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Displacement and Return Movement of Chloroplasts in the Marine Dinophyte Pyrocystis noctiluca . Experiments with Optical Tweezers
Author(s) -
Leitz G.,
Greulich K. O.,
Schnepf E.
Publication year - 1994
Publication title -
botanica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.871
H-Index - 87
eISSN - 1438-8677
pISSN - 0932-8629
DOI - 10.1111/j.1438-8677.1994.tb00413.x
Subject(s) - organelle , biophysics , optical tweezers , vacuole , cytoplasmic streaming , plastid , biology , cytoplasm , chloroplast , optics , microbiology and biotechnology , biochemistry , physics , gene
Abstract Infrared laser traps (optical tweezers) were used to study laser‐induced organelle movements in the marine alga Pyrocystis noctiluca (Dinophyta). These cells are highly suitable for optical micromanipulation due to their large size and extensive vacuole. Experiments were done with plastids held by optical tweezers and moved from the nuclear area into the vacuole. The subsequent retraction movement was analysed for speed. The displaced organelles remained connected to their original position by a thin cytoplasmic strand, often less than 1 μm in diameter. When the organelles were released they rapidly returned at an initial rate of 81.7 ± 7.8 μm . s −1 (overall displacement 50 μm, measured distance 20 μm, 25 °C ± 1 °C, number of cells 22), slowing down with progressive retraction of the connecting strand. The return movement was reduced to 4.2 ± 0.2 μ .s −1 (n = 10) when the organelles were displaced and held for 1 min. Displacement to a longer distance increased the rate of return movement. A change from a high to a low environmental temperature significantly reduced movement from 94.5 ± 9.0 . s −1 (30 °C ± 1 °C, n = 22) to 34.5 ± 2.7 μm .s −1 (5°C ± 1 °C, n = 22). Nocodazole and N‐ethylmaleimide (NEM), inhibitors of microtubules and acto‐myosin, respectively, did not affect the retraction of the connecting strand, but at high concentrations of NEM it became increasingly difficult to move organelles away from the nuclear area. We suggest that the return movement of organelles within laser‐induced artificial strands mainly depends on the viscoelastic properties of the tonoplast. The quantification of these properties by optical tweezers allows determination of reactions of plant cells to temperature changes.