Agriculture Reference
In-Depth Information
compared to the binary combinations. The present results were not completely with one
accord with the report by Florence et al. (2002) who showed that significant increases both in
sucrose and starch contents in cucumber mature leaves under 10 µg g
−1
Cu supplementary in
sand. Similarly, Moya et al. (1993) found that 0.1 mmol. L
-1
Cd and 0.5 mmol. L
-1
Ni induced
the decrease in net photosynthesis of treated plants, while, the total carbohydrate content in
the shoots of these plants was higher than in controls, thus, the starch and sucrose content in
the shoots of 0.5 mmol. L
-1
Ni treated plants were respectively up to 2.6 and 4.0 times greater
compared to controls. Authors suggested that the influence of Al and heavy metals on sucrose
concentration is very variable, depending mainly on the plant species or variety, and on the Al
and heavy metal activity and the combinations of metals in the nutritive solution.
4.
C
ONCLUSION
The toxicities of Al, Cd, and Cu separately and in combinations and the metals
interactions in this study were assessed by estimating the leaf trait, chlorophyll content,
photosynthesis, chlorophyll fluorescence and sugar content in barley leaves after 5-week
supply of the Al, Cd, and Cu excess in the nutrient solution. LA, LFW, LDW, LWC,
chlorophyll content, especially chlorophyll a content, Pn, gs, PS activity showed in
Fv/Fm
ratio, and sucrose content all decreased, while Ci and starch content increased significantly in
barley leaves when exposed to stress medium including low pH alone, especially for Shang
70-119. Binary metals combinations induced the further changes in these values when
compared with the Al alone treatment for both genotypes, indicating the existence of notable
synergistic interactions between Al and Cu or Al and Cd. However, ternary metals
combination produced different effects in two barley genotypes, thus, when compared with
the binary metals combinations, the more obvious changes were observed in Shang 70-119,
while the adverse results were detected in Gebeina. Further, compared to other leaf traits, leaf
fresh weight was the more sensitive endpoint, and consequently it would be a good parameter
to assess acid soil toxicity for barley plants. The analysis of chlorophyll content and
fluorescence, gs and Ci showed that the inhibition of Pn in barley seedlings by Al, Cd, and Cu
toxicity
in vivo
partly resulted from the reductions of chlorophyll content, the active PSII
reaction centers and gs, while the uncoupled changes of Pn and Ci indicated the reduction of
Pn by metal toxicity did not result from a stomatal closure.
A
CKNOWLEDGEMENTS
First author acknowledge the support provided by the Educative Department of Zhejiang
Province, Chinese and Australian Bureau of Cereal Research and Development (UT-8),
respectively.
