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Water Relations of Beetroot Seed Germination: I. Microbial Factors, with Special Reference to Laboratory Germination

W. HEYDECKER and R. S. CHETRAM
Annals of Botany
New Series, Vol. 35, No. 139 (January 1971), pp. 17-29
Published by: Oxford University Press
Stable URL: http://www.jstor.org/stable/42908312
Page Count: 13
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Water Relations of Beetroot Seed Germination: I. Microbial Factors, with Special Reference to Laboratory Germination
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Abstract

Laboratory test results obtained with two seed lots of the cultivar Detroit Globe have shown: (1) 8 ml of water in a 9-cm diameter petri-dish are excessive for good germination of 25 two-seeded clusters, either natural or 'rubbed', which germinate well in 3 ml of water. (2) Some of this depression in germination is due to a 'direct' effect of the excessive water-supply. (3) But the benefit from either surface sterilization or the use of aureomycin, a bacteriostatic antibiotic, indicates that some of the depression of germination in the presence of excess water is the result of bacterial colonization of the seed clusters. The excess water effect can also be mitigated by preliminary 'rubbing' of the seed clusters, presumably by removal of some of the bacterial inoculum, provided that the rubbing process itself does not injure the seeds. (4) There is good evidence that the bacteria depress the germination of the seeds by competing with them for oxygen. (5) The effect of the bacterial population on germination in excess water can be aggravated by preliminary washing of the seed clusters. This is probably due to a delicate equilibrium between the bacteria and at least part of the fungal population of the seeds which when retained may produce an antibacterial substance; but the water-soluble phenolic acids contained in the seed clusters may also be involved: at high concentrations these inhibit germination, but they may also depress bacterial activity, even at lower than germination-inhibiting concentrations. (6) Fungicides aggravate the depression of germination on over-wet paper in the laboratory, but are of value in the field. (7) There is evidence that different limiting factors may operate on different seed lots and care must be taken not to generalize from results obtained from a limited number of seed samples.

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