Botany Basics 4

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Botany Basics 4: 

Botany Basics 4 Crop Science 1 Fall 2004 October 12, 2004

Flowers: 

Flowers Sole function is sexual reproduction Important for plant classification Least influenced by environmental changes System of plant nomenclature was developed by Carl von Linné (Linnaeus) and is based on flowers and/or reproductive parts of plants

Structure: 

Structure A flower contains: A stamen A Pistil Accessory parts sepals, petals, and nectar glands

Stamen: 

Stamen Male reproductive organ Consists of anther pollen sac Supporting Filament Holds the anther in position, making the pollen available for dispersement by wind, insects, or birds

Pistil: 

Pistil Plant's female part Shaped like a bowling pin Located in the flower's center Consists of a Stigma - located at the top Style connects stigma to the ovary Ovary contains eggs, which reside in ovules If egg is fertilized, ovule develops into a seed

Sepal: 

Sepal Small, green, leaflike structures At the base of a flower Protect the flower bud Collectively called a calyx Dicots typically have sepals in multiples of four or five Monocots have multiples of three

Petals: 

Petals Highly colored portions of a flower May contain perfume Collectively, called a corolla Number of petals is used to help identify plant families

Types of Flowers: 

Types of Flowers Complete Has a stamen, pistil, petals, and sepals Rose Incomplete One of these parts is missing

Types of Flowers: 

Types of Flowers Perfect Contains both functional stamens and pistils May not contain petals and sepals Imperfect Lack stamens or pistils Pistillate (female) flowers have a pistil(s), but no stamens Staminate (male) flowers contain stamens, but no pistils

Types of Flowers: 

Types of Flowers Plants with imperfect flowers are classified as: Monoecious Have separate male and female flowers on the same plant (e.g., corn and pecan) Some bear only male flowers at the beginning of the growing season, but later develop both sexes (e.g., cucumbers and squash). Dioecious Have separate male and female plants (e.g. holly, ginkgo, and pistachio) To set fruit, male and female plants must be planted close enough together for pollination to occur

Types of Flowers: 

Types of Flowers Solitary flower Only one flower per stem Inflorescence A cluster of flowers Each flower in an inflorescence is called a floret Most inflorescences belong to one of two groups: Racemes The florets start blooming from the bottom of the stem and progress toward the top Cyme The top floret opens first and blooms progress downward along the peduncle

Pollination: 

Pollination The transfer of pollen from an anther to a stigma Pollinated by: Insects, animals, or birds Often have brightly colored or patterned flowers that contain fragrance or nectar Wind Often lack showy floral parts and nectar because they don't need to attract pollinators

Pollination: 

Pollination A chemical in the stigma stimulates pollen to grow a long tube down the style to the ovules inside the ovary When pollen reaches the ovules, it releases sperm, and fertilization typically occurs

Fertilization: 

Fertilization The union of a male sperm nucleus from a pollen grain with a female egg If successful, the ovule develops into a seed Pollination is no guarantee that fertilization will occur

Cross-Fertilization: 

Cross-Fertilization Combines genetic material from two parent plants The resulting seed has a broader genetic base May enable the population to survive under a wider range of environmental conditions Cross-pollinated plants usually are more successful than self-pollinated plants Consequently, more plants reproduce by cross-pollination than by self-pollination