Plants with Seeds Chapter 22-4, 22-5

Seed plants There are two groups of seed plants: Gymnosperms ~ seeds are found on the surfaces of cones Angiosperms ~ seeds are within a layer of tissue that protects the seed

Adaptations of Seed Plants Unlike mosses and ferns, seed plants do not require water for fertilization of gametes ADAPTATIONS that allow seed plants to reproduce without water: 1) flowers or cones 2) transfer of sperm by pollination 3) protection of embryos in seeds

Adaptation #1: Cones and Flowers Cones and flowers are sporophyte structures in which the gametophytes of seed plants grow Cones = seed-bearing structures of gymnosperms Flowers = seed-bearing structures of angiosperms

Adaptation #2: Pollen In seed plants, the male gametophyte is contained in a pollen grain The pollen grain is carried to the female reproductive structure by wind, insects or small animals  pollination

Pollination Pollination can occur through biotic and abiotic means (wind, water, birds, insects, etc…) Morphological characteristics of flowers attract specific pollinators

Insects – the Great Pollinators Conventional spectrum What bees see 

Bats as Pollinators

Adaptation #3: Seeds Seed = embryo of the plant (diploid) Seed has a seed coat (protective covering) and food supply that gives nutrients to the embryo The embryo develops from the zygote after fertilization

Development of Seeds Function of seed structures: Endosperm Nutrition for embryo Endosperm Cotyledon(s) Cotyledons Nutrition for embryo *Endosperm = food storage tissue *Cotyledons = first leaf or pair of leaves produced by the embryo of a seed plant

Overall, what is the function of a seed? Protects young embryo Provides nutrition for the developing embryo Allows dispersal of the embryo over time & space

Seed to Seedling

Fruits Fruit. Mature ovary of the a flower that protects dormant seeds and aids their dispersal Seeds are the product of pollination Seeds are located within fruits There are many different types of fruits

Fruit Types

Seed Dispersal Seeds are highly adapted to dispersal Examples of morphological characteristics would be buoyancy in fruits (coconut) and “wings” (maple seeds)

While others are simply blowing in the wind….

Some seeds are dispersed as a result of being eaten and mingling with feces….

GYMNOSPERMS: Non-Flowering Seed Producers

Transition from Ferns to Land Plants Medullosa – the seed fern

Gymnosperms began to dominate landscapes as climates became drier at the end of the Paleozoic era 245 mya Gymnosperms appear in the fossil record much earlier than flowering plants, and they: Lack enclosed chambers in which seeds develop. Are grouped into four divisions: Cycadophyta, Ginkgophyta, Gnetophyta and Coniferophyta.

GYMNOSPERMS: Plants with seeds that are not enclosed within a fruit, derive their name from the Greek words gymnos (naked) and sperma (seed). In this plant group, the seeds are produced on the open surface of a scale. Unlike flowering plants, the gymnosperms do not form true flowers or fruits. There are four divisions of gymnosperms. Examples of gymnosperms include cycads, ginkgo, conifers and gnetops. Kingdom  Plantae - Plants Subkingdom  Tracheobionta -- Vascular plants Superdivision  Spermatophyta - Seed plants Division  Cycadophyta - Cycads Class  Cycadopsida Order  Cycadales Family  Cycadaceae Genus Cycas- cycads

Evolutionary advancements of Gymnosperms over the ferns and allies: Seeds Lack of dependence on water for fertilization (air-borne pollen) Progressively more dominant sporophyte Life Cycle In the gymnosperms and the flowering plants, the sporophyte generation is dominant with the gametophyte contained in and dependent on the sporophyte. Vascular System They do have a well-developed vascular system of xylem and phloem and have true roots, stems, and leaves. The vascular tissues are significantly more efficient and effective than the vascular systems of the seedless plants such as the ferns. Gymnosperms are usually woody plants. The xylem form the wood if a tree and the phloem tissues are part of the bark (along with cork). The formation of wood from secondary growth is the reason that some sporophytes can reach such large sizes.

The Cycad – a fernlike gymnosperm. Note the cone, or strobilus Cycadophyta Class Cycadopsida Order Cycadales Cycadaceae Cycas sp. The Gymnosperms The Cycad – a fernlike gymnosperm. Note the cone, or strobilus

Male cones of Pinus nigra Unlike the seedless vascular plants, conifers are more prevalent in cooler regions and in desert habitats. leaf curled to reduce water loss evolved cold hardiness Female cones of Pinus nigra

The Gymnosperms Gnetophyta With angiosperm-like broad leaves, but still retaining cones, the Gnetophytes are another very close link to the Angiosperms

Welwitschia mirabilis growing in the desert Ephedra viridis Female cones More Gnetophytes! All bear cones, with naked seeds, which is an adaptation over the ferns, that produced spores Welwitschia mirabilis growing in the desert

The link between gymnosperms and angiosperms (note the fleshy seed) Ginkgophyta Ginkgo biloba The link between gymnosperms and angiosperms (note the fleshy seed)

Angiosperms Phylum Anthophyta Replaced Gymnosperms as the dominant plant type during the Cretaceous Period 60 million years ago Produce flowers, fruits, and seeds

Flowers and Fruits Flowers: Fruits: Are unique reproductive organs of angiosperms Contain ovaries which surround and protect the seeds Thus “angiosperm” = “enclosed seed” Fruits: A wall of tissue surrounding the seed Used to attract animals  dispersal of seeds

Can you guess what this is? The largest seed is produced by the coco de mer, or "double coconut palm", Lodoicea maldivica. The entire fruit may weigh up to 23 kilograms (50 pounds) and usually contains a single seed

Flower Morphology

Stored food (Endosperm) Monocot vs. Dicot Seeds Corn Bean Seed coat Stored food (Endosperm) Embryo plant

Monocot Seeds Endosperm One cotyledon Monocot seeds have: seed coat coleoptile radicle

Dicot Seeds Dicot seeds have: No endosperm at maturity Two cotyledons Seed coat First leaves Early root Cotyledon

Organization of primary tissues in a young dicot stem (eg. Bean)

The primary tissues of a young monocot stem (eg. Corn)

Primary tissues of a young dicot root

Cross-section through a monocot root

General Angiosperm Life Cycle Germination of Seed Seed develops into mature sporophyte Flower grows on sporophyte Flowers have Stamens and Carpels Pollen produced in Anther (Stamen) Female gametophyte produced in Carpel (ovule) Pollination by various methods Double fertilization to produce endosperm and embryo development of seed

Plant life spans Annual: flower plants that complete a life cycle within one growing season Marigolds, pansies, wheat, cucumbers Biennials: life cycle complete in two years (flowers in second year) Parsley, celery, foxglove Perennials: flowering plants that live for more than two years (most have woody stems) Asparagus, grasses, palm trees, maple trees

Understanding Concepts, page 575 Questions 13-24