Morphologic study of pollens of three cultivated Actinidia species by scanning electron microscopy

Abstract:【Objective】In order to obtain the knowledge of genetic variation and relationship of various cultivars in the genus Actinidia Lindl., the pollen morphological characteristics of three Actinidia specieswere investigated.【Methods】Scanning electron microscopy was used to observe pollen morphology of thir⁃ty samples collected from three cultivated Actinidia species, A. deliciosa, A. chinensis and A. arguta. Parameters of pollen grains such as the length of polar axis, length of equatorial axis, length of colpus andwidth of colpus were measured and analyzed using an image software (Imagepro-Plus).【Results】The pol⁃lens of A. deliciosa, A. chinensis and A. arguta were in the form of a single grain, being prolate or perprolate. Only one sample of A. deliciosa contained the prolate-shaped pollen grains whereas all samples of A. chinensis contained the perprolate-shaped pollen grains. A total of ten samples of A. arguta were includedin this study, four of them contained the prolate-shaped pollen grains while others contained perprolateshapedpollen grains. Each pollen grain contained three colpi which elongated along the polar axis tillthey reached the ends. One or two colpi could be observed in the equatorial view, whereas all three corpithat were furrows in trifid circular could be seen in the polar view. The results of the measurements of A.deliciosa pollen grain were as follows: The length of colpus was 18.08-31.48 μm and the coefficient variation was 9.59%. The width of colpus was 4.65-11.42 μm and the coefficient variation was 12.40%. Thelength of polar axis was 21.54-36.05 μm and the coefficient variation was 7.6%. The length of equatorialaxis was 9.60-17.66 μm and the coefficient variation was 10.01%. The ratio between the polar and theequatorial axis was 1.65-3.05 and the coefficient variation was 9.68%. The pollen size was 244.90-608.52 μm2 and the coefficient variation was 15.06%. The results of the measurements of A. chinensis pol⁃len grain were as follows: The length of colpus was 14.09-24.96 μm and the coefficient variation was14.00%. The width of colpus was 4.09-9.37 μm and the coefficient variation was 15.88%. The length ofpolar axis was 15.60-30.11 μm and the coefficient variation was 11.17%. The length of equatorial axiswas 8.85-17.87 μm and the coefficient variation was 11.80%. The ratio between the polar and the equatorial axis was 1.26-2.65 and the coefficient variation was 9.93%. The pollen size was 182.58-443.18 μm2and the coefficient variation was 21.52%. The results of the measurements of A. arguta pollen grain wereas follows: the length of colpus was 16.34-30.06 μm and the coefficient variation was 11.62%. The widthof colpus was 6.11-11.23 μm and the coefficient variation was 14.13%. The length of polar axis was18.66-32.11 μm and the coefficient variation was 9.21%. The length of equatorial axis was 8.76-18.42μm and the coefficient variation was 10.79%. The ratio between the polar and the equatorial axis was1.33-2.68 and the coefficient variation was 10.90%. The pollen size was 166.62-547.07 μm2 and the coef⁃ficient variation was 16.70%. There are three types of surface ornamentation in Actinidia pollens. (1) Thecorrugated ornamentation was covered with a smooth surface composed of irregular strips. Sixteen samplesshowed corrugated ornamentation, which accounted for 53.33% of the total samples used in this study.Among them, five samples belonged to A. deliciosa, which accounted for 38.46% of A. deliciosa pollens.Five samples belonged to A. chinensis, which accounted for 71.43% of A. chinensis pollens. Seven samplesbelonged to A. arguta, which accounted for 70% of A. arguta pollens. (2) The pollen with warty ornamentation was covered by regular or irregular block like protrusions. The size of these protrusions was irregular.Eleven samples showed warty ornamentation, which accounted for 36.67% of all samples included in thisstudy. Eight samples belonged to A. deliciosa, which accounted for 61.54% of A. deliciosa pollens. Twosamples belonged to A. chinensis, which accounted for 10% of A. chinensis pollens. One sample belongedto A. arguta, which accounted for 10% of A. arguta pollens. (3) The surface of pollens with granular orna⁃mentation was distributed with particles or in the pattern of granules. Three samples showed granular orna⁃mentation, which accounted for 10% of all samples included in this study. The samples with granular orna⁃mentation belonged to A. arguta which was originated from the province of Heilongjiang. It accounted for30% of A. arguta pollens.【Conclusion】There was a certain degree of conservation in pollen morphologyand size of Actinidia pollens derived from the same species or environmental background. Overall, the pollen size of A. deliciosa was the largest among these species, followed by A. arguta and A. chinensis. Thelength the polar axis, length of equatorial axis, length of colpus and width of colpus, of A. chinensis werelower than those of A. deliciosa. Hence, the morphological differences of pollens between A. chinensis and A. deliciosa would provide some evidence for taxonomy of these species.