Plant Anatomy 2006-2007

Basic plant anatomy 1 root root tip root hairs

1 Roots Roots anchor plant in soil, absorb minerals & water, & store food fibrous roots (1) mat of thin roots that spread out monocots tap roots (2) 1 large vertical root also produces many small lateral, or branch roots dicots root hairs (3) increase absorptive surface area 2 3

Basic plant anatomy 2 root shoot (stem) root tip root hairs nodes buds internodes buds terminal or apical buds axillary buds flower buds & flowers

stolons (strawberries) Modified shoots stolons (strawberries) rhizome (ginger) tuber (potato) bulb (onion)

Basic plant anatomy 3 root shoot (stem) leaves root tip root hairs nodes internodes buds terminal or apical buds axillary buds flower buds & flowers leaves mesophyll tissue veins (vascular bundles)

Leaves Function of leaves photosynthesis gas exchange transpiration energy production CHO production gas exchange transpiration simple vs. compound

colored leaves (poinsetta) Modified leaves tendrils (peas) spines (cacti) succulent leaves colored leaves (poinsetta)

Interdependent systems Both systems depend on the other roots depend on sugars produced by photosynthetic leaves shoots depend on water & minerals absorbed from the soil by roots sugars water & minerals

Plant TISSUES Dermal Ground Vascular epidermis (“skin” of plant) single layer of tightly packed cells that covers & protects plant Ground bulk of plant tissue photosynthetic mesophyll, storage Vascular transport system in shoots & roots xylem & phloem

Plant CELL types in plant tissues Parenchyma “typical” plant cells = least specialized photosynthetic cells, storage cells tissue of leaves, stem, fruit, storage roots Collenchyma unevenly thickened primary walls Support young parts of plant Sclerenchyma very thick, “woody” secondary walls support rigid cells that can’t elongate dead at functional maturity If I’d only had triplets!

Parenchyma (193 & 199) Parenchyma cells are unspecialized, thin, flexible & carry out many metabolic functions all other cell types in plants develop from parenchyma

Collenchyma Collenchyma cells have thicker primary walls & provide support help support without restraining growth remain alive in maturity the strings in celery stalks are collenchyma

Sclerenchyma Thick, rigid cell wall Cells for support cannot elongate mostly dead at maturity Cells for support

Structure–Function again! Vascular tissue vessel elements Xylem move water & minerals up from roots dead cells at functional maturity only cell walls remain need empty pipes to efficiently move H2O transpirational pull vessel element dead cells Aaaah… Structure–Function again! tracheids

Phloem: food-conducting cells carry sugars & nutrients throughout plant sieve tube companion cell sieve plate plasmodesmata living cells

Phloem: food-conducting cells sieve tube elements & companion cells

Structure–Function again! Aaaah… Structure–Function again! Phloem Living cells at functional maturity cell membrane, cytoplasm control of diffusion lose their nucleus, ribosomes & vacuole more room for specialized transport of liquid food (sucrose) Cells sieve tubes sieve plates — end walls — have pores to facilitate flow of fluid between cells companion cells nucleated cells connected to the sieve-tube help sieve tubes

Vascular tissue in stems dicot trees & shrubs monocot grasses & lilies collect annual rings

Vascular tissue in roots: dicot phloem xylem

Vascular tissue in roots: monocot xylem phloem

Plant Growth 2007-2008

Growth in Plants Specific regions of growth: meristems stem cells: perpetually embryonic tissue regenerate new cells apical shoot meristem growth in length primary growth apical root meristem lateral meristem growth in girth secondary growth

Growth in woody plants Woody plants grow in height from tip Primary xylem Growth in woody plants Woody plants grow in height from tip primary growth apical meristem Woody plants grow in diameter from sides secondary growth lateral meristems vascular cambium makes 2° phloem & 2° xylem cork cambium makes bark Primary phloem Epidermis Lateral meristems Secondary xylem Primary phloem Primary xylem Secondary phloem Annual growth layers Bark

Secondary growth Secondary growth growth in diameter thickens & strengthens older part of tree cork cambium makes bark growing ring around tree vascular cambium makes xylem & phloem

Why are early & late growth different? Vascular cambium Phloem produced to the outside Xylem produced to the inside bark phloem cork cambium xylem late vascular cambium early last year’s xylem

Woody stem How old is this tree? cork cambium vascular cambium late early 3 2 1 xylem phloem bark

Tree trunk anatomy tree girdling What does girdling do to a tree? Aaaargh! Murderer! Arborcide! Tree trunk anatomy tree girdling What does girdling do to a tree?