Effect of temperature and nodal cutting position on the growth of in vitro cultured coffee plants under photoautotrophic conditions.

摘要

Single nodal cuttings at the 1st, 3rd and 5th positions from the shoot apex of in vitro cultured coffee (Coffea x arabusta) plants were grown on half-strength MS agar medium under photoautotrophic conditions. Three photoperiod/dark period temperatures were selected as follows: 28/22, 26/26 and 22/16 degrees C. The culture was exposed to a CO2 concentration of 400-450 micro mol/mol and PPF of 120 micro mol m-2 s-1 under a 16 h photoperiod. The growth parameters of the coffee plants cultured in vitro from each nodal cutting were determined after 45 days. Under the 22/16 degrees C regime, plant growth was obviously retarded, regardless of the position of the nodal cuttings. There were differences in growth between the 26/26 and 28/22 degrees C regimes, with the same daily average temperature. The increase in the fresh weight and leaf area of the shoots under the 28/22 degrees C regime was significantly larger than that under the 26/26 degrees C regime when the nodal cutting positions were compared. The shoot elongation was significantly greater under the 28/22 degrees C regime for all the treatments. There was a gradual reduction in the leaf area depending on the position of the nodal cuttings from the apex. The value of the relative growth rate of the coffee plants cultured in vitro from the third nodal cutting under the 26/26 degrees C regime was the highest on day 45. However, the value of the net photosynthetic rate of the plants cultured in vitro, Pn, was highest under the 28/22 degrees C regime for the 1st nodal cutting position and the lowest under the 22/16 degrees C regime for the 5th nodal cutting position, when measured on day 20. Pn value of the plants grown under the 26/26 degrees C regime was lower than that under the 28/22 degrees C regime on both days 20 and 32..