POLLINATION AND THE WEATHER

ABSTRACT Immediate and small-scale weather effects may act as constraints on pollination. A review of existing studies, mostly involving crops, reveals opportunities for research exploiting recent advances in microclimatic technique. Intrafloral temperatures are modified in “disc,” “bowl-shaped,” “microgreenhouse,” “hairy hgat trap,” “hanging bell,” and thermogenic flowers. Protection from free water or extreme humidities is achieved by floral structures, movements, and patterns of wettability. Microclimate influences the timing of flower-opening, anther extrusion and dehiscence, the survival and germination of pollen grains, and the exposure and receptivity of the style. Weather- related effects on pollinator activity operate indirectly through floral reward (the secretion rate and sugar concentration of nectar, and the release, texture, and perhaps digestibility of pollen) or directly through the hygrothermal balance of the insect or bird, to an extent that depends on the shape of the flower and the deg...