Plantae  

Flickr: What plant is that? - worldwide ( I )
Flickr: Plant Family Recognition - worldwide ( I )
Missouri Botanical Garden: Tropicos - worldwide with focus on tropics
GardenWeb Galleries - worldwide
GardenWeb "Name That Plant" Forum - worldwide ( I )
USDA Plants - North America
USDA NRCS PLANTS Identification Keys - North America
E-Flora - British Columbia, Canada
University of British Columbia Garden Forums - North America ( I )
US National Arboretum - North America
Flickr: Califlora - California, USA ( I )
www.missouriplants.com/ - Missouri, USA
Field Museum Tropical Plant Guides - Central America & South America
Flora Iberica - Iberian Peninsula, Balearic Islands
BBC Plant Finder - UK?
Flickr: Flora of the British Isles: A Photographic Guide - UK ( I )
Flickr: the De Flora van Nederland (Flora of the Netherlands) - Netherlands
Flora von Österreich (Flora of Austria) Wiki - Austria
Botanik im Bild - Austria
Flora of Zimbabwe - Zimbabwe
Flora of Mozambique - Mozambique
Identifying Australian Rainforest Plants,Trees and Fungi - Australia

Rod-like reinforcements provide strength: plants
 

Vascular bundles in plants provide mechanical strength, serving as rod-like reinforcements.

 
  "Figure 5: Part of a stem of a robust grass, in cross section. Here mechanical strength of the stem is provided by the vascular bundles set in a matrix of thinner-walled cells, rather like rod reinforcements. Each vascular bundle has an outer sheath of fibres, forming a strong tube in which the two wide vessels can conduct water, and the strand of thin-walled, narrow cells (phloem) can transport sugar solutions with little risk of damage. Just to the inner side of the outer ring of smaller vessels the several layers of narrow cells eventually become thick-walled and provide additional strength in the form of a cylinder to the whole stem." (Cutler 2005:101)
  Learn more about this functional adaptation.

Surviving low nutrient, low light conditions: peatland plants
 

Plants in peatlands survive low nutrients and low light thanks to their perennial life cycle, which ensures a large biomass above and below ground.

 
  "Virtually all true mire vascular plants are perennial. This is a most effective way to ensure a large biomass, both below and above ground. In a nutrient-poor environment, a relatively large root biomass is required to obtain enough resources, and this cannot easily be built up within one season. Also, the large above-ground biomass which may be necessary for light capture in wooded mires can be built only by perennials." (Rydin and Jeglum 2006:50)
  Learn more about this functional adaptation.

Antenna structure efficiently gathers light: vascular plants
 

Light harvesting antenna of plants allow for very quantum efficient capture by high pigment density and long excited-state lifetime design.

 
  "Light harvesting in photosynthetic organisms is largely an efficient  process. The first steps of the light phase of photosynthesis, capture  of light quanta and primary charge separation processes are particularly  well-tuned. In plants, these primary events that take place within the  photosystems possess remarkable quantum efficiency, reaching 80% and  100% in photosystems II and I respectively. This paper presents a view  on the organisation of a natural light harvesting machine—the antenna of  the photosystem II of higher plants. It explains the key principles of  biological antenna design and the strategies of adaptation to light  environment which have evolved over millions of years. This article  argues that the high efficiency of the light harvesting antenna and its   control are intimately interconnected owing to the molecular design of   the pigment–proteins it is built of, enabling high pigment density  combined with the long excited-state lifetime. The protein plays the  role of a programmed solvent, accommodating high quantities of  pigments, while ensuring their orientations and interaction yields are  optimised to efficiently transfer energy to the reaction centres,  simultaneously avoiding energy losses due to concentration quenching.  The minor group of pigments, the xanthophylls, play a central role in  the regulation of light harvesting, defining the antenna efficiency and   thus its abilities to simultaneously provide energy to photosystem II  and protect itself from excess light damage. Xanthophyll hydrophobicity  was found to be a key factor controlling chlorophyll efficiency by  modulating pigment–pigment and pigment–protein interactions.  Xanthophylls also endow the light harvesting antenna with the remarkable  ability to memorise photosystem II light exposure—a light counter principle. Indeed, this type of light harvesting regulation displays hysteretic  behaviour, typically observed during electromagnetic induction of  ferromagnetic materials, the polarization of ferroelectric materials and  the deformation of semi-elastic materials. The photosynthetic antenna   is thus a magnificent example of how nature utilises the principles of   physics to achieve its goal—extremely efficient, robust, autonomic and   yet flexible light harvesting." (Ruban et al. 2011:1643)

  Learn more about this functional adaptation.