BANANA – a fruit with extra chromosomes wild banana Dwarf

BANANA – a fruit with extra chromosomes
Common name: Edible banana
Scientific Name: Musa acuminata (AAA Group) 'Dwarf Cavendish'
Banana plants are the largest flowering herbs on earth.
About 30 species of wild bananas grow in tropical Asia. Their flowers are
pollinated by bats and their sweet starchy fruit contain stony seeds.
Bananas have been cultivated for thousands of years. Cultivated edible
bananas produce fruit naturally without being pollinated and the fruit is sterile
– it does not contain seeds.
Most cultivated bananas are hybrids - they contain chromosomes from the
wild species Musa acuminata and Musa balbisiana. In fact the hybrids usually
contain an extra set of chromosomes – 33 in total – compared to the wild
bananas which have 22 chromosomes. Cultivated hybrid banana fruits are
larger than those of the wild species.
wild banana
2 4 6 ………… 22
Dwarf Cavendish banana
3
6
9 ………… 33
The Dwarf Cavendish (AAA Group) banana is susceptible to Panama disease
(the fungus Fusarium oxysporum). Breeders are trying to develop a banana
resistant to this disease before it devastates the banana industry.
PAPYRUS – used for making paper 5000 years ago
Common names: Paper reed, Papyrus sedge
Scientific Name: Cyperus papyrus
Papyrus sedge used to grow abundantly in the Nile delta and was used by the
ancient Egyptians to make paper, reed boats, sails, cloth and sandals.
The stems are triangular in cross-section and lack leaves. The inner pith of
these long stems, composed mainly of cellulose and lignin, is well suited to
textile-making. The pith can be cut into thin strips and laid side by side with
edges overlapping. Another layer of strips is laid on top at a right angle, then
the two layers are hammered together to make one sheet of paper. After
drying, the sheet is polished smooth.
In a dry climate papyrus is very stable. The Elephantine Papyri are a collection
of ancient Jewish manuscripts dating from the 5th century BC. They are legal
documents and letters written in Egyptian, Aramaic, Greek, Latin and Coptic
over a period of 1000 years. The Book of the Dead is an ancient Egyptian
funeral text, used from around 1550 BC to around 50 BC.
Birds use the flowering heads as nesting sites.
As with most sedges, pollination is by wind,
not insects, and the mature fruits are
distributed by water.
An ENORMOUS flower stem
Common names: Konjak, devil's tongue
Scientific Name: Amorphophallus rivieri
So named because the flowering stem looks like a large, deformed penis
(Amorpho = mis-shapen + phallus = penis), there are about 200 species found
in West Africa, Asia and the Pacific.
The flowering stem (inflorescence) has a dark red bract like a collar and a
spongy stem, which carries tiny female flowers near the base and male flowers
higher up. These flowers do not have petals.
As the inflorescence opens its temperature rises by several degrees giving off a
smell like rotting flesh. This attracts carrion flies, bringing pollen. The flies
become trapped in the ridges of the stem where they pollinate female flowers
while the male flowers are still closed. The next day, when the male flowers
open, the flies are showered with pollen before they escape to pollinate
another plant.
The plant has a swollen underground root, a
tuber, which is milled and used as flour in
Asia. The flour contains a high fibre gum called
glucomannan. Foods made from this in Japan,
such as konyaku and shirataki noodles, are
known as the "broom of the intestine".
CYCAD – a primitive seed plant
Common name: Sago cycad
Scientific Name: Cycas revoluta
Cycad fossils date back to 300 million years ago, which means that cycads were
part of the vegetation of the supercontinent Pangea. Cycads existed before
flowering plants evolved.
female
male
Pangea
Cycads were common during the Jurassic period, the era of the dinosaurs, as
the continents began to drift apart. Now there are about 300 species in 11
genera, found in the tropics and subtropics.
Cycads are either male or female. Their reproductive cone, at the top of the
stem, bears either pollen sacs or ovules. They are pollinated by insects,
especially weevils and beetles. Fertilised female cones can take anything from
4 to 18 months for the seeds to ripen.
The evergreen leaves and stem contain toxins which can paralyse or kill
foraging animals.
In addition to normal roots, cycads have specialized
organs called coralloid roots which grow upwards
towards the soil surface. These contain colonies of
cyanobacteria which provide nitrogen for the plant.
PASSION FLOWER – a natural mimic
Common name: Passion flower
Scientific Name: Passiflora boenderi
This rare passion flower, found in the rainforests of Costa Rica, was discovered
as a new species in 2003.
Heliconius butterflies almost always lay their eggs on passion flower plants.
When the larvae hatch as caterpillars, they feed on the leaves, which contain a
toxic cyanide compound. This would normally deter the caterpillars, but they
have evolved a cyanide defence, which allows them to eat the leaves without
harm. In fact the poison they maintain in their systems makes the caterpillars
(and the butterflies they become) taste unpalatable to predators.
Passiflora boenderi has evolved a second defence
mechanism against the butterflies. The leaves have a
pattern of yellow spots which resemble butterfly
eggs. This deters butterflies from egg laying – the
leaf looks as if another butterfly has already laid its
eggs there.
Better yet, these yellow spots are actually sugar
stores, called nectaries, which attract ants and other
predators that eat Heliconius larvae.
RUBBER TREE – the original Para rubber
Common name: Rubber tree
Scientific Name: Hevea brasiliensis
The Para rubber tree initially grew only in the Amazon rainforest of Brazil.
South American people were harvesting latex and making rubber from Hevea
brasiliensis long before it was known by Europeans.
The Aztec people used another rubber tree,
Castilla elastica, which grows in Central and
South America, to make balls for the ball game
ullamaliztli. Latex tapped from Castilla elastica
was converted into rubber by mixing it with the
juice of the morning glory vine.
The process of heating latex with sulphur, known
as vulcanisation, was discovered in the 19th
century. This lead to a “rubber boom” in Brazil and attempts were made to
plant rubber trees elsewhere. Today, most natural rubber is produced in
Southeast Asia.
The bark of the tree is cut early in the
morning, when the internal pressure of the
tree is highest. This releases latex from a
system of tubular vessels just beneath the
surface, which is collected in a cup. Trees
can be tapped for rubber once they are 5–
6 years old and they remain productive for
25 – 30 years.
Purified natural rubber is the chemical
polyisoprene. This can be produced
synthetically and now about half of all
rubber is chemically manufactured.
A POISONOUS climbing lily
Common name: flame lily, fire lily, gloriosa lily, superb lily, climbing lily
Scientific Name: Gloriosa superba
All parts of the Gloriosa lily contain the alkaloid toxin colchicine. CContact with
the stems and leaves can cause skin irritation. The tuberous roots have the
highest concentration; 3 grams of Gloriosa root can be fatal to an adult.
Colchicine has been used as a medicine for thousands of years. The autumn
crocus (Colchicum autumnale), another plant source of colchicine, was
described for treatment of rheumatism in the Ebers Papyrus, a 3500 year-old
Egyptian medical papyrus. Today, colchicine is prescribed for gout and other
inflammatory disorders.
Gloriosa lily is a climbing plant. Specialised
organs at the tips of the leaves (called
tendrils) curl around neighbouring plants
for support.
SPANISH MOSS in the hanging garden
Common name: Spanish moss, air plant
Scientific Name: Tillandsia usneoides
Despite its name, Spanish moss is not a moss, nor is it a lichen. Spanish moss
belongs to the Bromeliad family of flowering plants. More familiar members of
this family are the pineapple and the multi-coloured Brazilian bromeliad,
Neoregelia carolinae.
Spanish moss grows on trees, trailing its grey-silver
stems and leaves in the air. These are covered in tiny
scales that absorb water and nutrients directly from
the air.
Spanish moss and other bromeliads have a special
type of metabolism, known as Crassulacean acid
metabolism, which is typical of plants growing in arid
conditions. The leaf pores (stomata) open at night to
collect carbon dioxide, rather than during the day. The
carbon dioxide is stored overnight as an acid, malate,
and then used during the next day for photosynthesis.
The plants reproduce by seed when their tiny flowers
are fertilised, or by “cuttings”, when bits of the plant
are broken off by birds or the wind and transplanted
to a new location.
NEPENTHES – carnivorous pitcher plants
Common name: Monkey cup, pitcher plant
Scientific Name: Nepenthes alata x ampullaria
Nepenthes are tropical lianas – woody plants that climb on other plants –
found in Madagascar, the Seychelles, South East Asia, Australia and New
Caledonia. Most species are restricted to very small ranges, some are only
found on individual mountains.
They have shallow roots, from which
grows a long thin stem and leaves. The
midrib of each leaf extends as a tendril
that aids some species in climbing. The
tendril swells at the tip to form a cupshaped pitcher. Once this is filled with
rainwater and liquid produced by the
plant it becomes a killing chamber
where prey are drowned.
Nepenthes attract prey with their vivid
colours and the sweet scent of a sugary
nectar, produced by glands on the
pitcher lid. The rim of the pitcher is
coated in slippery wax that provides a
difficult foothold for spiders, insects and small reptiles trying to reach the
nectar. Once they fall into the trap, it is impossible to escape because the walls
of the pitcher are also coated in wax.
The struggles of the victim stimulate glands in the lower part of the cup to
produce a powerful digestive acid. Within hours the plant begins to absorb
nitrogen and phosphorous nutrients from the body of its prey.
Some Nepenthes species have a mutually beneficial relationship with tree
shrews who use it as a lavatory. The tree shew dung is an additional source of
valuable nitrogen for the plant.
WATER HYACINTH – a floating weed
Common name: Water hyacinth
Scientific Name: Eichhornia crassipes
This attractive, lilac-blue flowered aquatic plant, a popular ornamental species
for fish ponds, originally comes from the Amazon basin. One of the fastest
growing plants known, water hyacinth populations can double in two weeks.
The leaf stalk (petiole)
of water hyacinth is
inflated with spongy airfilled tissue which keeps
the plant afloat.
Water hyacinth is now known as one of the “world’s worst aquatic weeds.” It
has become a problematic invasive species in North America, Africa, Asia,
Australia and New Zealand. Parts of Lake Victoria (East Africa) are choked with
water hyacinth, preventing boat access and fisheries have been disrupted
because of the lower oxygen content of the water.
Herbicides used to control of the weed cause additional problems of water
pollution. Recently a planthopper insect, Megamelus scutellaris, from
Argentina was released in the USA as a way of controlling this weed.
Planthopper nymphs feed voraciously on the sap of water hyacinth and adults
can jump easily from one plant to another.
The ARUM family - tiny flowers
Common name: Flamingo flower
Scientific Name: Anthurium andraeanum
Flamingo flowers are found in Central and
South America. Similar in appearance to
Amorphophallus, both belong to the Arum
family. Their bright red bract surrounds a
long flower stem, the spadix, which carries
tiny female flowers near the base and male
flowers higher up.
All Anthurium species have an organ called a
geniculum, at the top of the leaf stalk. This
angular structure (genu = knee) permits the
leaf blade to change its orientation to collect
light.
Duckweeds, also in the Arum family, are the smallest flowering plants on earth.
These very simple plants, commonly found in
ponds, lack an obvious stem or leaves. They
consist of a small plate-like structure that floats
on the water surface.
Duckweeds usually multiply by budding off
daughter plants from an adult plant.
Occasionally they produce three tiny flower
parts that enable sexual reproduction. Two
male flower organs, the stamens, contain
pollen and one female flower organ, a pistil,
contains the egg cells. A single fruit the size of
a grain of table salt is produced after
fertilisation.
SPIDER LILY
Common name: Spider lily
Scientific Name: Hymenocallis acutifolia, Hymenocallis littoralis
The spider lily is a native of Central America. The flower has a beautiful scent
and pure white colour. Long trailing tepals surround a delicate membrane
called the staminal cup, an embellishment of the male reproductive organs.
Orange pollen-filled anthers can be seen at the tip of each stamen. At the
centre of the flower is the female reproductive organ, the gynoecium.
Some species of Hymenocallis are pollinated by moths and butterflies, while
others produce seed in the absence of pollination, a process called apomixis.