Chloroplast translocations induced by light pulses

Abstract

The effect of single blue-light pulses on chloroplast rearrangement was studied in the leaves of Tradescantia albiflora, Chlorophytum elatum, and Lemna trisulca. For measuring translocations in terrestrial plants the method of transmission changes was used; translocations in the water plant Lemna were studied by direct microscopic observation and counting. Strong light (30 W m(-2)) applied in the form of short pulses, shorter than a lag period of translocations, induces some transient effects in the following dark period. With short pulses, transient rearrangements of chloroplasts to a weak-light position were found. With longer pulse duration, biphasic responses took place in Tradescantia and Lemna: The initial movement to a partial strong-light position was followed by a wave of translocation to a weak-light arrangement. In Chlorophytum this type of response appeared only in a narrow fluence range. The validity of the reciprocity law in relation to fluence rate and time of irradiation was confirmed for Tradescantia. The results may give us an insight into the kinetics of the primary effects of light in the translocation process.

Fine tuning chloroplast movements through physical interactions between phototropins

“…Chloroplast responses to light pulses in Arabidopsis are similar to those observed for other plant species, reflecting their universal character (Gabryś et al , 1981). It was proposed that the chloroplast position inside the cell depends on the level of an active state produced by a photoreceptor with a half-lifetime of the order of minutes (Gabryś et al , 1981).…”

“…It was proposed that the chloroplast position inside the cell depends on the level of an active state produced by a photoreceptor with a half-lifetime of the order of minutes (Gabryś et al , 1981). Higher levels of this signaling state are needed for chloroplast avoidance; lower levels lead to accumulation.…”

“…Brief pulses of light followed by darkness lead to transient rearrangements of chloroplasts (Gabryś et al , 1981). In Tradescantia albiflora and Lemna trisulca , short pulses (20ms to 1s) of strong blue light (120 μmol m −2 s −1 ) induce transient chloroplast accumulation.…”

“…Pulses of longer duration (3–100s) result in a biphasic response of chloroplasts, initial transient avoidance being followed by accumulation. The responses to pulses obey the reciprocity law; that is, the same energy fluence brings about a response of the same amplitude and kinetics irrespective of the pulse duration and fluence rate (Gabryś et al , 1981). …”

Chloroplast Distribution in Arabidopsis thaliana (L.) Depends on Light Conditions during Growth

“…If the pulse lasts long enough (above 3-5 s), a typical bipolar response is generated. If it is shorter, the transient change in transmission reflects a partial response of chloroplasts toward the face arrangement (GabryS et al, 1981). Chloroplast responses to light pulses in A. thaliana were consistent with this general pattern; the mean amplitude of the whole response was similar for stL, sL, and WL plants despite their different dark transmission levels (Table I).…”