Apoplastic Content Research Articles

English

In this study, an examination was made of the effects of various iron fertilizers on the iron content of the various organs of tangerine plants. To this purpose, four different iron fertilizers [Fe-Citrate, FeSO4.7H2O, Fe-EDTA and Fe-EDDHA (Sequestren)] were applied to Satsuma plants. At the end of the experiment, the effects of the applications on the Fe and active Fe content of the roots, stems and leaves were examined. In addition, apoplastic Fe in the leaves was determined. Results showed that the highest values of all three parameters (total, active and apoplast Fe) were provided by Fe-EDDHA. The research showed that iron applied to the leaves affected active and apoplastic content in the order Fe-EDDHA (sequestren)>Fe-EDTA>FeSO4.7H2O>Fe-Citrate. Fe-EDTA followed the application of Fe-EDDHA. The highest total values of iron content in the roots were provided by Fe-Citrate and Fe-Sulfatin. Evaluation showed that Fe-EDDHA (sequestren) had a greater effect than the other Fe-containing fertilizers.   Key words: Satsuma tangerines (Citrus unshiu Marc.), iron, iron-containing fertilizers, active iron, apoplastic iron, chlorophyll.

Seasonal patterns of ascorbate in the needles of Scots Pine ( Pinus sylvestris L.) trees: Correlation analyses with atmospheric O 3 and NO 2 gas mixing ratios and meteorological parameters

In the present field study the role of ascorbate in scavenging the harmful atmospheric trace gases O3 and NO2 was examined. For this purpose ascorbate contents were determined in needles of adult Scots pine trees (Pinus sylvestris L.) during three consecutive years. Ascorbate contents were correlated with ambient tropospheric O3 and NO2 concentrations and with meteorological parameters. The results showed a strong correlation of atmospheric O3 but not of atmospheric NO2 concentrations with the apoplastic content of ascorbate during the seasonal course. Ascorbate contents in needle extracts did not correlate with ambient trace gas concentrations. In the apoplastic space, but not in needle extracts ascorbate contents correlate highly significantly with global radiation. From these results it is assumed that apoplastic ascorbate in Scots pine needles is adapted to the actual atmospheric O3 concentration to mediate immediate detoxification of O3, while the atmospheric O3 concentration itself is largely dependent on light intensity.

Difference in the retention of Ca and Al as possible mechanisms of Al resistance in upland rice

Genotypic differences between upland rice (Oryza sativa L.) varieties in the resistance to acid soil conditions were investigated in terms of the contents of Ca and Al in the apoplast of root tips. Apoplastic Ca and Al contents are assumed to be directly related to the inhibition of root cell elongation, which is the most typical symptom associated with cultivation in acid soils. The apoplastic content of Al eluted with BaCl2 was significantly different between the tolerant (Oryzica Sabana 6: SB6) and susceptible (Oryzica 1: OZ1) varieties when the Al concentration in the growth solution was in the range of 30 to 100 µM. The apoplastic Al content in SB6 was lower, probably reflecting the lower root CEC. On the other hand, the apoplastic Ca content showed significant genotypic differences when Ca was eluted with chelating solutions (Na-citrate and Na-EDTA) rather than with a BaClz solution. The apoplastic Ca content of OZ1 was much higher than that of SB6 in the absence of Al, but it decreased by half when the Al concentration increased to 30 µM, and then decreased further at higher Al concentrations. The apoplastic Ca content of SB6 was low even in the absence of Al treatment, and it did not decrease much further. The effect of solution Al on the Ca content in the root cell walls in the root elongation zone was examined in relation to the varietal differences between upland rice varieties in the resistance to acid soils.

A New Mechanism for the Regulation of Stomatal Aperture Size in Intact Leaves (Accumulation of Mesophyll-Derived Sucrose in the Guard-Cell Wall of Vicia faba).

At various times after pulse-labeling broad bean (Vicia faba L.) leaflets with 14CO2, whole-leaf pieces and rinsed epidermal peels were harvested and subsequently processed for histochemical analysis. Cells dissected from whole leaf retained apoplastic contents, whereas those from rinsed peels contained only symplastic contents. Sucrose (Suc)-specific radioactivity peaked (111 GBq mol-1) in palisade cells at 20 min. In contrast, the 14C content and Sucspecific radioactivity were very low in guard cells for 20 min, implying little CO2 incorporation; both then peaked at 40 min. The guard-cell apoplast had a high maximum Suc-specific radioactivity (204 GBq mol-1) and a high Suc influx rate (0.05 pmol stoma-1 min-1). These and other comparisons implied the presence of (a) multiple Suc pools in mesophyll cells, (b) a localized mesophyll-apoplast region that exchanges with phloem and stomata, and (c) mesophyll-derived Suc in guard-cell walls sufficient to diminish stomatal opening by approximately 3 [mu]m. Factors expected to enhance Suc accumulation in guard-cell walls are (a) high transpiration rate, which closes stomata, and (b) high apoplastic Suc concentration, which is elevated when mesophyll Suc efflux exceeds translocation. Therefore, multiple physiological factors are integrated in the attenuation of stomatal aperture size by this previously unrecognized mechanism.