GAS EXCHANGE IN PLANTS

• The plant's stem has two functions: support structure and serving as a transport system for the plant
• Soft stems are not as strong as woody stems, they are soft, green, and can bend, with cells containing chlorophyll and producing food
• Woody stems are often covered with bark, do not contain chlorophyll, and have a tough outer covering that serves as a protective layer
• The transport system in plants consists of two kinds of tissue:

  • Xylem: a series of tubes that moves water and minerals up the stem in one direction
  • Phloem: moves sugars made in the plant's leaves to other parts of the plant in a two-way transport route
• Xylem and phloem layers in a plant stem are separated by a layer called the cambium
• Gas exchange in plants occurs through small holes in leaves called stomata, allowing for the swapping of gases with the air or water around them
• Plants exchange gases through stomata, with photosynthesis happening during the day and respiration occurring all the time
• During the day, photosynthesis is faster than respiration, leading to carbon dioxide moving into the leaves and oxygen moving out; at night, respiration happens but photosynthesis doesn't, causing carbon dioxide to move out of the leaves and oxygen to move in
• Gas exchange surfaces in plants and animals have thin membranes, a large surface area, and many vessels
• Stomata are small holes in the bottom of a leaf that let gases in and out, while vessels are tubes that transfer fluids in an organism
• Photosynthesis is the process of producing glucose and oxygen from carbon dioxide and water, while respiration releases energy from glucose
• Plant cells respire 24 hours a day, while photosynthesis only occurs in daylight