Phloem Transport: Flow From Source To Sink
Chapter Name : Transport In Plants |
Sub Topic Code : 103_11_11_06_01 |
Topic Name : Phloem Transport: Flow From Source To Sink |
|
Sub Topic Name : The Pressure Flow Or Mass Flow Hypothesis |
|
Introduction
Plants make food in the leaves through photosynthesis. This food or sugars then transport to all the parts of the plant through phloem.
Pre-Requisites:
• Translocation, xylem and phloem. • Various transport processes in plant.
Real Life Question:
Plants make food through photosynthesis in the leaves. But how does food transports from the leaves to all the parts of the plant?
Key Words / FlashCards
| Key Words | Definitions (pref. in our own words) |
|---|---|
| Source and sink | Source is the part of the plant that synthesizes food i.e. leaf. Sink is the part of the plant that requires food i.e. fruit. |
| Phloem sap | Consists mainly of water and sucrose but other sugars, amino acids and hormones are also transported. |
| Pressure flow hypothesis | Mechanism for the translocation of sugars from the source to the sink. |
| Phloem tissue | Composed of sieve tube cells forming long columns with holes in their end walls called sieve plates. |
Learning aids / Gadgets
| Gadgets | How it can be used |
|---|---|
| A tree | Remove a ring of the bark of a tree up to the depth of the phloem layer. Observe for the swelling of the portion of the bark above the ring on the stem. This is due to the absence of downward movement of food as the phloem is cut. |
Real life uses :
Different parts of the plant get food through phloem. A pumpkin fruit receives over 0.5 gram of food from phloem.
Places to visit :
Garden or biology laboratory.
Practical examples around us
| Examples | Explainations |
|---|
What you learn in Theory:
Transport of food from the leaves to the different parts of the plants through pressure flow hypothesis.
What you learn in Practice:
How phloem transports the food from the source to the sink.