leaves and photosynthesis

Anmerkungen:

• Leaves are adapted for efficient photosynthesis in 3 main ways

1. Leaves are adapted for diffusion
   1. They're broad, so there's a large surface area for gases to diffuse
   2. They're thin which means carbon dioxide and water vapour only have to diffuse a short distance to reach the photosynthesising cells where they're needed
   3. The lower surface is full of little holes called stomata. They're there to let gases like co2 and o2 in and out. They also allow water to escape which is known as transpiration
   4. Leaves have guard cells surrounding each stoma to control when the stoma opens and closes. This allows the guard cells to control gas exchange
   5. There are air spaces in the spongy mesophyll layer. This allows gases like co2 and o2 to move between the stomata and the photosynthesising cells. This also means there's a large surface area for gas exchange-they have a very big internal surface area to volume ratio
2. Leaves are adapted to absorb light
   1. The leaves being broad also means there's a large surface area exposed to light
   2. Leaves contain lots of chloroplasts which contain chlorophyll and other photosynthetic pigments to absorb light energy
   3. the cells that contain the most chloroplasts are arranged in the pallisade layer near the top of the leaf where they can get the most light
   4. The upper epidermis is transparent so that light can pass through it to the pallisade layer
3. Leaves have a network of vascular bundles
   1. The vascular bundles are the transport vessels, xylem and phloem. They deliver water and other nutrients to every part of the leaf and take away the glucose produced by photosynthesis. They also help to support the leaf structure.