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1999 (2)
1Author    Juliane Peters, M. Soledad, Jim Énez, Domingo MoralesRequires cookie*
 Title    Effect of Extreme Temperature on Quantum Yield of Fluorescence and Membrane Leakage of the Canarian Endemic Pine (Pinus canariensis)  
 Abstract    The effect of extreme temperature on the quantum yield of fluorescence and membrane leakage of Pinus canariensis growing in 5 stands at different altitudes and orientation in Tenerife (Canary Islands, Spain) was determined. Needles were collected from the field and transferred to the laboratory where they were kept in a closed chamber with water-saturated air overnight. Then they were exposed for 30 minutes in plastic bags in a water bath at temperature treatments with steps of 2K between 56 °C and -2 4 °C and the effect was deter­ mined immediately and 24 hours after the treatment by chlorophyll fluorescence and electro­ lyte leakage. Needles presented incipient damage at temperatures ranging from -5 to -1 0 °C depending on the altitude and orientation of the stand. The results were more evident when the mea­ surements were done 24 hours after the cold treatment and values were consistent with the electrolyte leakage results. Different resistance to high temperature depending on the alti­ tude and orientation was also found, varying the temperature for incipient damage from 42 to 44 °C detected with the fluorescence parameters but not with the leakage of electrolytes which was not found until 50 °C. The amplitude of thermal limits for photosynthetic effi­ ciency alteration in needles of P. canariensis was relatively narrow and similar to that of evergreen Canarian laurel forest trees. 
  Reference    Z. Naturforsch. 54c, 681—6 (1999); received December 10 1998/February 20 1999 
  Published    1999 
  Keywords    Pinus canariensis, Low Temperature, High Temperature, Altitudinal Gradient, Chlorophyll Fluorescence, Electrolyte Leakage 
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 TEI-XML for    default:Reihe_C/54/ZNC-1999-54c-0681.pdf 
 Identifier    ZNC-1999-54c-0681 
 Volume    54 
2Author    Domingo Morales3, Juliane Peters3, M. Soledad, Jim Énez3, Michael Tauszb, Astrid Wonischb, Dieter GrillbRequires cookie*
 Title    Gas Exchange of Irrigated and Non-Irrigated Pinus canariensis Seedlings Growing Outdoors in La Laguna, Canary Islands, Spain  
 Abstract    Chlorophyll fluorescence, gas exchange, water potential and relative water content were measured in the needles of five year old seedlings of Pinus canariensis in order to know their response to mild water stress. Two trial plots of ten plants per plot, of similar age and characteristics were irrigated daily until the experiment was undertaken, then one of the plots was left without watering while the other one was irrigated as before. After a week of treatment, the water potential at midday did not change in any of the irrigated or non-irrigated plants maintaining around -0 .4 MPa, and the relative water content changed from 93% in irrigated to 84% in non-irrigated seedlings. The stomatal conductance decreased 60% in non irrigated plants and as a result C 0 2 assimilation decreased by 50% and transpiration was reduced at a higher proportion (70%), indicating a good control against water loss, before any change in water status in the needles could be observed suggesting an isohydric water economy in this plant. 
  Reference    Z. Naturforsch. 54c, 693—6 (1999); received December 14 1998/March 21 1999 
  Published    1999 
  Keywords    Pinus canariensis, Mild Water Stress, Gas Exchange, Water Potential, Chlorophyll Fluorescence, Seedlings 
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 TEI-XML for    default:Reihe_C/54/ZNC-1999-54c-0693.pdf 
 Identifier    ZNC-1999-54c-0693 
 Volume    54