Chapter 6

What does the guard cell do?

It surround the stomata for protection and regulates the rate of transpiration by opening and closing the stomata.

What are the external features of a leaf?

Petiole, Lamina, Vein, Margin, Midrib

What is the function of a Thin Broad Lamina and how?

It provides a short diffusion distance for gases and enables light to reach all mesophyll cells. A broad lamina provides a large surface area for maximum absorption of light.

What is the function of a Petiole?

It holds the leaf in position to absorb light energy.

What are the internal structures of the lamina/leaf?

Upper Epidermis, Mesophyll (Palisade Mesophyll and Spongy Mesophyll), Lower Epidermis and Stomata.

What is the function of the waxy cuticle on the upper and lower epidermis?

During evaporation it reduces water loss from the leaf and it also allows light to enter the leaf due to it being transparent.

What is the function of the stomata in the the lower epidermis?

It opens in the presence of light, allowing carbon dioxide to diffuse in and oxygen to diffuse out of the leaf.

What is the function of the chloroplasts containing chlorophyll all mesophyll cells?

Chlorophyll absorbs and transforms light energy to chemical energy used in the manufacture of sugars.

Why is there more chloroplasts in upper palisade tissues?

More light energy can be absorbed near the leaf surface.

Why is there interconnecting system of air spaces in the spongy mesophyll?

It allows rapid diffusion of carbon dioxide and oxygen into and out of the mesophyll cell.

What is the function of the veins containing xylem and phloem situated close to the mesophyll cells?

The xylem transports water and mineral salts to mesophyll cells. While the phloem transports sugars away from the leaf.

What happens to the glucose produced through photosynthesis, and why is glucose not a good storage molecule?

Glucose is used for respiration, converted to other molecules like oils and proteins, transformed into sucrose for transport via phloem, converted to cellulose for cell wall construction, and stored as starch. Glucose is not an ideal storage molecule due to its reactivity and solubility in water.

How can you test a leaf for photosynthesis, and what is the significance of the starch test?

To test for photosynthesis, one can perform the starch test by boiling the leaf, dissolving chlorophyll with hot alcohol, and detecting the presence of starch using iodine solution. The test indicates whether the leaf has been photosynthesizing.

What is the purpose of a greenhouse in optimizing conditions for photosynthesis, and how does it relate to plant growth?

A greenhouse allows the control of conditions to maximize the rate of photosynthesis, leading to faster growth and increased yield. It is especially beneficial in temperate countries with low light intensity and temperature or tropical countries with low CO2 levels.