2.2. Experiment in phytotrons
Eight 3-year-old potted air-layered longan trees (canopy size
about 1.5 m in height and 1.0 m in diameter) of cv. Chuliang that
bloomed in the mid April 2008 with similar initial fruit set were
selected and divided evenly into two groups. On May 6, i.e. 28
days after anthesis, when the fruit were about 4 mm in diameter,
the two groups of trees were moved into two phytotrons set for
cold and warm temperature regimes, respectively. The cold one
was 15/10
C (day/night temperatures), while the warm one was
28/23
◦
◦
C. Relative humidity in both phytotrons was set around 85%.
The cold temperature regime was maintained for 41 days, before it
was raised at a rate of 3
C per day from day 42 (June 18) to day 44
and finally to 28/23
◦
◦
C at day 45 and maintained at this temperature
regime until fruit matured.
Diameters of two labeled fruit on each of the three tagged clusters
in each trees were measured and numbers of fruit and cracked
fruit on each tagged cluster were counted every 4 days. Four fruit
from non-tagged clusters of each tree were taken biweekly but
more frequent sampling was carried out prior to and after temperature
shift.