2.3 Assessment of male gametophyte fertility
Viability of the male gametophyte was determined by microscopic observation of pollen grains stained with Alexander’s stain (Alexander, 1967) using Nikon Eclipse 90i microscope with attached Nikon DS-Ri1 camera for all opened flowers from time of suspension of watering to anthesis of the last bud after rewatering. Pollen stained red were considered viable. Pollen viability was calculated using the formula: