The morphology and exine ornamentation of fresh pollen from four dipterocarp species in Sabah

The pollen morphology and fine exine ornamentation of the dipterocarps
Parashorea tomentella (Symington) Meijer, Shorea multiflora (Burck) Symington, Shorea xanthophylla Symington and Shorea leprosula Miq. were investigated from individuals growing in Sepilok Forest Reserve, Sabah. Fresh pollen was extracted from flowers collected in the canopy and analyzed using a combination of light microscopy and Scanning Electron Microscopy (SEM). The size of pollen grains was estimated from their polar axis length and equatorial diameter, and systematic descriptions were developed from the SEM images. The four species had contrasting polar axis lengths and equatorial diameter dimensions that varied in the range 11.7–38.0 !m and 11.5–32.7 !m, respectively. The
pollen was monad, tricolpate and predominately spheroidal but the morphology varied among the species. Parashorea tomentella had narrow colpi and wide irregular muri. Shorea multiflora and S. xanthophylla had colpi covered by a colpus membrane with a microreticulate ornamentation. Pollen of S. leprosula were prolate spheroidal, subspheroidal or subprolate, lobate in polar view, with two obvious colpi and a microreticulate ornamentation. For these four species, pollen volume was significantly correlated to flower size. We conclude that with more research, pollen morphology could be a diagnostic tool for distinguishing among dipterocarp species in different sections of a genus (e.g. sections Mutica and Richetioides of Shorea) and between genera (Shorea and Parashorea). However, in our study, the two species of Shorea section Richetioides could
not be distinguished on the basis of morphological differences.