Unit 7 Plants
Ch. 24 Reproduction of Seed Plants
Structure of Flowers
Flowers are reproductive organs composed of 4 kinds of specialized leaves: sepals, petals, stamens, & carpals
Sepals & Petals
Sepals - green leaves that enclose the bud before it opens, & they protect the flower while it is developing
Petals - often brightly colored, found just inside the sepals– Attract insects & other pollinators to the flower
Stamens & Carpels
Stamen - the male parts, consist of an anther & a filament
Filament - a long, thin stalk that supports the anther
Anther - found at the tip of each filament, where pollen grains are formed
Stamens & Carpels
Carpels - (pistils) - the female parts, consists of an ovary, style, & stigma
Ovary - contains 1/more ovules where eggs are produced
Style - stalk connecting the ovary to the stigma
Stigma - top of the style, where pollen grains land
Pollination
Most gymnosperms & some angiosperms are wind pollinated, whereas most angiosperms are pollinated by animals
Seed & Fruit Development
As angiosperm seeds mature, the ovary walls thicken to form a fruit that encloses the developing seeds
Seed Dispersal
Dispersal by Animals– Seeds dispersed by animals are typically
contained in fleshy, nutritious fruits
Seed Dispersal
Dispersal by Wind & Water– Seeds dispersed by wind or water are typically
lightweight, allowing them to be carried in the air or to float on the surface of the water
Seed Dormancy
Dormancy - when the embryo is alive but not growing
Environmental factors such as temperature & moisture can cause a seed to end dormancy & germinate
Seed Germination
Germination - early growth stage of the plant embryo
Vegetative Reproduction
Vegetative reproduction - type of asexual reproduction
Vegetative reproduction includes the production of new plants from horizontal stems, from plantlets, & from underground roots
Vegetative Reproduction
Stolons - long, trailing stems that produce roots when they touch the ground– Ex.) strawberry plants
Plant Propagation
In plant propagation, horticulturists use cuttings, grafting, or budding to make many identical copies of a plant or to produce offspring from seedless plants
Plant Propagation
Cutting - cut part of the plant stem & plant it in the ground
Grafting - when a piece of stem or bud is cut from a parent plant & attached to another plant– The cut piece is called the scion
Plant Propagation
Budding - when buds are used as scions
Agriculture
Most of the people of the world depend on a few crop plants, such as wheat, rice, & corn, for the bulk of their food supply
Agriculture
Between 1970 & 2000, the amount of corn grown per acre in the US increased more than 60%