Distribution and Redistribution of Cd and Zn in the Heavy Metal Hyperaccumulator L.: Influence of Cadmium and Zinc Concentrations in the Root Medium.

Heavy metal redistribution is relevant for the quality of edible crops and the suitability of hyperaccumulators for bioremediation. Root-to-shoot transfer via the xylem and redistribution in the aerial parts via the phloem differ between various heavy metals. In general, cadmium is more slowly released to the shoot than zinc (e.

Drought stress and carbon assimilation in a warming climate: Reversible and irreversible impacts.

Global change is characterized by increased CO concentration in the atmosphere, increasing average temperature and more frequent extreme events including drought periods, heat waves and flooding. Especially the impacts of drought and of elevated temperature on carbon assimilation are considered in this review. Effects of extreme events on the subcellular level as well as on the whole plant level may be reversible, partially reversible or irreversible.

Effects of PEG-Induced Water Deficit in Solanum nigrum on Zn and Ni Uptake and Translocation in Split Root Systems.

Drought strongly influences root activities in crop plants and weeds. This paper is focused on the performance of the heavy metal accumulator Solanum nigrum, a plant which might be helpful for phytoremediation. The water potential in a split root system was decreased by the addition of polyethylene glycol (PEG 6000).

Dehydrin expression as a potential diagnostic tool for cold stress in white clover.

Cold acclimation is important for crop survival in environments undergoing seasonal low temperatures. It involves the induction of defensive mechanisms including the accumulation of different cryoprotective molecules among which are dehydrins (DHN). Recently several sequences coding for dehydrins were identified in white clover (Trifolium repens).

Phosphorus and nitrogen regulate arbuscular mycorrhizal symbiosis in Petunia hybrida.

Phosphorus and nitrogen are essential nutrient elements that are needed by plants in large amounts. The arbuscular mycorrhizal symbiosis between plants and soil fungi improves phosphorus and nitrogen acquisition under limiting conditions. On the other hand, these nutrients influence root colonization by mycorrhizal fungi and symbiotic functioning.

Selective uptake, distribution, and redistribution of (109)Cd, (57)Co, (65)Zn, (63)Ni, and (134)Cs via xylem and phloem in the heavy metal hyperaccumulator Solanum nigrum L.

The focus of this article was to explore the translocation of (109)Cd, (57)Co, (65)Zn, (63)Ni, and (134)Cs via xylem and phloem in the newly found hyperaccumulator Solanum nigrum L. Two experiments with the uptake via the roots and transport of (109)Cd, (57)Co, and (65)Zn labeled by roots, and the redistribution of (109)Cd, (65)Zn, (57)Co, (63)Ni, and (134)Cs using flap label in S. nigrum in a hydroponic culture with a standard nutrient solution were conducted.

Natural antisense transcripts of Trifolium repens dehydrins.

The recently described complex nature of some dehydrin-coding sequences in Trifolium repens could explain the considerable variability among transcripts originating from a single gene.1 For some of the sequences the existence of natural antisense transcripts (NAT s), which could form sense-antisense (SAS) pairs, was predicted. The present study demonstrates that cis-natural antisense transcripts of 2 dehydrin types (YnKn and YnSKn) accumulate in white clover plants subjected to treatments with polyethylene glycol (PEG), abscisic acid (ABA), and high salt concentration.

Identification and expression of different dehydrin subclasses involved in the drought response of Trifolium repens.

Reverse transcribed RNAs coding for YnKn, YnSKn, SKn, and KS dehydrin types in drought-stressed white clover (Trifolium repens) were identified and characterized. The nucleotide analyses revealed the complex nature of dehydrin-coding sequences, often featured with alternative start and stop codons within the open reading frames, which could be a prerequisite for high variability among the transcripts originating from a single gene. For some dehydrin sequences, the existence of natural antisense transcripts was predicted.

Effects of an extended drought period on physiological properties of grassland species in the field.

A very high percentage (around 70%) of the agronomic area in Switzerland is covered by grasslands at various altitudes where environmental conditions, management, community structure and productivity vary widely. As heat waves and drought are predicted to increase in future climate, survival of plant species in grasslands is a major issue of concern in Central Europe. The effect of summer drought on representative grasslands in Switzerland was studied through drought experiments (using rain-out shelters avoiding natural precipitation) to understand the response of predominant species to changed climatic conditions.

Genotypic variation in drought stress response and subsequent recovery of wheat (Triticum aestivum L.).

Three wheat (Triticum aestivum L.) genotypes, Sadovo, Katya and Prelom, with different tolerance to drought were comparatively evaluated in terms of leaf respiratory responses to progressing dehydration and consecutive rewatering. Under drought stress, the respiration of all varieties gradually decreased, as the drought-tolerant Katya showed the most pronounced decline at earlier stages of dehydration.

Proteolytic activity and cysteine protease expression in wheat leaves under severe soil drought and recovery.

The involvement of acidic proteases in soil drought response of winter wheat (Triticum aestivum L.) at seedling stage in three cultivars differing in water stress tolerance was studied. Withholding irrigation for seven days resulted in severe drought stress corresponding to 60% leaf water deficit.

Variety-specific response of wheat (Triticum aestivum L.) leaf mitochondria to drought stress.

The main objective of the present work was to examine leaf respiratory responses to dehydration and subsequent recovery in three varieties of winter wheat (Triticum aestivum L.) known to differ in their level of drought tolerance. Under dehydration, both total respiration and salicylhydroxamic acid (SHAM)-resistant cytochrome (Cyt) pathway respiration by leaf segments decreased significantly compared with well-watered plants.

Changes of photosynthetic traits in beech saplings (Fagus sylvatica) under severe drought stress and during recovery.

In the context of an increased risk of extreme drought events across Europe during the next decades, the capacity of trees to recover and survive drought periods awaits further attention. In summer 2005, 4-year-old beech (Fagus sylvatica L.) saplings were watered regularly or were kept for 4 weeks without irrigation in the field and then re-watered again.

Rubiscolytics: fate of Rubisco after its enzymatic function in a cell is terminated.

Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is the predominant protein in photosynthesizing plant parts and the most abundant protein on earth. Amino acids deriving from its net degradation during senescence are transported to sinks (e.g.

Steam-girdling of barley (Hordeum vulgare) leaves leads to carbohydrate accumulation and accelerated leaf senescence, facilitating transcriptomic analysis of senescence-associated genes.

Leaf senescence can be described as the dismantling of cellular components during a specific time interval before cell death. This has the effect of remobilizing N in the form of amino acids that can be relocalized to developing seeds. High levels of carbohydrates have previously been shown to promote the onset of the senescence process.

A petunia mutant affected in intracellular accommodation and morphogenesis of arbuscular mycorrhizal fungi.

The regulation of the arbuscular mycorrhizal (AM) symbiosis is largely under the control of a genetic programme of the plant host. This programme includes a common symbiosis signalling pathway that is shared with the root nodule symbiosis. Whereas this common pathway has been investigated in detail, little is known about the mycorrhiza-specific regulatory steps upstream and downstream of the common pathway.

Photosynthetic performance and water relations in young pubescent oak (Quercus pubescens) trees during drought stress and recovery.

The capability to withstand and to recover from severe summer droughts is becoming an important issue for tree species in central Europe, as dry periods are predicted to occur more frequently over the coming decades. Changes in leaf gas exchange, chlorophyll a fluorescence and leaf compounds related to photoprotection were analysed in young Quercus pubescens trees under field conditions during two summers (2004 and 2005) of progressive drought and subsequent rewatering. Photochemistry was reversibly down-regulated and dissipation of excess energy was enhanced during the stress phase, while contents of leaf pigments and antioxidants were almost unaltered.

Heavy metals in white lupin: uptake, root-to-shoot transfer and redistribution within the plant.

The translocation of manganese (Mn), nickel (Ni), cobalt (Co), zinc (Zn) and cadmium (Cd) in white lupin (Lupinus albus cv. Amiga) was compared considering root-to-shoot transport, and redistribution in the root system and in the shoot, as well as the content at different stages of cluster roots and in other roots. To investigate the redistribution of these heavy metals, lupin plants were labelled via the root for 24 h with radionuclides and subsequently grown hydroponically for several weeks.

Selective transport of zinc, manganese, nickel, cobalt and cadmium in the root system and transfer to the leaves in young wheat plants.

Background And Aims: The uptake, translocation and redistribution of the heavy metals zinc, manganese, nickel, cobalt and cadmium are relevant for plant nutrition as well as for the quality of harvested plant products. The long-distance transport of these heavy metals within the root system and the release to the shoot in young wheat (Triticum aestivum 'Arina') plants were investigated.

Methods: After the application of 65Zn, 54Mn, 63Ni, 57Co and 109Cd for 24 h to one seminal root (the other seminal roots being excised) of 54-h-old wheat seedlings, the labelled plants were incubated for several days in hydroponic culture on a medium without radionuclides.

Possible involvement of plant ABC transporters in cadmium detoxification: a cDNA sub-microarray approach.

As a nontolerant plant to a large number of toxic compounds, Arabidopsis thaliana is a suitable model to study regulation of genes involved in response to heavy metals. Using a cDNA-microarray approach, we identified some ABC transporters that are differentially regulated after cadmium treatments, making them putative candidates for being involved in Cd sequestration and redistribution in plants. Regarding yeast and fission yeast, in which Cd is able to form complexes either with glutathione (GSH) or phytochelatins (PC) subsequently transported into vacuoles via ABC transporters, it is also very likely that some plant ABC transporters are able to transport GS(2)-Cd or PC-Cd complexes into subcellular compartments or outside of the cell.

Knock-out of Arabidopsis metal transporter gene IRT1 results in iron deficiency accompanied by cell differentiation defects.

IRT1 and IRT2 are members of the Arabidopsis ZIP metal transporter family that are specifically induced by iron deprivation in roots and act as heterologous suppressors of yeast mutations inhibiting iron and zinc uptake. Although IRT1 and IRT2 are thought to perform redundant functions as root-specific metal transporters, insertional inactivation of the IRT1 gene alone results in typical symptoms of iron deficiency causing severe leaf chlorosis and lethality in soil. The irt1 mutation is characterized by specific developmental defects, including a drastic reduction of chloroplast thylakoid stacking into grana and lack of palisade parenchyma differentiation in leaves, reduced number of vascular bundles in stems, and irregular patterns of enlarged endodermal and cortex cells in roots.

Nitrogen metabolism and remobilization during senescence.

Senescence is a highly organized and well-regulated process. As much as 75% of total cellular nitrogen may be located in mesophyll chloroplasts of C(3)-plants. Proteolysis of chloroplast proteins begins in an early phase of senescence and the liberated amino acids can be exported to growing parts of the plant (e.