FLOWERS AND REPRODUCTIONDr. Gough

FIGURE 09.07A: (A) THE SEPALS OF THIS ROSE FORM A TIGHT COVERING OVER THE REST OF THE FLOWER AS IT DEVELOPS, PROTECTING THE INNER PARTS.

FLOWER STRUCTURE

Ovary Position Protect ovary from pollinators

Fig. 9-28

FLOWER STRUCTURE

Stem with leaf-like structures Terminology

• Pedicel and receptacle• Complete vs. incomplete flowers• Sepals (calyx)• Petals (corolla)• Stamens (androecium)• Carpels (gynoecium)

REPRODUCTION

Two forms of reproduction Produce identical genetic copies Produce genetically different offspring

What conditions favor which form? How does sexual reproduction produce

genetically different offspring? Some plants reproduce both ways

ASEXUAL REPRODUCTION

Many methods Fragmentation Rhizomes Stolons

FIGURE 09.02C: (C) ALL THE TREES IN THIS PHOTOGRAPH ARE A PART OF THE SAME PLANT, EACH A SPROUT FROM A SINGLE ROOT SYSTEM.

SEXUAL REPRODUCTION

In angiosperms, requires flowers Plant Life Cycle

Think of human/animal life cycle Meiosis Fertilization Mitosis

More complicated in plants “alternation of generations”

FIGURE 09.13: THIS IS THE TIP OF A GROWING POLLEN TUBE. IT WAS TREATED TO MAKE THE NUCLEI FLUORESCE SO THAT THEY CAN BE FOUND DESPITE BEING SO SMALL.

Courtesy of S. Muccifora

SEXUAL REPRODUCTION

Fertilization Following pollination Pollen tube growths through style to ovule

opening One sperm nucleus fertilizes egg Second sperm nucleus migrates into central cell

Only in angiosperms Becomes endosperm

“Double fertilization”

SEXUAL REPRODUCTION

Embryo and Seed Development Zygote continues dividing, growing Embryo

Radicle Hypocotyl Epicotyl

Monocotyledon Dicotyledon

FIGURE 09.19A: (A) THIS BEAN SEED HAS BEGUN GERMINATING; THE RADICLE HAS EXTENDED AND WILL DEVELOP INTO A TAPROOT.

FIGURE 09.19C: (C) THE SMALL LEAVES PRESENT ON THE EPICOTYL ARE EXPANDING DURING GERMINATION.

SEXUAL REPRODUCTION

Fruit Development Fruit is a mature ovary

FIGURE 09.21: IN APPLES, THE PETALS DIE AND FALL OFF AFTER POLLINATION.

FIGURE 09.22B: (B) COCONUTS IN STORES ARE USUALLY JUST THE ENDOCARP AND SEED.

FLOWER STRUCTURE AND CROSS-POLLINATION

Role of flowers in pollen and seed dispersal Cross-pollination

Vs. self-pollination Stamen and style maturation times Stigma and pollen incompatibility

FLOWER STRUCTURE AND CROSS-POLLINATION

Monoecious and dioecious species Imperfect vs. perfect flowers Monoecy Dioecy

Fig. 9-25

FLOWER STRUCTURE AND CROSS-POLLINATION

Animal-pollinated flowers Coevolution between plants and pollinators

Plant-insect pollination began about 120 mya What traits were favored? Some birds and bats pollinate too

Flower shape Actinomorphic/regular vs. zygomorphic

Usually positive relationship, but cheaters on both sides

FRUIT TYPES AND SEED DISPERSAL

More co-evolution! Seed (fruit) dispersal agents

Gravity Wind Water Animals

Often division of labor within fruit