ENVIRONMENTAL-EFFECTS ON POTATO PLANTS INVITRO

Effects of various environmental conditions on plant development and physiology were analysed in vitro on a tetraploid cultivar BF15. To preserve natural endogenic equilibrium, no growth regulators were added to the culture medium. Plants were submitted to different photoperiods, light intensities, light qualities and culture media. Their effects were analysed through morphological measurements (stem length, leaf area, node and usable node number) and biochemical assays (mean soluble protein content in upper and basal parts of stems). They provided good indicators of the development process, such as slow or rapid growth and aging. Three ways of development could be easily distinguished: (1) A 12 h/day photoperiod was a condition activating growth but retarding aging of the plants; other favouring agents were MS medium, low light intensity (L) and white fluorescent lighting (gro-), (2) Short days (8 h) were conditions opposing growth and inducing tuberization by accelerating aging, and (3) A 16 h/day photoperiod rapidly produced vigorous plants with large leaves but accelerated aging. The other factors increasing aging were: high light intensity (H), G medium (low nitrogen content) and Grolux fluorescent lighting (gro+) The effects of conditions (2) and (3) on plants are similar as far as aging and induction of tuberization are concerned.