葉の表皮組織における細胞形態と気孔分布に関する研究

学位の種別:課程博士University of Tokyo(東京大学

Radionuclide Analysis on Bamboos following the Fukushima Nuclear Accident

In response to contamination from the recent Fukushima nuclear accident, we conducted radionuclide analysis on bamboos sampled from six sites within a 25 to 980 km radius of the Fukushima Daiichi nuclear power plant. Maximum activity concentrations of radiocesium 134Cs and 137Cs in samples from Fukushima city, 65 km away from the Fukushima Daiichi plant, were in excess of 71 and 79 kBq/kg, dry weight (DW), respectively. In Kashiwa city, 195 km away from the Fukushima Daiichi, the sample concentrations were in excess of 3.4 and 4.3 kBq/kg DW, respectively. In Toyohashi city, 440 km away from the Fukushima Daiichi, the concentrations were below the measurable limits of up to 4.5 Bq/kg DW. In the radiocesium contaminated samples, the radiocesium activity was higher in mature and fallen leaves than in young leaves, branches and culms

Cortical microtubules and fusicoccin response in clustered stomatal guard cells induced by sucrose solution immersion

<p>We previously found that sucrose solution immersion treatment permitted ectopic guard cell differentiation, resulting in clustered stomatal guard cells. Using this system, we examined the effects of sucrose solution-induced stomatal clustering on guard cell cortical microtubules and the stomatal response to fusicoccin. Confocal observation revealed that the radial orientation of cortical microtubules was largely maintained in clustered guard cells. Outward movement of cortical microtubule plus-ends was also kept in the clustered guard cells. Fusicoccin treatment induced stomatal opening in both spaced and clustered stomata, although sucrose solution-treated guard cells had lower stomatal apertures. These results suggested that immersion treatment with sucrose solution perturbed the one-cell spacing of stomata but not the cortical microtubule organization required to open stomatal pores.</p

Breaking of Plant Stomatal One-Cell-Spacing Rule by Sugar Solution Immersion

<div><p>The spatial distribution of plant stomata is a model system to study epidermal cell pattern formation. Molecular genetic approaches have identified several key genes required for stomatal distribution patterning, but environmental conditions that perturb the stomatal spacing distribution have not yet been identified. We found that immersing hydroponic cultures in 1–5% sucrose solution induced abnormally clustered stomata in the cotyledons of Arabidopsis seedlings. Clustered stomata were also induced by treatment with glucose or fructose solution but not by mannitol solution, suggesting that osmotic stress was not a cause of the disturbed stomatal patterns. Stomatal lineage cell-specific enhancer trap lines revealed that the sugar solution treatment led to ectopic expression of stomatal lineage cell-specific genes in non-stomatal lineage cells. Aniline blue staining also showed that there was reduced deposition of callose, a plant cell wall component, in new cell walls during formation of stomatal precursor cells (meristemoids). These results suggested that the immersion treatment with sugar solution permitted ectopic guard cell differentiation through dysfunction of the cell wall dividing stomatal- and non-stomatal lineage cells. Our simple induction system for clustered stomata provides a suitable tool for further studies to investigate the one-cell-spacing rule during plant stomatal development.</p></div

Percentage of stomata in each cluster size class.

<p>Abaxial cotyledons from 12- to 15 day-old seedlings grown in sugar-free, 1, 3 or 5% sucrose (A), and 3% glucose, fructose or mannitol (B) solutions were subjected to quantitative analysis. Data are mean values of 20–68 independent observations. Significance with sugar-free conditions was determined using Mann–Whitney's U-test. <i>p</i>-value *<0.0001. Total number of stomata counted: <i>n</i> = 281–1843.</p

Aniline blue staining of cotyledon epidermal cells.

<p>Four day-old cotyledons immersed in sugar-free (A) or 3% sucrose (B) solutions were stained with 0.02% aniline blue for 1 week. Representative images from 24 (sugar-free) and 38 (3% sucrose) independent seedlings were shown. Note that aniline blue fluorescence was clearly detected in new cell walls forming in meristemoids immersed in sucrose-free solutions but not in 3% sucrose solutions. Scale bars  = 10 μm.</p

The radioactivity concentrations of bamboo leaves and branches.

<p>Because of space limitation, the species names are shown as Japanese names. Please refer to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0034766#s2" target="_blank"><b>Methods</b></a> for their scientific names.</p