Culture method and photosynthetic photon flux affect photosynthesis, growth and survival of Limonium 'Misty Blue' in vitro

Microcuttings (shoots each with two leaves) of Limonium 'Misty Blue' were cultivated in vitro for 28 days under photoautotrophic (sucrose-free culture medium CO2 and photosynthetic photon flux (PPF) enriched conditions), photomixotrophic (medium with 30 gl(-1) sucrose, CO2 acid PPF enriched conditions) and heterotrophic (medium with 30 g l(-1) sucrose; CO, non-enriched conditions) methods. Several growth variables were measured during and at the end of cultivation: shoot fresh and dry weight, percentage of shoot dry matter. root fresh weight, number of leaves, leaf area, chlorophyll and sugar content of leaves. stomatal density and size, net photosynthetic rate (NPR) and percent survival of plantlets ex vitro. Plantlets grown in photoautotrophic and photomixotrophic methods had more leaves, high chlorophyll and sugar contents, high NPR, and showed high percent survival. However, these plantlets possessed less number of stomata per square millimeter. In contrast, the plantlets grown by the heterotrophic method showed decreased values of these growth variables except for the number of stomata per square millimeter. These results indicate that CO2 enrichment for plantlets in vitro at a relatively high PPF would promote photosynthesis and hence growth of chlorophyllous explants/plantlets in vitro. The resulting plantlets were acclimatized better and sooner on ex vitro transplantation. (C) 2002 Elsevier Science B.V. All rights reserved.