Numerical analysis study of pollen grain populations of Eryngium Maritimum L. (Umbelliferae)

Statistical and numerical taxonomic methods reveal two groups of pollen populations in one plant of Eryngium maritimum L. growing at Noordwijk aan Zee (The Netherlands); one group includes the tertiary and primary lateral inflorescences which possess inhibited growth; the other group comprises the secondary lateral inflorescences showing normal growth. The effects of the physiological inhibition mechanism are complex and are shown by many pollen characters— the dimensions of P (polar axis) and E (equatorial diameter), the presence of a thickening of the exine in the intermediate zone, the shape of the internal contour of the endexine, etc. The differentiation of two types of pollen populations has not only taxonomic interest at the individual, locality, or species level, but also physiological significance. The shape of the internal contour of the endexine, which is a very important feature of “macroevolution” of pollen types in Umbelliferae (Cerceau-Larrival), is directly influenced by the inhibited growth.