Specific Intra‐Tissue Responses to Manganese in the Floating Lamina of Trapa natans L.

Abstract

Plant tolerance to heavy metals requires morpho-physiological mechanisms that are still poorly understood, especially in hydrophytes. This study focuses on the young floating lamina of the rhyzophyte Trapa natans exposed for 10 d to 130 microM Mn. The lamina has the ability to bioaccumulate Mn (> 3000 microg g(-1)). X-ray microanalysis of Mn cellular distribution revealed accumulation in the upper epidermis, in the first palisade layer, and in the idioblasts of the spongy tissue, which were shown with electron microscopy to contain osmiophilic vacuolar deposits, also observed to a minor extent in the control leaves. On the basis of biochemical and histochemical tests, these deposits were attributed to phenolic compounds that were probably able to chelate Mn. Net photosynthesis, photosynthetic pigments, room temperature microspectrofluorimetric analyses, and ultrastructural studies of plastids were performed to evaluate the status of the photosynthetic apparatus. A greater development of thylakoid membranes was observed in plastids of the second palisade and spongy tissue, which, however, did not accumulate Mn. Only the spongy tissue experienced inadequate assembly of PS II, but this did not significantly influence the photosynthetic yield of the whole lamina. It was concluded that T. natans can optimise productivity in the presence of Mn by means of specific intra-tissue responses within the framework of the floating lamina.

Changes in the ultrastructure of soybean cultivars in response to manganese supply in solution culture

“…This can also be confirmed by the morphometric assessments shown in Table 2. Under all Mn concentrations, there were no changes either in stomata length or stomata number both in the adaxial and abaxial face (Figure 2), a finding that agrees with the observations of Weiland et al (1975) and Baldisserotto et al (2004). However, under severe Mn toxicity conditions, there was high disorganization of the tissue, characterized by hidden stomata throughout the leaf area as well.…”

Genotypic Influence on the Absorption, Use and Toxicity of Manganese by Soybean

“…Under all Mn rates, there were no changes either in stomata length or stomata number both in the adaxial and abaxial face (Fig. 5), a finding that agrees with the observations of Weiland et al (1975) and Baldisserotto et al (2004). However, it should not be ignored that under severe Mn toxicity conditions, there was high disorganization of the tissue, characterized by hidden stomata throughout the leaf area as well.…”

Photosystem II organisation in chloroplasts of Arum italicum leaf depends on tissue location

“…Plastid variations within a single leaf have been characterised mainly by differences in the pigment content, plastid ultrastructure and more recently in Chl fluorescence (Terashima and Inoue 1985a, b;Baldisserotto et al 2004;Cordon and Lagorio 2007). The improvement in biochemical methods has opened the possibility of analysing how these plastid variations can also be the expression of the interplay among pigment-protein complexes in thylakoids (Romanowska et al 2008).…”

“…The emission light was collected by the objective lens and deviated to the detector system, coupled with an analogue/digital converter for data transfer to the ''Autolab'' software (RCS). The ''Autolab'' software was also used to set the recording range (620-780 nm) and to optimise the photomultiplier response (Baldisserotto et al 2004(Baldisserotto et al , 2007.…”

“…The Chl a/b ratio results indeed from co-ordinated changes in the amount of proteins of PSII and LHCII, and also of PSI, giving rise to several possible patterns of photosynthetic acclimation (Murchie and Horton 1998;Baldisserotto et al 2004;Ballottari et al 2007;Dietzel et al 2008). In the spongy tissue of Arum italicum lamina, while the amount of LHCII remains essentially unaffected, the PSI/PSII ratio decreases.…”