Kingdom PLANTAE Multi-celled / eukaryotic Autotrophic / chloroplast Cell wall - cellulose
Dec 26, 2015
Plants: Alternation of Generation Gametophyte (n): Haploid, produces eggs and sperms which then unite to form sporophyte
Sporophyte (2n): Diploid which goes through meiosis to produce spores which grow into gametophytes
Plants: Flowers Most plants are angiosperms, flowering plants
Angiosperm seeds protected and dispersed in fruits, which develop from ovaries
Plants: Flowering Plants Angiosperms, or flowering plants, are most familiar and diverse plants
Two main types of angiosperms Monocots: orchids, bamboos, palms, lilies, grains, and other grasses
Dicots: shrubs, ornamental plants, most trees, and many food crops
Comparison between dicot and monocot seeds
Figure 31.11B
Seed coat
Embryonicleaves
Embryonicroot
Embryonicshoot
Cotyledons
Fruit tissue
Seed coat
Endosperm
Embryonicshoot
Embryonicroot
Cotyledon
Embryonicleaf
Sheath
COMMON BEAN (DICOT)
CORN (MONOCOT)
The angiosperm flower is a reproductive shoot consisting of sepals petals stamen carpels
Plants: Flowering Plant Reproduction
Figure 31.9A
Stigma
Ovary
Carpel
Anther
Petal
Ovule Sepal
Stamen
Plants: Stamens - male reproductive organs of plants Pollen grains develop in anthers, at the tips of stamens
Carpels - female reproductive organs of plants Ovary at the base of the carpel has ovule
Life cycle of angiosperm involves several stages
Figure 31.9B
Ovary, containingovule
Fruit,containing seed
Seed
Embryo
Germinating seed
SeedlingMature plant withflowers, wherefertilization occurs
Plants: The ovule develops into a seed After fertilization, ovule becomes seed Fertilized egg inside seed - embryo
Other fertilized cell - endosperm, stores food for the embryo
Resistant seed coat protects the embryo and endosperm
Figure 31.11A
Triploid cell
OVULE
Zygote
Two cells
Embryo
Root SEED
Shoot
Endosperm
Cotyledons
Seed coat
Seed dormancy is an important evolutionary adaptation in which growth and development are suspended temporarily It allows time for a plant to disperse its seeds
It increases the chance that a new generation of plants will begin growing only when environmental conditions favor survival
Plant: Asexual Reproduction Asexual reproduction:
Bulbs: parts of root split and form new bulb (ex. tulip)
Tubers: modified underground stem have buds (ex. potato)
Runners: plant stem run above ground (ex. Strawberry)
Rhizomes: woody underground stem (ex. Iris)
Modified stems include runners, asexual reproduction
rhizomes, plant growth and food storage
tubers, food storage as starch
Figure 31.4B
STRAWBERRYPLANT
POTATOPLANT
IRISPLANT
Runner
TuberTaproot
Rhizome
Rhizome
Root
Vegetative propagation: cuttings or bits of tissue increase agricultural productivity But it can also reduce genetic diversity
Cutting: cut stem form roots Layering: bent stem touching ground form roots
Grafting: stock of one grafted on stem (scion) of another
Plant: Asexual Reproduction
Plants: Shoot and Root System
Root system Provides anchorage Absorbs and transports minerals and water
Stores food Shoot system
Consists of stems, leaves, and flowers in angiosperms
Stems: located above ground and support leaves and flowers
Leaves: main sites of photosynthesis in most plants
Plants: 3 Tissue Systems Instead of organs, plants have roots, stems, and leaves are made of three tissue systems The epidermis The vascular tissue system
The ground tissue system
PLANTS: Epidermis and Vascular Tissue
The epidermis covers and protects the plant The cuticle is a waxy coating secreted by epidermal cells that helps the plant retain water
The vascular tissue contains xylem and phloem It provides support and transports water and nutrients
Xy: high (water) Phlo: lo (nutrients) Rise of water: transpiration pull, capillary action, root pressure
Plants: Vascular & Ground Tissue Vascular tissue:
Xylem: inside, bring water up; usually dead cells act as tube
Phloem: outside bundle, brings nutrients down
Pith: storage and structure Cambium: growth tissue – divide into xylem and phloem (2nd growth)
The ground tissue system functions mainly in storage and photosynthesis
These microscopic cross sections of a dicot and a monocot indicate several differences in their tissue systems
Figure 31.6C
Three tissue systems in dicot leaves Epidermis: stomata (singular, stoma) surrounded by guard cells – regulate opening/closing of stomata
Figure 31.6D
Guard cells: control transpiration Opening and closing of stomata - adaptation to help plants regulate water content / adjust to changing environmental conditions
Plants: Guard cells control transpiration
Figure 32.4
Guard cellsH2O H2O
K+
H2O
H2OH2O
Vacuole
Stoma opening Stoma closing
H2O
H2O
H2OH2O
H2O
Most plants continue to grow as long as they live (as opposed to animals that stop growing)
Two types of growth:- primary growth (length)- secondary growth (width)
Plant Growth: Primary vs Secondary
Plants: Primary Growth Growth from tissue meristems
Meristems: unspecialized, dividing cells (like our stem cells)
Apical meristems: tips of roots and stems and terminal buds ; length growth
Primary growth (length growth) - new cell productions
Figure 31.7B
Vascularcylinder
Cortex
Epidermis
Root hair
Cellulosefibers
Apical meristemregion
Rootcap
DIF
FE
RE
NT
IAT
ION
EL
ON
GA
TIO
NC
EL
LD
IVIS
ION
Plants: Secondary growth Secondary growth: Increase in a plant's width
Lateral meristem (also called cambium): Vascular cambium (located between xylem and phloem)
Cork cambium (not in grasses or herbs, but found in woody dicots, ex. oaks)
Vascular cambium thickens stem by adding layers of secondary xylem, or wood, next to its inner surface Also produces secondary phloem- tissue of bark
Cork cambium produces protective cork cells located in bark
Plants: Secondary Growth Everything outside vascular cambium – bark Secondary phloem Cork cambium Protective cork cells
Woody log result of several years of secondary growth (inside “dead”; outside “growing”)
Figure 31.8B
Sapwood
Heartwood
Rings
Woodrays
Heartwood
Sapwood
Vascular cambium
Bark
Secondary phloem
Cork cambium
Cork
Plant behavior: Phototropism Gravitropism Geotropism thigmotropism
Plant: Behavior = Tropism
Figure 33.1A
Phototropism is the bending toward light It may result from auxin moving from the illuminated side to the shaded side of a stem
Figure 33.1A
Thigmotropism - response to touch Responsible for coiling of tendrils and vines around objects
Enables plants to use other objects for support while growing toward sunlight
Figure 33.9B
Hormone controls phototropism
Figure 33.1C
Light
Control Tipremoved
DARWIN AND DARWIN (1880) BOYSEN-JENSEN (1913)
Tip coveredby opaque cap
Tip coveredby trans-parent cap
Basecoveredby opaqueshield
Tipseparatedby gelatinblock
Tipseparatedby mica
Figure 33.1D
Shoot tip placed on agar block.Chemical (later called auxin)diffuses from shoot tip into agar.
Agar
Control
NO LIGHT
Block withchemicalstimulatesgrowth.
Offset blocks withchemical stimulatecurved growth.
Other controls:Blocks with nochemical haveno effect.
Auxin: stimulates cell division – phototropism and geotropism
Positive and negative geotropism (b/c unequal distribution of hormone, unequal growth & root grows faster)
Cytokinins: promote cell division Produced in actively growing roots, embryos, and fruits
Opposite auxin, so plant coordinates growth of root and shoot systems
Plants: Hormones
Cytokinins – develop side growth Ex grow branch
Auxin – stimulate length growth w/o auxin, plant becomes thicker b/c cytokinins Terminal bud
No terminal bud
Figure 33.4
Gibberellins: stimulate cell elongation and cell division in stems and leaves
Gibberellins: can stimulate seed growth
Plants: Hormones
Figure 33.5A
Gibberellins with auxin - influence fruit development
Grapes at right treated with gibberellin, left not
Figure 33.5B
Abscisic acid (ABA) inhibits germination of seeds
Ratio of ABA & gibberellins determines whether seed remain dormant or germinate
Also “stress hormone” – close stomata when too dry
Plants: Hormones
Seeds of many plants remain dormant until ABA inactivated or washed away Ex. flowers grow from seeds after rainstorm in Mojave Desert
Figure 33.6
Fruit growers use ethylene to control ripening Apple farmers slow down ripening action of natural ethylene
Tomato farmers pick unripe fruit and then pipe ethylene into storage bins to promote ripening