Why is there pollen in Melbournes air?
Plants are immobile and so cannot go searching for suitable mates the way animals do. To ensure their gametes reach receptive females, plants have developed many ways of distributing their pollen. Some species use the wind to carry pollen between plants. These plants have very simple, dry flowers that do not secrete the nectar that attracts birds and insects. Wind-borne pollen can drift considerable distances. Pine pollen, for instance, can be carried hundreds of kilometres. But, then pine pollen has wings that serve as floats! Pollen of wind-dispersed species such as rye grass, the major source of pollen in Melbourne’s air in the late spring and early summer, is relatively small in size, (usually <30 micrometers), has smooth outer surface, and is relatively dry and powdery. A number of factors, such as wind speed, humidity, down gradient, etc., determine how far such pollen will travel. Other plant species use insects and birds to carry their pollen between plants. These plants produc
