Biology coursework investigation: Comparing the length of ivy leaves (Hedera helix) in areas of greater illumination and shade

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Biology coursework investigation: “Comparing the length of ivy leaves (Hedera helix) in areas of greater illumination and shade”


The aim of this study was to compare the length of leaves of ivy plants (Hedera helix) climbing on two Hornbeam trees (Carpinus betulus) in two different light intensities. The hypothesis was that the lengths of Hedera helix exposed to a higher light intensity (“sun leaves”) would be shorter than Hedera helix exposed to a lower intensity of light (“shade leaves”). The light intensity was measured using a light meter and the lengths of the midrib vein of 30 leaves were measured from each of the two trees. The method describes how leaves were chosen to ensure that they were approximately the same age. The results were analysed using a students t statistical test and it was concluded that there was a significant difference between the lengths of the two groups of leaves. The main reason for this was concluded to be the structural differences in the Hedera helix in the sun and shade.

Background information on Hedera helix

Previous investigations have shown that there are structural differences between the leaves of ivy in areas of high light intensity and areas of low light intensity. Shade leaves of ivy are typically thinner than sun leaves and also have a larger area in comparison. This is due to them having a thinner cuticle and one layer of palisade tissue cells whereas sun leaves usually contain two or three layers of palisade cells that are often longer and also have a thicker cuticle. Low light intensity causes the shade leaves to grow rapidly producing long internodes thus helping the leaves to catch any light in the plant’s surroundings. This rapid growth helps the shoot to reach light subsequently helping the plant to survive in an area where light levels are low. The large leaves of the shade plant provide a larger surface area for trapping light energy for photosynthesis for maximum absorption. This is made further efficient by the chloroplasts which take up a position where they will absorb maximum light without shading other chloroplasts below them. In sun leaves however, the chloroplasts expose themselves to light at different times with those already having been exposed to light taking shelter in the shade of others so as to prevent overexposure, which would destroy the chloroplasts. High light intensity means that sun leaves do not have a need to grow as rapidly as shade leaves hence their shorter internodes and smaller leaves. Shade leaves also weigh more than sun leaves due to the fact that their chloroplasts contain more grana and therefore more chlorophyll (    


Hedera helix is a convenient plant for this study because it is a climbing plant able to survive in both shady and bright conditions. This makes it ideal for a study comparing leaf size in areas of high and low light intensities.

Hedera helix (common ivy) is a member of the Plantae Kingdom and is in the class of dicotyledonous plants. It is a part of the family Araliaceae (Ginseng) and is a woody, evergreen climber with perennial stems. Hedera helix grows well in adverse soil conditions, both basic and acidic soils, and is adaptable to different levels of light (Reichard, 2000) It is an evergreen climbing vine that attaches to the bark of trees, brickwork, and other surfaces by way of small root-like structures which exude a sticky substance that helps the vines adhere to various surfaces. Leaves are dark green with white veins, waxy to somewhat leathery, and arranged alternately along the stem. Hedera helix exists in both a juvenile and adult form. The leaf form of the juvenile plant is most often recognized by its thinly elongated, 3-5 lobed leaves that are typically a dark, glossy green with whitish veins (Reichard, 2000). In its juvenile form, Hedera helix has adventitious rootlets located at the leaf nodes on the stem. The rootlets allow the plant to climb trees, walls, and other vertical structures. The vine attaches to surfaces but does not penetrate through mortar or tree bark, thus it is not considered to be a parasite (Elliott, 1995).

Hedera helix thrives in dark, moist forest conditions but can climb to heights of 90 feet toward the canopy where greater amounts of light are available (Dirr, 1998). The leaves of the juvenile form of Hedera helix are more adapted to lower light levels (Devero, 2000). Though Hedera helix will grow in variable light conditions, it prefers shade, damp soils, and a moist, cool environment (Morisawa, 1999). This is apparent in the measurements of the two groups of leaves which show that the leaves in the shade were indeed longer than the leaves in the brighter area.

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The leaves of ivy (Hedera helix) exposed to a lower intensity of light will be have a greater length than the leaves of ivy exposed to a higher intensity of light.


Independent variable

  • The intensity of light each ivy plant is exposed to

Dependent variable

  • The length of the ivy leaves

Variables to be kept constant

  • The time of day
  • Temperature of the habitat
  • The point on the ivy plant where the leaves are located
  • The amount of CO2 and O2 available
  • The type of ivy measured
  • ...

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****A very good A-level experiment report, in which the key elements of a scientific paper are clearly attempted. To improve: 1)Give a more detailed explanation of the biology behind plant growth towards light and, the process of photosynthesis, and the role of chloroplasts and leaf structure in shade adaptation. Details should be concise, but illustrate understanding of the background biology 2)Reference all sources used in the text 3)Address sources of error and limitations of the procedure thoroughly and suggest solutions that could improve the method. This section lacks substance currently 4)Use standard format for the bibliography and evaluate sources