|Authors: ||S. Fuljahn, H.-J. Tantau|
|Keywords: ||apple, rooting, sugar-free culture, temporary-immersion system, CO2 dynamics|
A new system combining a temporary-immersion system (TIS) and sugar-free cultivation is currently being tested and optimized for the micropropagation and rooting of apple shoots (Malus × domestica ‘Holsteiner Cox’). The shoots were cultivated under photoautotrophic conditions for 4 weeks.
CO2 was regulated to (1,400 ± 200) μmol mol-1 and the photosynthetic photon flux (PPF) was 115 μmol m-2 s-1 (lateral) and 75 µmol m-2 s-1 (overhead) (high PPF). This method was compared to a shaken submersion culture and a conventional agar culture, both with and without the addition of sucrose (3%) under a PPF of 75 μmol m-2 s-1 (low PPF). Rooting was most successful on MS agar (100% with 3% sucrose) and in photoautotrophic TIS (PA-TIS) (60%), even the plants on agar without the addition of sugar rooted to some extent (27.7%) whereas shoots under submersion vitrified and did not develop roots.
It could be shown that the net photosynthetic rate (Pn) of plants grown in PA-TIS is strongly influenced by PPF, increasing it significantly from a maximum of 3.32 μmol CO2 h-1 plantlet-1 under low PPF to 11.85 μmol CO2 h-1 plantlet-1 at the most under high PPF.
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