Distribution And Dynamic Change Of Stomata On Developing Organs Of Brassica Chinensis

Stomata control gas and moisture exchanges between the plant and the external atmosphere. They play an important role in plant photosynthesis and transpiration. So we study the distribution and dynamic changes of stomata on Brassica chinensis L. var. parachinensis (Bailey) unsing light microscope.The primary results were showed in the following.1. Stomata were presented in the epidermis of hypocotyls, cotyledons, leaves, sepals, filaments and fruits. However, no stomata were presented in the epidermis of petals. The epidermal cells of hypocotyls and filaments were elongated with straight anticlinal walls. However, the epidermal cells of cotyledons, leaves and sepals were irregular with undulate anticlinal walls. All Stomata from these organs were anomocytic and showed elliptical shape. Guard cells showed kidney shape.2. Both epidermal cell density and stomatal density decreased gradually with the development of hypocotyls. Stomatal index decreased significantly from the 3-day-old seedling growth to 6-day-old seedling growth, and did not change significantly in the following development stages. Guard cell length increased gradually during the development of hypocotyls. In the constrast, guard cell width decreased gradully.3. During the development of cotyledons, both epidermal cell density and stomatal density in the adaxial and abaxial epidermis of cotyledons decreased gradually. The stomatal index in the adaxial epidermis changed variably during development of cotyledons. However, stomatal index in the abaxial epidermis decreased until the 9-day-old seedling growth, and did not change significantly in the following development stages. Guard cells length increased gradually while guard cell width did not change significantly during the development of cotyledons.4. Both epidermal cell density and stomatal density in the adaxial and abaxial epidermis of leaves decreased significantly until the 7d of leaves unfold, and did not change significantly in the following development stages. Stomatal index increased until the 10d of leaves unfold, and then decreased in the following development stages. Guard cell length in the adaxial epidermis increased until the 10d of leaves unfold, and then changed variably during the following stages. However, guard cell length in the abaxial epidermis increased gradually. Guard cell width in the adaxial epidermis did not change significantly until the 13d of leaves unfold, and increased in the following development stages. However, guard cell width in the abaxial epidermis decreased until the 7d of leaves unfold, then increased significantly at the 10d of leaves unfold, and did not change significantly in the following development stages.5. During the development of fruits, both epidermal cell density and stomatal density decreased gradually, but stomatal index increased gradually. Guard cell length increased gradually while guard cell width decreased gradually with the development of fruits.During the development of hypocotyls, cotyledons, leaves and fruits, epidermal cell density decreased gradually, suggesting that the size of epidermal cells increased continuously. At the early stages, the cell initiation was finished, so stomatal density decreased gradually due to the expanding cell mentioned above. Stomatal index in the epidermis of different organs changed variably during the developmental stages. Guard cell length increased gradually, while guard cell width decreased gradually with the development of hypocotyls and fruits, suggesting the guard cells were tranfromed from rounding kidney shape at the early stage to slimmer shape at the later stage.