The phloem carries nitrogen- and carbon-containing compounds.
Understanding Phloem Transport
The phloem is a vital part of a plant's vascular system, responsible for transporting essential substances throughout the plant. Here's a closer look at what the phloem carries and how:
Key Components of Phloem
- Sieve Elements (SE): These are the primary cells responsible for nutrient conduction.
- Companion Cells (CC): These cells provide metabolic support to the sieve elements, as mentioned in reference [82].
What Does the Phloem Transport?
* **Nitrogen-containing compounds:** These are essential for building proteins, nucleic acids, and other vital molecules.
* **Carbon-containing compounds:** Mostly in the form of sugars (like sucrose), produced during photosynthesis, the source tissues for these are usually the leaves. Source-to-Sink Transport
The phloem's transport system works on a source-to-sink principle:
- Source Tissues: These are typically areas where sugars and other nutrients are produced, such as leaves.
- Sink Tissues: These are regions where these nutrients are needed for growth or storage, such as roots, developing fruits, and growing shoots.
Example
* During the day, leaves produce sugars via photosynthesis (source tissues).
* These sugars are then transported through the phloem to developing fruits (sink tissues) which use the sugars for growth.In Summary
The phloem is crucial for distributing the products of photosynthesis, nitrogen-based molecules, and other metabolites throughout the plant, ensuring that all parts of the plant receive the resources they need for survival and growth. The phloem transports from source tissues to sink tissues, where the source tissues usually are leaves and the sink tissues can be roots or developing fruits. Reference [82] confirms that the phloem carries nitrogen- and carbon-containing compounds.
