Structural Development, Water Status, Pigment Concentrations, and Oxidative Stress of Zygophyllum fabago Seedlings in Relation to Cadmium Distribution in the Shoot Organs

Abstract

Cadtnium is s toxic pollutant, hur the relationships hetween morphological modifications and Cd accumulation in different organs, as well as the physiological impact of accumulated Cd in leaves of different ages, remain an open question. We compared Cd concentration in the primary branches and main stems of the perennial shrub Zygophyllum fabago L. Six weeks of treatment with 10 /xM Cd inhibited stem elongation and axillary bud development, and Cd accumulated to a higher level in the oldest leaves on the main stem than in ramification leaves. Although ramifications always contained lower amounts of Cd than main-stem leaves, ramification leaves were more sensitive to the pollutant. While Cd accumulation induced stomatal closure, a decrease in carbon isotope discrimination, and an increase in the water use efficiency of main-stem leaves, an inverse trend was recorded for primary-branch leaves. Cadmium induced an increa.se in chlorophyll concentration in the main stem but decreased it in latera! branches. Bypass flow, quantified by tbe 8-hydroxy-l,3,6-pyrenetrisulfonic acid trisodium salt fluorescent dye, correlated significantly witb Cd accumulation in leaves, suggesting tbat it contributes to Cd translocation tbrough the transpiration stream. Our study demonstrates tbat Cd absorbed by the roots Is unevenly distributed in tbe shoot leaves. Accumulated toxic ion, however, is not the only factor conditioning the organ response; for example, the physiological status of the tissues in relation to tbe leaf ontogeny may direaly influence tbe extent of metabolic disorders resulting from Cd accumulation.

Differential cadmium and zinc distribution in relation to their physiological impact in the leaves of the accumulatingZygophyllum fabago L.

“…Despite this rapid Cd accumulation, the decrease in leaf WC and osmotic Ψ s, already reported for this species (Lefèvre et al . , , ), occurred after only 28 d in response to Cd treatment. Cadmium induced a reduction of the leaf expansion compared with the controls and a resulting increase in stomatal density (Fig.…”

“…a) to reach a maximum value within less than a week, as previously shown by Lefèvre et al . (). Despite this rapid Cd accumulation, the decrease in leaf WC and osmotic Ψ s, already reported for this species (Lefèvre et al .…”

“…Back to the laboratory, the seeds were sown and seedlings were grown in a mixture of sand and compost under controlled environmental conditions as already described (Lefèvre et al . ). The 7‐week‐old plants were then transferred to hydroponic system: nine tanks of 50 L were filled with an aerated modified Hoagland solution (Lefèvre et al .…”

“…The 7‐week‐old plants were then transferred to hydroponic system: nine tanks of 50 L were filled with an aerated modified Hoagland solution (Lefèvre et al . ). Thirty seedlings per tank were placed in polystyrene plates floating on the solution, which was renewed every week and the pH adjusted to 6.00 ± 0.05.…”

Effects of Salinity on the Response of the Wetland Halophyte Kosteletzkya virginica (L.) Presl. to Copper Toxicity

“…As far as shoot is concerned, Cu-induced growth inhibition was more marked on lateral branches than on the main stem, thus leading to a modification of the plant architecture. It has already been reported in the perennial shrub Zygophyllum fabago L. exposed to heavy metals that ramifications are more sensitive to pollutant than the main axis, despite a lower rate of heavy metal accumulation (Lefèvre et al 2009). Since almost no Fig.…”