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The effect of light on plant activities

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Introduction

The effect of light on plant activities In this essay I will look at the different effects that light has on plant activities, in particular the effect it has on the flowering of plants. I will discuss the role of phytochrome in plants and how the two different types are dependant on the length of day. Light affects plant activities in various ways, but in order for these activities to take place, the plant must first have a method of absorbing and then utilizing the light - this is where phytochrome comes into play. Phytochrome is a blue-green pigment that is present in very small amounts throughout the plant, particularly at the growing tips. There are two types: phytochrome red (Pr) and phytochrome far-red (Pfr), with phytochrome red absorbing red light and phytochrome far-red absorbing far-red light. ...read more.

Middle

Therefore, in SDP's Pfr inhibits flowering. In order to decipher which wavelength of light has greatest effect on the plant's activites, one must first use an action spectrum. An action spectrum simply shows which wavelength of light is most effectively used in a given reaction. In the case of phytochrome, the red light and far-red light parts of the spectrum are used much more efficiently than any other. Therefore, the action spectrum graph would show spikes above the wavelengths representing the colors red and far-red. An absorption spectrum shows which part of the spectrum is most effectively absorbed, in this case, by a plant. The absorption peak of the red-absorbing form of phytochrome is 660nm and the absorption peak for the far-red form is 730nm. ...read more.

Conclusion

However, these findings did not account for the fact that SDP's grown under non-inducing conditions (thus producing gibberellin) will not cause flowering of grafted LDP's that are also under non-inductive conditions (thus producing anthesin). It is argued that florigen does not exist but instead, a particular ratio of other hormones must be achieved for the plant to flower. However, there are also strong arguments to suggest that it does exist. Recent experiments suggest that florigen does exist. Its existence is substantiated by experiments that indicate that the substance that triggers blooming is produced or activated in the leaves of the plant, and must be given time to pass out of the leaves before the plant can flower. In conclusion, light affects a plant activites in a number of ways. This is reinforced by the fact that that a plants level of activity changes depending on the time of day and therefore the intensity of light. ?? ?? ?? ?? ...read more.

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Here's what a star student thought of this essay

3 star(s)

Response to the question

Overall essay structure okay, but does not stick to the main point of the question and the title needs to be adjusted to reflect this.
Introduction is good, and sets out what the main body of the text will be ...

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Response to the question

Overall essay structure okay, but does not stick to the main point of the question and the title needs to be adjusted to reflect this.
Introduction is good, and sets out what the main body of the text will be about without going into too much depth, sets out the main investigations of the essay well, apart from the second half of the essay which should be introduced in the introduction as a point that is examined. Does not answer directly the question of the effect of light on plant activities but more investigates the effect of light, hormones and phytochrome on flowering plants. However, the essay itself is very clear. The conclusion is adequate, but needs to include the hormonal aspect as does the introduction.

Level of analysis

Explains accurately the need for Phytochrome. Clearly describes the link between phytochrome and how light affects flowering plants well, and the role of the two different types of phytrochrome and why there is two different types without me having to have any previous knowledge of the subject, therefore good links and analysis of research seen. Explains the use of an action spectrum which is not introduced in the introduction and should have been as it makes up the second half of the main body of text. Argues the different theories for plant hormones and their affects on flowering plants well but this is not related to the main aim of describing phytochrome and the different effects that light has, therefore the introduction should be expanded to include this as the point seems relevant of the control of flowering in plants which seems the main investigation here, rather than the effect of light on plant activities as the title suggests.

Quality of writing

Lack of paragraphs makes the main body of the text quite hard to read and does not split the paragraphs up into relevant topics and discussions. Spelling, grammar and punctuation all good.


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Reviewed by skatealexia 01/03/2012

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