Enhancement of cadmium effects on growth and nutrient composition of birch (Betula pendula) by buthionine sulphoximine (BSO)

Binding of Cd to non-specific metal-binding peptides (phytochelatins)in birch roots has been suggested as an explanation for toleranceto Cd toxicity in birch (Betula pendula). In the present study,the tolerance of birch roots to Cd was further investigatedby using buthionine sulphoximine (BSO) as an inhibitor of phytochelatinsynthesis. Birch seedlings, grown in nutrient solution at pH4.2, were exposed to 0 or 2 µM CdCl₂ combined with 0 or0.1 mM BSO for 6 d. Plant growth (fresh weight increase andshoot to root dry weight ratio) and the nutrient compositionin fine roots, whole roots and shoots were determined. The effectsof Cd on growth confirms the results of earlier studies on birch,suggesting a reduced shoot growth, but preserved or stimulatedroot growth. When Cd and BSO were combined, overall plant growthwas severely reduced. BSO was also shown to aggravate Cd-inducedreductions of root and shoot concentrations of K, Ca and Mgbut to impede the accumulation of Cd. The results suggest that phytochelatins participate in protectingthe root against Cd interferences with growth, possibly by restrictingCd-induced changes in the nutrient composition of the plant. Key words: Betula pendula, buthionine sulphoximine, cadmium, phytochelatins, roots, tolerance     

Cadmium and copper interactions on the accumulation and distribution of Cd and Cu in birch (Betula pendula Roth) seedlings

The effect of different external cadmium (Cd) and copper (Cu) regimes on the concentration of Cd and Cu in roots and shoots of birch (Betula pendula Roth.) seedlings was investigated. The seedlings were grown for 12 days in a weak nutrient solution (containing all essential nutrient elements including 0.025 µM Cu) at pH 4.2 with combinations of additional 0–2 µM CdCl₂ and 0–2 µM CuCl₂. Root and shoot concentrations of Cu were decreased by Cd in all treatments which included 0.1–2 µM of additional Cu in the treatment solution. When no extra Cu was added, only the shoot concentration of Cu was decreased by Cd whereas the root concentration was not affected. The shoot concentration of Cd was decreased by 0.5 and 2 µM of additional Cu in the treatment solution. The root concentration of Cd was decreased by Cu only when the concentration of additional Cu in the treatment solution was equal to or exceeded the concentration of Cd.     

Control of potassium influx in roots of birch (Betula pendula) seedlings exposed to cadmium

The nutrient status of the root may be a factor of vital importancefor plant tolerance to changes in the environment. In this studythe effect of Cd on the K+ uptake of birch plants, starved andnon-starved of potassium, was examined. Changes in potassiuminflux of birch [Betula pendula) roots, with time, were examinedin birch plants introduced to a nutrient solution containing125/jM K+ after a K+-starvation period. Cadmium was introducedduring the K+-recovery period and the effects of the heavy metalon the development of the uptake pattern was studied. When noCd was present K+ influx, in previously K+-starved plants, increasedwith time and reached a maximum after 6 h. When 2 or 5//M Cdwas supplied simultaneously with potassium to the root, K+ influxwas unchanged during an 8 h K+-recovery period, and the K concentrationin the roots did not increase as was the case when the plantswere given K+ without Cd. In another experiment Cd supply (2//M)to K+-fed plants gave an immediate 50% decrease in K+ influx.However, after prolonged exposure to Cd (up to 20 h), K+ influxrecovered to the control value. Key words: Birch, cadmium, influx, potassium, regulation     

Monitoring copper-induced changes in fine root geometry of birch (Betula pendula) using nutrient film technique (NFT)

Effects of copper on fine root geometry (number, length) and K and Cu content in birch ( Betula pendula Roth) were studied. After pre-cultivation, the plants were grown in a nutrient film technique (NFT) system and exposed to additional 0–5 μ M for a period of 8 days. The NFT system permitted undisturbed growth of the roots during monitoring. Copper experiments were carried out in a split-root setup both with a uniform and differentiated Cu supply to investigate growth responses of roots grown in a homogeneous and heterogeneous root environment, respectively. At uniform external Cu supply, average root length was affected by increased Cu concentration during the first four days while the next four days only the overall root length (product of root length and root number) was significantly reduced. During the first four days in the split-root experiments with differentiated Cu supply, additional Cu primarily reduced root number on the Cu-treated parts of the root system but at stronger Cu concentration the overall root length was also significantly reduced. In contrast, number and average root length of the part of the root system not exposed to Cu increased when 1, 2 and 5 μ M Cu was added to the other side. Growth parameters were affected differently in the beginning of the heavy metal exposure compared to later stages of exposure, which may indicate acclimatisation to Cu stress.