Does growth rate determine leaf form in Pisum sativum?

Abstract

W. 1989. Does growth rate determine leaf form in Pisum sativum? Can. J. Bot. 67: 2590-2595. We have examined the long-standing hypothesis that leaves are morphologically more complex following prolonged proximity to the shoot apical meristem. Growth rates of the petiole and rachis of conventional and mutant pea leaves were compared for successive nodes of insertion in seedling plants. Leaves were longer at higher nodes, though the relative growth rate did not vary. Mature afila leaves were longer than those of conventional and tendril-less genotypes. The afila leaf alone exhibited a transient, highly significant rise in relative growth rate during the plastochron interval P,,,-P,,,.This rise occurred after the stage at which leaves of the different genotypes were anatomically distinguishable (stage P,-P,). Rates of vertical displacement of the leaf primordiurn from the shoot apical meristem did not differ significantly among genotypes. Our data suggest that the rate of leaf extension is one of the consequences, rather than a cause, of leaf morphology. GOULD, K. S., CUTTER, E. G., et YOUNG, J. P. W. 1989. Does growth rate determine leaf form in Pisun1 sativum? Can.J. Bot. 67 : 2590-2595. Nous avons reconsidtrt l'hypothese qui existe depuis dtjB quelque temps, voulant que les feuilles soient morphologiquement plus complexes lorsqu'elles demeurent longtemps B proximitt apical de la tige. Les taux de croissance du pttiole et du rachis de feuilles conventionnelles et mutantes du pois ont Ct C comparts pour des neouds successifs d'insertion chez des semis. Les feuilles ttaient plus grandes aux noeuds suptrieurs quoique le taux relatif de croissance n'a pas varit. Les feuilles afiles complbtement difftrencites ttaient plus longues que celles des ginotypes conventionnels et sans vrilles. Seule la feuille afile a rnontrt une augmentation passagtre trts significative dans le taux relatif de croissance durant l'intemalle plastochronique P,., -P,,,. Cette augmentation est survenue aprbs le stade oh les feuilles de genotypes difftrents sont anatomiquement distinctes (stade P,-P,). Les taux de dkplacement vertical du primordiurn foliaire du mtristbme apical de la tige n'ont pas varit de manitre significative entre les gtnotypes. Nos donnees suggbrent que le taux d'expansion foliaire est une des constquences plut6t que la cause de la morphologie foliaire.[Traduit par la revue]

Auxin/gibberellin interactions in pea leaf morphogenesis

“…Based on the results of this study and the known interactions between auxin and GA in pea, we propose that pea leaves have co‐opted a previously existing auxin/gibberellin signalling pathway to regulate dissection. We presume that the pea leaf primordium is initiated from the shoot apical meristem at a point of high auxin concentration, and that the initial primordium possesses a gradient in auxin concentration that runs from tip to base, which persists for at least four plastochrons while pinna primordia are being initiated (Gould, Cutter & Young, 1989; DeMason & Schmidt, 2001). The auxin gradient is maintained by PAT.…”

Comparative leaf development of juvenile and adult Pseudopanax crassifolius

“…It has been proposed that leaf form is influenced by the length of time a primordium remains in close proximity to the shoot apex (Cutter 1965), the concentration of nutrients or other chemical factors provided by the apical meristem (Allsopp 1965), or the original mass of tissue contributed to the primordium by the apical meristem (Crotty 1955;Gould et al 1989). A larger apical meristem, associated with the adult phases of development in many species, is thought to provide greater chemical input, leading to larger, more complex adult leaf forms (Kaplan 1970;McLellan 1990).…”