There are also some other important parameters such as pollen tube length and germination speed to evaluate the pollen viability besides the germination rate during in vitro germination test.Pollen tube length is seldom mentioned in previous studies of pecanpollen probably due to the use of unstable method although it iswidely used in many other species as one of important indicatorsto determine pollen germination. Based on this new germination method, we found pecan pollen tube length was quite different from the germination rate on the sensitivity to temperature. While the germination rate is obviously influenced by both การคืนสภาพ and germination temperatures, the pollen tube length is mainly influenced by germination temperature which was obvious for RT-storage samples (Fig. 5B, C, E and F). And this effect of germination temperature on pollen tube length was not suppressed by burst since high germination rate at high temperature some-times was accompanied by high burst (Figs. 4B and D and 5C andF). But there are also some deficiency in the current germina-tion process when taking the pollen tube length as an indicatorof pollen viability since the growth of pollen tube seemed more