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1.
Edward M. Jhee Keri L. Dandridge Arthur M. Christy Jr. A. Joseph Pollard 《Chemoecology》1999,9(2):93-95
2.
Hyperaccumulation of metals by plants involves at least three processes: efficient absorption by roots, efficient root-to-shoot translocation and hypertolerance through internal detoxification. In this study, Thlaspi caerulescens was separately exposed to Cd and Zn at 0, 50, 100 and 200 μ M for 7 d to monitor plant responses in hydroponics. Significant dose-dependent accumulation was observed for both metals, mainly in roots (up to 3.2 and 9.2 mg g ?1 for Cd and Zn, respectively). However, Cd was more phytotoxic in terms of plant growth and photosynthesis. This higher toxicity was also evidenced by MetPLATE bioassay. Root exudation was significantly correlated to Cd and Zn translocation (r>0.85) proving its involvement in facilitating metal uptake. As for antioxidative responses, plants reacted to Cd and Zn by broadly exhibiting an elevation of glutathione reductase activity before declining at 200 μ M due to higher phytotoxicity. By contrast, superoxide dismutase activity was unlikely to be affected by both metals. Root-to-shoot apoplastic flow was traced using a fluorescent dye (trisodium-8-hydroxy-1,3,6-pyrenetrisulfonic acid; PTS), whose concentration in leaves increased to a certain extent with Cd and Zn accumulation, indicating that heavy metals have a comparable effect to drought or salinity in promoting the passive diffusion of water and solutes. Nevertheless, Cd at 200 μ M hindered the diffusion of PTS and consequently affected the apoplastic transport in plants. 相似文献
3.
Nest defence behaviours, such as attacking predators and defending against predator attacks, expose birds to risk of injury
and death. However, direct costs of such behaviours are poorly documented. To evaluate potential costs of nest defence behaviours
in lesser snow geese (Chen caerulescens), we (1) estimated the proportion of interactions between arctic foxes (Alopex lagopus) and geese that resulted in physical contact and (2) examined how nest defence behaviours varied between male and female
geese. We separated interactions into attacks initiated by foxes (attacks by foxes) and attacks initiated by geese (attacks by geese). Risks associated with attacks by geese were considerably lower than the risks associated with attacks by foxes; only 1
of 1,179 attacks by geese resulted in physical contact between foxes and geese, whereas 26 of 89 attacks by foxes involved
such contact (two female geese were killed during these attacks). Attacks by geese were made almost exclusively by male geese
(>97%), whereas female geese were involved in 75% of all attacks by foxes that resulted in physical contact with geese. There
was, thus, a considerable difference in risks associated with male and female nest defence behaviours. We suggest that parental
roles during nesting (i.e., females incubate and males guard) expose female geese to greater risk of injury and death. Male
geese may, however, reduce the risk of injury or death to their mates with pre-emptive attacks on foraging foxes. 相似文献