Cotton seeds (Gossypium hirsutum L.

Cotton seeds (Gossypium hirsutum L., Shiyuan 321) were
individually sown in plastic pots (30

12

18 cm) containing a
5:1 mixture of commercial peat moss (Pindstrup Mosebrug A/S,
Ryomgaard, Denmark) and perlite in four different climate growth
chambers. After full expansion of the four cotyledons, the seedlings
from different growth chambers were selected for uniformity, and
individually transplanted into plastic pots (20

9

15 cm) containing
the same mixtures. Sixteen seedlings were used in each
growth chamber. Plants within each climate chamber were
randomized weekly to avoid any positional effects. Each treatment
was replicated three times in all four treatments. Between the
replications, the CO2 concentration in each chamber was switched
to the other concentration to control for potential chamber effects,
hence to exclude pseudoreplication (Hurlbert, 1984). The plants
were watered every three days and fertilized weekly at a rate of
0.05 g (N:P:K = 20:20:20) per plant. The fourth and
fifth fully
expanded leaves from the top of the plants were chosen for all
experiments. Plants were sampled only once. Five plants were
harvested at random from each chamber at three sampling times,
45, 75 and 105 days, after sowing, and bulked into two independent
groups. One was used to assay dry matter content, N
concentration, C/N ratio, soluble sugar content, starch content,
total nonstructural carbohydrate and total phenolic concentration;
the other was used to analyze amino acid levels. The total
fifteen
plants (three replications) from each treatment were assayed at
each time point.