Although all cells in the green parts of a plant have chloroplasts, the majority of those are found in specially adapted structures called leaves . Certain species adapted to conditions of strong sunlight and aridity , such as many Euphorbia and cactus species, have their main photosynthetic organs in their stems. The cells in the interior tissues of a leaf, called the mesophyll , can contain between 450,000 and 800,000 chloroplasts for every square millimeter of leaf. The surface of the leaf is coated with a water-resistant waxy cuticle that protects the leaf from excessive evaporation of water and decreases the absorption of ultraviolet or blue light to reduce heating . The transparent epidermis layer allows light to pass through to the palisade mesophyll cells where most of the photosynthesis takes place.
Photosynthesis is the process where plants make their own food from sunlight. Most plants are able to make food directly from light energy, for example the Sun, instead of eating other organisms or relying on nutrients. Photosynthesis can happen in plants because they have chlorophyll. Chlorophyll is the pigment that makes plants green. Chlorophyll captures the Sun’s energy and uses it to make sugars out of carbon dioxide from the air and water. The sugars fuel a plant's roots, stems, and leaves so the plant can grow. After plants use the Sun's light to make their food, plants release oxygen into the air. This oxygen is very helpful because humans and animals need it to breathe. Make sure you thank plants for the oxygen you use everyday!
A lot of my college students still have trouble with this one. The reactions that happen in respiration and photosynthesis are different, but if we just look at what goes in and what comes out, they're opposites.
Carbon dioxide (CO 2 ) and Water (H 2 0) in, Oxygen and Sugar out.
Requires energy from the sun.
Here's cellular respiration:
Oxygen and Sugar in, CO 2 and H 2 0 out. Releases energy from the sugar.
Plants can do both. When they have light, they use it as an energy source to put the pieces of CO 2 and H 2 O to make sugar. They can put a bunch of sugars together to make starch (what foods are starchy?), cellulose (the stringy stuff you can't chew up), and wood.
When it's dark, they can do cellular respiration to break down the starch and sugar to release the energy they need.
Poor animals, we can only do cellular respiration. We need foods like starch, and oxygen, and we breathe out the CO 2 that's made. We don't get enough water from the process to take care of all of our needs so we have to drink more. Kangaroo rats don't have to drink water. They conserve water a lot better than we do.
Can plants live without animals? Can animals live without plants?
Thanks for asking.