POLLEN MORPHOLOGICAL STUDIES ON SOME TAXA OF THE TRIBE

ASTEREAE (ASTERACEAE) FROM SOUTH INDIA

INTRODUCTION

Pollen grain is the structural unit in angiosperms through which the entire male genetic characters are transmitted to the next generation. The pollen wall is composed of highly resistant sporopollenin, and exhibits various architectural patterns, distinctive for a particular species. The taxonomic diagnosis of pollen is an inevitable necessity in any applied aspect of palynological science. The present study was conducted on 6 genera under the tribe Astereae of the Asteraceae.

MATERIALS AND METHODS

Materials for the present study were collected from different localities of South India from live plants and herbarium specimens.The pollen preparations were made by acetolysis method (Erdtman1952; Nair, 1970). Pollen morphological features analysed include pollen aperture, exine ornamentation, pollen size and shape using LM/SEM

.Categorization of pollen shape and size were done following the classification of Erdtman (1952) and Walker and Doyle (1975) respectively. For describing the aperture type and exine ornamentation pattern of the pollen grains, the terminologies suggested by Nair and Lawrence (1985) have been used.

RESULTS AND DISCUSSION

Pollen morphological features are summerised in the Table

Name of Taxa

Aperture

Aperture

Exine

Overall

Shape

Characters

 

 

Type

Shape

ornamentation

size

 

 

 

 

 

 

type

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Excrescence

Aster laevis L.

3-zonocolporate

Lalongate

Spinate

Small

Prolate

with spines and

 

 

 

 

 

spheroidal

a hump

like

 

 

 

 

 

 

basal cushion.

 

 

 

 

 

 

 

 

 

 

 

 

 

Excrescence with

Conyza stricta

3-zonocolporate

Lalongate

Spinate

Medium

Prolate

rounded spine

Willd.

 

 

 

 

spheroidal

and prominent

 

 

 

 

 

 

basal cushion.

 

 

 

 

 

 

 

 

 

 

 

 

 

Excrescence

Dichrocephala

 

 

 

 

Prolate

with acuminate

 

 

 

 

 

 

 

integrifola (L.f.)

3-zonocolporate

Lalongate

Spinate

Small

spheroidal

spine

and

Kuntze

 

 

 

 

 

conical

basal

 

 

 

 

 

 

 

 

 

 

 

 

cushion.

 

 

 

 

 

 

 

 

 

Erigeron

 

 

 

 

 

 

 

karvinskianus

3-zonocolporate

Lalongate

Spinate

Medium

Prolate

Spines conical.

DC

 

 

 

 

spheroidal

 

 

 

 

 

 

 

 

 

 

Grangea

 

 

 

 

 

 

 

maderaspatana

3-zonocolporate

Lalongate

Spinate

Small

Prolate

Prominent

 

(L)Poir.

 

 

 

 

spheroidal

basal cushion.

 

 

 

 

 

 

 

 

Solidago

 

 

 

 

Prolate

Low

basal

canadensis L.

3-zonocolporate

Lalongate

Spinate

Medium

spheroidal

cushion.

 

 

 

 

 

 

 

 

 

The aperture is 3-zono colporate and spinate,spines being composed of a conical column and a basal cushion formed by the fusion of columella tips,and pores restricted to the base of the cushion or spread all over.

The pollen were medium- or small-sized, and prolate-spheroidal in shape.

Exine shape was spinate and endocolpium lalongate .

Occurrance of spinate condition reflects the evolutionary advancement of the tribe compared to Eupatorieae and Vernonieae (Usha and Vijayavalli, 2004).

Although morphology remains unchallenged as the major aspect in taxonomic study, additional evidence may be utilized from other disciplines like palynology during systematic considerations of plant groups.

 

REFERENCES

Erdtman G 1952

Pollen Morphology and Plant Taxonomy of Angiosperms Almquist and

Wiksell Stockholm

Nair PKK 1970

Pollen Morphology of Angiosperms A historical and phylogenetic study

Vikas Publishing House Delhi

Nair PKK & Lawrence R 1985 Pollen Morphology of Indian Compositae Advances in Pollen spore Research Vol 14 Scholar Publishing House

Walker JW & Doyle JA 1975 The basis of angiosperm phylogeny Ann Missouri Bot Gard 62 664-723

Usha SS & Vijayavalli B 2004 Studies in the Pollen Morphology of South Indian Species of Vernonieae, Eupatorieae and Astereae(Asteraceae) Journal of Palynology 40 67-120.