root Tip Transport**: Although auxins can also be found in the root tip, their concentration is much lower compared to the shoot tip. The growth hormones in roots do not contribute significantly to the overall auxin transport in the plant.

6. **Conclusion**: Based on the above points, the correct answer to the question of how native auxin is transported endogenously in the plant is that it is primarily transported from the shoot tip in a downward direction.