How in vitro light affects growth and survival of ex vitro cassava

Cassava is one of the most important food crops in Africa. Meristem culture is an effective method of eliminating viruses and other systemic diseases spread through the vegetative propagation of stems. However, in semi-arid c onditions, survival of ex vitro plants in the field is often disappointing. When an increasing range of light regimes in vitro was provided, the fresh and dry masses more than doubled their values between 29 and 369 mmol s(-1 ) m(-2) PPFDs. Increases in numbers of senescent leaves and stem thickness were also recorded with increasing PPFD. However, PPFD above 101 mmol s(-1) m(-2) resulted in 30-70% reduction in plant survival, with the thin plants with the smallest fresh and dry masses being the ones with highest surviva l rates. High light and temperature levels in the greenhouse were also foun d to be critical for plant survival. It was also shown that transpirational loss from detached leaves and epicuticular wax deposits were not good indi cators for predicting survival of ex vitro cassava plantlets during acclima tisation.