Ecophysiological and anatomical changes due to uptake and accumulation of heavy metal in Brachiaria decumbens

Abstract

The growth and developmental characteristics of grasses and their high biodiversity make such plants suitable for remediation of areas contaminated by heavy metals. Nevertheless, heavy metal toxic effect on the plants may cause alteration in their metabolic pathways, such as photosynthesis, respiration, and growth, modifying plant anatomy. This work aimed to evaluate the effect of levels of soil contamination (0, 7.5 % and 15 % m 3 m -3) on biomass production, on photosynthetic characteristics and on anatomical changes in roots and leaves of brachiaria (Brachiaria decumbens Stapf.). After seeds were planted, seedlings were uprooted and replanted in vases containing soil at different contamination levels, being left to rest for 120 days. At the end of that time, plants presented reduced yield of root and shoot dry matter, contents of chlorophyll a, chlorophyll b, total chlorophyll and potential photosynthesis with increased of soil contamination. The cell layers of endodermis and exodermis in the root tissues and the cell walls of the xylem and cortical parenchyma all thickened as contamination increased. In the leaf tissues, the adaxial and abaxial epidermis presented increased thickness while the leaf blade presented reduced thickness as contamination increased with consequent change in the root growth rate. In general, the effects of heavy metal increased with the metal concentration. Some results indicate that B. decumbens seems to have some degree of heavy metal tolerance.

Impact of phosphate on glyphosate uptake and toxicity in willow

“…In our study, plants submitted to glyphosate showed darker and thicker roots in relation to control (data not shown), recognized visual symptoms of stress [51][52][53]. Since glyphosate is known to induce oxidative damage in plants [54,55], we investigated oxidative stress markers to elucidate whether the process of glyphosate uptake by roots induces oxidative stress, and to evaluate the possible protective role of PO 4 3-in willow roots.…”

Structural changes in leaves and roots are anatomical markers of aluminum sensitivity in sunflower1

“…Previous studies also report that Al stress affects the roots of IAC-Uruguai plants more significantly than those of the Catissol cultivar (Jesus & Azevedo Neto 2013). Maintaining the membrane integrity is considered an important component of plant tolerance to Al stress (Gomes et al 2011). Thus, it is likely that reduced root growth with decreased membrane integrity and water status may at least partially explain the greater sensitivity of IAC-Uruguai to Al stress, when compared to Catissol plants.…”

Germination and initial development of Brachiaria brizantha and Brachiaria decumbens on exposure to cadmium, lead and copper

“…The levels of chlorophyll, of the enzymes activity of the Calvin cycle and photosystem II (or waterplastoquinone oxidoreductase) are susceptible to trace elements. In combination, both directly and indirectly, these factors contribute to the reduction of carbon assimilation (Gomes et al, 2011). The root tissue showed higher levels of Cd and Cu compared to the shoot for all species studied, as can be seen in Table 4.…”

“…In addition, the presence of trace elements accelerates maturation of the cell wall in mesoderm and endoderm (Gomes et al, 2011). The presence of trace elements may block the transport of water to the seeds due to the increase in the osmotic potential of the solution, resulting in a secondary effect caused by the low water absorption and not the element toxic effects on the embryo (Kranner and Colville, 2011).…”

“…stands out due to high dry matter, easy cultivation and adaptation to different soils, allowing cultivation throughout the year, and low maintenance cost of the cultivated area (Lucena et al, 2010). However, few studies are carried out with this genus on trace element contamination (Gomes et al, 2011).…”