Question
Identify the incorrect statement. [NEET (Sep.) 2020]
(a) Sapwood is involved in the conduction of water and minerals from root to leaf
(b) Sapwood is the innermost secondary xylem and is lighter in colour
(c) Due to deposition of tannins, resins. oils, etc., heartwood is dark in colour
(d) Heartwood does not conduct water but gives mechanical support
Answer/Explanation
Ans. (b)
Statement in option (b) is incorrect and can be corrected as :
Sapwood is outermost secondary xylem and is lighter in colour. There cell walls are not lignified and there is no deposition of organic compounds. Sapwood is involved in the conduction of water and minerals from root to leaf.
Question
The roots that originate from the base of the stem are [NEET (Sep.) 2020]
(a) primary roots
(b) prop roots
(c) lateral roots
(d) fibrous roots
Answer/Explanation
Ans. (d)
The roots that originates from the base of the stem are fibrous roots. In fibrous root system, the primary roots stop growing and becomes rudimentary, while new roots for anchorage and absorption develop from the base of the stem. This type of root formation is observed in monocot like wheat plant.
Question
Pneumatophores occur in [NEET 2018]
(a) carnivorous plants
(b) free-floating hydrophytes
(c) halophytes
(d) submerged hydrophytes
Answer/Explanation
Ans. (c)
Pneumatophores are breathing or respiratory roots which are found in halophytes like mangroves. Halophytes grow in saline swamps, therefore respiratory roots come out of water and pick up oxygen for respiration. Excess $\mathrm{CO}_2$ is also given out. It occurs through small pores, called lenticles.
Carnivorous plants, free-floating hydrophytes and submerged hydrophytes do not possess pneumatophores.
Question
Plants, which produce characteristic pneumatophores and show vivipary belong to [NEET 2017]
(a) mesophytes
(b) halophytes
(c) psammophytes
(d) hydrophytes
Answer/Explanation
Ans. (b)
Plants that produce pneumatophores, i.e. negatively geotropic roots and show vivipary, i.e. germination of seeds inside the fruits are halophytes. These plants are adapted to grow in highly saline areas such as mangroves.
Pneumatophores help these plants in respiration as they do not get sufficient axygen from the soil. On the other hand vivipary aids in perennation.
Question
Roots play insignificant role in absorption of water in [CBSE AIPMT 2015]
(a) sunflower
(b) Pistio
(c)pea
(d) wheat
Answer/Explanation
Ans. (b)
Pistia is a hydrophyte where absorption of water by root is insignificant.
Question
Roots of which plant contains an oxidising agent? [CBSE AIPMT 2001]
(a) Carrot
(b) Soyabean
(c) Mustard
(d) Radish
Answer/Explanation
Ans. (b)
Leghaemoglobin is present in roots of soyabean plants. It is an oxygen-binding haem protein, which is present in the cytoplasm of infected nodule cells at high concentration and gives the nodules a pink colour. It’s main function is to help in the transport of $\mathrm{O}_2$ to the respiring symbiotic bacterial cells in a manner analogous to haemoglobin. which transports $\mathrm{O}_2$ to respiring tissues in animals.
Question
The plant, which bears clinging roots, is [CBSE AIPMT 1999]
(a) Trapa
(b) orchid
(c) screw pine
(d) Podostemon
Answer/Explanation
Ans. (b)
Orchids have clinging roots that are modified adventitious roots meant for providing mechanical support. These arise from the axils of leaves or nodes of the stem and pierce the substratum plant to facilitate fixation.
Question
The plant which bears clinging roots is [CBSE AIPMT 1999]
(a) Podostemon
(b) orchid
(c) Trapa
(d) Screwpine
Answer/Explanation
Ans. (b)
Clinging roots are modified adventitious roots meant for providing mechanical support. These arise from the axils of leaves or nodes of the stem and pierce the substratum plant to facilitate fixation e.g. orchids, ivy.
Question
Buttress roots are found in [CBSE AIPMT 1995]
(a) Sorghum
(b) Banyan
(c) Terminalia
(d) Pandanus
Answer/Explanation
Ans. (c)
Buttress roots refer to irregular, broad-like the wood plants that arise from basal parts of main stem of older plants, and spread in different directions in the soil, e.g. Ficus religiosa (peepal), Terminalia, Bombax, etc. These roots aids in providing mechanical support to the trees.
Question
Velamen is found in [CBSE AIPMT 1991]
(a) roots of screwpine
(b) aerial and terrestrial roots of orchids
(c) leaves of Ficus elastica
(d) aerial roots of orchids
Answer/Explanation
Ans. (d)
The aerial roots of orchids, (e.g. Vanda) are surrounded by a spongy tissue, (velamen) which is hygroscopic and absorbs moisture from the surrounding air.