School of Sciences, Lautoka Campus BIO509 Botany Lecture 20:Pollen ecology of angiosperms Photo courtesy of Prof. Randy Thaman

Learning outcomes Know the similarities and difference between angiosperms and gymnosperms. Understand the major trends of specializations in flowering plants Know the reproductive structures and lifecycle of a flowering plant. Know the characteristics of flowers associated with specific types of pollinators.

Pollination Ecology

What is pollination? Pollination: The transfer of pollen from the male anther to the female stigma.

Why is pollination important? Allows plants directed mobility in seeking a mate. Cross-fertilization at high frequency. Sexual reproduction is advantageous to an organism only if it happens with someone other than itself.

How do plants get pollen from one plant to another? Bees Beetles Butterflies Moths Birds Flies Bats Wind Water

Reproductive floral organs: female Carpel or pistil – female reproductive organs; contains: Stigma – is where pollen sticks to Style – is the long tube that connects stigma to ovary Ovary – enlarged structure at the base of carpel/pistil where the ovules are located; it will become the fruit. Ovules – contains female gametophyte, becomes the seed carpel or pistil ovary

Reproductive floral organs: male Stamen – male floral organ, consists of: Anther – part of the stamen that produces pollen Filament – stalk-like structure that holds anther Pollen – immature male gametophyte

Non-reproductive floral organs Corolla – whorl of petals in a flower. Petals – whorl of flower organs that are often brightly colored to attract pollinators. (units of Corolla). Calyx – whorl of sepals in a flower. Sepals – whorl of leaf-like organs outside the corolla; help protect the unopened flower bud (units of calyx).

Function of flower To attract pollinators with colorful petals, scent, nectar and pollen.

Plant-pollinator relationships have evolved together. Flowers and insects have coevolved. Angiosperm evolution has contributed to insect diversity. In some cases relationship between pollinators and flowers have become specialized.

Animal/ insect-flowering plant interaction is a classic example of co-evolution Plants evolved elaborate methods to attract animal and insect pollinators. Pollinators evolved specialized body parts and behaviors that aid plant pollination. special structures on legs of a bee help to get more pollen. http://www.cyberbee.net/biology/ch3/thorax.html

Animal/ insect Pollination as Mutualism Usually viewed as mutualism (where both species benefit). Plant gets pollen transferred. Animals and insects get “rewards”.

Rewards Pollen is high in protein. Also has lipids, minerals, starch. Nectar - sugary fluid produced by nectar glands (nectaries) in flower. Some flowers may have amino acids too. (butterfly flowers). Rewards are renewable Floral nectaries are usually located at the base of the flower.

Lets look at some special modifications of flowers that came about during the course of their evolution in response to specific pollinators.

Bee pollinated flowers Bees are the most important group of flower pollinators. intelligent, lively insects. visual insects, have good eyesight (including UV light). good smellers (good sense of smell). active during the day. they live on the nectar and feed larvae, also eat the pollen.

Bee pollinated flowers Bees prefer blue and yellow, but rarely red (appears black). Some flowers have honey guides, sometimes visible only in UV light. Flowers have bee landing platforms. Flowers produce nectar and pollen to attract bees. Many are sweet and fragrant.

- sexual mimicry – pseudo-copulation Some evolutionary more advanced flowers particularly orchids have developed complex mechanisms that force bees to visit them. - complex passage ways. - sexual mimicry – pseudo-copulation A male wasp “mating” with an Ophrys flower (how embarrassing...) Ophrys an orchid species mimics female wasps

Beetle pollinated flowers Beetles are one of the common pollinators. Beetles are: Clumsy Have poor vision Active during the day (many flower-visiting ones). Derive nutrition from flower nectar, petals and fruits.

Beetle pollinated flowers Relatively large or grouped into large inflorescences. Light or dull colored . Have strong odor (fruity or spicy smell). Flowers often have inferior ovaries.

Moth and butterfly pollinated flowers Butterflies and moths have - Good vision - Good sense of smell - Long coiled tongue. - Must land on flower to visit it (can’t hover).

Moth and butterfly pollinated flowers Butterfly pollinated flowers are brightly colored, blue, yellow, and orange, and sometimes red. Yellow and white flowers appeal to night-flying moths.

Sweet fragrances. Landing platform present. Often have nectar at bottom of long floral tube or spur usually only accessible only to long sucking mouthparts of moths and butterflies.

Bird pollinated flowers Birds are regular visitors to flowers. have a good sense of color, they like yellow or red flowers. Do not have a good sense of smell Feed on fluid nectar in greater quantities than insects, usually have long beaks. Active during the day. Can hover (humming birds)

Bird pollinated flowers Flowers are usually red or orange. Odor less flowers. have nectar hidden by long floral tube no landing platform

Large and on tree trunk or in large inflorescences. Birds prefer copious amounts of nectar since energy needed. Pollen sticks to the feathers around their bill.

Fly pollinated flower Flies have good sense of smell, especially flesh flies. Attracted to rotting meat (lay eggs in meat, larvae are maggots).

Fly pollinated flowers Smell like rotting meat. Look like rotting meat (dark red, purple) Offer no reward: flies fooled by flower. Stapelia flower Rafflesia flower

Did you know? World’s largest known flower is pollinated by flies. Rafflesia arnoldii  from genus  Rafflesia is the largest individual flower on earth. Has a diameter of about 1m and can weigh about 11 kg. Has a strong odor of decaying flesh and is commonly known as the "corpse flower". It is an endemic plant that occurs only in the rainforest of Indonesia and Malaysia.

Bat pollinated flowers Bats are flying mammals. Flower visiting bats are usually found in tropical areas. Eyesight good but echolocate. Good sense of smell. Active during night (nocturnal). Can hover when visiting flower. Have long extensible tongues sometimes with brush like tip.

Bat pollinated flowers Flowers are open at night. Lots of pollen and nectar as rewards. White or light-colored. Large or in ball-like inflorescence. Fragrant (sweet).

Bat Pollinated Flowers May be pendant (hang from branches). Pendent flower

What are the benefits of animal/ insect mediated pollination?

Mutualism Exceptions Some flowering plants are wind pollinated. Some are water pollinated. Betula papyrifera – wind pollinated Vallisneria – water pollinated

Wind pollinated flowers Primary mode of pollination in grasses, sedges, etc. Flowers are small, grouped together. Flowers greenish (not colourful).

Usually large amounts of pollen is produced. Stamens often protruding and stigma sticky. Not a very efficient method (too chancy and wasteful)

Water pollinated flowers Submerged angiosperms. Pollen is transported underwater or floats. In some cases, pollen are thread like.

The shape and form of pollen is related to its method of pollination Insect-pollinated species have sticky of barbed pollen grains Wind-pollinated species is lightweight, small and smooth (corn pollen)

What would be the consequences if animal and insect pollinators went extinct?

Readings Chapter 23 Stern’s Introduction to Plant Biology Chapter 22 Biology of Plants.

Questions??