Sampling Stomatal Densities of Various Species of Plants The importance of stomata is the fact that they control the intake of carbon dioxide and the loss of water in plants. The ratio of intake to loss creates a better picture of which plants adapt would to their environment and which would not. Eight different plant species were sampled the stomatal densities and compared them to their environments. The densities were recorded for each species by painting clear nail polish on the adaxial side of leaf. Clear tape was laid over the nail polish then removed and placed on a microscope slide and placed under a compound microscope.
Three sections of each leaf were observed with the highest recorded. The number of stomata obtained was then concerted to stomata per mm2. The hypothesis predicted that hydrophytes would have the highest stomatal density followed by mesophytes with a medium amount and xerophytes with the least.
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It was shown that Kalinchoe delagoensis, xerophyte, Rhoeo spathacea, mesophyte, and Zebrina sp, hydrophyte. had the lowest stomatal densities. Cyperus papyrus, hydrophyte, and Hibiscus sp. mesophyte, had the highest stomatal densities. Bouganville and Monstera deliciosa both fell in the middle of the spectrum; while Fiscus sp.
also had a high stomatal density. Introduction The ecological field is growing everyday with one area of study in particular; stomatal density. This field of study is important because it shows how and when plants are more susceptible to environmental changes and how quickly they will adapt themselves. Stomata control gas exchange in the leaves of vascular plants. Open stomata allow carbon dioxide to enter the leaves and water and oxygen to leave. Stomata are located on the underside of the leaf to decrease descication. If the environment that the plant lives in is too sunny, cytochromes, membranes and pigments can ‘bake under
the sun’. As a coping mechanism, the stomata open and release water to lower their temperature; similar to the way humans sweat. When water is scarce, evaporation such as explained above can lead to desiccation of the plant. Xerophytes are plants that are able to survive in areas with very little moisture. Mesophytes are plants that are neither adapted to a dry nor wet environment. Hydrophytes are plants that have adapted to live in a very moist or aquatic environment (Campbell et al. 2008). In the following experiment there will be comparisons drawn upon these different types of plants.
In a study on Spartina (Maricle et al. 2009), thirteen species were studied of Spartina ranging high to low marsh and freshwater habitats. The scientists studying Spartina grasses used light and electron microscopes to measure and record the number of stomata on the adaxial side of the leaf. Thirteen species were collected and examined: Spartina alterniflora, Spartina anglica, Spartina argentineses, Spartina bakeri, Spartina densiflora, Spartina patens, Spartina spartinae, Spartina cynosuriodes, Spartina pectinata, and Spartina gracilis.
The species were compared against herbarium specimens and Flora from the North American Keys; but the populations used in the study were grown under greenhouse conditions in Fort Hays State University and Washington State University. The scientists studying Spartina grasses used light and electron microscopes to measure and record the number of stomata on the abaxial and adaxial side of the leaf. Results showed that in freshwater species, there were more stomata on both sides; conversely, in saltwater species, there were more stomata on the adaxial side.
Saltwater species were able to better adapt to their climate and water loss due to the number of stomata present (Maricle et al. 2009). Konrad and colleagues (2009) report that stomata changes are shown to be inversely proportional to atmospheric CO2 concentration. The article stated that fossils were used to introduce a model that described how stomata density responses to atmospheric CO2 concentration. The model is based on the diffusion of water vapor and CO2, photosynthesis and a principle of plants concerning water availability and gas exchange.
The model shows an association that stomata density is a response to the environment and CO2 concentrations. The model also showed that stomata pore geometry should also be considered because of the changes they can undergo with the changing environment (Konrad et al. , 2007). For this experiment eight different types of plants were chosen. Cyperus papyrus belongs to the family Cyperaceae. The species ranges in habitats from rain forests to tropical and sub-tropical deserts and is a hydrophyte. Monstera deliciosa belongs to family Archae and are found in climates such as San Diego, California with moist but not soggy envrionments.
Bouganvillea sp. Belongs to family Nyctaginaceae and is a xerophyte. It can be found in tropical areas such as Florida or Brazil with sufficient rainfall. Rheo spathacea is usually reguarded as a weed, and belongs to family Commelinaceae and is also a mesophyte. It can be found in southern Africa in countries such as Kenya and Tanzania, temperate Asia for example China and Japan, or southwestern USA Louisiana and Florida etc. Kalanchoe daigremontiana belongs to the family Crassulaceae. They are found in mostly warmer drier conditions and is a xerophyte. Fiscus sp.
belongs to the Moraceae family and is usually found in tropical zones. The Ficus sp. is a mesophyte. The Hibiscus sp. is of the Malyaceae family. This plant is usually found in tropical, sub-tropical, and temperate environments and is also a mesophyte. The final plant was the Zebrina sp. Is a hydrophyte and belongs to family Commelinaceae. It is found in places such as Borneo or the Philippines (Hargitt 2012). In this experiment, it is hypothesized that plants residing in drier and warmer environments will have a lower stomata density than those in wetter environments. Materials and Methods
The procedure used followed protocol of Grant and Vatnick (2004). Eight different species were sampled for stomatal density: Rhoeo spathacea, Hibiscus sp, Bouganvilea sp, Zebrina sp, Ficus sp, Kalinchoe delagoensis, Cyperus papyrus, and Monstera deliciosa. Twelve leaf samples of each species were sampled except Monstera leaf for which twelve samples were taken from one leaf. Each lower surface had a small section painted with clear nail polish. After the nail polish dried, a piece of clear tape was laid over each polished part of the leaf to remove an imprint of the stomata.
The clear tape was then placed onto a microscope slide and observed under a compound microscope. Each slide was examined and stomata counted in three different places on the leaf imprint. The field of view with the highest number of stomata was recorded. This was repeated for all twelve leaves for all eight species. A micrometer was used to measure the diameter of the field of view to calculate the area of field of view using the equation area of a circle = ? r?. Then all measurements were converted to the units stomata/mm?.
Data was graphed and statistically analyzed using an ANOVA. Results The data obtained from the twelve leaf samples varied significantly in results. Table one shows the mean, standard deviation, and percent confidence interval . The average number of stomata for Kalinchoe delagoensis was 7. 65 per mm2, Cyperus papyrus was 246. 15 per mm2, Rhoeo spathacea was 10. 324 per mm2, Zebrina sp. 22. 088 per mm2, Bouganvillea sp. was 101. 91 per mm2, Hibiscus sp. was 250. 00 per mm2, Fiscus sp. was 216. 28 per mm2, and Monstera deliciosa was 47. 147 per mm2.
The hydrophytes (Cyperus papyrus) had the highest amount of stomata. Zebrina sp. is also a hydrophyte but had a low stomata count. The xerophytes (Kalinchoe delagoensis and Bouganvillea sp) are supposed to have the lowest number of stomata. The standard deviation also ranged from 1. 72 to 58. 9 from Rhoeo spathacea to Hibiscus, both cases ending with Hibiscus on the higher end of the scale. Kalinchoe delagoensis has a mean of 7. 65 per mm2 while Hibiscus has a mean of 250. 00 per mm2 once again putting it on the higher end of the scale.
All of the data can be found on figure 1 as well as the ANOVA results graphed in figure 1 and figure 2. Discussion The stomatal densities were predicted to show correlation with different types of plants. The hypothesis predicted that hydrophytes would have the highest stomatal density. Results show that that part of the hypothesis was not fully supported. Cyperus papyrus is a hydrophyte about the same stomatal density as Hibiscus sp. or Fiscus sp. (mesophytes) for example. Zebrina sp. is also a hydrophyte but had a stomatal density in the lower region.
The hypothesis also predicted that xerophytes would have the lowest stomatal density. Kalinchoe delagoensis supported the hypothesis and had a low stomatal density. Conversely the other xerophyte, Bouganvillea had an inbetween stomatal density which did not support the hypothesis. The last part of the hypothesis predicted that mesophytes had mid range dnsities due to a medium amount of water indicating temperate terrestrial conditions. The only species that supported the hypothesis was the Monstera deliciosa. The Rhoeo spathacea was in the lower range and the Hibiscus sp.
and the Fiscus sp. were in the higher range. In the future, knowing the exact species identification of Hibiscus, Fiscus, Zebrina, and Bouganvillea would help in the identification of xerephyte, mesophyte, and hydrophyte. Identify carbon dioxide and oxygen levels in each of the plant’s habitats to determine if the levels have an impact on the densities or not. The natural habitat of each plant may influence the stomatal densities, but the fact that the species is a hydrophyte, mesophyte or xerophyte does not mean it will have a certain stomata density.