Growth of in vitro Oncidesa plantlets cultured under cold cathode fluorescent lamps with super-elevated CO2 enrichment

Abstract

Asinterestinhowtoincreasebiomassproductionthroughbiotechnologicalmeansgainstraction,focusis turning towards the use of photoautotrophic micropropagation under elevated levels of carbon dioxide (CO2) to maxi- mizeplantgrowthandproductivity.Theeffectofsuper-elevatedCO2withcoldcathodefluorescentlamps(CCFLs)onthe photoautotrophic growth of Oncidesa in vitro has been studied using a gas-permeable film culture vessel, the 'Vitron'. ThegrowthofOncidesa(formerlyOncidesaGowerRamsey'U-1')plantletsonVacinandWent (VW)mediumwasstimu- lated by 10 000 mmol mol 21 CO2. In particular, increasing the photosynthetic photon flux density (PPFD) from 45 to 60 mmol m 22 s 21 under 10 000 mmol mol 21 CO2 in the growth chamber remarkably increased the number of leaves and roots, and shoot and root fresh and dry weights compared with plantlets under the same level of CO2 under low PPFD (45 mmol m 22 s 21 ). However, there was a remarkable decrease in photosynthetic capacity, and chlorosis and browning of leaves. In stark contrast, plantlets grown on Kyoto medium at 10 000 mmol mol 21 CO2 under high PPFD hadahigherphotosyntheticratethanplantletsgrownonVWmedium,andnochlorosisorbrowningwasobserved.Fur- thermore, shoot growth was remarkably enhanced. Therefore, super-elevated CO2 (10 000 mmol mol 21 ) enrichment and growth under CCFLs can positively affect the efficiency and quality of commercial production of clonal Oncidesa plantlets.