Copyright © 2009 Pearson Education, Inc. PLANT STRUCTURE AND FUNCTION

Evolution and types of plants  Since the earth was once covered in water, plants had to make three adaptations to survive on land  The ability to prevent water loss  The ability to reproduce in the absence of water  The ability to absorb and transport nutrients  Plants can be placed under two groups  Vascular- having true roots, leaves, and stems  Ex. ferns, conifers, flowering plants  Nonvascular- not having true roots, leaves, and stems  Ex. mosses, liverworts, hornworts

Vascular Plants can be divided into two groups Seedless Plants  Made up of ferns and plants closely associated with ferns Seed Plants  Two types of seed plants  Gymnosperms- which includes pine trees, produce seeds that are not encased in fruit  Angiosperms- aka flowering plants, produce seeds within a protective fruit

 Monocots –One cotyledon –Parallel leaf venation –Scattered vascular bundles –Flower parts in 3s or multiples of 3 –Fibrous roots The two main groups of angiosperms are the monocots and the dicots

 Dicots- aka eudicots –Two cotyledons –Branched leaf venation –Ring of vascular bundles –Flower parts in 4s or 5s (or multiples) –Taproot system The two main groups of angiosperms are the monocots and the eudicots

Copyright © 2009 Pearson Education, Inc. A typical plant body contains three basic organs: roots, stems, and leaves  Plants absorb water and minerals from soil through roots  Plants absorb the sun’s energy and carbon dioxide from the air through shoots (stems and leaves)  Plant roots depend on shoots for carbohydrates produced via photosynthesis  Plant shoots depend on roots for water and minerals

Copyright © 2009 Pearson Education, Inc.  Plant roots –Anchor plant –Absorb water and nutrients –Store food  Plant shoots –Stems, leaves, and reproductive structures –Stems provide support –Leaves carry out photosynthesis A typical plant body contains three basic organs: roots, stems, and leaves

Root hair Root hairs Terminal bud Flower Node Internode Epidermal cell Taproot Stem Axillary bud Petiole Blade Leaf Root system Shoot system

Copyright © 2009 Pearson Education, Inc. Many plants have modified roots, stems, and leaves  Modifications of plant parts are adaptations for various functions –Food or water storage –Asexual reproduction –Protection –Climbing –Photosynthesis

 Root modifications –Food storage –Examples include carrots & potatoes Many plants have modified roots, stems, and leaves

 Stem modifications –Runners (allow for asexual reproduction) Many plants have modified roots, stems, and leaves

 Leaf modifications –Climbing –tendril –Example: pea plants –Protection –Thorns or spines –Example: Cactus spine Many plants have modified roots, stems, and leaves

Plant cells and tissues are diverse in structure and function  Plants cells have three structures that distinguish them from animals cells –Chloroplasts used in photosynthesis –A large, fluid-filled vacuole –A cell wall composed of cellulose

Copyright © 2009 Pearson Education, Inc. PLANT GROWTH

Copyright © 2009 Pearson Education, Inc. Primary growth Plants are categorized based on how long they live –Annuals complete their life cycle in one year –Biennials complete their life cycle in two years –Perennials live for many years

Primary Growth and Secondary Growth  Primary growth is the vertical growth of a plant (shoot growing up and root growing down).  Secondary growth is an increase in diameter of roots and shoots (getting thicker).  This growth does not occur at all parts of the body like in animals. This is because not all cells in a plant divide.  Meristem – small, unspecialized cells that divide continually

Meristem  There are two types of meristem cells. 1.Apical meristem – located at the tips of roots and shoots  Responsible for primary growth 2.Lateral meristem – cells responsible for creating more xylem / phloem and bark  Responsible for secondary growth

Axillary buds Terminal bud Arrows = direction of growth Root tips Primary growth allows roots to push downward through the soil and shoots to grow upward

Secondary growth increases the girth of woody plants Year 1 Early Spring Year 1 Late Summer Year 2 Late Summer

Copyright © 2009 Pearson Education, Inc. Secondary growth increases the girth of woody plants  Vascular cambium produces xylem and phloem  Cork cambium produces the outer bark

Vascular Tissue (monocot – complex arrangement; dicot – ring)  Xylem- transports water  Phloem- transports food

Secondary growth increases the girth of woody plants  Wood annual rings show when new growth starts each year. (This is the xylem. Phloem is sloughed off each year).  Sapwood (transport)- functional, lighter-colored wood near the outside of the trunk  Heartwood (storage)- the darker wood at the center of the trunk