This organism is an understory plant native to tropical rainforests found within Mexico and Southern America. As you can see in the image, the understories of rainforests, which is where M. deliciosa is most commonly found, have significantly low concentrations of Photosynthetically Active Radiation (PAR) in comparison to the canopy. PAR is the acceptable wavelength range of visible light which is required for photosynthesis.
Although a lot of stresses may arise due to the low PAR concentration on the forest floor; M. deliciosa is still able to tolerate these demanding conditions. Although this organism can tolerate low PAR intensity it prefers to inhabit the upper tree canopies in order to have access to the larger concentrations; therefore helping the plant reach full light saturation. So how does M. deliciosa reach the top of the canopies? |
Well upon germination M. deliciosa grows towards the most shaded area in a behaviour known as Skototropism, via mechanical manipulation of the molecular and chemical mechanisms that are responsible Phototropism; the growth towards light. Skototropism utilizes a lot of the plants limited energy whilst in low PAR conditions, thus the process has adapted to be very efficient and effective. So why does this organism grow towards the most shaded area? Typically within M. deliciosa’s habitat the most shaded areas are caused by large trees blocking the sunlight thus providing a large shaded area at the base of their trunk, it is this area that M. deliciosa is attracted to initially.
This adaptation however must mean that M. deliciosa allocates its resources effectively enough to provide their leaves with sufficient light absorbing pigments. As a result once M. deliciosa access larger concentrations of PAR it will start to grow more leaves and allocate resources in such a manner that allow these perforations to form thus increasing net absorption of PAR; increasing its effectiveness within this niche. All of these adaptations are examples of the ability for this organisms are examples to alter it's chemical, behavioural and physiological in response to it's environment; also know has Phenotypic Plasticity.
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M.deliciosa is an Epiphyte meaning it is a non-parasitic plant that grows on another plant, or tree, in order to obtain essential resources, in this example; the essential resource is light. This explains the organism’s skototropism behaviour. Once attached M. deliciosa may undergo re-allocation in order to ensure the ascent up the tree occurs as quickly as possible; allowing the plant to obtain the large concentrations of PAR in a minimal amount of time.
Even when M. deliciosa reaches the tree canopy there is still a lot of competition for PAR, therefore this plant has developed many adaptations. One in particular concerns the plants leaf morphology, the leaves of M. deliciosa have perforations either side of the main vein. This adaptation has a major benefit with regards to tolerating low light intensity, the perforations allow M.deliciosa’s leaf area to increase, the gaps in the leaf reduce the leaf’s mass thus; preventing over-straining the connecting stem system. The increase in leaf area allows for a larger surface area in which PAR can be absorbed by Chlorophyll; increasing the likelihood of full light saturation. |
These are just a few examples of how plants within the Under-stories of forests have adapted to tolerate low light intensity, for more click here.