Sm. Pereyra et al., MICROPROPAGATION OF POTATO CV SPUNTA - GROWTH IN RELATION TO EXPLANT SIZE AND POSITION ON SOURCE PLANTLET, Phyton, 61(1-2), 1997, pp. 127-132
Apical explants are routinely discarded in potato (Solanum tuberosum L
.) micropropagation, but there are no studies on the physiological bas
is for this practice. The present paper evaluates the effect of explan
t size, and position on source plant, on growth and physiological stat
e of potato plantlets, cv. Spunta, subcultured in vitro. Single node c
uttings were excised from the basal and apical portions of plantlets,
and the middle portion discarded. Single node cuttings from basal and
apical portions were cultured with leaf (leafed) and without leaf (lea
fless), in order to obtain small and large explants. Growth in terms o
f height, number of nodes and dry matter content in the shoots and phy
siological state, (such as N content, and dry weight/N ratio, of plant
lets originating from each type of explant) was measured. From the exp
erimental evidence, we conclude that, in potato plantlets cultivated i
n vitro: a) apical and basal explants have similar physiological chara
cteristics; b) differences in growth of apical and basal explants corr
espond to differences in growth rate; and c) explant growth rate is di
rectly related to leaf growth stage. Therefore, there is no physiologi
cal basis for discarding the apical portion of plants cultivated in vi
tro for micropropagation purpose.