Cucumber (C. sativus L. cv. jinchun 4) plants were grown in field
under natural sun light with about 14-h photoperiod (26–32 C)
and 10-h night (22–28 C). The maximum light intensity was about
1300 lmol m2 s1. Sufficient nutrients and water were applied to
avoid any potential nutrient and drought stresses. After growing
for about 5 weeks, expanding leaves with an area of about 20%,
30% 50% area of fully-expanded leaves (abbreviated as 20%A,
30%A, 50%A leaves) and fully-expanded leaves (abbreviated as
100%A leaves) were used in the experiment.