Auxin applications affect posttransplant CO2 exchange rate and growth of bare-rooted vinca [Catharanthus roseus (L.) G. Don] seedlings.

摘要

C. roseus cv. Cooler Peppermint seedlings with 4 true leaves were transplanted into diatomaceous earth and the plants were transferred to a growth chamber, where they were treated with NAA (0, 0.025, 0.25 or 2.5 mg/litre; 36 ml/plant). Whole-plant CO2 exchange rates of the plants were measured once every 20 min for a 28 day period. Seedlings treated with 0.025 or 0.25 mg NAA/litre recovered from transplant shock more quickly than plants in the 0- and 2.5-mg/litre treatments. NAA drenches containing0.025 or 0.25 mg/litre increased whole-plant net photosynthesis (Pnet) from 10 days, dark respiration (Rdark) from 12 days and carbon use efficiency (CUE) from 11 days after transplanting until the end of the experiment. The increase in CUE seemed to bethe result of the larger size of the plants in these 2 treatments and thus an indirect effect of the NAA applications. These differences in CO2 metabolism among the treatments resulted in a 46% dry mass increase in the 0.025-mg/litre treatment comparedto the control, but shoot-root ratio was not affected. The highest rate of NAA (2.5 mg/litre) was slightly phytotoxic and reduced the growth rate of plants.