Riverside Hybrids


Passiflora hybrid pollen SEM | Passiflora polyploid hybrid pollen SEM | Passiflora species pollen SEM

Passiflora colinvauxii pollen

Image © 2005 Frans Holthuysen All Rights Reserved
 

  Sporopollenin

  • A great word and a fascinating substance. In 1865 Rosanoff observed in anthers of Mimosaceae tiny spherical objects called orbicules also known as Ubisch bodies. They and the remarkably sculpted outer coats (exine) of pollen grains and spores are primarily made up of sporopollenin.

  • It is probably the toughest substance in the natural world, being incredibly resistant to both enzymic and acid attack. For this reason its structure is still uncertain. Individual pollen grains may survive for up to 500 million years in sedentary rock. Sporopollenin is also found in peatlignitecoal. Accordingly analysis of pollen grains in core samples tells us a great deal about the past climate and flora make-up. See work by Dr. Paul Colinvaux.

  • Despite the above Passiflora pollen is not very tough (prone to bursting when wet) and is not as far as I am aware found in fossil records. This is probably because the pollen does not need to be built to last and so there is a low ratio of sporopollenin to cellulose in the exine.

  • Wikipedia suggests ''Analyses of sporopollenin have revealed a mixture of biopolymers, containing mainly long chain fatty acids, phenylpropanoids, phenolics and traces of carotenoids. Tracer experiments have shown that phenylalanine is a major precursor, but other carbon sources also contribute. It is likely that sporopollenin derives from several precursors that are chemically cross-linked to form a rigid structure.with suggestions varying from carotenoids may consist of an oxidative polymer of carotenoids and carotenoid esters.''

  For more information on pollen see Passiflora pollen.