Navigation Links
Stoma



In botany, a stoma (also stomate; plural stomata) is a tiny opening or pore, found mostly on the undersurface of a plant leaf, and used for gas exchange. Air containing carbon dioxide and oxygen enters the plant through these openings where it gets used in photosynthesis and respiration. Waste oxygen produced by photosynthesis in the chlorenchyma cells of the leaf interior exits through these same openings. Also, water vapor is released into the atmosphere through these pores in a process called transpiration. The opening and closing of a stoma is controlled by guard cells that surround the opening and involves cellular sodium-potassium pumps.

Dicotyledons usually have more stomata on the lower epidermis than the upper epidermis. As these leaves are held horizontally, upper epidermis is directly illuminated. Less number of stomata on the upper epidermis can then prevent water loss.

Monocotyledons are different. For their leaves are held vertically, they will have the same number of stomata on the two epidermis.

If the plant has floating leaves, there will be no stomata on the lower epidermis as it can absorb gases directly from water through cuticle. If it is submerged leaf, no stomata will be present on both sides of it.

Stoma in Greek means "mouth".

Stoma Paradox

As the key reactant in photosynthesis, carbon dioxide, is found in the atmosphere, most plants require the stoma to be open during daytime. The problem is that during hot weather, this causes plants to lose huge amounts of water through transpiration. This problematic situation is known as the stoma paradox. A small group of plants evolved with a solution to the paradox; they open the stoma at night and store the carbon dioxide for use during the following day, allowing the stoma to close at dawn. These plants are known as CAM plants.

Viewing Stoma

The easiest way to view stomata on a leaf is to take a nail varnish impression of it.

  1. Paint about one square centimeter of the underside of the leaf with transparent nail varnish.(or thin layer of PVA glue)
  2. Allow to dry out thoroughly (takes a good 30 minutes).
  3. Peel off and place on a microscope slide.

The stomata leave clearly visible impressions in the nail varnish. A graticule slide allows for the counting of how many stomata (per unit area) are on the leaf surface, a characteristic of physiological significance.


'"/>


(Date:8/29/2014)... and number of connections in transcription factor networks (TFNs) ... a study published in PLOS Computational Biology ... signature contributes to a network,s resilience against mutations. ... assortativity of TFN models has a greater effect on ... of assortativity," said Dov A. Pechenick, PhD, lead author ...
(Date:8/29/2014)... in German . ... is considered the oldest form of communication. Acting as ... example, the sexual attraction between males and females. Fish ... coordinate reproductive behavior in males and females. Scientists at ... Algarve in Faro, Portugal, and at the Max Planck ...
(Date:8/29/2014)... a cell,s nucleus, chromosomal DNA is tightly bound ... biologists call chromatin. Until about two decades ago, ... mere packing material around which the glamorous DNA ... a greater appreciation for how DNA/histone interactions govern ... research institutions studying the sequence of the genome ...
Breaking Biology News(10 mins):Assortativity signatures of transcription factor networks contribute to robustness 2Ready for mating at the right time 2Ready for mating at the right time 3'K-to-M' histone mutations: How repressing the repressors may drive tissue-specific cancers 2'K-to-M' histone mutations: How repressing the repressors may drive tissue-specific cancers 3
... 25, 2013) A team of researchers at The ... Scott Noggle, PhD, Director of the NYSCF Laboratory and ... Alzheimer,s Disease, and Michael W. Nestor, PhD, a NYSCF ... three-dimensional cultures of induced pluripotent stem (iPS) cells called ...
... California sagebrush in the southern part of the ... populations in the north, according to UC Irvine researchers ... with the Center for Environmental Biology. The results ... Change Biology , will assist land management and policy ...
... 2013 Listed below are the selected highlights for the ... Genetics . The April issue is available online ... Vol. 193, April 2013, Copyright 2013. Please feel ... these articles on a wide array of topics including methods, ...
Cached Biology News:NYSCF scientists develop 3-D stem cell culture technique to better understand Alzheimer's disease 2Southern California sagebrush better suited to climate change, UCI study finds 2Genetics Society of America's Genetics journal highlights for April 2013 2Genetics Society of America's Genetics journal highlights for April 2013 3Genetics Society of America's Genetics journal highlights for April 2013 4
Other biology definitionOther Tags