Table 2. Effects of additives on CCT activity ex situ.

Added ions	Relative 3H incorporation (% of control ± range)
Control a	100 ± 5.4
10 mM Ca2+	125 ± 21
10 mM Fe2+	101 ± 8
10 mM Mg2+	90.4 ± 9.2
10 mM Ni2+	89.5 ± 15.0
10 mM Zn2+	69.4 ± 5.4*
10 mM K+	94.4 ± 29.1
10 mM Co2+	66.1 ± 3.2**
10 mM EDTA	108 ± 18
Control b	100 ± 8.0
10 mM dithiothreitol	91.1 ± 10.4

In two independent experiments, an enzyme extract [prepared in 350 mM succinate (Na⁺), pH 5.5, with 1% v/v Triton X-100 and 1% w/v polyvinylpolypyrrolidone] from pea epicotyl epidermis was added to 10 mg heat-denatured and thoroughly dried pea epidermis with 0.36–0.62 kBq [³H]HHA plus the ions listed. After 24 h at 20°C, ³H incorporated into ester-linked CCT reaction products (equivalent to extract f of Figure 2) was recorded. Data show mean ± range (n = 2 biological replicates). * P < 0.05; ** P < 0.01.