Tag Archives: water

Help with floating fern

29 November 2012 – 3.01pm

I’ve recently learnt that the introduced Azolla pinnata (ferny azolla) has been found in the Wellington region. I’m interested in its distribution and would be grateful for help in looking for more. Azolla plants are fairly easy to spot: look for a red plant covering still bodies of water.

Azolla plants often become red in full sunlight, and they can become so abundant that they carpet ponds, drains, and other still bodies of water. This is Azolla rubra in a pond on Mana Island, Wellington. Photo Leon Perrie. © Te Papa.

Azolla are ferns, believe it or not! They are free floating, and while individual plants are only a few centimetres across, they can proliferate in good conditions to ‘carpet’ large areas of water surfaces.

There are two species in New Zealand: the native Azolla rubra (Pacific azolla, previously known as Azolla filiculoides); and the exotic Azolla pinnata, which is an introduction from the tropics.

Azolla pinnata has largely replaced the native Azolla rubra in the northern North Island. It is therefore a concern that A. pinnata was found near Waikanae in recent weeks, after being found near Whanganui a few years ago. It seems it is continuing to spread south.

The introduced Azolla pinnata has very regular branching. Plants can be red or green depending on whether they are in the open or shade, respectively. The green ovals are Lemna duckweed (a flowering plant). Photo Leon Perrie. © Leon Perrie.

The branching of the native Azolla rubra is irregular. Photo Leon Perrie. © Te Papa.

Can you help please?

I would like to better document the distribution of the two Azolla species in New Zealand, and particularly the spread of the introduced A. pinnata. The southern North Island is the primary interest, but anything that adds to what we already know would be useful (see the link to the map below).

Map of Te Papa’s collections of Azolla.

If you see Azolla (either species), you could post a comment or send me an email. If you have landowner permission, you could make a collection for possible addition to Te Papa’s specimens: post me 20-30 plants enclosed within a watertight plastic bag, with locality details, and your contact details. My address is: Leon Perrie, Te Papa, PO Box 467, Wellington 6011.

Thanks very much.

By Leon Perrie | Posted in Biodiversity, Ferns, Plants | Also tagged , , , , | Comments (1)

Folding up to save water

30 March 2010 – 2.43pm

Did you know that Hook Grasses can control water loss by folding up their leaves? 

Contrary to their common name,  Hook Grasses are not grasses but Sedges and they belong to the family Cyperaceae.  Sedges are commonly found in wet or poorly drained habitats. Hook Grasses, however, can be found in a much greater diversity of habitats.

In New Zealand, Hook Grasses can grow in costal scrub, forests, swamps, grasslands or herbfields in sub-alpine and alpine habitats.

 

Habitat of a native New Zealand hooked grass. Photo by C.A. Lehnebach (c) Museum of New Zealand Te Papa Tongarewa.

Habitat of a native New Zealand Hook Grass. Photo by C.A. Lehnebach (c) Museum of New Zealand Te Papa Tongarewa.

Although Hook Grasses have colonised drier habitats, water is still important for their survival and they use a very clever system, operated by so-called bulliform cells, to regulate water loss. Bulliform cells are large, bubble-shaped cells found in the upper surface of the leaves. In Hook Grasses these cells are found all along the midrib. 

Cross section of a leaf of a hooked grass under the microscope. Photo by C.A. Lehnebach (c) Museum of New Zealand Te Papa Tongarewa.

Cross section of a leaf of a Hook Grass under the microscope. Photo by C.A. Lehnebach (c) Museum of New Zealand Te Papa Tongarewa.

When water availability is low, these cells shrink causing the leaf blade to fold. Each side of the leaf blade, at either side of the midrib, moves towards each other like closing a book. By folding their leaves these sedges reduce the area exposed to sunlight and therefore water loss by evaporation. 

This mechanism allows water to be maintained inside the plant. Once water is available again, these cells enlarge and the leaf blade unfolds again.

By Carlos A. Lehnebach | Posted in Plants, Sedges | Also tagged , , , | Comments (4)
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