Respiration and Vitality of Binucleate and Trinucleate Pollen

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Abstract
The respiration and vitality of ungerminated bi‐ and trinucleate pollen were studied in order to determine the influence of relative humidity and temperature on metabolic activity. The gas exchange, germination capacity and staining with tetrazolium bromide were followed under standardized conditions.A constant respiration rate occurred under conditions of high relative humidity (97%). Per mg pollen, the trinucleate grains of Compositae and Gramineae respired 2 to 3 times as intense as 6 species of binucleate grains. Per unit of pollen protein the differences were even larger. In contrast to binucleate pollen, the longevity of trinucleate pollen was very short and the ability to germinate was lost twice as fast as the respiration capacity. This limits the use of tetrazolium bromide as an indicator of viability.At reduced relative humidities respiration was strongly restricted, but the longevity of bi‐ and trinucleate pollen considerably increased.Pollen of Gramineae, however, was very sensitive to changes in relative humidity; short exposure to low relative humidity decreased both the vitality and the capacity to respire.