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  • 1
    Electronic Resource
    Electronic Resource
    The xanthophyll cycle and acclimation of Pinus ponderosa and Malva neglecta to winter stress (1999)
    Springer
    Oecologia 118 (1999), S. 277-287 
    Details
    ISSN: 1432-1939
    Keywords: Key words Energy dissipation ; Low-temperature stress ; Malva neglecta ; Pinus ponderosa ; Xanthophyll cycle ; Zeaxanthin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Seasonal differences in the efficiency of open PSII units (F v/F m), leaf pigment composition and xanthophyll cycle conversion (Z+A)/(V+A+Z), leaf adenylate status, and photosynthetic capacity were investigated in Pinus ponderosa (Ponderosa pine) and Malva neglecta. In P. ponderosa, acclimation to winter involved a lower photosynthetic capacity, higher carotenoid to chlorophyll ratio, persistent reductions in F v/F m corresponding to persistent retention of Z+A, and no change in foliar ATP/ADP ratios. In contrast, M. neglecta characterized in winter exhibited higher rates of photosynthesis than in summer with no change in carotenoid to chlorophyll ratio, while small nocturnally persistent reductions in F v/F m were observed exclusively on colder winter nights when nocturnal retention of Z+A, and high ATP/ADP ratios were also present. Upon removal of winter-stressed leaves or needles from the field to room temperature, a portion of F v/F m relaxed within 15 min of warming and recovery was completed within 5 h in M. neglecta but required 100 h in P. ponderosa. In M. neglecta, the entire recovery of F v/F m correlated with decreases in the foliar ATP/ADP ratio, while in P. ponderosa this ratio remained unchanged. Possible ATP-dependent forms of sustained (Z+A)-dependent energy dissipation are discussed including a nocturnally retained pH gradient on cold winter nights. The slow recovery in pine involved not only retention of Z+A, but apparently also a persistent engagement of Z+A for energy dissipation via an unidentified mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050728
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Differences in the susceptibility to light stress in two lichens forming a phycosymbiodeme, one partner possessing and one lacking the xanthophyll cycle (1990)
    Springer
    Oecologia 84 (1990), S. 451-456 
    Details
    ISSN: 1432-1939
    Keywords: Carotenoids ; Chlorophyll fluorescence ; Lichens ; Light stress ; Phycosymbiodeme
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effect of high light levels on the two partners of a Pseudocyphellaria phycosymbiodeme (Pseudocyphellaria rufovirescens, with a green phycobiont, and P. murrayi with a blue-green phycobiont), which naturally occurs in deep shade, was examined and found to differ between the partners. Green algae can rapidly accumulate zeaxanthin, which we suggest is involved in photoprotection, through the xanthophyll cycle. Blue-green algae lack this cycle, and P. murrayi did not contain or form any zeaxanthin under our experimental conditions. Upon illumination, the thallus lobes with green algae exhibited strong nonphotochemical fluorescence quenching indicative of the radiationless dissipation of excess excitation energy, whereas thallus lobes with blue-green algae did not possess this capacity. The reduction state of photosystem II was higher by approximately 30% at each PFD beyond the light-limiting range in the blue-green algal partner compared with the green algal partner. Furthermore, a 2-h exposure to high light levels resulted in large reductions in the efficiency of photosynthetic energy conversion which were rapidly reversible in the lichen with green algae, but were long-lasting in the lichen with blue-green algae. Changes in fluorescence characteristics indicated that the cause of the depression in photosynthetic energy conversion was a reversible increase in radiationless dissipation in the green algal partner and “photoinhibitory damage” in the blue-green algal partner. These findings represent further evidence that zeaxanthin is involved in the photoprotective dissipation of excessive excitation energy in photosynthetic membranes. The difference in the capacity for rapid zeaxanthin formation between the two partners of the Pseudocyphellaria phycosymbiodeme may be important in the habitat selection of the two species when living separate from one another.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00328159
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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