Morphological and qualitative study of pistachio (Pistacia vera L.) pollen grains and effect of different temperatures on pomological traits

The viability, pollen tube growth and morphological characters associated with pistachio pollen quality are important for plant breeders and growers. Different kind of pollens of fruit trees has shown different morphological and pomological characteristics. Germination rate and growth of dry and wet pollen requires to be studied if confronted to low temperatures. This research was conducted, in order to investigate the effect of macro and microelements, protein content, morphological characteristics, in natural and artificial conditions, on germination of dry and wet pollens of four mid-season flowering male genotypes of pistachio. A factorial experiment in a completely randomized design (CRD) was applied with 33 treatments and 3 replications. Size of measured pollens was different from 20 to 24 mu m; most of them were circular shaped with different surface characteristics. The highest and lowest germination rate of fresh pollens was 85% and 53% for type R28 and N2 and after 3 days, the germination was decreased to 16% and 8% respectively. The highest contents of B and Ca were measured in pollens with the highest percentages of germination as 4.2mg/100g and 386mg/100g respectively. Keeping wet pollens more than 4 hours or shorter under 0 degrees C caused reduction in percentage of germination. Long storage of pollen grains under temperatures lower than 0 degrees C in dried condition was possible, but 7 days after drying of pollen grains and keeping under-20 degrees C, the percentage of germination were decreased to 30%. This descending trend continued quickly toward day 30 under-20 degrees C and after that with lesser intensity.