RESULTS and DISCUSSION: FLOWER/PETAL

STOMATA

The flower of Hamelia patens exhibits a raceme type of flower wherein they are found in clusters growing at the end of various growing points. The Hamelia patens flower/petal contains a few closed paracytic stomata, a type of stomata wherein one or more subsidiary cells are found bordering the stoma parallel to or with the long axis of the guard cells (Esau, 1979). They are fewer than those found in the leaves of the plant since they are mainly used in reproduction though they are also capable of reducing the transpiration rate due to the closed stomata. Due to the fact that even the petals of the plant has a few stomata, which functions for gaseous exchange and reduction of water loss, the plant Hamelia patens is able to or prefer to thrive in a warm and sunny environment.

TRICHOMES

As observed, the petals of Hamelia patens also contain trichomes located on the epidermis of the petals. The trichomes observed were simple hairs. These trichomes are unicellular, unbranched and hair-like. The simple hairs trichomes are found on the epidermis of the flower because of this they are able to decrease radiation absorbance thus also reducing the heat load over the surface of the petal (Vogelmann, 1993). Ultimately, this leads to the reduction of water loss by transpiration since the humidity around it is increased making the water potential between the petal tissue and surrounding air layer is reduced (Ehleringer, 1984). Since Hamelia patens grows and develops in an environment with a higher temperature and more sunlight, this could be an adaptation of the plant to its surroundings as trichomes increase density when placed in such extreme conditions in order to avoid damage and in order to cope up with water shortage (Gonzales et al. 2008). These trichomes may also function for protection since they constitute a mechanical barrier that hinders the movement & the feeding of an insect (Baur et al., 1991).

CRYSTALS

Crystals were also observed in the petals of Hamelia patens as well. The crystals found were needle-like crystals known as Raphides. Raphides are solid, white needle-like crystals that tapered sharply to a point at both ends (Snyder et al., 1979). The solidness of the crystals was due to the fact that they were composed mainly of calcium oxalate. Their acicular shape is said to be a critical component in the mechanisms of defense of the plant (Howard, 2010). These defences include the paralysation and/or death of small animals or merely the irritation of larger animals. These are caused solely by the mechanical action of the intact needles on the epidermis of the animal (Snyder et al., 1979). The function of this primarily to the petal is to prevent or avoid predation.

CONCLUSION

The anatomical study of the petals of Hamelia patens proved to be present with types of stomata, trichomes, and crystals. The type of stomata present was characteristically paracytic with a closed stomatal pore. Although the stomata are few in number, they mainly function for the reduction of transpiration rate and water loss as well as for efficient gaseous exchange. Simple hairs were the only type of trichomes observed in the petals of Hamelia patens. Since simple hairs were located on the epidermis, they mainly function for the reduction of radiation absorbance as well as the heat load over the surface of the petal. Moreover, these trichomes help increase density especially when the plant is exposed to extreme environmental conditions in order to prevent the plant from water shortage. Also, simple hairs function for protection against predators. Raphides were the only type of crystals observed in the petals. These crystals were characteristically needle-shaped which makes them efficient for protection by causing irritation even paralysation of usually small animals.

References:

Arnott, H.J. and Webb, M.A. (2000). Twinned Raphides of Calcium Oxalate in Grape (Vitis): Implications for Crystal Stability and Function. International Journal of Plant Sciences. Vol. 161. 1.

Baur, R., Benz, G., Binder, S. (1991). Nonglandular leaf trichomes as short-term inducible defense of the gray alder, Alnus Incana , against the chrysomelid beetle, Agelastica Alni. Acta Oecologia 87. 219–226

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