Monocots

Skyrail Nature Diary: November 2013


This month we will be looking at Monocots which are a common type of flowering plant. Well known examples include palms, pandans, lilies, irises, orchids, grasses and sedges. Despite their appearances, none of these are real trees. Why? Because no monocots have thickness growth on the stems, only tip growth on the top of the plant. Monocots are considered more modern than the dicots due to mounting evidence pointing to trees being more primitive than herbs. Grazing by giant dinosaurs is considered a possible reason why some plants developed into herbs. Herbs have little or no wood in their stems and grow very fast in many cases as well as producing countless offspring. Big trees take longer to colonise newly opened up areas giving herbs a decisive edge until the trees finally mature.

So what is a monocot? Well, monocots have a simple set of characteristics that set them apart from other flowering plants. First of all they have no tap roots, only clusters of adventitious roots. This allows them to spread out looking for minerals rapidly when conditions are favourable. The leaves have a simplified venation (leaf plumbing) with only straight lines on the leaf surface. The vascular system in the trunks is spread throughout, instead of in an outer ring like in the dicots. The flowers have petals in sets of threes rather than fours, fives or sevens. The most successful group of monocots by far are the grasses due to their tolerance to fire. The roots are only rarely singed and quickly regrow new leaves.

The pandans are a large family of four genera with about 900 species of trees, shrubs and root climbers found in the Old World tropical and subtropical regions, from West Africa through the Pacific. Stems have aerial prop roots to provide support and display sympodial branching. The stems bear prominent leaf scars. Pandans are palm like trees and shrubs with separate sexes. Often called palms, but these plants are not closely related to palm trees. The leaves are very long and narrow, sheathing, simple, undivided, with parallel veins. The leaf margins and adaxial midribs are typically very prickly. Both male and female flowers lack petals and sepals. The flowers are tiny and are borne on structures with sometimes brightly coloured bracts. The two most common species in Barron Gorge are the Scrub Breadfruit and the Climbing Pandan/

Weevil Lily, also known as Ground Orchid, is an unusual monocot that is neither a lily nor an orchid. Weevil Lily is a palm like shrub that never develops much of a stem. The leaves are long, fibrous and flat like young palm fronds. The yellow flowers are borne on the short stem under the large fronds and turn into hairy edible fruits. These plants have become very popular ornamentals over the last few years. The fibres of this plant have been used to make nets in the past. Weevil Lilys prefer shady spots, is easy to propagate and can easily fill up a garden when conditions are ideal.

Schelhammera is a beautiful relative of the lilies that is quite common in Barron Falls. The plant itself is an unexpected tiny ground herb with straight lily like leaves in a small ring. The flowers are white with six petals, each with a tiny dot in the middle. These plants appear to prefer moderately dry rocky areas similar to the conditions found at Barron Falls station. They have certainly never been observed at Red Peak station.

Orchids are one of the most common of the monocots in the rainforest even though the palms are easily the most obvious. Orchids usually have thick leathery leaves and fibrous stems. Orchids display three main lifestyles in the wild; ground, epiphyte and parasite. Ground Orchids are the least common in the rainforest, growing as a normal low light adapted herb with adventitious. The Christmas Orchid is the best known species in Barron Gorge, found almost exclusively at Red Peak. The flowers are white and have petal lips descending in three floors. Epiphytes are the standard kind of Orchid in the rainforest. Epiphytic Orchids have symbiotic fungi in their roots that collect minerals from the air, rain and bark of the host tree. They also have pseudobulbs, which were occasionally eaten by the Djabugandjii. The leaves are succulent to conserve water and they tend to breathe only at night. This means that CO2 has to be stored overnight as malic acid to avoid some of the gas dissolving in the cells’ water and lowering the pH to as little as three, which is toxic to most plants. Next morning this is turned back to CO2. Cacti do exactly the same thing in the desert. The King Orchid is the most common Orchid at Red Peak. There are no parasitic Orchids in Barron Gorge. These plants are parasites on a fungus of all things and have no chlorophyll whatsoever!

 

By Tore Linde