Scanning electron microscopy analysis of apricot pollen grains

Abstract

Morphology and ultrastructure of pollen grains were studied in nine apricot cultivars using scanning electron microscopy (SEM) technique. The following characteristics were examined in dried pollen grains: Length of polar axis (P), length of equatorial axis (E), P/E ratio, length of the colpus, width of the mesocolpium, and exine characteristics (number of ridges 100 μm-2 area, width of a ridge, and width of a furrow). All studied cultivars had isopolar, radially symmetric and tricolpate pollen grains, which had been classified as large in size. Length of polar axis ranged from 55.6 μm in 'Hungarian Best' to 59.5 μm in 'Goldrich', and length of equatorial axis from 27.0 μm in 'Sylred' to 30.5 μm in 'Goldrich'. Pollen shape was identified as prolate in six cultivars, and as perpolate in three cultivars. Colpus length and mesocolpium diameter varied in a range of 48.4-55.6 and 14.5-18.4 μm, respectively. All studied cultivars had striate exine ornamentation. Number of ridges 100 μm-2 of the exine surface was the lowest in cultivar 'NS-4' (21.3), and the largest in cultivar 'Laycot' (29.7). Ridge and furrow width varied in a range of 0.28-0.35 and 0.24-0.32 μm, respectively. SEM examination indicated that some pollen morphological characteristics such as size, shape, and exine ornamentation can potentially be used in the identification of apricot cultivars.