Trait variations of male Torreya grandis trees

Key words: 
• botany /
• Torreya grandis /
• male tree /
• staminate strobilus

Abstract: Variation in traits associated with male trees of Torreya grandis were studied using a survey of leaf length，width，and thickness；size of staminate strobilus；pollen weight；and flowering time. A scanning electron microscope （SEM） was used to observe pollen grains and a pollination test with pollen from different 3 locations and 2 individual male trees of the same location was conducted in T. grandis Merrillii that is the only female cultivar of T. grandis. Results showed that for male trees on the average，leaf length was 2.12 cm （ranging from 1.53 to 3.20 cm），width was 0.32 cm （0.28-0.39 cm），and thickness was 0.23 mm （0.17－0.32 mm） with the length longer than that of leaves from female trees （1.1－2.5 cm）；for staminate strobilus，length was 0.79 cm （ranging from 0.49－1.32 cm），width was 0.42 cm （0.32－0.54 cm），and weight was 1.19 g （0.33－2.66 g）；and pollen weight was 0.170 g （ranging from 0.151－0.548 g）. For leaf and staminate strobilus characteristics，CVs （coefficients of variation） varied from 55.3% for pollen weight to 8.8% for leaf width. Male trees mainly started flowering from the 16th to the 18th of April with a 1-week difference between one another in flowering time. Also，pollen was ball-shaped with a diameter of 22－26 m. No differences were found in pollen morphology among different origins or individuals located in the same area. Finally，pollen of different origins had a strong effect （P=0.016） on the young fruit-setting percentage of T. grandis Merrillii. Thus，differences in flowering time，especially selecting those late in flowering，could be used to select male trees when establishing a T. grandis Merrillii plantation，and the fruit-set indicated a potential for selection of T. grandis male，elite individuals.［Ch，2 fig. 4 tab. 27 ref.］