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Plant surface beauties

© Narayan Dattatray Wadadekar

Let us take a look at the surface beauties of some plants. These are the dimples and the pimples and the goosebumps ….many appendages on the plant surfaces. The appendages include – hydathodes, hair, scales, and glands.

Plants like ferns have secretory structures on upper surface of their leaflets. These are the hydathodes. These look like dimples. A leaflet of fern has on its upper surface on both its edges rows of hydathodes. A hydathode, under the microscope, looks like a tiny badminton racket. A veinlet ends up at hydathode and supplies it with water. The bulk of the glandular tissue is called epithem . Cells of the epithem absorb mineral nutrients out of the xylem sap. Along with water these come to the leaf surface. Water is secreted out of the tissues ( guttation), and as water evaporates calcium salts are left behind in the form of white chalk like crust. Hydathodes are therfore also known as chalk glands or water stomata.

Here is a picture of a hydathode –   

Just as animals have bristles and hair on their surfaces several varieties have trichomes. These are hair like projections. They can be sensory, secretory, defensive, stinging and single threadlike or branched with or without a knoblike end. Their defensive function can be carried out in two ways. They act as a barrier to small predators,or they may secrete toxic compounds

The trichomes may be useful in cooling leaves as water evaporates from their large surfaces.

Come have a look at an unbranched beautiful trichome.

and at a glandular trichome- http://www.esb.utexas.edu/mauseth/weblab...

Trichomes can help in predation. In the insect eating plant Venus flytrap, leaf blade has sensitve hair. An insect walking on it trips onto a few of them makes the leaf suddenly close. The trapped insect is digested in 2-3 days time with the help of enzymes secreted by some multicellular hairs on the leaf lamina.

Sundews, that is Drosera plants have attractive coloration and sweet nectar from glands on the upper leaf surface. These lure the tiny insects. Look at some attractive insectivorous plants. http://www.botgard.ucla.edu/html/botanyt...

Some kinds of flowering plants like Cactus have glands on their surfaces called extrafloral nectaries. As the name suggests they producenectar. But it is not for the purpose of pollination. These extrafloral nectaries can be very tiny and barely visible to elaborate cup like organs on leaves, stems, petioles, stipules, flowers stalks, and even on the outside of flowers.

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