Phylogenetic relationships among Pisum L. species from Asia Minor inferred from pollen and seed coat morphology

Abstract

Abstract Morphological data from light microscopy (LM) and scanning electron microscopy (SEM) of pollen and seeds are used to explore phylogenetic relationships between four taxa of cultivated and wild Pisum including P. sativum subsp. sativum var. sativum and var. arvense, P. sativum subsp. elatius and P. fulvum. Characteristics investigated include pollen shapes and ornamentation, polar axis (P) and equatorial diameter (E), P/E ratio, exine thickness (Ex) and intine thickness (In), lumina diameter (L), muri thickness (M) and seed coat ornamentations in three accessions each of the four taxa. Pollen of Pisum is subprolate, reticulate and tricolporate. Ratios of P/E of the cultivated peas are higher than those of the wild species while diameter of lumina in the cultivated peas is smaller than that of the wild species. The cultivated pea has a smooth seed coat, in contrast to the rough surface of the wild species. The results of SEM micrographs reveal that seed coat ornamentation in each four-taxon set is typical papillose with thicker ribs than in the wild specimens. Differences in corolla colour, even among the five petals, are also noted for the taxa studied. The results suggest that pollen shapes and ornamentation are of limited taxonomic significance, while the seed coat ornamentation may be important for distinguishing taxa of Pisum.