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  • 1
    Electronic Resource
    Electronic Resource
    Modulation of photosystem 2 reactions mediated by aluminium toxicity in Zea mays (1997)
    Springer
    Photosynthetica 34 (1997), S. 151-156 
    Details
    ISSN: 1573-9058
    Keywords: Al ; carotenoids ; chlorophyll ; fluorescence induction ; Hill reaction ; maize ; singlet oxygen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two weeks old maize (Zea mays L. cv. XL-72.3) plants were submitted to 0 to 81 g m-3 Al for 20 d in a growth medium of low ionic strength. The increasing Al concentrations sharply increased chlorophyll (Chl) concentrations. The rates of photosystem 2 activities (H2O→DCPIP and DPC→DCPIP) increased at 9 g(Al) m-3 but at higher Al doses they decreased again. A slight decrease of qE and qN coupled to an increase of qP was also observed until the 27 g m-3 Al. The Al-induced decline in cytochrome (cyt) b contents per Chl unit was parallel for the b559LP and cyt b559HP forms, but on a leaf area basis more or less opposite trend in both these cyt forms was observed. Increased Al concentrations also decreased carotene and zeaxanthin contents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006833816920
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  • 2
    Electronic Resource
    Electronic Resource
    Aluminium modulation of the photosynthetic carbon reduction cycle in Zea mays (1997)
    Springer
    Photosynthetica 34 (1997), S. 393-400 
    Details
    ISSN: 1573-9058
    Keywords: Al, fructose-1,6-bisphosphatase ; intercellular CO2 concentration ; maize ; NADP-malate dehydrogenase ; net photosynthetic rate, photosystems 1 and 2 ; saccharides ; stomatal conductance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two-weeks-old maize (Zea mays L. cv. XL-72.3) plants were submitted to Al concentrations of 0-81 g m-3 for 20 d, after which the A1 concentration-dependent effects on CO2 uptake by the mesophyll tissue and subsequent CO2 assimilation in the photosynthetic carbon reduction cycle of bundle sheath cells were investigated. The net photosynthetic rate (PN) and stomatal conductance (gs) increased continuously up to 27 g m-3 Al, whereas the intercellular CO2 concentration showed minimum values with the 27 g m-3 Al treatment. Moreover, the starch and saccharide concentrations, and fructose-1,6-bisphosphatase did not change significantly with increasing Al concentrations. The photosynthetic electron transport rates along with photosystems 2 and 1 started falling from 9 g m-3 Al onwards, while thylakoid acyl lipid composition did not show a clear pattern. With the Al concentration at 81 g m-3, NADP-malate dehydrogenase activity decreased to minimum values, whereas the opposite occurred with those of pyruvate dikinase, NADP-malic enzyme, and phosphoenolpyruvate carboxylase. Thus in vivo Al concentrations modulate the photosynthetic reduction cycle, possibly by interacting with the carbon flow rate exported to the cytosol. Although the inhibition of NADP-malate dehydrogenase activity might limit pyruvate dikinase, NADP-malic enzyme, and phosphoenolpyruvate carboxylase activities, in vivo the balance between phosphoenolpyruvate production and its carboxylation remains unaffected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006812118254
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of Drought on Photosynthetic Performance and Water Relations of Four Vigna Genotypes (1999)
    Springer
    Photosynthetica 36 (1999), S. 79-87 
    Details
    ISSN: 1573-9058
    Keywords: drought ; gas exchanges ; water relations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of drought on plant water relations and photosynthesis of Vigna glabrescens (Vg) and Vigna unguiculata (cvs. 1183, EPACE-1 and Lagoa), which differ in their drought resistance, was compared. With the increase of drought severity, Vg showed a more gradual stomatal closure and maintained significantly higher levels of stomatal conductance (gs) and photosynthetic activity (PN) than the other genotypes even when minimum relative water content (RWC) values were observed. Furthermore, Vg was the only genotype able to accumulate significant amounts of proline already under moderate water deficit, what could explain the lower osmotic potential (ψs) values observed in these plants. The three V. unguiculata cultivars presented a similar stomatal control under increasing water deficit. A mesophyllic impairment of photosynthetic capacity (Pmax) was detected for cv. 1183 from the beginning of drought onset (85-75 % RWC) while in the Vg plants the values remained unaffected along the whole drought period, indicating that PN decrease observed in this genotype is mainly a consequence of stomatal closure. Such Pmax maintenance suggests the existence of a high mesophyllic ability to cope with increasing tissue dehydration in Vg.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007018804086
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Partial decline of Arachis hypogaea L. photosynthesis triggered by drought stress (1997)
    Springer
    Photosynthetica 33 (1997), S. 81-90 
    Details
    ISSN: 1573-9058
    Keywords: carbon assimilation ; chlorophyll fluorescence ; cultivars ; electron transport ; peanut ; photosynthetic capacity ; photosystems 1 and 2 ; ribulose 1,5-bisphosphate carboxylase/oxygenase water stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photosynthetic capacity (PC) of three peanut cultivars (Arachis hypogaea L. cvs. 57-422, 73-30, and GC 8-35) decreased during drought stress (decline in relative water content from ca. 95 to 70 %) and recovered two days after rewatering. Mild water stress was not limiting for the total ribulose-1,5-bisphosphate carboxylase/oxygenase activity, since this enzyme activity increased under drought. Photosystem (PS) 2 and PS1 (the latter only in cv. GC 8-35) electron transport activities decreased under drought. The ratio of the variable to maximal chlorophyll fluorescence (Fv/Fm) decreased mainly in the cv. GC 8-35. All cultivars showed decreases in photochemical quenching (qP) and quantum yield of PS2 electron transport (Φe). Increase of basal fluorescence (F0) was observed in the cvs. 73-30 and GC 8-35, while the cv 57-422 showed a decrease. After rewatering a sharp increase was observed in the majority of the parameters. Thus under the present stress conditions, the cv GC 8-35 was the most affected for all the parameters under study. The cv. 57-422 showed a higher degree of tolerance being gradually affected in photosynthetic capacity (PC) in contrast to the two other cvs. which showed a sharp decrease in PC at the beginning of the drought cycle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022179322721
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Aluminium Toxicity Modulates Nitrate to Ammonia Reduction (1998)
    Springer
    Photosynthetica 35 (1998), S. 213-222 
    Details
    ISSN: 1573-9058
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two weeks-old maize (Zea mays cv. XL-72.3) plants were exposed to Al concentrations 0 (Al0), 9 (Al9), 27 (Al27) or 81 (Al81) g m-3 for 20 d in a growth medium with low ionic strength. Thereafter, the Al concentration-dependent interactions on root nitrate uptake, and its subsequent reduction to ammonia in the leaves were investigated. Al concentrations in the roots sharply increased with increasing Al concentrations while root elongation correspondingly decreased. Root fresh and dry masses, acidification capacity, and nitrate and nitrogen contents decreased from Al27 onwards, whereas leaf nitrogen, nitrate, nitrite, and ammonia concentrations decreased starting with Al9. Electrolytic conductance increased by 60 % in root tissues from Al0 to Al81 but it did not increase significantly in the leaves. In Al9, Al27, and Al81 plants a decrease in shoot fresh and dry masses was observed. Al concentrations between 0 and 27 g m-3 increased net photosynthetic rate, stomatal conductance, and the quantum yield of photosynthetic electron transport, whereas the intercellular CO2 concentration was minimum in Al27 plants. In the leaves, nitrate reductase (E.C. 1.6.6.1) activity increased until Al27, and nitrite reductase (E.C. 1.6.6.4) activity until Al81. Hence there may be an Al mediated extracellular and intracellular regulation of root net nitrate uptake. Nitrate accumulation in the roots affects the translocation rates and, therefore, the nitrate concentration in the leaves. The in vivo reducing power generated by the photosynthetic electron flow does not limit nitrate to ammonia reduction, and the increase of maximum nitrate and nitrite reductase activities parallels the decreasing nitrate, nitrite, and ammonia concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006906722469
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    Paper (German National Licenses)
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