Plant growth and development are directly influenced by the movement and positioning
of the chloroplasts. Chloroplast movement is stimulated by varying external stimuli;
(Kadota, Sato and Wada, 1996) submergence, water stress, low temperature, etc. and among
these light-induced chloroplast movement is the most researched and commonly established.
Chloroplasts in photosynthesizing plant cells change their arrangement in response to irradiation
from light. This is believed to maximize their photosynthetic activity and minimize photo
damage. This essay will try to expand on the concepts of chloroplast movement in plant cells by
discussing the mechanisms involved and machinery employed through irradiated light settings &
light receptors, and cytoplasmic filaments including Ca+ flux & actins.
Firstly, chloroplasts found in plant species change their location in a cell in response to
ambient light settings. Particularly, the “concentration” of the admitted light plays an importance
to the movement and relocation of the chloroplast for specific arrangement in a cell. Low
fluence-rate (LFR) is generated by weak light and as a result(Haupt and Scheuerlein, 1990) it
allows the chloroplasts to seek the best position possible in order to receive the greatest light
absorption. In contrast high fluence-rate (HFR) forces the chloroplasts to move to a position
where lowest possible light absorption takes place, in order to evade photo-damage. (Serlin and
Roux, 1984) during high fluence irradiation the chloroplasts are situated in periphery and move
onto the anticlinal walls.
Secondly, chloroplast movement in plant species is revealed to be most effective under
blue light. In a model study involving Arabidopsis thaliana, it was found that flavoprotein
phototropins (phot 1 and phot 2) were recognized (Kadota, Sato and Wada, 2000) blue light
photoreceptors work in the transfer of chloroplasts. Photobiological analyses of mesophyll cells
in this study revealed that light photoreceptors and phytochromes are arranged in the surrounding
area of plasma membrane to control chloroplast photo-orientation movement (Kagawa and Wada
2000) but the study is still inconclusive.
Third, under light (Mineyuki and Nagai, 1991) observed the Mougeotia cell behavior of
the cytoplasmic filaments in correlation with chloroplasts movement and came to the
understanding that the filaments originated from the moving edge of the chloroplasts. After the
orientation of the chloroplast, the filaments departed and...