Question
To obtain virus-free healthy plants from a diseased one by tissue culture technique, which part/parts of the diseased plant will be taken? [CBSE AIPMT 2014]
(a) Apical meristem only
(b)Palisade parenchyma
(c) Both apical and axillary meristems
(d) Epidermis only
Answer/Explanation
Ans. (c)
Both apical and axillary meristems are free of virus for the healthy plant cultivation because of strong interferon activity in this region. These tissues form a protective impermeable covering around themselves, which is non-penetrable by any pathogen. Hence, these tissue are used in the production of disease free plants by tissue culture.
Question
Somaclones are obtained by [CBSE AIPMT 2009]
(a) plant breeding
(b) irradiation
(c) genetic engineering
(d) tissue culture
Answer/Explanation
Ans. (d)
Somaclones are obtained by tissue culture. The plant regenerated from cell and tissue cultures shows heritable variation for both qualitative and quantitative traits. Plant breeding is the branch of biology, which is concerned with developing varieties superior to existing ones. Irradiation means exposure to any form of radiation. Genetic engineering is defined as the manipulation of genes by man.
Question
In order to obtain virus-free plants through tissue culture the best method is [CBSE AIPMT 2006]
(a) meristem culture
(b) protoplast culture
(c) embryo rescue
(d) anther culture
Answer/Explanation
Ans. (a)
Virus free plants can be developed by using meristem as explant in tissue culture. In infected plants, virus concentration decreases as they approach the apical meristem.
It is because the cells of apical meristem undergo rapid mitotic divisions and virus cannot divide so fast and thus it cannot keep pace with the fast dividing meristematic cells.
So, apical meristems are generally virus free or they contain very low concentration of virus. Before meristem culture, viruses associated with meristem are eliminated by in vitro heat treatment (thermotherapy). Morel and Maetin (1952) successfully obtained virus free Dahlia plants through meristem culture of infected plants.
Question
Haploid plant cultures are got from [CBSE AIPMT 1994]
(a) leaves
(b) root tip
(c) pollen grain
(d) buds
Answer/Explanation
Ans. (c)
Haploid plant cultures are obtained from pollen grains as they are haploid while leaves, root tip and buds are diploid.