Poster: Late and Moved Abstracts

Abs # 1434: Tropical plantlets cultured in vitro with low sucrose and natural light improve their photosynthesis and growth under ex vitro conditions

Presenter:	Santamaria, jorge M, jorgesm@cicy.mx
Authors	Santamaria, jorge M (A)   Fuentes, Gabriela  (A)   Talavera, Carlos  (A)   Espadas, Francisco  (A)
Affiliations:	(A): Centro de Investigación Cientifica de Yucatán
Web Site:	http://www.cicy.mx

In a typical growth room, plantlets grow with artificial low light and high sucrose in the medium. Sucrose is added to provide C skeletons and energy for growth while light for plant greening. However, in vitro germinated plantlets show slow growth when transferred ex vitro . This slow growth ex vitro may result from their low photosynthetic capacity (Pn). Exogenous sucrose (S) reduces Pn, therefore it was expected that lowering S and increasing light intensity (LI)in growth rooms (GR) would result in enhanced Pn and better ex vitro growth. In vitro plantlets under standard GR (LI, 50 µmol PFD m^-2 s^-1) and with 45 gl^-1 S, showed low Pn (2 µmol CO₂ m^-2 s^-1) compared with their seedlings counterparts (10 µmol CO₂ m^-2 s^-1). A reduction (or elimination) of S resulted in improved Pn (3 µmol CO₂ m^-2 s^-1), while plantlets with high S (90 g l^-1) shown very low Pn (1.6 µmol CO₂ m^-2 s^-1). Increased LI to 400 µmol PFD m^-2 s^-1 resulted in a 25% increase in Pn for all S treatments on average, except for those with high S that suffered a further reduction of 40%. The impact of increased LI and lowered S was reflected in improved Pn in A/Ci and light-response curves and improved carboxylating efficiencies. However, the negative effect of high S, particularly at high LI, resulted from photoinhibition (low photo-system efficiency of PSII) When transferred ex vitro (greenhouse), plantlets under low LI and no S died after 1 month, however, those with 45.0 g l^-1 sucrose shown the best growth at field conditions. The positive effects of increased LI on Pn was confirmed in experiments where plantlets were cultured in vitro under natural light (glasshouse) resulting in improved Pn to 5.5 mmol m^-2s^-1. Relationship between Pn in vitro with both ex vitro Pn and growth will be discussed.