Epidermal cells of plant roots increase their absorption surface by having
- A.Scales
- B.Root hairs
- C.Endodermis
- D.Stomata
Correct answer
Explanation
The correct answer is B, Root hairs. Root hairs are thin outgrowths of the root's epidermal cells that greatly increase the area for absorbing water and minerals.
Each root hair is a single epidermal cell that pushes out a long, narrow tube into the soil. Millions of them form a zone just behind the root tip, called the root-hair zone, and they reach into the spaces between soil particles. Water enters them by osmosis and minerals by diffusion and active transport, and then moves inward to the xylem.
A is wrong: scales are reduced leaves found on stems such as onion bulbs, not structures for absorption on roots.
C is wrong: the endodermis is an inner layer of the root around the vascular tissue; it controls what passes into the xylem but is not part of the epidermis.
D is wrong: stomata are pores mainly on leaves for gas exchange and transpiration; roots do not absorb water through them.
Exam tip: root hairs = absorption of water; stomata = gas exchange; endodermis with Casparian strip = control of entry to the xylem.
Practice Questions
View allQuartz is extensively used as a piezoelectric material. It contains
- A.Hg
- B.Si
- C.Ti
- D.Sn
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Quartz is silicon dioxide (SiO 2 ), so it contains silicon and oxygen. Quartz is one of the most common minerals in the Earth's crust and the main part of sand.
Read the full explanation →Bending of shoot of a plant towards light can be referred to as
- A.photonasty
- B.positive phototropism
- C.negative phototropism
- D.photoperiodism
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A shoot growing towards the light is moving in the direction of the stimulus, which makes it a positive tropism.
Read the full explanation →Which of the following organisms belongs to Coelenterata (Cnidaria)?
- A.Planaria and liverfluke
- B.Sea urchin and sea cucumber
- C.Hydra and sea anemone
- D.Euplectella and sycon
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Both are cnidarians, simple aquatic animals with stinging cells. Members of phylum Coelenterata (Cnidaria) have radial symmetry, two body layers, a single opening that works as both mouth and anus, and stinging cells called cnidoblasts on their tentacles, used to catch prey and for defence.
Read the full explanation →Recently, there was a growing awareness in our country about the importance of Himalayan nettle (Girardinia diversifolia) because it is found to be a sustainable source of
- A.anti-malarial drug
- B.biodiesel
- C.pulp for paper industry
- D.textile fibre
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The Himalayan nettle yields a strong natural fibre that can be spun and woven into cloth. Girardinia diversifolia, known as Himalayan giant nettle or allo, is a stinging shrub that grows wild in the moist forests of the Himalayas, including Uttarakhand, Himachal Pradesh and the North-east, as well as Nepal.
Read the full explanation →Which of the following statements are correct regarding the general difference between plant and animal cells ? 1. Plant cells have cellulose cell walls whilst animal cells do not. 2. Plant cells do not have plasma membrane unlike animal cells which do. 3. Mature plant cell has one large vacuole whilst animal cell has many small vacuoles. Select the correct answer using the code given below:
- A.1 and 2 only
- B.2 and 3 only
- C.1 and 3 only
- D.1,2 and 3
Show answer
Plant cells have a cellulose wall and one large central vacuole, but they do have a plasma membrane, just like animal cells.
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