Pinot Meunier
In research, Paul K. Boss and Mark R. Thomas of the CSIRO Plant Industry and Cooperative Research Centre for Viticulture in Glen Osmond, Australia, found that Pinot Meunier has a mutation ("VvGAI1") that stops it from responding to gibberellic acid, a plant growth hormone. This leads to different, white-haired, leaf and shoot growth, and also to a slight stunting in growth, explaining why Pinot Meunier plants tend to be a bit smaller than Pinot noir. The mutation exist only in the outermost cell layer of the cultivar, the L1 or 'epidermal' layer, meaning Pinot Meunier is a chimera. Through tissue culture, it is thus possible to separate out plants containing both the mutant (L1) and non-mutant (L2) genotypes, yielding a normal Pinot noir -like genotype and an unusual looking L1-genotype vine with compressed internodes and thickly clustered leaves. The mutants could not produce full-grown tendrils, it seems that gibberellic acid converts grapevine flower buds into tendrils.