The effect of light availability on the phenotypic responses of Hedera sp.; leaf colour, area, and thickness, and abundance of hairs.
             Plant species are able to grow in many different habitats all around the world. They can show different growth forms in different locations as they depend on a variety of environmental factors such as light, water availability, soil type, and abundance of nutrients (to name a few). Differences between plants in various environments can be due to the genetic differences between the plants or the different appearances can be due to phenotypic plasticity. Phenotypic plasticity is the ability of a genotype (genetic constitution) to alter its phenotype (outward appearance) in response to the environment. Usually a plant's genotype does not change in accordance to environmental situations but its genotype may (Biology 108 2002).
             Valladares et al. (2002) observed the phenotypic responses of oak and birch seedlings to various light intensities and state that full sunlight can limit photosynthesis but deep shade can also be detrimental to plant growth and survival. Plants require very different mechanisms to cope with sun and shade so they must therefore specialize to one end of the environmental gradient or improve their ability to satisfy their phenotypes to the light currently presented at each particular site.
             Using sun and shade, this experiment will examine the effect of light availability on the variations in morphology of English Ivy (Hedera sp.). It is likely to see variation in the following characteristics: leaf colour, type and abundance of hairs, degree of lobing or dissection of the leaf blade, leaf size (area), leaf thickness (more or less differentiated palisade layer, internode thickness, stem thickness, degree of branching, number, length and degree of branching in roots, and weight of both roots and shoots. Due to time restrictions we will be primarily concerned with observing and...