POLLEN PRODUCTION IN ANEMOPHILOUS TREES

A study was made of the total pollen production per individual tree in ten anemophilous arboreal species (including wild, cultivated and orn amental species) of considerable aerobiological importance: Pinus pina ster, Ulmus minor, Juglans regia, Platanus hispanica, Quercus rotundif olia, Salix atrocinerea, Populus nigra, Acer negundo, Olea europaea an d Fraximus angustifolia. For each species three isolated well-shaped s pecimens of medium height were chosen, and the number of flowers per i ndividual tree and the number of pollen grains per anther was estimate d. The values of total pollen production varied between a little over 1000 million grains in Juglans regia and more than 500,000 million in one single tree in Quercus rotundifolia. For the production of pollen grains per anther, the values oscillated between 3000 grains in Juglan s, regia and 100,000 in Olea europaea. There is an exponential correla tion between the size of the anthers and the number of pollen grains t hey contain. A linear correlation is also evident between the volume o f the tree crown and the total production of inflorescences, Bowers, a nthers and pollen grains per individual tree. Based on this, a mean co efficient of the number of grains/meter of diameter of the tree crown is obtained which varies between 3.4 x 10(8) for Juglans regia and 550 .9 x 10(8) for Quercus rotundifolia. The ratio between the number of a nthers per inflorescence and the number of pollen grains per anther ca rries out a hyperbolic function; thus, the inflorescences with the mos t anthers have the anthers with the least pollen and vice-versa. This ratio is also manifest between the number of grains per flower and the number of flowers per tree, as well as the number of grains per inflo rescence and the number of inflorescences per tree.