Everything Life Sciences Grade 10

Write down your results

Observations:

Record your observations.

Conclusions:

What did you conclude from this experiment?

Movement of manufactured food DUMMY

Plants use carbon dioxide and water to manufacture glucose, yielding oxygen as a by-

product. Sunlight or radiant light and enzymes are necessary for photosynthesis to occur.

Once the food is manufactured in the leaves it needs to be distributed to the entire plant

so that the glucose can be used by each cell for respiration and some of the photosynthetic

products are then stored for later use.

The glucose is manufactured mainly in the palisade cells where there are more chloroplasts,

and then passes into the phloem. Glucose is transported to where it is needed in the the

plant via phloem sap, and may be stored in roots, stems or fruit. Transport of food material

from leaves to other parts of the plant is calledtranslocation. Understanding the phloem

structure is important to understanding how it transports food.

Figure 6.29: Aphids feeding on phloem sap which is rich in glucose.

How the phloem functions

While the transport of water is usually unidirectional in xylem (upward or lateral), the move-

ment of sugars in the phloem is multi-directional, and occurs byactive transport, an energy-

dependent process. Glucose is actively transportedagainsta concentration gradient into

sieve-tube elements. The sieve-tube elements have no nuclei but the adjacent companion

cells do. Companion cells are closely associated with sieve tubes and carry out all the cel-

lular functions of the sieve tubes. The cytoplasm of sieve tubes and companion cells is con-

nected through numerous channels calledplasmodesmata. These cytoplasmic connections

184 6.4. Uptake of water and minerals in the roots