Where It Can Be Grown What Is the Premier Species for Athletic Fields
Turfgrasses are narrow-leaved grass species that class a uniform, long-lived footing cover that can tolerate traffic and low mowing heights (ordinarily two inches or below). Only a few grass species produce adequate turf in the northern U.Due south. These grasses are referred to as the cool-season turfgrasses. (Warm-season turfgrasses include species that are all-time adapted to southern areas of the U.S. and are not discussed in this publication.)
Introduction
The study of cool-season turfgrasses begins with learning the basic structures of grass plants and how they develop from seed to mature plants. Once you understand how turfgrasses abound and develop, it is easier run across how they function equally long-lived communities and how they tolerate traffic, mowing, and other problems.
The Basic Structures of Grass Plants
A mature, unmowed grass plant is equanimous of leaves, roots, stems, and a seed head. The diagram of a grass institute in Fig. 1 shows these bones structures. Go on in mind that some grass species do not take all the structures shown and that mowed grasses typically lack flower stems and seed heads.
Figure i. Diagram of a mature grass plant
Leaves
A grass leaf is divided into 3 parts: the blade, sheath, and neckband region (Fig. two). The blade is long and narrow and grows more or less horizontally away from the main shoot. The sheath is the portion of the leaf that envelopes the shoot or stem. The collar region is located where the blade and sheath meet and may or may non have structures called the collar, ligule, and auricle (Fig. 3). The shine surface area on the back side of the leaf where the blade and sheath meet is the collar. It is usually a lighter colour than the blade and may go on across the width of the leaf or exist divided in half by a large mid vein. A ligule is a thin piece of tissue that extends merely higher up the summit of the leafage sheath and can vary in size and shape. An auricle is some other pocket-size piece of leaf tissue that grows from the collar and can also vary in size and shape.
Figure 2. Diagram of a grass leaf, including blade, neckband region, and sheath.
Figure iii. The collar region of a grass leaf with ligule and auricle.
Roots
Roots: Roots are the below-basis role of a grass plant that ballast it in the soil and take-upward water and nutrients. Turfgrass roots are fibrous, branching, and very slender. There are two types of root systems in grasses, the primary and the secondary. The difference between the 2 volition be explained after in this section.
Stems
Three types of stems occur in grasses; the crown, horizontal stems (rhizomes and stolons), and the bloom stem. Although the crown is a stem, it does not look like the other stem types constitute in grasses. It is very pocket-sized (only a fraction of an inch long), white, and completely enclosed by leaf sheaths. The crown is located in a protected position between the roots and shoot near the soil surface.
Horizontal stems begin to course in the crown and develop into rhizomes or stolons. Rhizomes grow below ground for a curt altitude, so ascent to the soil surface to form new shoots. In some grass species, rhizomes produce growing points (often referred to as nodes) which give rise to roots and shoots forming new or 'girl' plants. Rhizomes are unremarkably white. Stolons abound above-ground and form nodes which give rise to new plants. Stolons are light-green and can creep over other grasses and bare spots in lawns, oft forming round patches.
Flower stems are also formed in the crown, normally in tardily spring or early on summer in nearly absurd-season grasses. Typically, they are not seen in turf since they are mowed off before they accomplish maturity. On unmowed grass, flower stems grow vertically and give rise to seed heads.
Seed Heads
The seed head is the flowering part of the grass found. The basic unit of the seed head is called the spikelet. A spikelet is made up of grass flowers, the small stalks that support them, and bracts (small, papery leaves that encompass the flowers) (Fig. four). There are three types of seed heads based on the arrangement of the spikelets; panicle, spike, and raceme (Fig. 5). In the panicle type, the spikelets are borne on branches that are arranged along the central or main stem. The chief stalk is basically an extension of the flower stalk. Kentucky bluegrass is a turfgrass with a panicle-type seed head. The spike-type seed head has spikelets that are borne directly on the primary stem. Perennial ryegrass is a turfgrass with a fasten-type seed head. In the raceme type, spikelets are borne on very curt branches along a main stem. Truthful raceme seed heads are rare in grasses and none of the cool-flavour turfgrasses produce them. Crabgrass, a common annual grass weed, has a modified spike-like raceme.
Figure 4. A spikelet, the basic unit of the seed heads.
Figure five. Three types of turfgrass seed heads; panicle, fasten, and receme.
Growth and Evolution
Grass Seed and Seed Germination
The 'seed' of grass is really a dried fruit called a caryopsis (Fig. 6). The caryopsis is fabricated-up mainly of the embryo and endosperm. The embryo contains the beginnings of the leaves, growing points, and roots of the grass plant. The endosperm makes up the bulk of the caryopsis and contains the food (primarily starch) required by the developing plant every bit it germinates and grows. The unabridged caryopsis is surrounded by the pericarp, sometimes referred to equally the ovary wall (Fig. seven). The caryopsis and pericarp are enclosed by two papery structures called the lemma and palea.
The basic requirements for germination of turfgrass seed are adequate moisture, favorable temperatures, and oxygen. The starting time step in seed germination is absorption of h2o (sometimes referred to equally imbibition). The charge per unit at which grass seed absorbs h2o depends on the amount of water present and the permeability of the seed. As water is absorbed, the seed swells. Shortly thereafter, enzymes produced by the embryo intermission downwards the endosperm and convert the starch into carbohydrates. Carbohydrates can be used directly by the embryo and developing bulb for energy and growth.
Effigy half-dozen. Diagram of grass seed.
Figure 7. Cross-section of caryopsis including the embryo, endosperm, and pericarp.
| Species | Temperatures (°F) |
|---|---|
| Kentucky bluegrass | 59 - 86 |
| Crude bluegrass | 68 - 86 |
| Chewings fescue | 69 - 77 |
| Creeping red fescue | 59 - 77 |
| Sheep fescue | 59 - 77 |
| Tall fescue | 68 - 86 |
| Perennial ryegrass | 68 - 86 |
| Annual ryegrass | 68 - 86 |
The first evidence that the seed has germinated occurs when the embryonic root or radicle breaks through the seed coat (Fig. 8). Soon after, the get-go leafage emerges from the seed. At this bespeak germination has occurred and the found is considered a bulb.
Figure 8. Germinating grass seed with radicle and first leaf breaking through seed coat.
Leafage Growth and Development
The first truthful leaf to emerge from the seed during germination is enclosed within a protective structure called the coleoptile. Soon after germination, the coleoptile and first leaf begin to elongate and abound towards the soil surface. The coleoptile stops growing just afterwards information technology reaches the soil surface, just the leaf continues to elongate and breaks through the coleoptile sheath (Fig. 9). As the leaf expands and elongates it begins to produce its own food through a process called photosynthesis. Soon later on the first leaf emerges, the developing seedling produces a second leaf from the growing signal or node enclosed in the coleoptile. All succeeding leaves follow the same route -- emerging from the growing signal and growing upward within the folds of the older leaves. Eventually, the coleoptile withers away and is no longer visible.
Figure 9. Turfgrass seedling
The growing point that gives rise to leaves on mature turfgrass plants is at the tip of the crown and is called the stalk apex. This construction looks like a small dome with ridges rise alternately from each side (Fig. 10). These ridges are the ancestry of the new leaves. As a leaf begins to develop, it encloses the entire stem noon. This foliage continues to elongate and expand and somewhen forms a fully-developed leafage with a blade, sheath, and collar region. The fact that grass leaves begin to grow from the stem apex located at the base of operations of the plant is the main reason why grass tin be mowed without sustaining serious injury. Growth continues from the base of operations of the leafage after a portion of the leaf blade is mowed off.
Figure ten. Stem apex of grass plant. The ridges are the starting time of new leaves. As a leaf begins to develop, it encloses the stalk apex.
New leaves are produced from other ridges on the stem apex and emerge from the folds of the older leaves. Thus, the oldest leaves are on the outside of the plant and the youngest are located in the middle of the plant. Turfgrass leaves alive for a period of time then die and are replaced past new ones. Under favorable environmental weather condition, the number of leaves per found remains the same equally new leaves replace those that die.
The rate of leaf growth is dependent on many factors including temperature, moisture, nutrition, and to some extent, daylength. Optimum temperatures for leaf growth among the cool-flavor turfgrasses range from threescore° to 75°F. Leaf growth increases with increasing daylength as long as temperatures are inside the optimum range and wet is adequate. Application of nitrogen fertilizer tin can greatly increase leaf growth if moisture and temperature are not limiting.
Root Growth and Evolution
Soon after the radicle emerges from the seed, the starting time true roots develop from the embryo. These roots are called primary roots and begin taking-upward water and nutrients from the soil when they are fully adult. Although the primary roots proceed to function for up to a year afterward germination, water and nutrient uptake is gradually taken over by the secondary roots (sometimes referred to equally accidental roots) which become more than numerous equally the grass constitute matures. Secondary roots are produced from nodes in the crown or from nodes on horizontal stems.
Turfgrass roots are very unlike from leaves and stems (Fig. xi). The growing point or meristem is located at the tip of the root. This is where all new root cells are produced. The meristem is protected from the annoying effects of the soil by a structure chosen the root cap. In the surface area but behind the meristem, new cells grow generally in length. This expanse is called the region of prison cell elongation. Behind the region of cell elongation, cells begin to develop into tissues that absorb water and nutrients. Amidst these tissues are root hairs -- tiny hair-like outgrowths that grow from the root surface into the surrounding soil. The primary role of root hairs is h2o and food uptake. Root hairs number in the billions for a fully-developed root arrangement and tin can greatly increment the corporeality of soil the roots contact. Water and nutrients are transported from root hairs to the interior of the root where special conducting tissues move water and nutrients to the leaves and shoots.
Figure 11. Diagram of the root tip including meristem, root cap, region of cell elongation, and root hairs.
Turfgrass root growth is affected mainly past soil temperature, moisture, and oxygen. The optimum temperatures for root growth of cool-season grasses are lower than those for shoot growth. Although the optimum temperature range for rooting differs somewhat among turfgrass species, near cool-season turfgrasses produce the all-time root growth at soil temperatures between fifty° and 65°F. When temperatures attain 90°F in the surface inch of soil, Kentucky bluegrass root growth is profoundly reduced. Roots of cool-flavor grasses can grow at soil temperatures below fifty°F, only growth slows dramatically as temperatures arroyo freezing (32°F). Root growth is greatest for absurd-season grasses during spring and fall and much reduced during the summertime and winter months.
Turfgrasses take-upward water from the soil through their root system. The amount of water the roots absorb will depend primarily on the number of roots, the depth of rooting, and the amount of water in the soil. Since the rooting depth of cool-season grasses is usually between two and half dozen inches, near h2o absorption initially occurs most the soil surface. As the surface water is depleted, roots begin using upwardly water deeper in the soil. A well-developed and actively-growing root system can take reward of this deeper soil moisture as surface moisture is depleted in dry periods. Reverse to pop belief, roots practise not 'seek out' water, instead they abound more vigorously and proliferate where water is bachelor.
Turfgrass roots need an acceptable supply of oxygen for normal growth and evolution. Severely compacted soils take limited supplies of oxygen and will non support good root growth fifty-fifty when favorable temperatures and moisture levels are present. As well much h2o will as well deplete the soil of oxygen and crusade deterioration of turfgrass roots. Soils with loose, crumbly construction and good drainage are ideal for root growth and development.
Other factors that have an result on root growth and development are soil pH, fertilization practices, table salt concentrations, herbicides, diseases, and insects. These will exist discussed in other sections of this transmission.
Stem Development and Tillering
Of the iii stem types mentioned previously, the crown is the near important. It gives rise to leaves, secondary roots, and other stems. Considering new leaf growth occurs at the base of the establish, grass plants can tolerate mowing and some other types of minor injury to foliage blades. However, crowns can be damaged by mowers when blades are set besides low. When this happens, plants are severely damaged and new leaf growth is unlikely.
Since new secondary roots are produced from the crown, some of the existing root organisation can exist damaged without killing the constitute -- provided that the root-initiating portion of the crown is non injured. Sod producers routinely sever a portion of the grass root system with sod harvesters, so send the sod to a new location. The newly-laid sod generates a new root organisation from secondary roots formed in the crown.
Rhizomes and stolons begin to grow from nodes in the crown and suspension through the surrounding leaf sheaths to spread laterally. Rhizomes of Kentucky bluegrass and creeping cherry-red fescue grow beneath the soil surface and then turn up towards the soil surface to form new shoots (Fig. 12). Some other grasses (mostly warm-flavor grasses and weed grasses) accept long rhizomes that produce nodes that can branch and produce shoots and roots, forming new plants.
Figure 12. Rhizomes of Kentucky bluegrass
Rhizomes are a desirable trait in turfgrasses because they allow plants to send new shoots into areas that are thin or damaged past traffic, drought, and/or disease. Kentucky bluegrass is the premier sod grass in the northern U.S. because its rhizomes allow turf to 'knit' and hold together as the sod is cut, rolled, and lifted. Kentucky bluegrass is a desirable species for utilize in athletic fields because its rhizomes provide superior basis for athletes.
Stolons abound along the soil surface and can creep over established turf (Fig. 13). New shoots are produced from nodes or from tips of the stolon as it turns upwards. Although the stoloniferous cool-season turfgrasses, rough bluegrass and creeping bentgrass, are desirable for some applications, they can be very troublesome weeds if mixed with other lawn grasses since they course lite-colored, circular patches as they creep over the more desirable turfgrasses.
Figure 13. Stolons of creeping bentgrass
Tillers are shoots that develop from crown tissues and abound vertically within the sheaths that surround the crown (Fig. 14). Mature tillers produce leaves, stems, and root systems; thus, they can role independently of the mother plant. Tillers increment the shoot density of lawns past replacing shoots that dice in winter and summer. Individual tillers alive for about a yr and germination of new tillers is stimulated by cool temperatures, short daylengths, moderately low mowing heights, and high mowing frequencies. Acme tiller germination occurs in early spring and fall. Turfgrass stands are long-lived because dying shoots are constantly being replaced by new tillers. This process is so gradual that the transition is unnoticeable.
Figure 14. 2 tillers developing from the crown of a grass plant.
Carbohydrates -- The Real Plant Food
Backyard fertilizers are oftentimes marketed as 'establish food'. Although most people realize that nutrients from fertilizers are required past plants for proper growth and development, they may not realize that fertilizers are not actually institute nutrient. Plants make their own nutrient through photosynthesis, a chemical reaction in leaves involving water, carbon dioxide (COii ) and light energy. The stop products, carbohydrates, are used by plants for energy and growth and are the true institute food.
Carbohydrates can be stored in stem and crown tissues when they are made faster than they are used. Storage is greatest in fall and is benign since the plant needs carbohydrates for recovery from injury when turf is damaged by pests, drought, heat, and mower injury the following year. Depletion of carbohydrates is fastest in bound, especially under low mowing heights and loftier nitrogen fertility. If depleted besides quickly, the turf may go into the summer months in a weakened land. This is one reason why turfgrass professionals do not apply excess amounts of nitrogen and mow below optimum heights of cut in spring.
Prepared by Peter Landschoot, professor of turfgrass science
Source: https://extension.psu.edu/the-cool-season-turfgrasses-basic-structures-growth-and-development#:~:text=Kentucky%20bluegrass%20is%20the%20premier,provide%20superior%20footing%20for%20athletes.
0 Response to "Where It Can Be Grown What Is the Premier Species for Athletic Fields"
Publicar un comentario