Transcript The Temple of Flora

The Temple of Flora
Exploring the Biology of Plants 2
What is a plant?
According to the Oxford English Dictionary a
Plant is “A member of the lower of the two
series of organized living beings i.e. of the
vegetable kingdom; a vegetable; generally
distinguished from an animal by the absence
of locomotion and of special organs of
sensation and digestion, and by the power of
feeding wholly upon inorganic substances”.
Spermatophyta (Seed Plants)
• Seed plants are divided into two groups:
• Gymnosperms
• Angiosperms
• Angiosperms are also divided into two groups:
• Dicotyledons
• Monocotyledons
Gymnosperms
• ‘Flowers’ are cones, with separate male and
female cones (or, in some instances, plants).
• Water-transporting veins composed of
tracheids not vessels (more about this next
week).
• Well-known plants include cycads, spruces,
pines, junipers, cypresses, maidenhair tree.
Cycas circinalis
Picea abies
Pinus sylvestris
Gingko biloba (and Adiantum
capillus-veneris)
Angiosperms
• Flowering plants
• Dicotyledons have two leaves in each seed –
these constitute the bulk of the many tens of
thousands of species.
• Monocotyledons have only one leaf in each
seed – such groups as grasses, orchids, bulbs
(eg lily family, daffodil family), palms.
Classification
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Kingdom PLANTAE
Division Spermatophyta
Class Magnoliopsida
Order Ranunculales
Family Ranunculaceae
Genus Ranunculus
Species Ranunuculus acris
Classification
• The level (above genus and species) at which
botanists work seems to depend on the group
on which they are working.
• Flowering Plant botanists most commonly
work at the Family level.
• Algal botanists (phycologists) tend to work at
order, rather than family (or even, on a
broader scale, at Class level).
Rhododendron griersonianum
Rosa ‘Red Chateau’
Pelargonium peltatum
Disa uniflora
Haemanthus multiflorus
Crocosmia crocosmiiflora
Meconopsis cambrica
Rudbeckia
Calendula officinalis ‘Neon’
Ranunculus acris
Paeonia lutea ludlowii
Narcissus
Dendrobium densiflorum
Euphorbia cyparissias
Alchemilla mollis
Acer pseudoplatanus
Primula bhutanica
Lactuca perennis
Cichorium intybus
Myosotis arvensis
Delphinium elatum
Saintpaulia
Viola canina
Echinacea purpurea
Iris spuria ‘Lucky Devil’
Ornithogalum umbellatum
Anemone japonica
Campanula latifolia
Geranium phaeum ‘Samabor’
Some thoughts on names
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Fuchsia magellanica
Rhododendron forrestii
Campanula latifolia
Fucus vesiculosus
Meconopsis betonicifolia
Nepenthes alata
Epilobium montanum
Ammophila arenaria
Lithothamnium glaciale
Primula bhutanica
What are flowers for?
• ‘Flowers are created for the protection of the seed; they
spread over it and cover it. Some of them protect it either
against damage by wind, so mostly in fruit trees, or against
damage by water in watery plants, such as the bugloss.’[1]
• [1] Barhebraeus Butyrum VI, 3.2.4. (Nicolaus Damascenus –
De Plantis – Five Translations edited and introduced by
Drossaart Lulofs and Poortman. Amsterdam: North Holland
Publishing Company. (1989: 100)).
Who IS this man?
• Nicolaus of Damascus was born in Damascus,
c. 64 B.C., the son of wealthy parents probably
of Macedonian origin and received an
expensive liberal education. He became such a
distinguished scholar that he came to the
attention of Herod the Great, King of Judaea,
and spent his life in the service of Herod and
of his son Archelaus. It is not known what
happened to him after the latter’s death.
Why are flowers coloured?
• ‘Colours then and shapes of plants are developed by the
vegetative soul which underlies each of the mixed causes
without being sentient, so that they become fair and comely –
comparable to the natural power in the liver, the kidneys and
in other parts of animals, which attracts the suitable, forces
out the residue, makes the food similar to what feeds itself,
and performs other amazing and marvellous actions, though
it is not sentient.’[1]
• [1] Barhebraeus Butyrum VI, 4.2.1. (Nicolaus Damascenus –
De Plantis – Five Translations edited and introduced by
Drossaart Lulofs and Poortman. Amsterdam: North Holland
Publishing Company. (1989: 108)).
Three separate processes
• Pollination
• Fertilisation
• Seed Dispersal
• Students frequently (one might almost say
invariably) confuse these – particularly the
first and the last.
Reproduction in plants
• ‘If a reader calls a body male that by nature has a capacity for
moving a matter to receive a form similar to its own, and
female a body that has a passive capacity for receiving a form
in the above mentioned way, then plants have male and
female, and it is possible that a single plant is male and female
at the same time: female because the said matter is
generated in it, and male because the said moving capacity
originates in it.’[1]
• [1] Barhebraeus Butyrum VI, 1.3.1. (Nicolaus Damascenus –
De Plantis – Five Translations edited and introduced by
Drossaart Lulofs and Poortman. Amsterdam: North Holland
Publishing Company. (1989: 74)).
Pollination
• Movement of pollen from where it is
produced (the anther) to the stigma (female
receptive part of the flower). Period (as they
would say on the other side of the Atlantic).
• Plants may be self-pollinated (in which case
pollen lands on a flower of the same plant (or
same flower) or cross-pollinated (where two
separate individuals are involved).
Cross Pollination
• Ensures genetic variability.
• In many species there are mechanisms to
ensure that only cross pollination can take
place.
Heterostyly in Primula
i.e. Pin- and Thrum- Flowers
Heterostyly in Primula
i.e. Pin- and Thrum- Flowers
Male/Female ripen at different
times, as in Arum maculatum
Pollination
• A whole host of vectors are used in the
different species to transport pollen – wind,
water, insects (quite often specific groups or
species), slugs, birds, small mammals (bats,
tree-shrews, for example) to give just a few
examples.
• Plants have evolved in parallel with their
pollinator, and floral morphology is very
dependent on this.
Abiotic pollination
These do not attract animal pollinators.
• Wind pollination (anemophily)
• Flowers may be small and inconspicuous, as well as green and not showy.
They produce enormous numbers of relatively small pollen grains (hence
wind-pollinated plants may be allergens, but seldom are animal-pollinated
plants allergenic). Their stigmas may be large and feathery to catch the
pollen grains. Insects may visit them to collect pollen; in some cases, these
are ineffective pollinators and exert little natural selection on the flowers,
but there are also examples of ambophilous flowers which are both wind
and insect pollinated. Anemophilous, or wind pollinated flowers, are
usually small and inconspicuous, and do not possess a scent or produce
nectar. The anthers may produce a large number of pollen grains, while
the stamens are generally long and protrude out of flower.
Anemophilous flowers
Wind Pollination
• ‘When over the heart of a palm tree something from the
flower of a male is sprinkled, it ripens the fruit and prevents
its falling off. The males in all trees are more dense and
branching, harder and less fat; their fruits are small and do
not ripen; with the females, however, it is the other way
round. Many times, when the wind is strong, it carries the
power of the male to the female.’[1]
• [1] Barhebraeus Candelabrum II, 3.3.2. (Nicolaus Damascenus
– De Plantis – Five Translations edited and introduced by
Drossaart Lulofs and Poortman. Amsterdam: North Holland
Publishing Company. (1989: 62)).
Coconut Palm
Abiotic pollination
These do not attract animal pollinators.
• Water pollination (hydrophily)
• Water-pollinated plants are aquatic and pollen is released into
the water. Water currents therefore act as a pollen vector in a
similar way to wind currents. Their flowers tend to be small
and inconspicuous with lots of pollen grains and large,
feathery stigmas to catch the pollen. However, this is
relatively uncommon (only 2% of pollination is Hydrophily)
and most aquatic plants are insect-pollinated, with flowers
that emerge into the air.
Biotic pollination syndromes
• A whole host of different animal groups
pollinate flowers.
• Although there are different terms for each
group of insects, the general term for insectpollination is Entomophily.
Bee pollination (melittophily)
• Bee-pollinated flowers can be very variable in their size, shape and
colouration. They can be open and bowl-shaped (radially symmetrical) or
more complex and non-radially symmetric ("zygomorphic") such as many
peas, foxgloves, etc.
• Some bee flowers tend to be yellow or blue, often with ultraviolet nectar
guides and scent. Nectar, pollen, or both are offered as rewards in varying
amounts. The sugar in the nectar tends to be sucrose-dominated.
• There are diverse types of bees, however. Honeybees, bumblebees, orchid
bees, etc. are large groups that are quite distinctive in size, tongue length
and behaviour (some solitary, some colonial). Thus generalization about
bees is difficult. Some plants can only be pollinated by bees because their
anthers release pollen internally, and it must be shaken out by buzz
pollination (also known as "sonication"). Bees are the only animals that
perform this behaviour. Bumblebees sonicate, but honeybees do not.
• Bee pollination from mobile beehives is of great economic value for
orchards such as apple or almond
Actinomorphic and Zygomorphic
Flowers
Nectar Guides
Nectar Guides
Nectar Guides 3
Ophrys apifera
Butterfly pollination (psychophily)
• Butterfly-pollinated flowers tend to be large
and showy, pink or lavender in colour,
frequently have a landing area, and are usually
scented. Since butterflies do not digest pollen
(with one exception), more nectar is offered
than pollen. The flowers have simple nectar
guides with the nectaries usually hidden in
narrow tubes or spurs, reached by the long
tongue of the butterflies.
Platanthera bifolia
Moth pollination (phalaenophily)
• Among the more important moth pollinators are the hawk
moths (Sphingidae). Their behaviour is similar to
hummingbirds: they hover in front of flowers with rapid
wingbeats. Most are nocturnal or crepuscular. So mothpollinated flowers tend to be white, night-opening, large and
showy with tubular corollas and a strong, sweet scent
produced in the evening, night or early morning. A lot of
nectar is produced to fuel the high metabolic rates needed to
power their flight.
• Other moths (Noctuids, Geometrids, Pyralids, for example) fly
slowly and settle on the flower. They do not require as much
nectar as the fast-flying hawk moths, and the flowers tend to
be small (though they may be aggregated in heads).
Night-scented stock
Fly pollination (myophily and
sapromyophily)
• Flies tend to be important pollinators in high-altitude and high-latitude
systems, where they are numerous and other insect groups may be
lacking. There are two main types of fly pollination: myophily and
sapromyophily.
• Myophily includes flies that feed on nectar and pollen as adults particularly bee flies (Bombyliidae), hoverflies (Syrphidae), and others and these regularly visit flowers. In contrast, male fruit flies (Tephritidae)
are enticed by specific floral attractants emitted by some wild orchids
which do not produce nectar. Chemicals emitted by the orchid act as the
fly's sex pheromone precursor or booster. Myophilous plants tend not to
emit a strong scent, are typically purple, violet, blue, and white, and have
open dishes or tubes.
• Sapromyophiles, on the other hand, normally visit dead animals or dung.
They are attracted to flowers which mimic the odour of such objects. The
plant provides them with no reward and they leave quickly unless it has
traps to slow them down. Such plants are far less common than
myophilous ones
Beetle pollination (cantharophily)
• Beetle-pollinated flowers are usually large, greenish or offwhite in colour and heavily scented. Scents may be spicy,
fruity, or similar to decaying organic material. Most beetlepollinated flowers are flattened or dish shaped, with pollen
easily accessible, although they may include traps to keep the
beetle longer. The plant's ovaries are usually well protected
from the biting mouthparts of their pollinators. Beetles may
be particularly important in some parts of the world such as
semi-arid areas of southern Africa and southern California and
the montane grasslands of Kwa-Zulu Natal in South Africa.
Magnolia soulangeana
Bird pollination (ornithophily)
• Although hummingbirds are the most familiar nectar-feeding
birds (as seen on TV), there are analogous species around the
world: sunbirds, honeyeaters, flowerpeckers, honeycreepers,
bananaquits, flowerpiercers, lories and lorikeets.
Hummingbirds are the oldest group, with the greatest degree
of specialization on nectar. Flowers attractive to
hummingbirds that can hover in front of the flower tend to be
large red or orange tubes with a lot of dilute nectar, secreted
during the day. Since birds do not have a strong response to
scent, they tend to be odourless. Perching birds need a
substantial landing platform, so sunbirds, honeyeaters, and
the like are less associated with tubular flowers.
Rhododendron thomsonii
Bat pollination (chiropterophily)
• Bat-pollinated flowers tend to be large and showy, white or
light coloured, open at night and have strong odours. They are
often large and bell-shaped. Bats drink the nectar, and these
plants typically offer nectar for extended periods of time.
Sight, smell, and echo-location are used to initially find the
flowers, and excellent spatial memory is used to visit them
repeatedly. In fact, bats can identify nectar-producing flowers
using echolocation. In the New World, bat pollinated flowers
often have sulphur-scented compounds, but this does not
carry to other parts of the world. Bat-pollinated plants have
bigger pollen than their relatives.
Cobaea scandens
Ranunculaceae
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Includes:
Ranunculus
Trollius
Anemone
Hepatica
Aconitum
Delphinium
Thalictrum
Ranunculus repens
Trollius europaeus
Anemone blanda
Hepatica triloba
Aconitum vulparia
Delphinium
Thalictrum minus
Primulaceae
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Includes:
Primula
Androsace
Dionysia
Cyclamen
Dodecatheon
Primula griffithii
Androsace pyrenaica
Dionysia aretioides
Cyclamen creticum
Dodecatheon alpinum