The determination of pea leaves,leaflets, and tendrils |
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Authors: | Kevin S Gould Elizabeth G Cutter J Peter W Young |
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Institution: | Plant Science Group, School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand
Department of Cell and Structural Biology, Williamson Building, University of Manchester, Manchester, M13 9PL U.K.
Department of Biology, University of York, York, YOl 5DD U.K. |
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Abstract: | Pea leaf determination was examined by culturing excised leaf, leaflet, and tendril primordia of different ages on a nutrient medium. Pinna primordia were designated as 1) determined, if they grew normally in culture; 2) undetermined, if they grew into differentiated structures that were morphologically and anatomically different from either leaflet or tendril; or 3) partially determined, if the two pinnae of an opposite pair developed unequally in isolation, or for leaflet pinnae only, if laminae were initiated but did not develop completely. The compound pea leaf as a whole is determined over four plastochrons of development. Proximal pinnae are determined during the second leaf plastochron, approximately 0.8 plastochron after their initiation. The second most proximal pair of pinnae is determined during the third plastochron, and the terminal portion of the rachis is determined last, during the fourth plastochron. Determination of leaflet dorsiventrality is gradual, requiring a critical minimum period with the leaf in physiological contact with the shoot system. The rachis primordium, when isolated from the shoot, does not affect determination of its pinnae as leaflets or tendrils. Afila and tendril-less homeotic mutations do not alter the timing of pinna determination. |
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