Phenotypic plasticity and stability of leaf form in Plantago paradoxa Hook, f. in mosaic environments

Abstract

Phenotypic polymorphisms in leaves are correlated with three distinct microhabitats that occur in each of two populations of Plantago paradoxa. Progeny testing demonstrates that there are differences in leaf form between the populations but that these are masked by canalization within populations. In one of the populations, plants from all three microhabitats exhibit phenotypic plasticity of leaf form, both transplants and progeny adopting the same form in a common environment. However, plants having one of the three leaf forms in the second population are stable. Foliar applications of gibberellic acid show that about two-thirds of the phenotypically plastic plants subsequently produce leaf forms that mimic the stable leaf form in the glasshouse. The occurrence of leaf forms which are stable or subject to phenotypic modification is dependent on the particular microhabitat the plants occupy.