❀Queensland Orchids ✿


Queensland



There are roughly 26,000 to 30,000 species in the Orchidaceae family known globally. The state of Queensland in Australia is very important in providing the natural habitats for many species of orchids, especially the epiphytes, which contribute to a sizable portion of the overall biodiversity in (sub)tropical forests whose resident orchids evolve myriad ways to adapt to life in the canopy. In fact, Queensland is the only state in Australia whose floral emblem is an orchid. According to Australian Orchid Genera – an information and identification system:

Orchidaceae comprises about 9% of the Australian flora. Of the approximate 1700 indigenous species, about 1300 have been named and the rest await formal botanical recognition. The Australian orchid flora is mainly dominated by terrestrial species (86%) with the remainder (14%) adopting an epiphytic habit. Many terrestrial species are prominent flowering elements of the understorey in a range of habitats in the mesic parts of Australia, whereas the majority of epiphytes occur in tropical Queensland.

These epiphytes have the following characteristics and adaptations to ensure their survival in their respective niches:

Description

Epiphytes are plants which grow above the ground, that grow on top of other plants. They are not planted in the soil and are not parasitic (i.e. they do not feed on other plants, however some types still damage their host in various ways). By growing on other plants, the epiphytes can reach to the light better or where they can avoid struggling for light. Many mosses and lichens are epiphytes, as are approximately 10 per cent of all seed plants and ferns. Epiphytes are common in some groups of plants, such as ferns, mosses, Strangler figs, lichens, and algae. Over half of the 20,000 species of orchids are epiphytes.

Habitat

Most epiphytic seed plants and ferns are found in tropical and subtropical rainforests because they need high humidity to survive. The areas which most epiphytes grow are the montane rainforests. Epiphytic orchids are found on many positions of the host tree, depending on species requirements and size, some large species will grow in a fork, whereas some small species scramble through thin branches, other species will climb up the trunk etc. etc. The trees provide many habitats with different conditions of temperature, contact and light. In temperate places, epiphytes are most common in moist forests, such as the rainforests in Queensland.

Adaptation

Epiphytes are not adapted to droughts in the same way are other flora, because they don’t have access to the ground, but they still have some mechanisms to help them survive. Some become completely dormant for months at a time; many epiphytes show CAM (crassulacean acid metabolism), which involves taking in CO2 at night, and photo-fixing it during the day with closed stomata to reduce water loss by transpiration. They also contain absorptive plants that are capable at quickly taking up water when it is available and preventing drought when water is scarcer. CAM can be impeded by higher night-time temperatures, dehydrated tissues, and high saturation deficits in the surrounding air, which lower the “stomata conductance” of the epiphytes, reducing the CO2 uptake, which in turn reduces growth and reproduction and even induces carbon loss. Higher temperatures, strain on evaporation, and contact to light cause CAM-idling, which is the epiphyte closing its stomata when it becomes stressed, that brings down the range of habitats a species can inhabit. Epiphyte species work biomasses are much more sensitive to different relative moisture levels than other plants.

The Orchidaceae has more CAM species than any other family of plants. The paper Carbon Dioxide Concentrating Mechanisms and the Evolution of CAM in Vascular Epiphytes by H Griffiths (1989) has the following estimates of the relative abundance of CAM species in four plant families:

Family

Species

Epiphytic Species

CAM Species

Orchidaceae
30,000 20,000 ~60%
Cactaceae
1,800 120 100%
Bromeliaceae
2,500 1,144 ~50%
Crassulaceae
1,000 5 100%

Carlos Cruz from Glendale, CA in the USA in Xeric World Forums distilled from the reference book Crassulacean Acid Metabolism in Australian Vascular Epiphytes and Some Related Species by K Winter (‎1983) that

there are relatively few terrestrial succulents in Australia. However, approximately two thirds of the epiphytic/lithophytic orchids studied were CAM plants. Orchids with thicker leaves generally had a greater degree of CAM…as did those from more exposed habitats. Heat plays an important role so lower elevation orchids tend to be more CAM than those at higher elevations.

Basically, even though an epiphytic orchid might live in a rain forest, its micro-habitat on the tree can possibly be considered xeric…depending on where on the tree it’s growing. Orchids on the outer branches tend to be more exposed to sun and wind so they’ll dry out faster than orchids in crooks or low down on the trunk.


Commonly designated regions of Queensland

Commonly Designated Regions of Queensland

The most famous Dendrobium is none other than the Cooktown Orchid:

Cooktown_Orchid

Cooktown Orchid (Dendrobium bigibbum, Dendrobium phalaenopsis or Vappodes phalaenopsis) growing on a Frangipani tree. Illustrated by Vera Scarth-Johnson (Photo credit: Wikipedia)

Dendrobium bigibbum var. superbum ‘Samantha Louise’

Floral Emblem of Queensland: Dendrobium bigibbum var. superbum ‘Samantha Louise’ ACC/QOS 1999

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10 thoughts on “❀Queensland Orchids ✿

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