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WHAT IS LAYERING?A method of asexual propagation in which roots are formed on a stem or root while it is still attached to the parent plant. The stem or root which is rooted is called a layer.
CONTD…In Layering method of plant propagation, rootsare produced on an aerial plant parts likestem/branches.Rooted layer is then detached and planted asan independent plant. Layering method has a high success rate andproduces large number of plants. It as animportant method of propagation in fruit crops.
METHODS OF LAYERING: Simple or Tongue layering Compound or Serpentine layering Mound or Stool layering Air or Goottee layering Trench or continuous layering Tip Layering Herbaceous layering
SIMPLE OR TONGUE LAYERINGA growing branch of fruit trees is given a tongue shaped upward cut and bent to the ground. Cut portion of the branch is buried in soil, leaving the terminal branch exposed in air. Rooting takes place at the wounded part of branch after which the layer is separated from mother plant using sharp knife. e.g. Guava.
COMPOUND OR SERPENTINE LAYERING Compound layering is similar to simple layering except that the branch is alternately buried in soil / growing media and exposed along its length. Stem / Branch to be operated for compound layering must be longer and flexible to be layered at different locations. Creepers, Climbers and Vines like Grapes, Clematis, Wisteria, etc. can be propagated by Serpentine method of layering.
MOUND OR STOOL LAYERING Plant stems are cut back at the ground level during the dormant season and allow them to sprout new shoots. Circular ring of bark is removed from the tender shoots and the wound is treated with plant growth regulator like Indol Butyric Acid ( IBA). Wound on shoot is buried in mound of soil. Injured part of shoot develops roots and are separated from mother plant. e.g. Apple
AIR OR GOOTTEE LAYERING• Air layering is method of root formation on aerial plant parts / shoots.• Circular bark on branch is removed and rooting medium like sphagnum moss is tied on branch.• Roots initiate on the upper side of the wound where Sphagnum moss supply moisture till root initiation. e.g. Pomegranate
TRENCH OR CONTINUOUS LAYERING Selected branch of plant is bent in a shallow trench in horizontal position and shoots are covered in soil for rooting. Rooted layers are separated from mother plants and planted in a nursery. Trench layering is successful in woody fruit crop species like Apple, Pear, Cherry etc.
TIP LAYERING• In tip layering, rooting takes place near the tip of current season growth. Shoot tips are buried 2 to 5 cm deep in soil.• These shoot tips grow upward to produce a bend in the stem and roots initiate at the curve of stem.• Rooted tips are separated from the mother plant and maintain in nursery or planted in field. e.g. Blackberries, Raspberries.
HERBACEOUS LAYERING In herbaceous layering, very young shoots of plants are used for producing new plants. In this layering first of all sandy compost is placed around the plant to be layered. Young shoots are selected and their lower leaves are removed. Now a slit near the base about halfway through the stem and in an upward direction is made. The stem is then bent so as to open the slit and at this point is pegged down firmly into the soil and covered with an inch or so with compost. The layer will root by autumn and then be severed and potted or planted in the nursery. Ex. Carnation.
NATURAL FORMS OF LAYERING Sometimes layering occurs naturally, without the assistance of a propagator. Runners and offsets are specialized plant structures that facilitate propagation by layering. A runner produces new shoots where it touches the growing medium. Plants that produce stolons or runners are propagated by severing the new plants from their parent stems. Plantlets at the tips of runners may be rooted while still attached to the parent or detached and placed in a rooting medium. Examples- strawberry and spider plant.
PHYSIOLOGY OF LAYERING The physical attachment of the stem to the plant during rooting allows for a continual supply of water, minerals, carbohydrates, and hormones through the intact xylem and phloem to the rooting area. Accumulation of photosynthates and hormones in the rooting area is an important factor in the rooting is an important factor in the success of root initiation observed during layering. This can be promoted by girdling, incision, or bending of the stem.
CONTD… Light exclusion in the rooting zone is another aspect of the success with hard to root clones. The greatest stimulus to root induction during layering occurs when the growing shoots are progressively covered by the rooting medium as they develop to produce etiolation. Root initiation and development on stems during layering is associated with seasonal patterns. In most cases, layering is started in the spring with the dormant hardwood shoots.
ADVANTAGES OF LAYERING Easy to perform and does not require much facility. Effective means of propagating species that usually do not root easily by cutting. It does not require precise control on water, relative humidity or temp. as require for other methods. It is possible to produce large sized plant with layering in short time. Layering is useful for producing relatively smaller no. of plants of good size with minimum propagation facilities.
DISADVANTAGES OF LAYERING It is not possible to produce large no. of plants with in short time. It is costlier techniques in areas where labour availability is a problem. The plants produced through layering usually have brittle roots. The beneficial effect of root stock on the cultivar can’t be exploited. The mortality rate is usually high in layers.eg- air layering.
FACTOR’S AFFECTS LAYERING1. Nutrition2. Stem treatment3. Etiolation treatment4. Physiological condition of mother plant5. Rejuvenation of the stock plant6. Treatment with growth regulators7. The environmental conditions