Jyc. Reekie et al., THE INTERACTIVE EFFECTS OF CARBON-DIOXIDE ENRICHMENT AND DAYLENGTH ONGROWTH AND DEVELOPMENT IN PETUNIA-HYBRIDA, Annals of botany, 80(1), 1997, pp. 57-64
Plants were grown at either 350 or 1000 mu l l(-1) CO2 and in one of t
hree photoperiod treatments: continuous short days (SD), continuous lo
ng days (LD), or short switched to long days at day 41 (SD-LD). All pl
ants received 9 h of light at 450 mu mol m(-2) s(-1) and LD plants rec
eived an additional 4 h of light at 8 mu mol m(-2) s(-1). Growth of SD
plants responded more positively to elevated CO2 than did LD plants,
due largely to differences in the effect of CO2 on unit leaf rate. Hig
h CO2 increased height and decreased branching under SD conditions, bu
t had no effect under LD conditions. Elevated CO2 also increased the n
umber of buds and open flowers, the effect for flower number being gre
ater in short than in long days. The specific leaf area of plants grow
n at 1000 mu l l(-1) CO2 was reduced regardless of daylength. High CO2
also decreased leaf and increased reproductive allocation, the magnit
ude of these effects being greater under SD conditions. Bud formation
and flower opening was advanced under high CO2 conditions in SD plants
but bud formation was delayed and there was no effect on flower openi
ng under LD conditions. The effects of CO2 on plants switched from SD
to LD conditions were largely intermediate between the two continuous
treatments, but for some parameters, more closely resembled one or the
other. The results illustrate that daylength is an important factor c
ontrolling response of plants to elevated CO2. (C) 1997 Annals of Bota
ny Company.