X-ray Microanalysis of Elemental Composition of Vitis sylvestris Pollen Grains

The flowering and fruit set of grapevines are determined by many morphological, physiological, and environmental factors. Although the elemental composition of pollen grains plays a crucial role in the fruit set, there is still a considerable gap in our knowledge. To date, no study has been conducted on the elemental composition of Vitis vinifera subsp. sylvestris (hereafter V. sylvestris) pollen grains. The aim of this work was to investigate the elemental composition of pollen grains of V. sylvestris using scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX). The pollen grains of ten V. sylvestris individuals (eight male and two female) and one hermaphrodite cultivar 'Plavac mali crni' were analyzed. SEM-EDX analysis revealed the presence of eight elements (carbon-C, oxygen-O, magnesium-Mg, phosphorus-P, potassium-K, calcium-Ca, molybdenum-Mo, and aluminum-Al) in the pollen grains. Interestingly, aluminum was detected exclusively in the pollen of the cultivated grape cultivar 'Plavac mali crni', while it was not present in the genotypes of V. sylvestris. No significant differences between genotypes were found for oxygen and phosphorus, while significant differences were found for other elements. Pollen dimorphism was not associated with differences in element composition, although principal component analysis separated the genotypes into two distinct groups, with two female individuals (Pak10 and Pak12) and one male (Im19) tending to form separate clusters. This study is the first report on the elemental composition of pollen grains of V. sylvestris genotypes and provides valuable insights for further studies on pollen functionality.