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PROTANDRY AND THE SEQUENCE OF FLOWER OPENING IN THE ONION ( ALLIUM CEP A L.)
Author(s) -
CURRAH LESLEY,
OCKENDON D. J.
Publication year - 1978
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.1978.tb02647.x
Subject(s) - umbel , biology , pollen , botany , horticulture , stamen , pollination , pollinator , anthesis , outcrossing , cultivar
SUMMARY To assess the importance of protandry in promoting outbreeding in onions, detailed observations were made of the sequence of flower opening in onion umbels. Six stages of flower development were defined, covering the period from flower opening to withering of the style. Regular counts were made in the 1976 season of the total number of flowers at each stage during the flowering of twenty‐nine umbels representing four cultivars and six inbred lines. The pattern of flowering was similar in all cases, although the number of flowers per head varied from 126 to 681. At first the number of flowers opening was small, but rapidly increased, giving a peak, which lasted for a mean of 4–10 days. During the middle of the peak flowering period the maximum number of flowers open at one time was often more than 50% of the total flowers on the head. A particular flower could not easily be pollinated with its own pollen because the stigma did not become receptive until about 2–3 days after the anthers had started to dehisce. Protandry was not considered to be effective in preventing pollination between flowers on a single umbel because there was abundant pollen available from the time the first stigmas became receptive, almost until the end of flowering. Other factors which may account for high out‐crossing rates in onions are discussed.