Unfertilized ovary pushes wheat flower open for cross-pollination. (30th November 2017)

• Record Type: Journal Article
• Authors: Okada, Takashi; Jayasinghe, J E A Ridma M; Nansamba, Moureen; Baes, Mathieu; Warner, Patricia; Kouidri, Allan; Correia, David; Nguyen, Vy; Whitford, Ryan; Baumann, Ute
• Is Part Of: Journal of experimental botany. Volume 69:Number 3(2018)
• Page Start: 399
• Page End: 412
• Publication Date: 2017-11-30
• Subjects: Fertilization -- flower -- ovary -- pericarp -- pollination -- wheat; Botany -- Periodicals; Botany, Experimental -- Periodicals; Plant physiology -- Periodicals; 580
• DOI: 10.1093/jxb/erx410
• Languages: English
• ISSNs: 0022-0957

Abstract

Abstract : Wheat flower opens when self-pollination fails. The unfertilized ovary pushes the palea and lemma apart by increasing radial size associated with cell enlargement and suppression of pericarp degradation, therefore facilitating cross-pollination. Abstract: Bread wheat is strongly autogamous; however, an opportunity for outcrossing occurs when self-pollination fails and florets open. The first phase of floret opening at anthesis is short and induced by lodicule turgidity. Some wheat florets re-open post-anthesis for several days, known as the 'second opening', for which the underlying mechanisms are largely unknown. We performed detailed physiological, anatomical, and histological investigations to understand the biological basis of the flower opening process. Wheat florets were observed open when the ovary was unfertilized. Unfertilized ovaries significantly increased in radial size post-anthesis, pushing the lemma and palea apart to open the florets. The absence of fertile pollen was not directly linked to this, but anther filament elongation coincided with initiation of ovary swelling. The pericarp of unfertilized ovaries did not undergo degeneration as normally seen in developing grains, instead pericarp cells remained intact and enlarged, leading to increased ovary radial size. This is a novel role for the ovary pericarp in wheat flower opening, and the knowledge is useful for facilitating cross-pollination in hybrid breeding. Ovary swelling may represent a survival mechanism in autogamous cereals such as wheat and barley, ensuring seed set in the absence of self-fertilization and increasing genetic diversity through cross-pollination.