Morphological features as indicators of maturity in acclimatized Pinus pinaster from different in vitro origins

Acclimatized Pinus pinaster Ait. plants originating from five different in vitro culture origins were compared morphologically. After one growing season in the greenhouse, the plants displayed the following order of maturity from juvenile to mature): (i) young seedlings, (ii) plants produced by adventitious budding from cotyledons; (iii) plants derived from micrografted meristems of 2-year-old seedlings; (iv) plants derived from micrografted meristems of a 13-year-old mature clone; and (v) plants derived from microcuttings of axillary shoots of the same 13-year-old mature clone. Plants derived from micrografts exhibited substantial variability with regard to morphological characteristics. This variability included some striking demonstrations of morphological rejuvenation among the mature clone micrografts which, on average, showed more juvenile traits than the microcuttings of the same clone.