Studies of the pollen morphology and taxonomy of the tribes Loteae and Coronilleae (Papilionoideae; Leguminoseae). 3, Coronilla L. and related genera and systematic conclusions

Abstract

The pollen morphology of 48 taxa has been studied with light and electron microscopy. The pollen is three-zonocolporate, elliptical or more or less rectangular, sometimes circular, in equatorial outline and circular or triangular in polar outline; small or medium size, P × E = (14−30) × (9−26) μm. The colpi are long, the endoapertures lalongate. The ornamentation is perforate, microreticulate, granulate-verrucate, striate-rugulate perforate-granulate or finely granular. Exine is 0.5–2 μm thick at the mesocolpium. The endexine thickened at the equator, thinner at the poles, the foot layer very thin or absent, the infratectum columellate; the columellae are sometimes almost granular often widely spaced with expanded bases and the tectum thick. Ornamentation is the primary basis for the division into types. Five pollen types are recognised. With the exception of Securigera, which has similar pollen to Coronilla, the types correspond well with the genera recognised in the group. The pollen morphology of Scorpiurus is distinct from that of the rest of the group. Pollen morphology is discussed in relation to the taxonomy of the group and its significance to relationships and evolution of the tribes is considered. It is concluded that there is little evidence from pollen morphological studies to support the separation of the Coronilleae and Loteae as two tribes. It is suggested that the group Loteae shows some affinities in pollen morphology with tropical tribes as for example Phaseoleae as well as with temperate herbaceous tribes.