Ploidy Level and Basic Chromosome Number in Some Species of Jatropha L.
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Abstract:
The young developing inflorescence of ten species of the genus Jatropha and one interspecific hybrid between Jatropha curcas × Jatropha integerrima were fixed in Carnoy's fluid. Pollen mother cells were well stained with 2% acetocarmine. Eight species and one hybrid (J.curcas × J.integerrima) exhibited 11 bivalents and 2n =22 and x=11. But the other two species, J.villosa var. villosaand and J.villosa var. ramnadensis showed only 10 bivalents and 2n number of 20 chromosomes and x=10. The study concluded the occurrence of two kinds of haploid chromosome numbers of n =10 and n =11. Except Jatropha tanjorensis, cytological investigation in all species exhibited normal and complete pairing and bivalent formation in metaphase I with equal separation of chromosomes in anaphase indicating that the course of meiosis was normal. Jatropha tanjorensis did not exhibit normal course of meiosis and no proper count of chromosomes could be made. The present investigation revealed the existence of two basic chromosome numbers x = 5 and x = 6 in the genus Jatropha.Keywords:
Jatropha
Jatropha curcas
Bivalent (engine)
Chromosome number
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Meiosis was studied in control and seed-irradiated progenies of Triticum aestivum in order to understand the effects of gamma irradiations on chromosomal behavior during meiotic division. The main chromosomal aberrations were stickiness, precocious separations, univalents, multivalents, unoriented bivalents, laggards, bridges, fragments, disturbed polarity, unequal separations of chromosomes and micronuclei. The stickiness, stray bivalents and multivalents at metaphase, laggards, bridges and fragments at anaphase/telophase were the dominant anomalies. The degree of occurrence of all these meiotic abnormalities essentially coincided with the increase in the treatment of gamma irradiations. These chromosomal aberrations also affected the qualitative composition of postmeiotic products, i.e. tetrads and pollen grains. The effect of gamma rays on chiasma frequency and pollen fertility was also studied in which dose dependent decrease was clearly noticeable. Moreover, higher doses (25kR-50kR) markedly decreased seed germination whereas lower dose (5kR-20kR) showed no significant effect (P<0.01) on the germination percentage with respect to the control.
Chiasma
Telophase
Gamma Irradiation
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