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Botany Basics

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Courtney Wilson

on 9 September 2016

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Transcript of Botany Basics

Botany Basics
Parts of a Plant Song
Non-vascular plants must rely on each cell directly absorbing the nutrients that they need.
Often these plants are found in water in order to make this possible.
Only vascular plants are capable of large production capacities on dry land.

Vascular Plants
In horticulture we tend to focus on vascular plants
Vascular plants are those that contain water- and nutrient-conducting tissues called xylem and phloem
Ferns and seed-producing plants fall into this category

Monocots (e.g., grasses and cereal grains) produce only one seed leaf
The seed leaf is the leaf that emerges first from the seed
This leaf is often protected by the coleoptile
Dicots (e.g. beans, cucumbers, tomatoes) produce two seed leaves
The vascular systems, flowers, and leaves of the two types of plants also differ
These differences will become important in understanding plant growth and development.

An annual, such as a zinnia, completes its life cycle in 1 year.
Annuals are said to go from seed to seed in 1 year or growing season.
During this period, they grow, mature, bloom, produce seeds, and die.
There are both winter and summer annual weeds, and understanding a weed's life cycle is important in controlling it.
Summer annuals complete their life cycle during spring and summer
Most winter annuals complete their growing season during fall and winter.

A biennial requires all or part of 2 years to complete its life cycle.
During the first season, it produces vegetative structures (leaves) and food storage organs.
The plant overwinters and then produces flowers, fruit, and seeds during its second season.
Swiss chard, carrots, beets, Sweet William, and parsley are examples of biennials.

Understanding how plants grow and develop helps us capitalize on their usefulness and make them part of our everyday lives.

Objective: The student develops technical skills associated with the management and production of horticultural plants. The student is expected to:

(A) classify horticultural plants based on physiology for taxonomic or other classifications;

(B) manage the horticultural production environment;

(C) propagate and grow horticultural plants;

(D) create a design using plants that demonstrates an application of design elements and principles;


If a flower has a stamen, pistil, petals, and sepals, it is called a complete flower.
If one or more of these parts are missing, it is called an incomplete flower.
The male stamen and the female pistil are the most essential parts of the flower because they are involved in seed production
If a flower has both functional stamens and pistils, it is called a perfect flower
If either are lacking, it is imperfect

Monocots vs. Dicots
Which one is the monocot?
Plant Life Cycles
Annuals
Based on its life cycle, a plant is classified as an annual, biennial, or perennial.

Biennial
Sometimes biennials go from seed germination to seed production in only one growing season.
This situation occurs when extreme environmental conditions (e.g. drought or temperature variation)
A plant will pass rapidly through the equivalent of two growing seasons.
This phenomenon is referred to as bolting.
Sometimes bolting occurs when biennial plant starts are exposed to a cold spell before being planted in the garden.

Perennials
Perennial plants live more than 2 years
They are grouped into two categories: herbaceous perennials and woody perennials.
Herbaceous perennials have soft, non-woody stems that generally die back to the ground each winter.
New stems grow from the plant's crown each spring.
Trees and shrubs, on the other hand, have woody stems that withstand cold winter temperatures.
They are referred to as woody perennials.

In a perennial life cycle, seed production can occur every year or every other year.
Pruning may be necessary in some perennials (particularly fruit trees and berries) in order to have annual production.

Internal Plant Plants
Plant Cells: Most plant reactions (photosynthesis, respiration, cell division, etc.) occur at the cellular level
A unique feature of plant cells is that they are totipotent.
Totipotent: cells retain all of the genetic information (encoded in DNA) necessary to develop into a complete plant
This characteristic is the main reason that vegetative or asexual reproduction works (such as grafting or stem cuttings)
For example, the cells of a small leaf cutting from an African violet have all of the genetic information necessary to generate a root system, stems, more leaves, and ultimately flowers.

Plant Tissue
Plant tissues (meristems, xylem, phloem, etc.) are large, organized groups of similar cells that work together to perform a specific function.
Meristems are the site of rapid, almost continuous cell division
In many cases, you can manipulate meristems to make a plant do something you want, such as change its growth pattern, flower, alter its branching habit, or produce vegetative growth.


Xylem & Phloem
Xylem:
Carries water and inorganic solutes (N, P, K) from the roots to the leaves
Usually xylem tubes are located inside the plant
Phloem:
Carries organic solutes (e.g. sucrose) from the leaves throughout the plant
Usually phloem is located outside of xylem

A node is an area on a stem where the buds are located
Nodes are a site of great cellular activity and growth, where small buds develop into leaves, stems, or flowers
When pruning, it is important to locate a plant’s nodes
Generally you want to cut just above, but not too close to a node
This encourages the buds at that node to begin development
The area between two nodes is called an internode

Internodal length
Stem Structures
Stems are a crucial part of plant physiology and perform the following functions for plants
Offer physical support for the leaves
Serve as conduits for moving water, minerals, and food throughout the plant

Shoot – a young stem (1 year old or less) with leaves
Twig – A young stem (1 year old or less) that is in the dormant winter stage (no leaves)
Branch – A stem that is more than 1 year old typically with lateral stems radiating from it
Trunk – A woody plant’s main stem

Stem Termenology
The vasculature system of a stem includes 3 main components –
Xylem – carries water and dissolved minerals up the plant
Phloem – carries food down the plant
Vascular Cambium – the cambium is a layer of meristematic tissue that separates xylem and phloem
The Cambium also produces the xylem and phloem tubes and creates the new tissue that is responsible for the change in girth of a stem
E.g. cambium would create the rings of a tree trunk


All of this happens in the stem..
In a monocot, the xylem and phloem are arranged in bundles and dispersed throughout the stem
In dicots, the vascular system forms continuous rings inside the system
The ring of phloem is near the bark and eventually becomes part of the bark in mature woody stems
The xylem forms the inner ring; in woody plants, it becomes the sapwood and heartwood


Monocot vs Dicot Vascular System
Internodal length can be an easy visible indicator of a plant’s health and productivity
Several factors can affect internode length
Reduced soil fertility decreases internode length
Applications of high-nitrogen fertilizer can greatly increase internode length
Lack of sunlight, or too low intensity of lighting, can increase internode length, causing a spindly stem
A situation where plants have a spindly stretched stems is called Etiolation
This often occurs in seedlings started indoors and in houseplants that get too little light
Internode length varies with the season
Early-season growth has long internodes; late season growth has longer internodes
If a stem’s energy is divided among three or four side stems, or is diverted into fruit growth and development, internode length is shortened
Plant growth regulators and herbicides will also change internode length

Parts of a Stem
Leaf Functions
The main function of leaves is to absorb sunlight and use this energy to produce sugars
This is the process of photosynthesis
Photosynthesis is the creation of sugar from carbon dioxide and water using the energy of the sun
Leaves are usually flat so that they can absorb the maximum amount of light as efficiently as possible.

Specialized epidermal cells called
guard cells
are like valves to a leaf
They can open and close in response to weather, light, and moisture
They regulate the passage of water, oxygen, and carbon dioxide
The openings in guard cells are called
stomata.
Most stomata are found on the underside of leaves
Conditions that would cause a plant to lose water (high temp, low humidity) cause the guard cells to close, sealing off the stomata.
Guard cells also close in absence of light

A leaf is connected to the stem by a structure called the
petiole
.
The base of the stem where the petiole connects is called the
node
Where the petiole connects to the leaf is called the
axil
The axil is where we happen to find buds, clusters, and emerging leaves.

A leaf blade consists of several layers
The outer layer (top and bottom) is the epidermis
Its main function is protection of the leaf

The
mesophyll
layer is found in the
middle

of the leaf
The mesophyll has two layers
The dense upper layer is called the palisade layer
The air-filled soft lower layer is called the spongy mesophyll
The mesophyll is important because this is where photosynthesis takes place

Scale leaves
(cataphylls) are found on rhizomes and buds, which they enclose and protect.
Seed leaves
(cotyledons) are found on embryonic plants. They store food for the developing seedling.
Spines and tendrils
, such as those found on barberry and pea plants, protect a plant or help support its stems.
Storage leaves
, such as those on bulbous plants and succulents, store food.
Bracts
often are brightly colored. For example, the showy structures on dogwoods and poinsettias are bracts, not petals.

Leaf Anatomy
Cross Section of a Leaf
The epidermis layer can be specialized
For example, some leaves have hairs for protection.
The cuticle is a part of the epidermis that produces cutin
Cutin is a waxy layer that protects the plant from dehydration and disease.
Increasing light intensity will increase the thickness of the cutin layer
Hence the need for hardening off before moving plants

Cutin
Cutin also repels water
This can make some pesticides less effective unless they have additives to help them penetrate the cutin layer
Without these additives, the insecticide would completely flow off of the plant

Guard Cells
Mesophyll
Types of Modified Leaves
Structure and Anatomy of Flowers
The primary purpose of a flower is sexual reproduction
The color and fragrance of a flower is the result of adaptive strategies
They are only pleasing to humans as a coincidence of evolution

Flowers, like leaves, are key to classification.
This classification system, or Linnaean system, was developed by Linnaeus and is characterized by each species having a Latin genus and species name.
In flowers, the name is based on the flowers or other reproductive part of the plant
This turned out to be a fortunate turn of events, as flowers are the part of the plant least affected by environmental factors
A knowledge of flowers is essential for anyone who will use plant ID as a part of their career.

Classification
The flower has both male and female organs.
The male organ is the
stamen
The female organ is the
pistil
, but may also include the
sepals, petals, and nectar glands.

Flower Structures
The stamen is the male reproductive organ
The stamen consists of the anther (pollen sac) and a long, supporting filament
The filament holds the anther in position, making it more available for birds, bees, or the wind to carry pollen away

The
pistil
is the female part of the plant
It is generally shaped like a bowling pin and is usually located in the center of the flower
The pistil consists of a stigma, style, and ovary
The
stigma
is located at the top and receives pollen
The
style
serves as a ‘neck’ connecting the stigma to the pistil
The
ovary
contains the eggs which reside in ovules
If the egg is fertilized, the ovule becomes a seed.

Petals
are typically the colorful portion of the flower
Collectively, the petals form the
corolla
Below the petals are the protective leaf-like structures called the
sepals
Collectively, the sepals are called a
calyx.

Petals and leaves are useful in determining whether a plant is a monocot or a dicot
Monocots have parallel veins and flower petals that come in three or mutliples of three
Dicots have net-veined leaves and flower petals in fours or fives

Petals & Leaves
Flower Terminology
Full transcript