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Ecology of Proteaceae in South-West Tasmania

Further information: Proteaceae

Proteaceae is a family name that is not native to Australia. However, it has been believed that the genus Protea from which the family name is derived from was originated from central and southern Africa. In Australia, there are about 1600 species from 80 genera. In Tasmania, there are about 28 species from 12 genera. This Southern Hemisphere family consists of high diversity in Australia.

Bellendena montana

Proteaceae is a large capricious family of trees and shrubs which consists of small prostrate shrubs, under shrubs and large timber tress which sometimes have spectacular flowers and due to their large inflorescences, Proteaceae are very attractive to a large variety of insects and birds such as sugarbirds, sunbirds and honeyeaters where these birds obtain nectars from the Proteaceae plants. Some Proteaceae produce berries which attracts further bird species. It has been known that some Protea spp. along with Telopea spp. and Banksias pp. are normally grown as ornamental plants in Australia.

Description

Leaves

The leaves of Proteaceae can be alternate, opposite or in whorls, simple or compound. They are often leathery with hairs which helps in reducing transpiration.

• 
  Orites acicularis
• 
  Cenarrhenes nitida
• 
  Telopea truncata

Flower

Proteaceae plants are often dioecious. The flowers are complex, frequently in the shape of a cone or spike or they can be in dense heads. Occasionally, a large number of flowers are produced but often only a few fruit development is observed. The flowers can be seen as either axillary or terminal, solitary or in raceme or spikes which are frequently reduced into umbels or heads that are normally surrounded by an involucres of bracts, bisexual or occasionally unisexual. The perianth is seen as either regular or irregular with a single whorl of four segments which are petaloid valvate. The bud consists of claws that are joined together to form a cylindrical tube with the blades.

The flower consists of 4 stamens. Opposite the perianth-stamens, free in Bellendena, but usually with filaments adnate to the perianth and sometimes with anthers sessile at the bases of the blades. Proteaceae also comprises of nectar scales that alternate with the stamens or they are either reduced in number or variously joined. The ovary is observed to be either superior, sessile or stipulate.

• 
  Agastachys odorata
• 
  Banksia marginata
• 
  Bellendena montana

Fruit

The fruit of Proteaceae plants are an indehiscent nut or drupe, or a dehiscent coriaceous or woody follicle.

• 
  Cenarrhenes nitida
• 
  Orites revoluta
• 
  Persoonia gunnii

Distribution

Proteaceae are known as the diverse group of plants where they can be found in variety range of environments. They can be found typically on infertile sandy soils and lateritic gravels and in Western Australia, they grow frequently in deep sand, sand over clay or limestone, and lateritic soil types where in such conditions, there were 14 species per 100 square-meters plot recorded by Lamont (1985). It has been observed that limestone and granite substrates do not aid the growth of many species of this family. It is also believed that some species can be found in seasonally wet swamps. Such soil types are known not to promote tall tree growth for this family and the vegetation generally differs from low heath to tall shrub land.

Orites revoluta

Proteoid Roots

Many Proteaceae have adapted to low nutrient soils and very dry conditions as a result of having proteoid roots which are strange clumps of short roots. It is found in most of the genera in this family, however not in Persoonia. Many of the Proteaceae produce proteoid roots which are dense clusters of white roots that grow from the sides of the normal roots that are close to the surface, providing a much greater area for the absorption of nutrients. The formation of this type of root is known to be aided by soil bacteria where the substances that the bacteria produces starts the development of the root.

Proteoid roots are heaps of lateral roots and hairs that form a radial absorptive surface. They are produced during the seasonal growth at the layer where there is leaf litter and shrivel at the end of the growth season. Proteaceae plants develop these roots in order to be able to adapt to poor, phosphorus-deficient soils and release carboxylates that gather together phosphorus to gain access to limited water and nutrients. The main characteristic of proteoid roots is that increases battle for nutrients against its own root clusters. Proteaceae are known not to form any symbioses with arbuscular mycorrhizal fungi because of these specialized proteoid roots.

Further information: Proteoid Root

Pollination

Proteaceae plants are usually pollinated by birds, small marsupials and insects where they make their flowers attractive for pollen to be collected and dispersed to other flowers. The nectar produced by many Australian species of Banksia, Hakea and Grevillea is either sucked from the flowers or soaked in water to produce a sweet nectar drink. Most genera of the proteaceae family consists of a modified style-end behind the stigma that is sometimes associated with a brush of papillae or bristle-like hairs and when the style breaks free, mass amount of pollen from the flower gets carried upon the pollen-presenter in mass amount. Through the transfer of the pollen by insect or bird to the sigma of another flower, cross-pollination is able to take place. The genus Persoonia demonstrates a unspecialised condition where pollination happens through the transfer of pollen between anther and stigma with no separate intermediate pollen-presenting organ.

Fire

Fire is known to aid in increasing the nutrients in the soil so that the seedlings have a fertile environment in to germinate. Many species are adapted to fire for survival and regeneration through their habitat. It is believed that the chemical in the smoke is the reason to stimulate the growth of species.

To ensure the survival of the species, the family Proteaceae evolved in several different methods. One way would be by the production of lignotubers bearing many dormant shoot buds. Lignotubers are swollen, woody structures that develop at ground level, or just below the ground. The dormant shoot buds are stimulated to grow into new shoots once the above ground parts of the plant gets ruined by fire. Such method is seen in the Banksia species where they employ this method to deal with fire. This method is also found in a few Hakea species where they grow many branches that crop up from the lignotuber and develop a rounded shrub.

Some taller species, such as Banksia and Hakea have very thick fire resistant bark which protects the dormant buds and allow the plant to reshoot after the fire. Some Persoonia species which have thick papery bark also have this ability to protect buds and allow regeneration. Most Hakea and many Banksia species have employed another method of withstanding fire or if the plant dies for other reasons is where they have woody fruits that mature and remain closed until a fire destroys the plant. Subsequently, the follicles open up and the seeds get released.