Botany Basics 2 Crop Science 1 Fall 2004 September 21, 2004

Botany Basics 2Botany Basics 2

Crop Science 1Crop Science 1

Fall 2004Fall 2004

September 21, 2004September 21, 2004

StemsStems

Support buds and leavesSupport buds and leaves Serve as conduits for carrying water, minerals, Serve as conduits for carrying water, minerals,

and food (photosynthates)and food (photosynthates) The vascular system inside the stem forms a The vascular system inside the stem forms a

continuous pathway from the root, through the continuous pathway from the root, through the stem, and finally to the leaves. It is through this stem, and finally to the leaves. It is through this system that water and food products move.system that water and food products move.

Root Root Stem Stem Leaf Leaf

Stem TerminologyStem Terminology

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 (has 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.

Vascular SystemVascular System

It can be thought of as a plant's plumbingIt can be thought of as a plant's plumbingConsists of:Consists of: Xylem tubes Xylem tubes

conduct water and dissolved minerals conduct water and dissolved minerals Phloem tubes Phloem tubes

carry food such as sugars. carry food such as sugars. Vascular cambium Vascular cambium

A layer of meristematic tissue that separates the xylem and A layer of meristematic tissue that separates the xylem and phloemphloem

continuously produces new xylem and phloem cellscontinuously produces new xylem and phloem cells This new tissue is responsible for a stem's increase in girthThis new tissue is responsible for a stem's increase in girth

Vascular SystemVascular System

ExampleExample The tissues on a grafted scion and rootstock The tissues on a grafted scion and rootstock

need to line upneed to line up Careless almond shaking can strip the bark Careless almond shaking can strip the bark

off the tree, thus injuring the cambium and off the tree, thus injuring the cambium and causing the tree to diecausing the tree to die

Monocots vs DicotsMonocots vs Dicots

The vascular The vascular systems of monocots systems of monocots and dicots differand dicots differ

Both contain xylem Both contain xylem and phloemand phloem

Structures are Structures are arranged differently arranged differently in each. in each.

MonocotsMonocots

The xylem and The xylem and phloem are paired in phloem are paired in bundlesbundles

Which are dispersed Which are dispersed throughout the stem throughout the stem

DicotsDicots

Vascular system is Vascular system is continuous continuous

Forms rings inside the Forms rings inside the stem stem

Ring of phloem is near Ring of phloem is near bark, and turns into bark bark, and turns into bark in mature woody stemsin mature woody stems

Xylem forms the inner Xylem forms the inner ring (sapwood and ring (sapwood and heartwood)heartwood)

Why We Need to Know Why We Need to Know ThisThis

Some herbicides affect only one group Some herbicides affect only one group For exampleFor example

2,4-D kills only plants with a continuous 2,4-D kills only plants with a continuous vascular system (dicots) vascular system (dicots)

NonselectiveNonselective herbicides (e.g., glyphosate- herbicides (e.g., glyphosate-Round Up) kill plants regardless of their type Round Up) kill plants regardless of their type of vascular systemof vascular system

NodesNodes

Area on a stem where buds are located Area on a stem where buds are located A site of great cellular activity and growth A site of great cellular activity and growth Where small buds develop into leaves, Where small buds develop into leaves,

stems, or flowersstems, or flowers

Pruning at NodesPruning at Nodes

When pruning, it is important to locate a When pruning, it is important to locate a plant's nodes. plant's nodes.

Want to make a pruning cut just above, Want to make a pruning cut just above, but not too close to, a node but not too close to, a node

Pruning in this manner encourages the Pruning in this manner encourages the buds at that node to begin development buds at that node to begin development and form new stems or leavesand form new stems or leaves

InternodeInternode

The area between The area between two nodes is called two nodes is called an internode an internode

Factors Influencing Factors Influencing Internode LengthInternode Length

Water stress decreases internode length, increased Water stress decreases internode length, increased irrigation increases internode lengthirrigation increases internode length

Reduced soil fertility decreases internode length, while Reduced soil fertility decreases internode length, while an application of high-nitrogen fertilizer can greatly an application of high-nitrogen fertilizer can greatly increase itincrease it

Varies with the season. Early-season growth has long Varies with the season. Early-season growth has long internodes, late-season growth has much shorter internodes, late-season growth has much shorter internodesinternodes

If a stem's energy is divided among three or four side If a stem's energy is divided among three or four side stems, or is diverted into fruit growth and development, stems, or is diverted into fruit growth and development, internode length is shortenedinternode length is shortened

Plant growth regulator substances and herbicides also Plant growth regulator substances and herbicides also can influence internode length can influence internode length

StemsStems

Must have buds or leavesMust have buds or leaves May be long, with great distances between the May be long, with great distances between the

leaves and buds (e.g., branches of trees, leaves and buds (e.g., branches of trees, runners on strawberries) runners on strawberries)

May be compressed, with short distances May be compressed, with short distances between buds or leaves (e.g., crowns of between buds or leaves (e.g., crowns of strawberry plants, fruit spurs) strawberry plants, fruit spurs)

Commonly grow above groundCommonly grow above ground Sometimes grow below ground in the form of Sometimes grow below ground in the form of

rhizomes, tubers, corms, or bulbs rhizomes, tubers, corms, or bulbs

Aboveground StemsAboveground Stems

CrownsCrowns (on strawberries) (on strawberries) Compressed stems with Compressed stems with

leaves and flowers on leaves and flowers on short internodes. short internodes.


SpursSpurs short, stubby, side stems that short, stubby, side stems that

arise from a main stemarise from a main stem Are the fruit-bearing stems Are the fruit-bearing stems

on pear, apple, and cherry on pear, apple, and cherry treestrees

If severe pruning is done If severe pruning is done close to fruit-bearing spurs, close to fruit-bearing spurs, can revert to nonfruiting can revert to nonfruiting stems eliminating the year's stems eliminating the year's potential fruit croppotential fruit crop


StolonsStolons Fleshy or semiwoody, Fleshy or semiwoody,

elongated, horizontal elongated, horizontal stems that often lie stems that often lie along the soil surface along the soil surface

Strawberry runners are Strawberry runners are stolons that have small stolons that have small leaves at the nodesleaves at the nodes Roots develop from these Roots develop from these

nodes, and a daughter nodes, and a daughter plant is formedplant is formed

Belowground StemsBelowground Stems

Tubers Tubers (potato)(potato) ““Eyes" are actually Eyes" are actually

the stem's nodesthe stem's nodes Each eye contains a Each eye contains a

cluster of budscluster of buds


RhizomesRhizomes Resemble stolons Resemble stolons Grow horizontally from Grow horizontally from

plant to plantplant to plant Some are compressed Some are compressed

and fleshy (e.g., iris), and fleshy (e.g., iris), while others are slender while others are slender and have elongated and have elongated internodes (e.g., internodes (e.g., bentgrass). bentgrass).

The spreading capability The spreading capability of Johnsongrass’s of Johnsongrass’s rhizomes makes it a rhizomes makes it a difficult weeddifficult weed


Bulbs Bulbs (onion)(onion) Shortened, compressed Shortened, compressed

underground stems underground stems Surrounded by fleshy Surrounded by fleshy

scales (leaves) that scales (leaves) that envelop a central bud at envelop a central bud at the tip of the stemthe tip of the stem

After the plant flowers, its After the plant flowers, its phloem transports food phloem transports food reserves from its leaves reserves from its leaves to the bulb's scalesto the bulb's scales

It utilizes the stored food It utilizes the stored food when it begins growing in when it begins growing in the spring the spring


CormsCorms Shaped like bulbs, Shaped like bulbs,

but do not contain but do not contain fleshy scalesfleshy scales

A solid, swollen stem A solid, swollen stem with dry, scale-like with dry, scale-like leavesleaves


Tuberous stemTuberous stem Modified Modified

underground stemunderground stem Short, flat, and Short, flat, and

enlargedenlarged Buds and shoots Buds and shoots

arise from the top arise from the top (crown), and fibrous (crown), and fibrous roots grow from the roots grow from the bottombottom

How to Distinguish Roots How to Distinguish Roots and Stems?and Stems?

Stems have nodesStems have nodes Roots do notRoots do not

Additional Types of Additional Types of StemsStems

CanesCanes Grapes, blackberries, and Grapes, blackberries, and

raspberries raspberries Stems with relatively large pith Stems with relatively large pith

(the central strength-giving (the central strength-giving tissue) tissue)

Live only 1 or 2 yearsLive only 1 or 2 years It is important to know: It is important to know:

Which canes to pruneWhich canes to prune How to prune themHow to prune them When to prune them. When to prune them.


VineVine A plant with long, trailing A plant with long, trailing

stemsstems Some vines grow along the Some vines grow along the

ground, must be supported ground, must be supported by another plant or by another plant or structurestructure

Twining vines circle a Twining vines circle a structure for support structure for support Some circle clockwise (hops)Some circle clockwise (hops) Some circle counterclockwise Some circle counterclockwise

(pole beans)(pole beans)


Vine Vine (Continued)(Continued) Climbing vines are Climbing vines are

supported by supported by Aerial roots (poison ivy)Aerial roots (poison ivy) Slender tendrils that encircle a Slender tendrils that encircle a

supporting object (cucumbers, supporting object (cucumbers, grapes)grapes)

Tendrils with adhesive tipsTendrils with adhesive tips

Trees and ShrubsTrees and Shrubs

Trees generally have one, but occasionally Trees generally have one, but occasionally several, main trunks, which usually are more several, main trunks, which usually are more than 12 feet tall when maturethan 12 feet tall when mature

Shrubs generally have several main stems, Shrubs generally have several main stems, which usually are less than 12 feet tall when which usually are less than 12 feet tall when maturemature

Most fruit trees, ornamental trees, and shrubs Most fruit trees, ornamental trees, and shrubs have woody stemshave woody stems These stems contain relatively large amounts of These stems contain relatively large amounts of

hardened xylem tissue in the central core hardened xylem tissue in the central core (heartwood or sapwood) (heartwood or sapwood)

Herbaceous PlantsHerbaceous Plants

Herbaceous or succulent stems contain Herbaceous or succulent stems contain only a little xylem tissueonly a little xylem tissue

Usually live for only one growing seasonUsually live for only one growing season In perennial plants, new herbaceous In perennial plants, new herbaceous

stems develop from the crown (root-stem stems develop from the crown (root-stem interface) each yearinterface) each year

Stem PropagationStem Propagation

Using sections of aboveground stems that Using sections of aboveground stems that contain nodes and internodes is an effective contain nodes and internodes is an effective way to propagate many plantsway to propagate many plants Stem cuttings produce roots and, eventually, new Stem cuttings produce roots and, eventually, new

plantsplants Below-ground stems also are good propagative Below-ground stems also are good propagative

tissuestissues Divide rhizomes into piecesDivide rhizomes into pieces Remove small bulblets or cormels from their parentRemove small bulblets or cormels from their parent Cut tubers into pieces containing eyes and nodesCut tubers into pieces containing eyes and nodes

Stems as FoodStems as Food

The edible portion of:The edible portion of: Asparagus and kohlrabi is an enlarged, Asparagus and kohlrabi is an enlarged,

succulent stem succulent stem Broccoli is composed of stem tissue, Broccoli is composed of stem tissue,

flower buds, and a few small leaves flower buds, and a few small leaves A potato tuber is a fleshy underground A potato tuber is a fleshy underground

stemstem Cauliflower is proliferated stem tissueCauliflower is proliferated stem tissue

BudsBuds

An undeveloped shoot from which leaves An undeveloped shoot from which leaves or flower parts growor flower parts grow

The buds of temperate-zone trees and The buds of temperate-zone trees and shrubs typically develop a protective shrubs typically develop a protective outer layer of small, leathery scalesouter layer of small, leathery scales

Annual plants and herbaceous perennials Annual plants and herbaceous perennials have naked buds with green, somewhat have naked buds with green, somewhat succulent, outer leavessucculent, outer leaves

DormancyDormancy

Buds of many plants require exposure to a certain Buds of many plants require exposure to a certain number of days below a critical temperature before number of days below a critical temperature before resuming growth in the springresuming growth in the spring

Varies for different plantsVaries for different plants For example, requires a relatively short rest period and grows For example, requires a relatively short rest period and grows

at the first sign of warm weather. at the first sign of warm weather. Peaches require 700 to 1,000 hours of temperatures below Peaches require 700 to 1,000 hours of temperatures below

45°F45°F Dormant buds can withstand very low temperatures Dormant buds can withstand very low temperatures After dormancy buds are susceptible to damage by After dormancy buds are susceptible to damage by

cold temperatures or frost.cold temperatures or frost.

Types of BudsTypes of Buds

Leaf bud Leaf bud Composed of a short Composed of a short

stem with embryonic stem with embryonic leaves. leaves.

Less plump and more Less plump and more pointed than flower budspointed than flower buds

Flower budFlower bud Composed of a short Composed of a short

stem with embryonic stem with embryonic flower parts flower parts

In the case of fruit crops, In the case of fruit crops, flower buds sometimes flower buds sometimes are called fruit budsare called fruit buds

Bud LocationBud Location

Buds are named for their location Buds are named for their location on the stemon the stem

Terminal buds are located at Terminal buds are located at the apex (tip) of a stem the apex (tip) of a stem

Lateral (axillary) buds are Lateral (axillary) buds are located on the sides of a stem located on the sides of a stem and usually arise where a leaf and usually arise where a leaf meets a stem (axil) meets a stem (axil) In some instances, an axil In some instances, an axil

contains more than one bud.contains more than one bud.

Bud LocationBud Location

Adventitious buds arise at sites other than Adventitious buds arise at sites other than the terminal or axillary position. the terminal or axillary position. They may develop from roots, a stem They may develop from roots, a stem

internode, the edge of a leaf blade, or callus internode, the edge of a leaf blade, or callus tissue at the cut end of a stem or root. tissue at the cut end of a stem or root.

Adventitious buds allow stem, leaf, and root Adventitious buds allow stem, leaf, and root cuttings to develop into entirely new plants.cuttings to develop into entirely new plants.

Buds as FoodBuds as Food

Enlarged buds or parts of buds form the edible portion of Enlarged buds or parts of buds form the edible portion of some horticultural crops. some horticultural crops.

Cabbage and head lettuce are examples of unusually Cabbage and head lettuce are examples of unusually large terminal buds. large terminal buds.

Succulent axillary buds are the edible part of Brussels Succulent axillary buds are the edible part of Brussels sproutssprouts

Globe artichoke, the fleshy basal portion of the flower Globe artichoke, the fleshy basal portion of the flower bud's bracts is eaten, along with its solid stembud's bracts is eaten, along with its solid stem

Broccoli is the most important horticultural plant with Broccoli is the most important horticultural plant with edible flower buds. In this case, portions of the stem, edible flower buds. In this case, portions of the stem, as well as small leaves associated with the flower as well as small leaves associated with the flower buds, are eaten.buds, are eaten.

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Botany Basics 2 Crop Science 1 Fall 2004 September 21, 2004