Wheat Growth and Development

Last updated on February 23, 2014

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The following is derived from three publications:

Growth Staging of Wheat, Barley and Wild Oat Growth Staging of Wheat, Barley and Wild Oat

Growth and Development Guide for Spring Wheat

Growth and Development Guide for Spring Barley

Cereal Grain Development Scales

Staging Plants

Small Grain Growth Stages and Management

Profitable small grain production requires a thorough knowledge of crop development and growth, and how cultural and environmental factors can influence crop development. Crop and weed response to inputs such as fertilizers, pesticides, plant growth regulators and supplemental irrigation depend on the stage of development rather than on calendar date. Improper application timing may reduce chemical or fertilizer effectiveness, and, in some cases, result in crop injury and yield loss.

Wheat ( Triticum aestivum L.) can be classified as winter or spring growth habit based on flowering responses to cold temperatures. Winter wheat development is promoted by exposure of the seedlings to temperatures in the 38 degrees to 46 degrees F range. Such types are usually planted in the fall which exposes the seedlings to cold temperatures during late fall and winter. Spring-types, however, do not require exposure to cold temperatures for normal development and can be planted in spring. Both winter- and spring-types, when properly grown, head in the late spring or early summer and mature by mid- to late-summer.

Barley ( Hordeum vulgare L. ) originated in the Eastern Mediterranean region. Barley can be distinguished by differences in head type and growth habits. In a six-rowed barley, three kernels are formed at each node of the head while in a two-rowed type, only a single kernel forms at each node. Barley is also classed by its requirement for cold temperatures. Winter barley must be planted so that seedlings will be exposed to cold (vernalized), which enables it to later produce heads and grain normally. Winter barley is usually sown in the fall for exposure to low temperatures during the winter and then development is completed during the following spring and summer. Spring barley does not require exposure to winter temperatures and can be sown in spring. Winter types usually mature somewhat earlier than spring types. Differences in maturity exist among varieties.

Cereal Grain Development Scales

The development and growth of cereal grains have been translated into several numeric scales to quantify development for scientific and management purposes. Industry is now adopting these staging scales as a means of properly identifying application times for certain products. The most commonly used scales are the Feekes, Zadoks and Haun.

The Feekes scale is probably the best known and most widely used numerical staging scale. Eleven development stages describe physical plant changes from the first-leaf stage through grain ripening. For example, a six-leaf plant with one node would be stage 6. The heading and ripening stages are subdivided for greater detail. The Feekes scale recognizes eleven major growth stages starting with seedling emergence and ending with grain ripening. The Feekes scale is frequently used to identify optimum stages for chemical treatments, such as fungicide applications, that focus on the plant development period from the start of stem elongation (Feekes stage 6) to the completion of flowering (Feekes stage 10.53).

The Haun system is concerned mainly with the leaf production stage of development. However, tiller and grain development are not described. A number, called a growth unit, is assigned to each leaf as it develops, and to flag leaf sheath elongation, booting, heading and peduncle elongation. Each growth unit is subdivided into decimal fractions which begin with its own appearance and end with the appearance of the next growth unit. The length of each emerging leaf is expressed as a fraction of the length of the preceding fully emerged leaf. For example, a 3.2 indicates that three leaves are fully emerged, and a fourth leaf has emerged two-tenths of the length of the third. Although this system can be modified, it is not as useful in the field where decisions are made using development indicators other than leaf numbers.

The Zadoks scale provides more detailed information during early development stages than the Feekes scale. The scale is based on ten principal plant development stages, which are divided into secondary stages. A new leaf is counted as fully emerged when 50 percent of the leaf blade has unfolded. Two or more codes may be used to describe a plant using the Zadoks scale. For example, wheat that has six leaves unfolded (16), three tillers (23) and one node on the main stem (31) would be staged as 16, 23, 31.

The Zadoks system applies to any small grain and its stages are easy to identify in the field. It is more detailed than other systems and allows for precise staging. The first digit of this two-digit code refers to the principal stage of development beginning with germination (stage 0) and ending with kernel ripening (stage 9). Use of the second digit between 0 and 9 subdivides each principal growth stage. A second digit value of 5 usually indicates the midpoint of the principal stage. For example, a 75 refers to medium milk stage of kernel development. In seedling growth, principal growth stage 1, the second digit refers to the number of emerged leaves. To be counted, a leaf must be at least 50 percent emerged. A 13, for example, indicates that three leaves are at least 50 percent emerged on the main shoot. Tiller leaves are not counted.

For the tillering principal stage (stage 2), the second digit indicates the number of emerged tillers present on the plant. Since stages may overlap, it is possible to combine Zadoks indexes to provide a more complete description of a plant's appearance. For example, a plant with one tiller and three leaves could be described by either or both of the Zadoks stages 13 and 21. As the plant matures, the Zadoks stages describing kernel development are usually used alone. For purposes of herbicide application, the seedling stage (stage 1) identifying the leaf numbers is useful.

Another way of quantifying leaf appearance is in terms of accumulated heat units calculated by summing the number of degrees above 40 degrees F for each day. Heat units for each day are calculated with the following equation:

Growing degree unit = ((max. temp. + min. temp.)/2) - 40 degrees F

The ten major growth stages that the small grains plant progresses through during its life cycle are all familiar to farmers:

  1. Germination
  2. Seedling
  3. Tillering
  4. Stem elongation or Jointing
  5. Booting
  6. Heading
  7. Flowering or Anthesis
  8. Milk
  9. Dough
  10. Ripening

Cereal grain development stages by Zadoks, Feekes and Haun scales.

Zadoks Scale Feekes Scale Haun Scale Description

Germination

00 - - Dry Seed
01 - - Start of imbibition
03 - - Imbibition complete
05 - - Radicle emerged from seed
07 - - Coleoptile emerged from seed
09 - 0.0 Leaf just at coleoptile tip
Seedling Growth
10 1 - First leaf through coleoptile
11 - 1.0 First leaf extended
12 - 1.+ Second leaf extending
13 - 2.+ Third leaf extending
14 - 3.+ Fourth leaf extending
15 - 4.+ Fifth leaf extending
16 - 5.+ Sixth leaf extending
17 - 6.+ Seventh leaf extending
18 - 7.+ Eighth leaf extending
19 - - Nine or more leaves extended
Tillering
20 - - Main shoot only
21 2 - Main shoot and one tiller
22 - - Main shoot and two tillers
23 - - Main shoot and three tillers
24 - - Main shoot and four tillers
25 - - Main shoot and five tillers
26 3 - Main shoot and six tillers
27 - - Main shoot and seven tillers
28 - - Main shoot and eight tillers
29 - - Main shoot and nine tillers
Stem Elongation
30 4-5 - Psuedo-stem elongation
31 6 - First node detectable
32 7 - Second node detectable
33 - - Third node detectable
34 - - Fourth node detectable
35 - - Fifth node detectable
36 - - Sixth node detectable
37 8 - Flag leaf just visible
39 9 - Flag leaf ligule/collar just visible
Booting
40 - - -----
41 - 8-9 Flag leaf sheath extending
45 10 9.2 Boot just swollen
47 - - Flag leaf sheath opening
49 - 10.1 First awns visible
Inflorescence Emergence
50 10.1 10.2 First spikelet of inflorescence visible
53 10.2 - 1/4 of inflorescence emerged
55 10.3 10.5 1/2 of inflorescence emerged
57 10.4 10.7 3/4 of inflorescence emerged
59 10.5 11.0 Emergence of inflorescence completed
Anthesis
60 10.51 11.4 Beginning of anthesis
65 - 11.5 Anthesis 1/2 completed
69 - 11.6 Anthesis completed
Milk Development
70 - - -----
71 10.54 12.1 Kernel watery-ripe
73 - 13.0 Early milk
75 11.1 - Medium milk
77 - - Late milk
Dough Development
80 - - -----
83 - 14.0 Early dough
85 11.2 - Soft dough
87 - 15.0 Hard dough
Ripening
90 - - -----
91 11.3 - Kernel hard (difficult to divide by thumbnail)
92 11.4 16.0 Kernel hard (can no longer be dented by thumbnail)
93 - - Kernel loosening in daytime
94 - - Overripe, straw dead and collapsing
95 - - Seed dormant
96 - - Viable seed giving 50% germination
97 - - Seed not dormant
98 - - Secondary dormancy induced
99 - - Secondary dormancy lost

How to Select Plants

 
Characteristic Barley Wheat Wild oat
ligule membranous membranous membranous
auricles short and hairy long, clasping without hair absent
blades and collars usually hairy without hair long hair on margins
sheaths usually hairy without hair usually without hair
blade twist clockwise clockwise counter-clockwise

Staging Plants

Locate the first leaf

The first leaf:

  • Is the lowest leaf and has a blunt tip.
  • May be dead or missing. Look for leaf and sheath remnants at the crown.
  • Sheath encloses all later leaves.
  • Arises on the opposite side of the plant as the coleoptilar tiller (if present) and the remnants of the coleoptile.

Position the plant.

Hold plant so that the first leaf points to your left and carefully fan-out the leaves and tillers. Follow this procedure for consistent results in staging.

Locate the main shoot or stem.

The main shoot or stem is usually the tallest and has the most leaves. Count the leaves on the main shoot or stem. Leaves arise on opposite sides of the main shoot or stem. Count the youngest leaf when it is at least one-half the length of the leaf below it when using the Feekes or Zadoks scale. However, when using the Haun scale, count the youngest leaf as a fraction of its length relative to the length of the leaf below it. Dead or missing leaves must be counted. Look for leaf and sheath remnants at the crown.

Count the tillers.

Each tiller has its own sheath called a prophyll belong to the main shoot or to other tillers. Secondary and tertiary tillers also may be formed, so more than one tiller may emerge from each leaf axil of the main shoot. Tillers that emerge after the fifth leaf has emerged are not likely to produce heads and need not be counted.

Count the nodes.

Nodes can easily be seen or felt on the stem above ground level. If no nodes are detected above ground, split the main shoot lengthwise to determine if stem elongation has begun. The elongating internode is hollow between the crown and the elevated growing point. In solid stem varieties the internode is not hollow but nodes are still easily identified.

Has the flag leaf emerged?

The flag leaf emerges after at least three nodes are present above the soil surface. To confirm flag leaf emergence, split the leaf sheath above the highest node. If the developing head and no additional leaves are contained inside, then the last leaf emerged was the flag leaf.

Has boot stage begun?

Boot stage in the Zadoks scale begins following emergence of the flag leaf collar and continues until heading. In the Feekes and Haun scales, boot stage follows flat leaf extension and continues until heading.

Has head emergence and flowering occurred?

Heading begins when the first awns become visible through the flag leaf collar. Examine florets to determine if flowering has occurred. Most barley varieties flower prior to head emergence while most wheat varieties flower following head emergence.

Determine grain development stage.

Grain development stages include watery ripe, milk, soft dough, hard dough, kernel hard and harvest ripe.

Helpful Hints

All normal small grain plants follow the same general pattern of development. But the specific time interval between stages, the number of leaves and nodes on the main stem and number of tillers may very due to varieties, season, planting dates and locations.

For example:

  • An early-maturing variety may progress through some development stages at a faster rate than a late-mature variety.
  • The rate of development for any variety is directly related to temperature (accumulated heat units), except under extremely dry conditions.
  • The amount of grown (leaf size, number of tillers, etc.) for any variety is directly related to nutrient and moisture availability.

Small Grain Growth Stages and Management

Germination and Emergence

Under adequate growing conditions, the planted seed absorbs water and growth begins. Metabolic activity within the seed rises sharply when seed water concentration approaches 45 to 49 percent. A root called the radicle is the first plant part to emerge from the swollen seed. It elongates downward, anchors in the soil and absorbs water and nutrients. The radicle and four to five later-emerging lateral seminal roots comprise the primary root system. Following radicle emergence, the coleoptile emerges from the seed and elongates until the tip breaks the soil surface, where elongation is terminated in response to light. The coleoptile is a leaf sheath that encloses and protects the embryonic plant.

In wheat and barley, the coleoptile develops from the second or the third node on the plant. Since these nodes are normally located in the seed and their internodes do not elongate, the coleoptile originates from the level of seed. The internode between the coleoptilar node and the next higher node, often called the subcrown internode, has the ability to elongate and position the crown within one inch of the soil surface. At planting depths to one inch this internode will not elongate but at deeper planting depths it may elongate up to four inches if necessary. At planting depths greater than three inches the next higher internode may also elongate. A plant is judged completely emerged when 50 percent of the first leaf has emerged from the coleoptile and begins expanding above the soil surface.

Several nodes, separated by internodes that do not elongate, from the crown. Leaves, tillers and roots develop from the crown nodes. The node that bears the first leaf is designated node 1; the second leaf is node 2; and so on. The coleoptilar node is node 0 and the two nodes in the seed are designated negative numbers, such as -1,-2, etc. Crown depth is determined by variety, planting depth and the extent of internode elongation. The growing point is located at the crown until it is elevated by stem elongation.

Leaf and Tiller Development

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A new leaf is counted when it is one-half the length of the leaf below it when using the Feekes of Zadoks scale. When using the Haun scale the development stage of the youngest leaf is based on its length relative to the length of the leaf below it. Great care must be exercised when staging plants with more than five leaves because lower leaves die and are sloughed off the stem. Dead, dying or missing leaves must be counted. Look for leaf and sheath remnants at the crown.

When the seedling has about three leaves, tillers usually begin to emerge. Ability of plants to tiller is an important method of adapting to changing environmental conditions. When environmental conditions are favorable or if the plant density is reduced, compensation is possible by producing more tillers. Under typical cultural conditions, tillers emerge during about a 2-week span with the total number formed depending on the variety and environmental conditions. Deep seeding and high seeding rates usually decrease the number of tillers formed per plant. There may be more tillers formed when early season temperatures are low, when the plant population is low, or when the soil nitrogen level is high. Some tillers initiate roots, contributing to the nodal root system. About four weeks following crop emergence, some of the previously formed tillers begin to die without forming a head. The extent to which this premature tiller death occurs varies depending on the environmental conditions and the variety. Under poor or stressed growing conditions, plants respond by forming fewer tillers or by displaying more premature tiller death.

A tiller may form a bud located at the coleoptilar node (coleoptilar tiller) and at each crown node (axillary tillers). The coleoptilar tiller can emerge at any time, independent of the number of leaves on the main stem. Axillary tillers usually begin to emerge when the plant has three leaves. Rarely are more than five axillary tillers formed on a plant.

Tillers are identified numerically based on the leaf and node from which they arise. The coleoptilar tiller, tiller 0, emerges from the axil of the coleoptile; tiller one, from the first leaf axil and so on. Tiller leaves emerge from a sheath, called the prophyll, which can later be found enclosing the base of the tiller. The prophyll can be used to identify tiller leaves from those on the main stem or other tillers.

Secondary tillers may arise from the prophyll node and leaf nodes of the primary tillers. In the same manner, tertiary tillers may occasionally be produced by secondary tillers. The primary tillers are usually the tallest of the tillers that emerge from a leaf axil. Leaves on primary tillers are positioned at right angles to the main stem leaves.

Tillering capacity is a varietal trait and a physiological means of adapting to changing environmental conditions. More tillers may be produced when environmental conditions are favorable, plant populations are low, or soil fertility levels are high. Under stress, plants respond by producing fewer tillers or by aborting initiated tillers.

Tillers are counted as soon as they emerge above the soil surface or the leaf axil. The contribution of each tiller to final yield is directly related to the development stage achieved when reproductive development is initiated. Late developing tillers contribute little to overall yield. Tillers that emerge after the fifth main shoot leaf are likely to abort or not produce heads.

Adventitious Root Development

The adventitious or secondary root system is composed of roots that arise from the crown nodes of the main shoot and tillers. Two or more adventitious roots are generally formed at each crown node. Each tiller may produce its own adventitious root system as does the main stem, except that a single root instead of a pair is usually reduced at each node. The plant gradually becomes more dependent upon the adventitious root system as it develops to become the predominant root mass.

Generally, by flowering, the root system is fully established. The adventitious root system of spring wheat eventually becomes a profuse mass of fibrous roots, which may penetrate the soil to a depth of three to four feet. Winter grains and spring barley are generally deeper rooted than spring wheat. Degree of branching and depth of penetration depend upon variety, type and depth of soil, soil compaction, water, aeration and fertility level.

Wild Oat Development

Wild oat is ranked as the worst weed problem by wheat and barley producers in many western states. Wild oat infests more than 28 million acres of small grain in the United States resulting in an estimated annual yield loss and prediction cost of $304 million (WSSA Wild Oat Situation Report-1976.). Wheat and barley yields are sharply affected by wild oat infestations. Ten wild oat plants per square feet can reduce spring barley grain yield by 10 to 30 percent, depending on production practices and environmental conditions. Winter wheat usually is more competitive against wild oat than spring barley. Spring wheat is less competitive against wild oat compared to spring barley.

Wild oat develop in a similar manner to wheat and barley with the exception of the positioning of the coleoptilar node during seedling emergence. In wild oat, the internode below the coleoptilar node elongates to elevate the shoot to within one inch of the soil surface where the crown will form. The coleoptilar node is the lowest-positioned crown node.

Wild oat susceptibility to post-emergence herbicides is influenced by development stage. Tillers begin to emerge during the application time period for most wild oat herbicides. The wild oat stage scales presented on product labels do not distinguish between leaves and tillers which confuses product selection and application timing decisions. To determine the proper time to apply the herbicide, some product labels count tillers as leaves while other labels count only leaves and do not consider tillers.

Head Initiation

Plant interactions with temperature and day length prompt the transition from vegetative to reproductive stages. Reproductive development of true winter varieties is initiated by vernalization during exposure to cool temperatures for a required length of time. Temperatures between 32 and 50F induce cold hardening and satisfy vernalization requirements. The required period of low temperature exposure varies with variety and decreases with lower temperatures and advancing plant development. In addition to vernalization, exposure to progressively longer day length periods is necessary to initiate reproductive development. Spring varieties do not possess an absolute vernalization requirement. Reproductive development in most spring varieties is triggered by light and accumulative heat units (growing degree days).

The head or spike is initiated on each tiller during the fourth-leaf stage and before stem elongation begins. The maximum number of kernels that may mature on each head is determined by the number of florets that are initiated. Florets are first initiated in the middle portion of the microscopic head and then outward toward the ends. Stress conditions may cause florets to abort in the reverse order in which they were initiated, resulting in empty or sterile florets at the ends of the head. Once head formation is complete, stem elongation elevates the terminal growing point of each tiller upwards within the leaf sheaths.

Stem Elongation

Stem elongation or jointing occurs as a result of internode elongation. Usually a plant has about five to six leaves on the main shoot when internode elongation first begins. Throughout development, the lower four nodes remain in the crown. The fifth node may remain in the crown or be elevated slightly and nodes six and seven are generally elevated above the soil. The elongating internode is hallow between the crown and the elevated growing point, except in solid stem varieties. Rapid stem or internode elongation brings the developing head above the soil surface. Each elongation internode becomes progressively longer and eventually leads to head emergence.

Stems can be split with a knife to determine if a plant is in early stem elongation stage. As the internodes elongate, the nodes become visually detectable on the stem and are easily counted. The mature stem of most wheat and barley varieties has form three to four visible nodes.

The peduncle, the last elongated internode which supports the head, accounts for a good proportion of the overall stem length. Height is genetically determined but is subject to environmental influence. Certain growth regulators reduce plant height and increase lodging resistance. Their application is timed to inhibit peduncle elongation.

The period of rapid head growth in which individual florets become ready for pollination and fertilization, parallels stem elongation. Tiller development is in synchronization with the main stem so that tillers flower soon after the main stem.

Flag Leaf

The flag leaf is the last leaf to emerge before the head. It begins to emerge just after the third above-ground node is observed of most varieties. The flag leaf contributes 75 percent or more of the photosynthate needed for maximum grain yield. Flag leaf emergence is a visual indicator that the plant will soon be in the boot stage.

Boot Swollen

Following flag leaf development, the flag leaf sheath and the peduncle elongate and the developing head is pushed up through the flag leaf sheath. The leaf sheath swells to form the boot as the head continues to develop. The boot stage is complete when the awns (or the head in awnless varieties) become visible at the flag leaf collar and the sheath is forced open by the developing head.

Pollination usually takes place in barley just before or during head emergence from the boot. Pollination begins in the central portion of the head and proceeds toward the tip and base. Since pollen formation is sensitive to stress, water deficits and high temperatures at this time will decrease the number of kernels that form and may reduce yields. These yield reductions can be diminished by planting early so that pollination and early grain filling is completed before late season stresses occur.

Head Emergence and Flowering

Heading occurs as the peduncle continues elongation and pushes the head out of the flag leaf collar. Flowering (pollination) may occur either before or after head emergence depending on plant species and variety. Pollen formation and pollination are very sensitive to environmental conditions.

Cereals are classified as either open-flowering or closed-flowering types. Flowering usually occurs in closed-flowering varieties prior to head emergence and in open-flowering varieties shortly after head emergence. Many winter barley varieties are open-flowering whereas spring barley varieties are usually closed-flowering. Most varieties of wheat are of the open-flowering type.

Flowering in open varieties is usually observed by anther extraction from each floret, although this may not occur under stress conditions. In closed-flowering types, the anthers remain inside each floret. If the anthers within a floret are yellow or gray, rather than green, it is reasonably certain that flowering has occurred.

Generally, flowering in wheat begins within three or four days after head emergence, while flowering in barley usually occurs just before or during head emergence. Flowering begins from about the middle section of the main stem head and progress to the top and bottom of the head. All heads of a plant flower within a few days. Within a few hours of pollination, the embryo and endosperm begin to form.

Grain Development Stages

Watery Ripe Stage

During the watery ripe stage, kernel length and width are established and the kernel rapidly increases in size, but does not accumulate much dry matter. A clear fluid can be squeezed from the developing kernel. The plant is green, but the lower leaves begin to die.

Milk Stage

During the milk stage a white, milk like-fluid can be squeezed from the developing kernel. By the end of milk stage the embryo is fully formed and about 1/32 inch in length. During the course of this stage, nutrients stored in lower leaves are redistributed to the upper plant, including the developing kernels, causing several of the bottom leaves to die.

Soft Dough Stage

The water concentration of the kernel has decreased to the point where the material pressed out of the kernel is no longer a liquid but has the consistency of meal or dough. The kernel rapidly accumulates starch and nutrients and by the end of this stage the green color begins to fade. Most of the kernel dry weight is accumulated in this stage. In barley, the palea and lemma become firmly adhered to the kernel. Once kernel water concentration decreases to about 75 percent, swathing of spring wheat can begin without reducing yield, test weight, or protein level.

Hard dough stage

The kernel reaches physiological maturity at the end of this stage. At physiological maturity, the glumes and peduncle are no longer green and little green coloring remains in the plant. Kernel water concentration decreases from a level of 40 to 30 percent. The main reductions in yield beyond this stage result from harvest losses, and environmental injuries, such as hail and sprouting.

Kernel Hard Stage

The plant has become completely yellow and the kernel has become firm. The kernel is difficult to physically divide by thumbnail but the surface of the grain can be dented with the edge of the thumbnail. Kernel water concentration is 20 to 25 percent. Unless drying facilities are available, the crop must be swathed and windowed at this stage because the grain water concentration is too high for safe storage.

Harvest Ripe Storage

The plant has become dry and brittle and the kernel is hard. The kernel cannot be crushed between thumbnails and is difficult to dent its surface with the edge of the thumbnail. If the kernel is crushed by other means, it fragments. When the kernel water concentration has decreased to 13 to 14 percent the grain is ready for direct combining and storage.

Dry Matter Accumulation

Dry matter accumulation in the aerial parts of wheat and barley change with plant development stage. From emergence to about the two-leaf stage, all of the aerial dry matter is in leaves. From that stage forward, dry matter begins accumulating rapidly in the stems. The developing head, which is initiated at about the four-leaf stage, is regarded as part of the stem until heading. By the flag-leaf stage about 30 percent of the total aerial dry matter is accumulated and it is almost equally distributed between leaves and stems. About 55 percent of the total aerial dry matter is accumulated by the time the heads are completely emerged. Dry matter accumulation in the stems declines after heading and all additional dry matter is accumulated in the kernels. By kernel hard stage dry matter is distributed essentially between stems and heads.

Adverse environmental conditions during any of the growth periods of a kernel can reduce the rate of dry matter accumulation and decrease yield. As a rule, the longer the adverse condition lasts, and the earlier it occurs during grain filling, the greater its effect on yield.

Leaf area establishment and duration

Since photosynthesis provides energy for growth and dry matter for yield, it is important that leaf area be established rapidly and protected throughout the growing season. Early in the plant's growth, the leaf blades are the major photosynthetic organs. The rate of leaf area establishment depends on temperature, but can be increased by high nitrogen fertilization and seeding rates. The duration of leaf function is also important for maximum grain yield. The maximum leaf area is usually reached about heading, then declines during grain growth when the demand is great for photosynthate (products of photosynthesis). As the lower leaves die, the upper leaf blades, leaf sheaths, and heads become very important as photosynthetic sources for grain filling. For maximum yields, the last two leaf blades and sheaths, as well as the head and awns, are particularly important. Barley also has a limited capacity to mobilize substances that were produced and stored earlier in the growing season if conditions reduce the capacity of the plants to produce current photosynthate.

Glossary of Terms

Adventitious roots - Roots produced by crown nodes on the main shoot and tillers.

Anther - The reproductive portion of a flower which produces and releases the pollen.

Anthesis - The time of flowering or pollination.

Auricles - A pair of claw-like projections at the junction of the sheath and blade.

Axillary tillers - The tillers that emerge from the leaf axils.

Blade - The flat expanded portion of a leaf.

Coleoptile - The leaf sheath which surrounds and protects the embryonic plant as it emerges from the seed.

Coleoptilar tiller - The tiller that emerges from the coleoptilar node.

Collar - The junction of the leaf blade and leaf sheath.

Crown - Several nodes whose internodes do not elongate.

Endosperm - The area of starch and protein storage in the kernel.

Floret - The flower contained in the spikelet.

Glumes - The husk of the spikelet.

Growing point - The plant part where differentiation of leaves, tillers and the head occurs.

Internode - The region between two successive nodes.

Leaf axil - The junction of the leaf with the main stem.

Lemma - The outer, lower bract enclosing the flower in a spikelet.

Ligule - A short membrane or row of hairs of the inside of the leaf at the junction of the blade and sheath.

Nodes - The area of active cell division from which leaves, tillers and adventitious roots arise.

Palea - The inner, upper bract enclosing the flower in a spikelet.

Peduncle - The last elongated internode which supports the head.

Photosynthate - The products of photosynthesis.

Plant Growth Regulator - A chemical used to inhibit peduncle elongation and increase lodging resistance.

Pollen - The powder-like matter produced by the anthers which functions as the male element in pollination.

Pollination - Fertilization of the embryo by pollen.

Primary tiller - A tiller produced by a node on the main stem.

Prophyll - The sheath which encloses the base of a tiller.

Radicle - The first root to emerge from the seed.

Secondary tiller - A tiller produced by a primary tiller.

Seminal roots - The roots originating from the seed.

Sheath - The tubular portion of a grass leaf that encloses the stem.

Spikelet - Subdivision of the head.

Subcrown Internode - The internode between the coleoptilar node and the next higher node which elongates to position the crown within one inch of the soil surface in wheat and barley.

Tertiary tiller - A tiller produced by a secondary tiller.

Tiller - A shoot that arises from buds at the base of a plant.

Vernalization - Plants must be subjected to low temperatures for a period of time before they enter the reproductive stages of development.

References

Anderson, P.M., E.A. Oelke, and S.R. Simmons. 1985. Growth and Development Guide for Spring Barley . University of Minnesota Agricultural Extension Folder AG-FO-2548.

Anderson, P. M., E.A. Oelke, and S.R. Simmons. 1985. Growth and Development Guide for Spring Wheat . University of Minnesota Agricultural Extension Folder AG-FO-2547

Bauer, A., C.V. Eberlein, J.W. Enz, and C. Fanning. 1984. Use of Growing-Degree Days to Determine Spring Wheat Growth Stages. North Dakota State University Extension Bulletin 37.

Bauer, A., C. Fanning, J. W. Enz and C. V. Eberlein. 1994. USE OF THE GROWING-DEGREE DAYS TO DETERMINE SPRING WHEAT GROWTH STAGES. North Dakota Coop. Ext. Ser. EB-37. Fargo, N.D.

Bauer, A., A. B. Frank and A. L. Black. 1984. ESTIMATION OF SPRING WHEAT LEAF GROWTH RATES AND ANTHESIS FROM AIR TEMPERATURE. Agron. J. 76:829-835.

Bauer, A., A. B. Frank and A. L. Black. 1987. AERIAL PARTS OF HARD RED SPRING WHEAT. I. DRY MATTER DISTRIBUTION BY PLANT DEVELOPMENT STAGE. Agron. J. 79:845-852.

Bauer, A., D. Smika and A. Black. 1983. CORRELATION OF FIVE WHEAT GROWTH STAGE SCALES USED IN THE GREAT PLAINS. AAT-NC-7. Agricultural Research Service USDA.

Briggs, D. E. 1978. BARLEY. Chapman & Hall, London.

Dyer, W., P. Fay, P. Rardon and V. Stewart . 1983. THE WILD OAT STAGING CARD. Montana Agricultural Experiment Station Capsule Information Series Number 30.

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