After the cold acclimatisation period there were significant
reductions in total glucosinolate content in plants that were previously
grown at 12 h photoperiod in combination with low growth
temperature (15/9 C). This was due to significant reductions in the
content of all individual glucosinolates for this treatment (Tables 1
and 2). Cold acclimatisation of plants from both growth treatments,
12 h at high growth temperature (21/15 C) and 24 h at
low growth temperature (15/9 C), produced no significant change
in the total content of glucosinolates, whilst leaves from 24 h photoperiod
and high growth temperature (21/15 C) had a slightly
higher content after cold acclimatisation (Table 2). High growth
temperature in combination with 24 h day length had a 51% higher
content of glucoiberin after cold acclimatisation. Also, the content
of sinigrin was generally highest after cold acclimatisation, and
high growth temperature combined with 24 h photoperiod had a
65% higher content of sinigrin after cold acclimatisation. After
the cold acclimatisation period, the levels of sinigrin were highest
when the plants were previously grown at high growth temperatures.
The predominant indolic glucosinolate, glucobrassicin, was
in addition to being reduced in plants from 12 h at low growth
temperature, also reduced by cold acclimatisation in plants from
24 h at low growth temperature.