Plant diversity continued Chapter 30 Plant diversity continued

Bryophytes (mosses, liverworts, hornwarts) Hornworts

Homosporous vs. Heterosporous alternation of generations Eggs The sporophyte’s sporangia Bisexual gemetophyte Single type of spore Sperm HETEROSPOROUS Megaspore Female Gametophyte Eggs The sporophyte’s sporangia Male Gametophyte Microspore Sperm

Bryophytes are non-vascular plants The Gametophyte is the dominant generation.

The bryophyte sporophyte The sporophyte has specialized structures that produce spores called Sporangia.

Pteridophytes: The first seedless vascular plants (Ferns) Have lignified xylem tissue so they can grow taller than mosses. The dominant generation is the Sporophyte  In Pteridophytes, sporophyte is branched and independent of the gametophyte. Gametophyte

The Seeded Plants: Gymnosperms and Angiosperms Continued reduction of the gametophyte The advent of the seed The evolution of pollen

QUESTION: Why is the gametophyte reduced in size and is more associated with the mature, dominant sporophyte?

Gymosperms and Angiosperms continued to reduce the gametophyte generation Delicate gametophytes (structures that produce the delicate gametes) are reduced and develop within the sporophyte. WHY??  Protection from environmental stresses. In seeded (gymnosperms and angiosperm) plants the gametophyte is microscopic.

The evolution of the seeds Important to disperse your young Recall that spores (n) develop into gametophytes which produce gametes  Spores are single celled and have a thick coat  can resist harsh environmental conditions Seeds (2n)  multicellular and more complex than Spores (n) Seeds have an embryo and nourishment in the form of the female gametophyte or in angiosperms, called endosperm. All seeded plants are heterosporous

From Ovule to Seed

Pollen: Eliminated the liquid water for fertilization. Megasporangium is to ovule (Megasporangium produces the megaspore inside the ovule  female gametophyte  egg) AS Microsporangium is to pollen (Microsporangium produces the microspore  pollen male gametophyte Sperm)

Advantage of Pollen Very resistant to environmental conditions Can travel far (along the wind) By bringing airborne pollen together with ovules anchored in the archegonium of the female gametophyte  This adaptation lead to great success on land

THE GYMNOSPERMS The production of naked seeds usually in cones

Life Cycle of the Pine is a great example of the reduction of the gametophyte in seeded plants.

Figure 30.9 The life cycle of a pine (Layer 1)

Figure 30.9 The life cycle of a pine (Layer 2)

Figure 30.9 The life cycle of a pine (Layer 3)

Angiosperms: Flowering plants Two main classes; Monocots and Dicots Refinements in vascular tissue : Xylem tissue has tracheids like gymnosperms. Angiosperms have additional Xylem cells called Vessel Elements. Use of an attractor to ensure less random and wind dependent pollination

Monocots vs. Dicots

Vessel elements in Angiosperm Xylem

Structure of a flower Female portions (includes Megaspores and female gametophyte and ovary) Male portions (includes Microspores and male gametophyte)

Example: SAFFRON the most expensive spice on the planet Comes from the stamens of the male crocus plant. The cost per gram of the best saffron is more than that of gold! GOLD = $13.50/gram

The Rhodora The Rhodora Ralph Waldo Emerson The Rhodora On being asked, whence is the flower. In May, when sea-winds pierced our solitudes, I found the fresh Rhodora in the woods, Spreading its leafless blooms in a damp nook, To please the desert and the sluggish brook. The purple petals fallen in the pool Made the black water with their beauty gay; Here might the red-bird come his plumes to cool, And court the flower that cheapens his array. Rhodora! if the sages ask thee why This charm is wasted on the earth and sky, Tell them, dear, that, if eyes were made for seeing, Then beauty is its own excuse for Being; Why thou wert there, O rival of the rose! I never thought to ask; I never knew; But in my simple ignorance suppose The self-same power that brought me there, brought you. The Rhodora On being asked, whence is the flower. In May, when sea-winds pierced our solitudes, I found the fresh Rhodora in the woods, Spreading its leafless blooms in a damp nook, To please the desert and the sluggish brook. The purple petals fallen in the pool Made the black water with their beauty gay; Here might the red-bird come his plumes to cool, And court the flower that cheapens his array. Rhodora! if the sages ask thee why This charm is wasted on the earth and sky, Tell them, dear, that, if eyes were made for seeing, Then beauty is its own excuse for Being; Why thou wert there, O rival of the rose! I never thought to ask; I never knew; But in my simple ignorance suppose The self-same power that brought me there, brought you.

Types of fruit produced by angiosperms Simple Fruits  Single ovary, one flower Aggregate Fruits  Many ovaries, one flower Multiple Fruits  Many ovaries, clustered flowers

Life cycle of an angiosperm

Note that the egg and the female gametophyte become fertilized. The fertilized egg develops into the embryo which then develops into the mature sporophyte plant. The fertilized gametophyte develops into the food (endosperm) for the developing embryo in the seed.

Why double fertilize both egg and female gametophyte? To ensure synchronous food source for a viable embryo.