We observe growth movements among plants in our daily life. Growth movements are curvature movements caused by differential or unequal growth in plant organs, which results in their bending in the direction of a particular stimuli, for instance light. Such movements which are induced by external stimuli are called trophic movements. A trophic movement of plant organs in response to the source of light is known as Phototropism. The stem grows towards the direction of light, and is therefore said to exhibit positive phototropism. For instance, we have observed that shoot apices of Helianthus annus (Sunflower) plants exhibit phototropism by growing towards the direction of sunlight (Dr.Sharma, J.P.2006).
Dr.Sharma,J.P.(2006). Comprehensive laboratory manual in Biology(pp.169-170). New Delhi:Laxmi Publications Private Ltd.,
Question: Does the direction of sunlight affect phototrophic movements in plants?
Hypothesis: "The direction of sunlight plays an active role regarding phototrophic movements in plants."
Prediction: "If a plant is placed in a heliotropic chamber or card board box with a hole on one side and provided with unidirectional sunlight, then it exhibits phototropism by growing towards the direction of sunlight."
Controlled Experiment and Methods:
An experiment is conducted to test the above mentioned hypothesis by using the materials such as two pots, soil, mustard seeds, heliotropic chamber or card board box with a hole on one side, and water.
Procedure of the experiment:
Two pots are prepared by filling them with soil, and are labelled as A and B. A few (2-3) mustard seeds are sown in each of them. The conditions necessary for germination of seeds such as oxygen, moisture (water), and optimum temperature are provided in order to allow them to germinate and grow in both the pots A and B for a period of three days. Thus, the amount of moisture (water), availability of oxygen, temperature, the number...
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