Is Chloroplast Movement in Tobacco Plants Influenced Systemically after Local Illumination or Burning Stress?

Abstract

Chloroplast movement has been studied in many plants mainly in relation to the local light, mechanical or stress effects. Here we investigated possible systemic responses of chloroplast movement to local light or burning stress in tobacco plants (Nicotiana tabacum cv. Samsun). Chloroplast movement was measured using two independent methods: one with a SPAD 502 Chlorophyll meter and another by collimated transmittance at a selected wavelength (676 nm). A sensitive periodic movement of chloroplasts was used in high or low (2 000 or 50 μmol/m 2 per s photosynthetically active radiation, respectively) cold white light with periods of 50 or 130 min. Measurements were carried out in the irradiated area, in the non-irradiated area of the same leaf or in the leaf located on the stem below the irradiated or burned one. No significant changes in systemic chloroplast movement in non-irradiated parts of the leaf and in the non-treated leaf were detected. Our data indicate that chloroplast movement in tobacco is dependent dominantly on the intensity and spectral composition of the incident light and on the local stimulation and state of the target tissue. No systemic signal was strong enough to evoke a detectable systemic response in chloroplast movement in distant untreated tissues of tobacco plants.Key words: burning; chloroplast movement; irradiance; systemic response; tobacco. Higher plants respond to changing environmental factors affecting either the whole plants (changing temperature, water deficit, excess light intensity) or the part (local response) of a plant body (wounding) by initiating various defense-related processes. These processes include, for example, the accumulation of defense-related proteins, changes in respiration, stomatal and photosynthetic apparatus responses and also chloroplast movement. Important characteristics of self-defense responses of plants are their velocity and ubiquity. Fast (minutes to hours) responses to injurious factors have been detected in the site of injury and in distant regions (systemic response) at the tissue, cellular and molecular levels in various plants (Herde et al. 1996;Baldwin et al. 1997;Rakwal et al. 2002;Koziolek et al. 2004;Hlaváčková et al. 2006 suggest that a signal moves from the injured tissue to the distant untreated parts of the plants and leads to systemic changes. Precise control of organelle positioning is important for plant responses at the cellular level to environmental conditions and stresses (Nagai 1993;Wada and Suetsugu 2004). In particular, chloroplast photo-movement is one of the responses observed in the cells of many species (including tobacco plants used in our study, Augustynowicz et al. 2001) and occurs throughout the plant kingdom . Chloroplasts move towards the illuminated area under weak light conditions, whereas they move away from the area when the light is too strong. The accepted interpretation of the ecological role of these responses is to optimize light harvesting for photosynthesis. Kasahara et al. (2002) reported that chl...

SPAD chlorophyll meter reading can be pronouncedly affected by chloroplast movement

“…When exposed to high light, chloroplasts migrate to cell walls parallel to the incoming light (side position). This chloroplast movement causes pronounced changes in T (Berg et al 2006;DeBlasio et al 2005;Gorton et al 1999), and thus can influence the SPAD reading and its relationship with the chlorophyll content as has been already mentioned (Hoel and Solhaug 1998;Martínez and Guiamet 2004;Nauš et al 2008;Uddling et al 2007). It has been shown that the chloroplast position can pronouncedly differ during the day according to varied natural light conditions and that responsiveness of the chloroplast movement to light can be quite rapid (Williams et al 2003).…”

“…The partly collimated leaf transmittance (T C ) was measured in the spectral range 400-800 nm using Spectroradiometer LI-1800 (LI-COR Lincoln, NE, USA) and light guide by the method described in Nauš et al (2008). Briefly, the incident light is collimated and the incident beam is perpendicular to the plane of the leaf.…”

Chloroplast avoidance movement as a sensitive indicator of relative water content during leaf desiccation in the dark

“…The T C dependence on time of blue light exposure, the T C (t) curve, reflecting the chloroplast avoidance movement, was characterized by a sigmoidal increasing shape (see Nauš et al 2008, Frolec et al 2010. We used an illumination time of 25 min, which was time necessary to reach the beginning of the T C plateau in control leaves (Fig.…”

“…This method is described in detail in Frolec et al (2010) and Nauš et al (2008). Briefly, the leaves were illuminated from the adaxial side by blue light (Schott KL 2500 LCD cold light source (Schott Glass AG, Mainz, Germany) in combination with blue Schott BG12 glass filter).…”

“…Our method (Nauš et al 2008;Frolec et al 2010) is simpler and more straightforward, as we detect the leaf transmittance not in the red region but at the wavelength of minimal transmittance in the blue region (around 436 nm). In other words, a part of the blue light stimulating chloroplast movement is used simultaneously as the measuring light.…”