Behavioural studies on the pollen grains of Pinus roxburghii collected from Lucknow, India–A report

Abstract

We have long recognized that natural climatic shifts influence the development of plants on earth. These slow temperature fluctuations have resulted in either the extinction or evolution of various species. A careful study of the comparative morphology of the living and fossil type suggests that the modern coniferous families originated independently from a group of extinct conifers called the transition conifers by Florin. The conifers reached their climax in the mid–Mesozoic times and have been on the decline ever since. Pinaceae is one such family whose pollen grains have been located as long back as in the Gondwana flora and have demonstrated morphological variations since then due to climatic changes. Pinus is the most dominating genus of the family Pinaceae in gymnosperms. Pine grains are large due to their sacs or bladders, which make them one of the easiest pollen grains to identify. They are rich in non–enzymatic anti–oxidants, like provitamin A, B complex, C, D and E plus a host of minerals and amino acids. Apparently pine pollen is also a great defense against radioactive caesium that is appearing in dairy and other foods in the U.S. The present study examines the changes occurring in one of the most sensitive phases of plant development in the living genus of Pinus, i.e. the behaviour of pollen, found to be dependent on number of genetic or environmental factors. The major environmental factors contributing to this abnormal behaviour include light intensity and quality, temperature and moisture and level of pollutants in atmosphere. During present study, the Pinus cones were collected from five experimental areas of Lucknow that exhibited different level of deformities probably due to different levels of environmental stress or other genetic reasons. The clusters were unique in having deformed cones on the side facing the road while they were near normal on the side away from road indicating that the area around the roadside being more polluted and may be playing a detrimental role in cone morphology. Pollen of normal cones were bilateral, analept, usually bisaccate, spherical, slightly elliptical with verrucate corpus and sacci having pila, normal average size being 60μ–65μ including sacci and sacci attached almost full width of corpus, exine thick in proximal part of reticuloid corpus. While pollen grains of abnormal cones show abnormalities in their size, shape, size and number of wings, size and shape of corpus and development of pollen tube within microsporangium. The abnormalities were observed using scanning electron microscopic studies and its percentage was calculated using a light microscope.