Do Now: Lengthwise growth of a root tip into the soil results mainly from… Cone bearing plants are known as… Which of the following statements about bryophyta is correct? (1.) they have true roots and stems (2.) they can be small or grow large (3.) they lack vascular tissue (4.) the archegonium produces flagellated sperm (5.) the zygote grows into a haploid structure

Plant Diversity I: How Plants Colonized Land 2

More than 280,000 species of plants inhabit the earth today Although some are aquatic, most are terrestrial: deserts, grasslands, forests Land plants evolved from certain green algae called charophyceans 3

There are four main groups of land plants: bryophytes, pteridophytes, gymnosperms, and angiosperms Bryophytes: mosses; distinguished from algae by advances that allow for life on land 4

Pteridophytes: ferns; contain vascular tissue (transport water and food); “seedless plants” Gymnosperms: conifers; “naked seed” (seeds are not enclosed in a special chamber) Seed: consists of a plant embryo packaged with food and a protective coat 5

Angiosperms: flowering plants; “container seed”; most modern-day plants algal ancestors  bryophytes  vascular plants  the origin of seeds  the evolution of flowers 6

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Charophyceans are the green algae most closely related to land plants Plasma membranes contain rosette cellulose-synthesizing complexes - synthesize the cellulose of cell walls Same enzymes in peroxisomes that help minimize the loss of product due to photorespiration 8

- growth in length is from apical meristems Several terrestrial adaptations distinguish land plants from charophycean algae - growth in length is from apical meristems - multicellular, dependent embryos - alteration of generations: gametophyte and sporophyte 9

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Alternation of generation does not occur in the charophyceans Alternation of generation does not occur in the charophyceans. This suggests that alternation of generation arose independently in land plants.

1.) sporophyte -- multicellular diploid plant body producing spores 2.) spores -- haploid structures from sporophyte 3.) gametophyte -- multicellular haploid plant that develops from a spore -- produces the gametes 4.) gamete 5.) zygote -- produced by fusion of gametes 6.) The zygote develops into a mature sporophyte to start this cycle all over again. 13

There are other adaptations that are common in many land plants Adaptations for water conservation: - formation of a cuticle - stomata contain guard cells 14

cuticle of a stem 15

Adaptations for water transport: Except for bryophytes, land plants have true roots, stems, and leaves with vascular tissue - xylem: carry water and minerals up from root - phloem: distribute sugars and amino acids throughout the plant 16

Phloem Xylem 17

Land plants evolved from charophycean algae over 500 mya - chloroplasts: chlorophyll b and beta-carotene - homologous cell walls - peroxisomes 18

Charophycean zygote undergoes meiosis to produce haploid spores Alteration of generations in plants may have adapted by delayed meiosis Charophycean zygote undergoes meiosis to produce haploid spores Plant zygote undergoes mitosis to produce a multicellular sporophyte to produce haploid spores by meiosis 19

Adaptations to shallow water preadapted plants for living on land - natural selection would favor those that could withstand occasional drying 20

Bryophytes are represented by 3 phyla: Hepatophyta (liverwarts), Anthocerophyta (hornworts), and bryophyta (mosses) 21

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- sporophytes are typically smaller and present only part of the time The gametophyte is the dominant generation in the life cycle of bryophytes - sporophytes are typically smaller and present only part of the time - up to 50 million spores can be generated in one spore capsule 23

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Mosses are able to exist in very harsh climates - able to loose most of their body water without dying, then rehydrate later Bryophytes were the only plants on earth for 100 million years 27

Differ from bryophytes - contain phloem and xylem Modern vascular plants include ferns (pteridophytes), gymnosperms, and flowering plants (angiosperms) Differ from bryophytes - contain phloem and xylem - dominant sporophyte generation 28

Pteridophytes provide clues to the evolution of roots and leaves 2 phyla of seedless vascular plants: phylum Lycophyta and phylum Pterophyta (ferns) Pteridophytes provide clues to the evolution of roots and leaves 29

Most pteridophytes have true roots with lignified vascular tissue Lycophytes have small leaves with only a single unbranched vein; known as microphylls - modern leaves are known as megaphylls 30

Concept 29.4 31

A sporophyte-dominant life cycle evolved in seedless vascular plants Homosporous plants: produce one type of spore Heterosporus plants: produce megaspores (female) and microspores (male) 32

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