Mycorrhizal fungi and trees

With the recent dramatic arrival of winter, we start seeing fungi fruiting bodies appearing in the bush, in parks and gardens and on nature strips. The wonderful, sometimes beautiful, sometimes weird ‘mushrooms’ and ‘toadstools’ (unscientific terms often used interchangeably) are just the fruiting body of the fungal organism that is mostly hidden underground.

It’s important to understand that fungi are not plants: they do not reproduce from seed, rely on sunlight for their energy or photosynthesize like plants do.

Most trees, in fact probably 90% of all plant species, require an association with fungi in the soil. This symbiotic relationship is called mycorrhiza. Some plants benefit from a mycorrhiza from one species of fungi. Some trees gain benefit from hundreds of different fungi and some plants, some orchids for example, will ONLY grow if there is just one particular fungus in the vicinity. Some trees can grow without the help of any fungi but this pretty rare.

Fungi have a network of thin fibres called hyphae growing through the substrate (the organic matter on which they grow). This network of root-like threads is called the mycelium. 

Hyphae on the underside of a piece of bark

The mycelium of mycorrhizal fungi connects with the root systems of nearby trees and enables the exchange of various substances from the fungus to the tree (and vice versa). It has been recently discovered that the mycelium can even enable the exchange of substances between the trees themselves.

Austropaxillus sp - a mycorrhizal fungus often found in eucalypt woodland.

In this way, the fungus increases the absorptive area of the tree roots by as much as 700%.

The familiar Fly Agaric mushroom is an introduced mycorrhizal fungus associated with exotic trees such as oaks and pines. There is some evidence this fungus might be adapting to native trees.

The increased quantity of water and minerals picked up by the tree is converted to carbohydrates through photosynthesis using carbon dioxide from the air, sunlight and chlorophyl in the leaves. Some of these carbohydrates are then returned, via the hyphae, to the fungus enabling it to grow: both organisms benefit.

Mycorrhizal fungi are just one group of fungi. Saprotrophic fungi only grow on dead organic matter and they recycle nutrients back to the soil. Parasitic fungi only grow on living organisms, plants and animals, and they absorb nutrients directly from their host generally to the benefit of the fungus only. Parasitic fungi can be so detrimental to a host plant or animal that it can cause its complete demise. When this happens, some parasitic fungi can change to become saprotrophic and continue to survive on the dead host.

Left: Saprotrophic Mycena sp growing on dead wood.   Right: Parasitic Cordyceps sp growing on moth larvae  under the ground.

The humble fungus deserves proper respect for its role in the environment. Our trees certainly need them.

 

  

Plibersek replaces Ley as Minister for the Environment

Sussan Ley, the former Minister for the Environment in the Morrison Liberal Government has been replaced by Tanya Plibersek, the Minister for the Environment and Water in the Albanese Labor Government.

Sussan Ley, Wikipedia LINK: “Ley was born in Nigeria to English parents. She grew up in the UAE and England before moving to Australia as a teenager. Prior to entering politics, she worked as a commercial pilot, farmer and  public servant based in Albury, New South Wales. She was educated at Campbell High School, Dickson College, La Trobe University, the University of New South Wales and Charles Sturt University, and has master's degrees in taxation and accountancy.”

“Ley was elected to the House of Representatives at the 2001 election.”

“Also in March 2022, Ley approved a Coalition decision to scrap 176 out of 185 recovery plans designed to prevent the extinction of threatened species and habitats…”  (See article The Guardian LINK.)

Before becoming the Minister for the Environment in 2019, Ley held various roles in departments of Children’s Affairs, Agriculture, Fisheries and Forestry, Housing, Status of Women, Customs and Justice, Treasury, Employment, Early Childhood Learning, Regional Development, Health, Sport and Aged Care.

Tanya Plibersek, Wikipedia LINK: “Plibersek was born in Sydney to Slovenian immigrant parents and grew up in Sutherland Shire. She has degrees from the University of Technology Sydney and Macquarie University, and worked in the NSW Government's Domestic Violence Unit before entering parliament. Plibersek studied journalism at the University of Technology Sydney, graduating with a Bachelor of Arts in Communications. She then took a master’s in Public Policy and Politics at Macquarie University.”

“Plibersek was elected to the House of Representatives at the 1998 federal election, aged 28.”

Plibersek has had roles in portfolios covering Youth, Status of Women, Childcare, Human Services and Housing, Social Inclusion, Health and Education and Training.

Do either side of politics take the environment seriously?

 

Further reading:

Anthony Albanese ‘snubs’ Tanya Plibersek and hands education portfolio to Jason Clare News.co.au LINK.

New frontbench sworn in as deputy prime minister denies Tanya Plibersek was 'demoted' SBS News LINK

Five priorities for Tanya Plibersek, The Guardian LINK

  

Mistletoe

 What is Mistletoe?

Mistletoe is a semi-parasitic plant that grows on a host tree or shrub. The Mistletoe gets its water and nutrients from the host plant but produces its own energy through photosynthesis. Some Mistletoes are epi-parasitic and only grow on other Mistletoes.

Mistletoe infestation - Thornell's Reserve Longwarry North

Many Mistletoes very obviously use eucalypts as their host tree however many Mistletoes parasitize acacias, casuarinas, banksias, angophoras, melaleucas and numerous other native Australian trees and shrubs.

There are over 90 species of Mistletoe in Australia and nearly all of them are endemic. Mistletoes can be found on all continents except Antarctica and worldwide there are more than 1500 species.

What benefits do Mistletoes provide?

Mistletoes generally have long flowering and fruiting seasons. Because the roots are tapping into the host plant, Mistletoes can flower even through dry times, making them a dependable nectar and fruit source for fauna species when little else is available.

Mistletoes provide habitat for a wide range of fauna, especially birds, possums, bats, gliders and insects. These animals using Mistletoe as a resource are often themselves important pollinators in the broader ecosystem. More than 30 bird species are known to feed on Mistletoes and over 200 bird species have been recorded nesting in Mistletoe.

The caterpillars of many Australian butterflies use Mistletoes for a food plant.

Imperial White butterfly emerging from its pupal stage on a Mistletoe plant

How are Mistletoes dispersed?

Research has shown that Mistletoes rely principally on birds for pollination and seed dispersal. The Mistletoebird is one of the main seed dispersers of the plant.

Male Mistletoebird

Do Mistletoes kill trees?

Mistletoes do not kill healthy trees. Mistletoes rely on their host tree for their own survival. Some trees are capable of defending themselves from Mistletoe infestation by dropping infected limbs.

In general, trees with Mistletoe will die due to a range and combination of health factors – soil compaction or erosion, dieback, salinity, fire, drought, persistent inundation, etc.

Dead Mistletoe on a struggling host

Mistletoes are not resistant to fire in the way that many native trees are. Bushfire in fact can be seen as a cleansing agent in regard to Mistletoe infestation.