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Studies in the physiology of the onion plant
Author(s) -
Heath O. V. S.
Publication year - 1943
Publication title -
annals of applied biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.677
H-Index - 80
eISSN - 1744-7348
pISSN - 0003-4746
DOI - 10.1111/j.1744-7348.1943.tb06706.x
Subject(s) - bolting , biology , bulb , long day , inflorescence , horticulture , vernalization , ripening , growing season , botany , photoperiodism
This paper completes the survey of the effects of five factors on flowering behaviour, bulbing, and ripening of onions grown from sets (Heath, 1943) and deals with the factors day length and temperature in the second season. The results from both papers are discussed and the main conclusions are as follows: Flowering is greatly reduced or completely inhibited by submitting the plants to high temperature whether (1) during the whole period of growth from seed to set, (2) during the first part or whole of the storage period (Oct.‐Mar.), or (3) throughout the second season of growth from set to mature onion bulb. Unless very high temperature (35d̀; C.) is reached, heat storage restricted to the last part of the dormant period may only delay but not reduce flowering. Cold storage (od̀; C.) throughout or for the first part of the storage period reduces flowering; when restricted to the last part it tends to increase bolting, but at any other period in the life history of the onion plant bolting is apparently favoured by medium temperature (10–15d̀ C). Long days (16 hr.) throughout the second season inhibit inflorescence emergence irrespective of temperature within the range investigated. Conditions of day length and temperature in the second season favourable to bulbing are inimical to flowering: thus both long days and high temperature tend to encourage bulbing and prevent bolting, while short days inhibit bulbing but allow of bolting if the temperature is not too high. Late planting of sets in the field therefore reduces bolting. Leaf emergence ceases abruptly when bulbing begins at high temperature, and even at low temperature few if any more leaves expand. The relation of this fact to optimal time of planting and the use of American varieties capable of bulbing in short photoperiods is discussed. Seedlings apparently need a longer photoperiod for bulbing than plants grown from sets. A day length just adequate for bulbing at high temperature will not allow of bulbing at low temperature, with the result that seedlings sown very late produce good bulbs at high temperature but may fail to bulb at low temperatures. High‐temperature storage, especially during the last part of dormancy, tends to the production of distorted leaves, especially when followed by growth of the sets at high temperature. Such plants show a high mortality. Heat storage also delays and restricts bulbing, which is reflected in the increased number of expanded leaves. Ripening is similarly delayed; this effect is not directly due to water loss during storage.