Sex in the Garden…From the plant’s perspective

Linda R McMahan, Extension HorticultureOregon State University, Yamhill County Extension Service

Question: Define Sex

Courtesy of Google

• sexual activity, e.g., "they had XXX in the back seat“

• either of the two categories (male or female) into which most organisms are divided

• tell the sex (of young chickens)• the properties that distinguish organisms on the

basis of their reproductive roles

More

• an Australian television series that ran from 1992 to 1993 on the Nine Network

• an album by popular Greek artist Elli Kokkinou• a 1926 play, written by, and starring, Mae West• est le titre d'un livre écrit par Madonna sorti en

1992 accompagnant son neuvième album Erotica. ...

Our Version

• Plant reproduction by whatever means, with the “intention” to produce more plants!

Various Reproductive Strategies• Cross-pollination• Self-pollination• Vegetative

Reproduction

Some “Choices” for Plants• Generalist vs. Specialist• Many Small Seeds vs. Few Large Seeds• Vegetative vs. Sexual• Self-pollinated vs. Cross-fertilization• Various modes of pollination and relationship

to abundance of pollinators, presence of wind or water, flowering time, and so on.

Some Vegetative Strategies

Piggyback plant – Tolmiea menziesii - produces plant “offsets” on the leaves

Crocus – division of the bulbs in the ground

Dune strawberry, Fragaria chiloensis, reproducing by runners

Some others methods include underground stems such as rhizomes and tuberous stems, new plant production from underground roots or tuberous roots, bulbils, and various strategies of rooting by forms of layering, such as when plant stems bend over and a new plant grows when it touches the ground.

So now ask yourself “Why do plants have flowers?” And then, “Why do plants have pretty flowers?”

Purpose of Flowers?

“The accomplishment of fertilization is the primary function of the flower”

1907 A Textbook of Botany

Purpose of Flowers?

• Produce pollen and ovules that combine to create embryos that are dispersed in seeds

Flowers are “Pretty” To Attract Attention

• Potential pollinators• Potential dispersal in other ways, such as by

people in gardens and landscapes

Flowers are a Form of Advertising

• To create a “sale” to pollinators or dispersers, an offer must take place. This is usually in the form of pollen or nectar.

• Then the plant needs to advertise the availability of the offer – hence the flower, which sometimes produces an odor attractive to the potential pollinator.

• The flower must then accept “payment” from the pollinator as a method to transfer of pollen to a stigma. Bargain complete.

Characteristics of Wind Pollinated Flowers – The Pollinator is Not a Creature in this Case

• Produce large amounts of pollen, often in catkins.

• Pollen is small to travel on the wind.• Timing takes advantage of seasonal wind

patterns.• Flowers may or may not be attractive, but are

usually small with little color or odor.• Grasses and conifers are typically wind

pollinated.

Wind Pollination

Western Hazelnut – Corylus nutalli

Willow – Salix species Stinging nettle, Urtica dioica

Plantain, Plantago Ginkgo biloba

Silk tassel bush, Garrya elliptica

Most conifers, this juniper for examples, are wind pollinated

Characteristics of Bee Pollinated Flowers

• Typically but not always blue or yellow.

• Produce ample pollen and nectar.

• Ultraviolet coloration and nectar guides.

• Sweet smell and strong “center.”• Have places for bees to land

safely to collect the pollen and nectar.

Photo of Lithodora and bee by Carolyn Devine.

Some Bee flowers

sunflower

Flannel bush, Fremontodendron californicum

Blueblossom, Ceanothus thyrsiflorus, bees, also beetles

Stream violet, Viola glabella, note nectar guides

Bumblebee on snowberry, Symphoricarpos alba. Many members of the heath family, Ericaceae, are pollinated by bumblebees

More Examples of Ericaceae Flowers

Strawberry tree, Arbutus unedo

Ghost plant, Monotropa uniflora

Salal, Gaultheria shallon

More Bee Flowers

Camas, Camassia

Douglas aster

Cat’s ear, Calochotus sp.

More bee flowers

Fairy slipper orchid, Calypso bulbosa

Fritillaria

Bleeding heart

Characteristics of Butterfly Pollinated Flowers

• Brightly colored – can be red

• Little if any odor• Flower arrangements

create landing platforms and places to walk around

• Plants with these flowers are often also hosts for the larval stage of particular butterflies

More Butterfly Flowers

Yarrow, Achillea millefolium

Wild carrot

Garden phloxYellow twig dogwood

More Butterly Flowers

Coltsfoot

Sedum spathulifolium

Ocean spray, Holodiscus discolor—also attracts other insects

More Butterfly Flowers

Sedum ‘Autumn Joy’

Echinacea ‘White Swan’ – odor of coneflowers may have developed especially to attract butterflies

Characteristics of Fly Pollinated Flowers

• Sometimes purple, brown, brownish red, OR in other plants, white

• Unattractive odor, at least to humans, such as rotting meat or dung OR slightly sweet odor – Depends on intended fly

Asarum caudatum, wild ginger

More Fly Flowers

Skunk cabbage, Lysichiton americanum

Slinkpod, Scoliopis bigelovii

Rubus parviflorus, thimbleberry, a “generalist” – bees, flies, beetles

Characteristics of Bird Pollinated Flowers

• Typically red, pink, or orange

• No odor• Facilitate hovering

or gathering nectar and pollen from the air

Bottlebrush, pollinated by honeyeater birds in its native Australia

More bird flowers- hummingbirds

Red flowering currant, Ribes sanguineum

California fuschia, Epilobium canum (Zauchneria californica)

More Bird flowers

Western columbine, Aquilegia formosa, also attracts other insects including spinx moth

Cape fuschia, PhygeliusWestern bleeding heart, Dicentra formosa

Other pollinators

• Moths – typically white or flowers with “big” sweet scent that are open at night.

• Beetles – attracted to many flowers where pollen is readily available.

• Spiders occasionally. Darlingtonia californica may be pollinated by a tiny spider.

• A vast variety of flying insects like wasps and many forms of flies.

• In other parts of the world, pollinators may be bats or other mammals.

Opuntia sp., prickly pear cactus

Guess the Pollinator

Guess the Pollinator

Clarkia sp.

Guess the Pollinator

Cistus sp.

Camellia sasanqua

Guess the Pollinator

Darmera peltata, umbrella plant

Guess the Pollinator

Iris tenax, Oregon iris

Guess the Pollinator

Guess the Pollinator

Trillium ovatum

Guess the Pollinator

Redwood sorrel, Oxalis oregana

Guess the Pollinator

Oleander

Ribes roselii

Guess the Pollinator

Some Plants Change the rules•Apomixis - replacement of the normal sexual

reproduction by asexual production of seeds but without fertilization. •Agamospermy - production by plants of seeds in

which the embryo is derived (without fertilization) from diploid cells of the parent.•Parthenogenesis - a form of reproduction in which

the egg develops into a new individual without fertilization.•Cleistogamy - production of flowers which do not

open, and are self-fertilized in the bud

Apomixis

• Seeds are produced, but they are genetically identical to the parent.

• Advantage may be to pass on genetic material that is highly useful. Example: Dandelions are apomictic.

• Embryo arises from an unfertilized egg.

• Techniques are being developed to use this feature in plant breeding programs to ensure identical nature of crops.

Agamospermy

• Includes any mechanism that produces a genetically identical seed, including Apomixes.

• This and similar strategies may be advantageous in disturbed habitats.

• Very common in Aster family, and sometimes found in roses and other plants.

• You cannot tell by looking at the flower.

Parthenogenesis

• Mother cell does not divide, but itself contributes the genetic identify to the seed.

• Apomixes, when it does not involve pollen, is considered to be a plant form of parthenogenesis.

Cleistogamy

• Individual flowers are obligate self-pollinators.• They are often colorless, and do not open.• Happens in many violets, peanuts and ground

nuts, for example.

Sometimes, like in Viola glabella, some of the flowers are insect pollinated and others, often the later ones, are self-pollinated and look very different from the insect-pollinated flowers

Seed Dispersal—How Seeds Get Around Once they are Formed

Western hazelnut, Cornus nuttalliWestern lupine, Lupinus polyphyllusBigleaf maple, Acer

macrophyllum

Techniques of dispersal vary considerably and include wind and water, consumed and transported by birds or animals, or dropping close to the parent plant. Dispersal animals include mammals, humans, ants, insects, birds, and probably many more.

Slinkpod, Scoliopis bigelovii – pollinated by flies but dispersal helped by slugs which often eat the edges of the pods and expose the seeds.

Asian pear dispersal?

Prickly pear cactus fruits attach to passer-by for a free ride to a new location, or because of their attractive taste and appearance, may be eaten and transported in that way

English ivy, dispersed by birds, but the birds often get sick in the process

Thank You for Coming Today!

Any questions?Linda.mcmahan@oregonstate.edu

Time to Travel Home—Thank You