Relationship between tissue growth, CO2 level and tendril formation during in vitro culture of grape (Vitis vinifera L.)

In vitro cultures of grapevine cultivar Arka Neelamani growing in MURASHIGE and SKOOG (1962) medium containing 3% sucrose and incubated under 16 h light (30-10 mu mol.m(-2)s(-1)) per day showed high CO2 levels (600-11900 ppm) at the end of the dark period and a significant decline during the light period (330-980 ppm) indicating photosynthetic activity and photomixotrophic growth characteristic. The CO2 level at the end of a 8-h-dark period was shown to be related to the total tissue weight (wt) per culture Vessel while that during the light period was governed by the root to shoot fresh wt ratio suggesting a notable contribution by roots and inadequate light supply for full CO2 utilization. Plant growth was improved by higher light intensities (40-50 mu mol degrees m(-2 degrees)s(-1)). Tendril production, a characteristic of adult plants, was common during the first year of culture but showed a gradual decline by the second and third year suggesting a gradual rejuvenation effect in vitro. Transformation of tendril, an organ homologous to inflorescence, to leafy structure in some plants and better rooting with more subcultures in vitro further supported the rejuvenation hypothesis. In general, tendril production was mon common in vessels with higher CO2 levels. Plants established ex vitro invariably showed tendril production within 1-3 months indicating that the in vitro rejuvenation effect was not transmitted to the field.