A Model of the Effect of Temperature and Moisture on Pollen Longevity in Air-dry Storage Environments

Data on the survival of pollen ofTypha latifoliaL. stored forup to 261 d over seven different saturated salt solutions (providing0.5 to 66% relative humidity) and six different constant temperatures(from -5 to +45 °C) were analysed to quantify the effectof air-dry storage environment on pollen longevity. Pollen survivalcurves conformed much more closely to negative cumulative normaldistributions than to negative exponential relations. Estimatesofp₅₀(storage period required to reduce pollen viability to50%), provided by negative cumulative normal distributions,were available from 37 different storage environments in whichpollen viability was reduced below 50%. Once observations at0.5% and 5.5% relative humidity were excluded from analysis,there was a negative logarithmic relation between these estimatesof longevity and pollen moisture content (%, wet basis) anda curvilinear semi-logarithmic relation between longevity andtemperature. When the negative logarithmic relation betweenlongevity and moisture content was replaced by a negative semi-logarithmicrelation between longevity and the relative humidity of thestorage environment the resultant model was less satisfactory,principally because pollen longevity over saturated solutionsof calcium nitrate (43–62% relative humidity) and sodiumnitrite (60–66% relative humidity) were consistently greaterand smaller, respectively, than fitted values. Notwithstandingthese errors, comparison between the fitted relations and observationsat the two lowest relative humidities provided estimates ofthe lower-relative-humidity limits to these relations. Theseprovisional estimates varied with storage temperature beinglowest at 25 °C (<5.5% relative humidity). However, therewas no linear trend to that variation (P>0.25): the meanestimate was 11.9 (s.e.=1.4)%. The considerable similaritiesamong models of pollen longevity in air-dry storage, and theirestimated lower limits, and those developed previously for orthodoxseeds and spores are discussed.Copyright 1999 Annals of BotanyCompany. Typha latifoliaL., pollen, storage, survival, longevity, relative humidity, moisture content, temperature.