Physiological factors affecting yield in Allium cepa cv. kelsae

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Louis, D.V., 1985. Physiological factors affecting yield in Allium cepa cv. kelsae. PhD, Nottingham Trent University.

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Abstract

The interactive control engendered between light quality and day- length and light quality with different plant growth regulators applied exogenously was studied on a range of gross morphological and cellular characters affecting yield in Allium cepa cv. Kelsae. In regard to light quality, attention was focused on the possible roles performed by the low and high R:FR ratios emitted from Philips Colour 37 (C37) and Atlas White (AW) fluorescent light sources respectively. The influence of multifarious plant growth regulators on bulbing was also determined under greenhouse and field conditions.

Increasing the daylength from 11 to 20 h with C37 rather than AW light, not only enhanced leaf blade and leaf sheath length, but also initiated bulbing with a concurrent cessation in leaf development when the daylength exceeded 14 h. Furthermore a daylength extension from 17 to 20 h shortened the time to bulb inception by 2 weeks.

C37 light increased the leaf area, fresh and dry weight of the total plant, leaves and combined basal region & leaf sheaths when compared to AW light, whereas the contrary applied to the root fresh and dry weight. Furthermore the enhancement in leaf area by C37 light was largely attributed to an augmentation in epidermal and palisade meso- phyll cell width and length expanding both leaf length and width. IAA, GA 4/7and ethrel C inhibited plant growth and interacted with light quality on certain plant characters by reducing the expected increase under C37 light to the level achieved with AW light and the relevant plant growth regulator. In contrast phosphon D particularly augmented leaf expansion with the response being greater under C37 rather than AW light. Notable leaf area diminutions affected by IAA, GA 4/7 and ethrel C were chiefly ascribed to the former two reducing epidermal and palisade mesophyll cell width and hence leaf breadth, whilst the latter retarded epidermal and palisade mesophyll cell length and thereby leaf height. On the other hand greater cell division activity may be responsible for the enlarged leaf width exacted by phosphon D.

Under greenhouse and field conditions GA 4/7 and GA3 produced torpedo shaped bulbs and tillers', whilst only the former character developed following treatment with IAA. In contrast round bulbs were predominantly evoked by phosphon D, whereas early development of small flat shaped bulbs characterised the response to ethrel C.

As in other species the regulation of growth and development in Allium cepa cv. Kelsae appears to be complex. Furthermore the responses evoked by light and plant growth regulators on this particular variety are discussed in relation to effects produced and possible mechanisms involved in other onion cultivars and different plant species.

Item Type:

Thesis

Creators:

Louis, D.V.

Date:

1985

ISBN:

9781369325782

Identifiers: