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Ethnobotanical Leaflets 12: 553-56. 2008. Global Warming and
Stomatal Complex Types Abdulrahaman, A. A.1 and Oladele, F. A.2 Department of Plant Biology 1abdulrahamanaa@yahoo.com; abdulrahamanaa@unilorin.edu.ng Issued Ozone depletion and its
ultimate effect, global warming are main concerns in climate change in the
world today. The phrase ‘climate change’ is growing in preferred use to
‘global warming’ because it helps convey that there are changes in addition
to rising temperatures. Accumulation
of greenhouse gases in the atmosphere depleted the ozone layer and
consequently causes global warming. Gases that trap heat in the atmosphere
are often called greenhouse gases. That the Earth has warmed by 0.74oC
over the last hundred years and that around 0.4oC of this warming
has occurred since the 1970s is unequivocal fact that leaves little room for
doubt that human activity is the primary driver of these changes (May, 2006).
Among factors that emit the greenhouse gases into the atmosphere are burning
of woods (fuel woods) and deforestation. Removal of plants on the surface of
planet Earth is no doubt contributing greatly to the accumulation of
greenhouse gases and thus the global warming. World
leaders, public health specialists, engineers, atmospheric chemists,
hydrologists, quantum physicists, mathematicians, botanists, zoologists, have
all being striving to stop further release of more greenhouse gases into the
atmosphere, and in the occurrence of these gases, they are trying to
purifying or cleansing them. One of the cleaners or purifiers that can be
employed is stomata. Figures 1 to 8 showed different types of stomatal
complex systems in some species of Amaranthus.
Stomata are microscopic openings or pores located majorly on the abaxial or
lower, and adaxial or upper surfaces of leaves of plants. Though sometimes,
stomata are present on the stems, petioles and sepals but in very small
number. Meanwhile, plants have the ability to absorb
carbondioxide for carbonxylation and subsequently for production of
carbohydrates (especially by the tuberous plants) and for production of woods
and fibres (by trees) through photosynthesis. Photosynthesis is the major
process by which plants produced carbohydrates, and the major ingredient in
this process is carbondioxide. Unfortunately, carbondioxide is one of the
greenhouse gases (other examples include methane [CH4], nitrous
oxide [N2O], fluorinated gases – hydrofluorocarbons, perfluorocarbons
and sulfur hexafluoride). The accumulation of these gases in the atmosphere
strengthened the greenhouse effect, which occurs when the heat produced by
the sun’s rays entering the atmosphere is retained, causing global warming.
Some greenhouse gases such as carbondioxide occur naturally and are emitted
to the atmosphere through natural processes and human activities. Other
greenhouse gases (e.g. fluorinated gases) are created and emitted solely
through human activities. About 99% carbondioxide used in photosynthesis is
absorbed through stomata (lenticels and cuticles also absorb carbondioxide to
lesser extent). Earlier studies by Carr and Carr (1990), Obiremi and Oladele
(2001) and Oyeleke et al. (2004) had confirmed that the more the subsidiary cells
surrounding the guard cells, the faster the opening of the stoma (i.e. pore
between the two guard cells) and vice versa. In relation with this, plants that possessed stomata
with many subsidiary cells (e.g. tetracytic and anomocytic types) will play
important role in reducing greenhouse gases especially carbondioxide. To
proof this fact, Obiremi and Oladele (2001) and Oyeleke et al (2004) studied
the relationship between the stomatal complex types and transpiration rate in
some selected Citrus species and
some afforestation tree species respectively. In both studies, stomatal
complex types with many subsidiary cells transpired higher than those with
less number. This translates to mean that the latter opens faster to allow
carbon dioxide to enter the leaves and water vapour to escape to the
atmosphere via the stomatal openings than the former. More over the other
aspect of stomatal opening that favour water loss to the atmosphere (i.e.
encouraging high rate of transpiration) is also advantageous by humidifying
the atmospheric air. However, to achieve reasonable atmospheric
purification, plants with hypostomatic nature of the leaves (i.e. stomata
being found or located on the abaxial surface only), lower frequency of
stomata with many subsidiary cells (e.g. anisocytic, tetracytic and
anomocytic), higher frequency of stomata with frequency of stomata with
little subsidiary cells (e.g. cyclic, paracytic and diacytic), less
heterogeneous composition of stomatal complex types, less stomatal density and
index (i.e. less distribution of stomata on the surface of leaves), and
lastly, probably occurrence of trichome (Figures 9 – 11) may be more suitable
for afforestation in dry locations. Plants with opposite conditions of the
above stomatal features may be more suitable for afforestation in wet
environments. These conditions had earlier identified by Oyeleke et al.
(2004) and AbdulRahaman and Oladele (2003; 2004).
REFERENCES AbdulRahaman, A. A. and
Oladele, F. A. (2003). Stomatal complex types, stomatal size, density and
index in some vegetable species in AbdulRahaman, A. A.
and Oladele, F. A. (2004). Types, density and frequency of trichomes in some
Nigerian vegetable species. Nigerian Journal of Pure and Applied
Science, 19; 1653-1658. May, L. R. (2006).
Securing a global future. New Scientist. p. 17. Obiremi, E. O. and
Oladele, F. A. (2001). Water-conserving stomatal systems in selected Citrus
species. South African Journal of
Botany, 67: 258-260. Oyeleke, M. O.,
AbdulRahaman, A. A. and Oladele, F. A. (2004). Stomatal anatomy and
transpiration rate in some afforestation tree species. Nigerian Society for Experimental Biology Journal, 4(2): 83-90. |
