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Moon flower (or) Ipomoea alba shows photonasty just opposite to that of Dandelion.

Stomata

Glucose.

Non-directional response of a plants part to stimulus is known as nastic movement.

Materials required: Glass trough, sand, flower pot, plugged at the bottom, pea or bean seeds and water.
Procedure:
1. A glass trough is taken and is filled with sand. A flower pot containing water, plugged at the bottom is kept at the centre of the glass trough.
2. Soaked pea or bean seeds are placed around the pot in the sand, what do we observe after 6 or 7 days?
Observation: It will be observed that radicle has grown towards the pot and moisture instead of growing vertically downward.
Inference: It proves that primary root is positively hydrotropic.

Aim: To show that sunlight is necessary for photosynthesis.
Materials Needed: Potted plant, black paper, boiling water, alcohol and iodine solution.
Procedure:
(i) Potted plant is placed in a dark room for 2 days to de-starch its leaves.
(ii) One of its leaves is covered with the thin strip of black paper on both sides.
(ill) The potted plant is kept in bright sunlight for 4 or 6 hours.
(iv) The selected covered leaf is plucked and the black paper is removed.
(v) This leaf is immersed in boiling water and then in alcohol to remove chlorophyll.
(vi) The leaf is now tested with iodine solution
(vii) The covered part of the leaf does not change blue-black colour because it did not receive sunlight.
(viii) The uncovered part of the leaf which received sunlight has able to synthesise starch and so it turns blue-black in colour.
Conclusion: This proves that light is essential for photosynthesis.

The root and shoot move towards the direction of the stimuli, whereas the movement of the opening and closing of the flowers are not directed towards stimuli. Such movements in plants are called as Nastic movements. Unlike tropic movement, nastic movements are independent of the stimuli direction and may or may not be growth movement.

The flower of Taraxacum officinale (common Dandelion) blooms in the morning and evening it closes (Photonasty). Ipomoea alba (Moonflower) does exactly he opposite. They open in the night and hence the name moon flower and closes in the day time. Just a casual touch is enough to make the Mimosa pudica (Touch-me-not) leaves fold up and droop (Seismonasty or thigmonasty).

Tropism is generally termed "positive" if growth is towards the signal and "negative" if it is away from the signal. While the shoot in a plant-moves towards the light, the roots move away in the opposite direction. Thus the shoots are said to have positive phototropism, while the roots have negative phototropism.

(a) To prove that sunlight is essential for photosynthesis.
(b) To destarch the plant.
(c) By Iodine test
(d) CO₂, H₂O and Chlorophyll