PJB-2018-422
Pollen morphology and systematic significance of some Onosma L. species (Boraginaceae) distributed in pan Himalayan regions
Paras Mazari and Quan-Ru Liu
Abstract
The pollen morphology of 15 Onosma L. species has been examined by SEM for the first time from Pan Himalayan regions of Pakistan and China.
Generally, the pollen grains are single, isocolpate, radially symmetrical, isopolar or heteropolar, 3-colporate or 3-syncolporate, small to medium in size. The mean polar axis ranged from 10.00-25.43 µm long while the equatorial diameter ranged from 8.68-16.93 µm. The mean P/E ratio generally ranged from 1.04-1.56 µm. On the basis of P/E ratio, three pollen shapes have been recognized (prolate spheroidal, subprolate and prolate). Ornamented aperture membrane and lolongate ora uniformly observed among all studied taxa. However, the results show great diversity within species in regard of polarity, apertures and exine ornamentation (spinulose, rugulate, rugulate-echinate, rugulate to granulate). On the basis of aperture type, two basic pollen types have been recognized. Type-I 3-syncolporate observed in five species (O. confertum, O. dicroanthum, O. hispida, O. limitaneum and O. paniculatum) and Type-II 3-colporate in 10 species (O. exertum, O. fistulosum, O. glomeratum, O. hookeri var. hirsutum, O. hookeri var. longiflorum, O. maaikangense, O. multiramosum, O. sinicum, O. waddellii, and O. waltonii).
On the basis of 10 different pollen characters (seven qualitative and three quantitative) and 24 characters states two types of numerical analyses (PCA and CA) have been carried out in order to determine the potential of the pollen morphological characteristics for determination of the species relationships. The present palynological data therefore provides new information about pollen morphology of all Onosma L. species especially O. glomeratum and O. multiramosum, O. hookeri var. hirsutum, O. hookeri var. longiflorum. The current study can be helpful to analyze the pollen variation within Onosma L. species. It also highlights the significance of pollen characters used to determine intraspecific relationships as well as correlation of pollen characters with the taxonomy of the genus.
To Cite this article:
Mazari, P. and Q.R. Liu. 2019. Pollen morphology and systematic significance of some Onosma L. species (Boraginaceae) distributed in pan Himalayan regions. Pak. J. Bot., 51(6): DOI: http://dx.doi.org/10.30848/PJB2019-6(16)
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