<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Niinemets, Uelo</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Photosynthesis and resource distribution through plant canopies</style></title><secondary-title><style face="normal" font="default" size="100%">PLANT CELL AND ENVIRONMENT</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">acclimation kinetics</style></keyword><keyword><style  face="normal" font="default" size="100%">age effects</style></keyword><keyword><style  face="normal" font="default" size="100%">foliage aggregation</style></keyword><keyword><style  face="normal" font="default" size="100%">leaf longevity</style></keyword><keyword><style  face="normal" font="default" size="100%">leaf structure</style></keyword><keyword><style  face="normal" font="default" size="100%">light acclimation</style></keyword><keyword><style  face="normal" font="default" size="100%">nitrogen content</style></keyword><keyword><style  face="normal" font="default" size="100%">support costs</style></keyword><keyword><style  face="normal" font="default" size="100%">tocopherol content</style></keyword><keyword><style  face="normal" font="default" size="100%">xanthophyll cycle</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2007</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2007///</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">30</style></volume><pages><style face="normal" font="default" size="100%">1052 - 1071</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Plant canopies are characterized by dramatic gradients of light between canopy top and bottom, and interactions between light, temperature and water vapour deficits. This review summarizes current knowledge of potentials and limitations of acclimation of foliage photosynthetic capacity (A(max)) and light-harvesting efficiency to complex environmental gradients within the canopies. Acclimation of A(max) to high light availability involves accumulation of rate-limiting photosynthetic proteins per unit leaf area as the result of increases in leaf thickness in broad-leaved species and volume: total area ratio and mesophyll thickness in species with complex geometry of leaf cross-section. Enhancement of light-harvesting efficiency in low light occurs through increased chlorophyll production per unit dry mass, greater leaf area per unit dry mass investment in leaves and shoot architectural modifications that improve leaf exposure and reduce within-shoot shading. All these acclimation responses vary among species, resulting in species-specific use efficiencies of low and high light. In fast-growing canopies and in evergreen species, where foliage developed and acclimated to a certain light environment becomes shaded by newly developing foliage, leaf senescence, age-dependent changes in cell wall characteristics and limited foliage re-acclimation capacity can constrain adjustment of older leaves to modified light availabilities. The review further demonstrates that leaves in different canopy positions respond differently to dynamic fluctuations in light availability and to multiple environmental stresses. Foliage acclimated to high irradiance respond more plastically to rapid changes in leaf light environment, and is more resistant to co-occurring heat and water stress. However, in higher light, co-occurring stresses can more strongly curb the efficiency of foliage photosynthetic machinery through reductions in internal diffusion conductance to CO2. This review demonstrates strong foliage potential for acclimation to within-canopy environmental gradients, but also highlights complex constraints on acclimation and foliage functioning resulting from light x foliage age interactions, multiple environmental stresses, dynamic light fluctuations and species-specific leaf and shoot structural constraints.</style></abstract><issue><style face="normal" font="default" size="100%">9</style></issue><notes><style face="normal" font="default" size="100%">The following values have no corresponding Zotero field:&lt;br/&gt;pub-location: 9600 GARSINGTON RD, OXFORD OX4 2DQ, OXON, ENGLAND&lt;br/&gt;publisher: BLACKWELL PUBLISHING</style></notes></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Escudero, a</style></author><author><style face="normal" font="default" size="100%">Arco, J. M.</style></author><author><style face="normal" font="default" size="100%">Sanz, I. C.</style></author><author><style face="normal" font="default" size="100%">Ayala, J.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Effects of leaf longevity and retranslocation efficiency on the retention time of nutrients in the leaf biomass of different woody species</style></title><secondary-title><style face="normal" font="default" size="100%">Oecologia</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">leaf longevity</style></keyword><keyword><style  face="normal" font="default" size="100%">nitrogen</style></keyword><keyword><style  face="normal" font="default" size="100%">Nutrient use efficiency</style></keyword><keyword><style  face="normal" font="default" size="100%">phosphorus</style></keyword><keyword><style  face="normal" font="default" size="100%">retranslocation</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1992</style></year><pub-dates><date><style  face="normal" font="default" size="100%">1992///</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.springerlink.com/index/10.1007/BF00317812</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">90</style></volume><pages><style face="normal" font="default" size="100%">80 - 87</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">A study was made of the retention times of N and P in the leaf biomass and their relationship with the retranslocation percentages and the leaf longevities in some woody species in Central Spain. The retention times of both nutrients were strongly related to the nu- trient status of each species. These results suggest that a prolonged retention time is a way of increasing nutrient use efficiency in conditions of low nutrient availability. Plants can increase the retention time of nutrients in their leaf biomass by means of an increase in leaf longevity and/or by means of an increase in retranslocation effi- ciency. However, the effect of the retranslocation effi- ciency on retention times was almost negligible compared with the effect of leaf longevity. This suggests that an increase in leaf longevity is probably the best adaptation for increasing efficiency in the use of nutrients.</style></abstract><issue><style face="normal" font="default" size="100%">1</style></issue></record></records></xml>