Amazonian water lily
With leaves reaching two metres across by mid-summer, this water lily does not just look strong enough to support the weight of a small child, it actually is! These spectacular pie-dish-like leaves have a super-structure of veins supporting the underneath surface like a tent frame with canvas stretched across it. This plant is closely related to Victoria amazonica, the original inspiration for Joseph Paxton's design of the Crystal Palace for the 1851 Great Exhibition. In the same year, Charles Daubeny, Professor of Botany in Oxford, had the glasshouse lily pond built at the Botanic Garden, after being invited by Paxton to see Victoria amazonica growing at Chatsworth, Derbyshire.
Leaf veins provide strength but are also armed with vicious spines that reach across the entire underside of the leaf surface. This protection against predators can also catch out the unwary trainee horticulturist!
In the watery territory of the Amazon, it is important that a leaf this size can shed water efficiently. One look at the leaf will reveal the 'pouring spout' on each side of the giant structure, presumably a natural over-flow to cope with torrential downpours. But a closer look will also reveal pores or channels through the leaf, scattered right across its surface, which may also allow water to drain through the leaf.
Although perennial in the Amazon, this plant is cultivated as an annual under glass in the UK and grown from seed each spring. The stunning white blooms, which open for the first time late one evening in mid-summer, are attractive to dynastid beetles that are its pollination partner. A warming mechanism raises the temperature of the flower's interior by over ten degrees, which this helps to release a beetle-enticing scent as the flower opens. This process is known as thermogenesis. Should a beetle arrive, it will find a starchy reward in the form of staminodes, or non-functional stamens (the pollen bearing male parts of the flower), upon which it feasts until the flower closes, trapping the beetle inside. During the course of the following day, the petals turn from white to pink and on the second evening the flower opens again, releasing the beetle, now covered in pollen. The beetle that has been released then flies off to seek out a new white flower ready to receive the pollen. However, the beetles are not native to Oxford, so the skilled horticultural team undertake the pollination themselves.
Prance GT, Arius JR 1975. A study of the floral biology of Victoria amazonica (Poepp.) Sowerby (Nymphaeaceae). Acta Amazonica 5, 109-139. 1975.
Seymour RS, Matthews PGD 2006. The role of thermogenesis in the pollination biology of the Amazon waterlily Victoria amazonica. Annals of Botany 98, 1129-1135.