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Photosynthesis depends on the diffusion of carbon dioxide (CO 2) from the air through the stomata into the mesophyll tissues. Oxygen (O 2), produced as a byproduct of photosynthesis, exits the plant via the stomata. When the stomata are open, water is lost by evaporation and must be replaced via the transpiration stream, with water taken up by ...
Stoma in a tomato leaf shown via colorized scanning electron microscope image A stoma in horizontal cross section The underside of a leaf. In this species (Tradescantia zebrina) the guard cells of the stomata are green because they contain chlorophyll while the epidermal cells are chlorophyll-free and contain red pigments.
The guard cells differ from the epidermal cells in the following aspects: The guard cells are bean-shaped in surface view, while the epidermal cells are irregular in shape; The guard cells contain chloroplasts, so they can manufacture food by photosynthesis (The epidermal cells of terrestrial plants do not contain chloroplasts)
Idioblast cells are believed to be the precursors for guard cells, trichiomes, gland cells, and subsidiary cells of stomata. [8] The uneven division of idioblasts causes extreme differentiation in their daughter cells, with many daughter cells having different functions from their parent cell.
The epidermal cells are the most numerous, largest, and least specialized and form the majority of the epidermis. They are typically more elongated in the leaves of monocots than in those of dicots. Chloroplasts are generally absent in epidermal cells, the exception being the guard cells of the stomata. The stomatal pores perforate the ...
They are either shed when their main function has been completed, or are incorporated into structures where, when dead, they serve a protective or supportive purpose. catenulate In the shape of a chain; formed of parts or cells connected as if chained together, e.g. some diatoms, algae, and cyanobacteria such as Anabaena. See also concatenate ...
As the leaf grows, the pavement cells will also grow, divide, and synthesize new vacuoles, plasma membrane parts, and cell wall components. A thick external cell wall influences the direction of growth by impeding expansion towards the outside of the cell and instead promote expansion parallel to the epidermis layer. [7]
The shape of parenchyma cells varies with their function. In the spongy mesophyll of a leaf, parenchyma cells range from near-spherical and loosely arranged with large intercellular spaces, [ 2 ] to branched or stellate , mutually interconnected with their neighbours at the ends of their arms to form a three-dimensional network, like in the red ...