Pollen morphology of genus Rubus L. Part III. Studies on the Malesian species of subgenera Chamaebatus L. and Idaeobatus L.

Abstract

The results of pollen morphology of Malesian Rubus species are presented. The pollen samples represented 2 subgenera; 2 species of subgenus Chamaebatus (R. calycinus, R. pectinellus) and 13 species of subgenus Idaeobatus (R. acuminatissimus, R. alpestris, R. archboldianus, R. chrysogaeus, R. copelandii, R. ellipticus, R. ferdinandi-muelleri, R. fraxinifolius, R. niveus, R. lorentzianus, R. macgregorii, R. montis-wilhelmi, R. papuanus). The examination of these species has been made by SEM for the first time and also by LM. Detailed descriptions of the pollen grains are given. As in the majority of Rubus species, pollen grains of both subgenera are isopolar and trizonocolporate. The pollen grains were small for some species of the subgenus Idaeobatus only, medium for both subgenera: Chamaebatus and Idaeobatus. The thickest exine was observed among the species of subgenus Chamaebatus and in R. macgregorii of subgenus Idaeobatus. The ornamentation of the studied pollen has shown a great variability. Except for the typical striate ornamentation of the genus, rugulate (R. archboldianus), striatescabrate (R. lorentzianus) and striate-rugulate (R. macgregorii) ornamentation has been observed.

New Guinean morphologically similar pinnate Rubus ferdinandi-muelleri, R. montis-wilhelmi, R. papuanus, have pollen with specific type of striate pattern, which is characterised by relatively high muri with variable thickness and lumina filled with granules. Some of their muri resemble baculae typical only for R. chamaemorus. The pollen morphology analysis leads to the conclusion that Rubus montis-wilhelmi and R. papuanus of subgenus Idaeobatus are the closest related species and morphologically very close to R. ferdinandi-muelleri. Since Focke placed the latter species in section Pungentes of the subgenus Idaeobatus, and the two first species were unknown to him - the authors suggest to include them into this section.

Despite of the different origin and various types of leaves R. chrysogaeus, R. acuminatissimus and R. niveus have shown similarities in pollen morphology and are grouped together. On the basis of the same criteria, R. copelandii, R. ellipticus and R. fraxinifolius could have been grouped together, as well as R. alpestris and R. macgregorii. Trifoliolate R. archboldianus and R. lorentzianus have not shown similarities of pollen ornamentation to each other and to the previous mentioned species.