Most of us are well aware of the use of ‘qalam,’ or stem cuttings, to propagate roses. This art of using stem cuttings for propagation extends beyond plants and shrubs to towering forest trees. The technique has been exploited in forestry since primitive times to obtain identical clones of any species. Theophrastus, the father of Botany who lived in Greece from 371 to 287 BC., while describing stem cuttings in olive tree also made a reference to the concept of juvenility and its relation to successful rooting of the cuttings.
Thomas Barnes in 1758 published his research on cutting propagation and the techniques that can lead to success of propagation. The widely cited book in research “Hartmann & Kester’s Plant Propagation: Principles and Practices” was first published in 1960. The book has a wide reference of the propagation technique through cuttings and the key factor that affects its success.
What is the science behind clonal propagation?
Hartmann and others describe clonal propagation as the art and science of multiplying plants and preserving their unique qualities by asexual means. Exact duplication of parent plant is possible because of two unique plant characteristic; totipotency and dedifferentiation. Totipotency refers to the ability of a single plant cell, particularly a vegetative cell, to carry all the genetic information necessary to regenerate an entire organism. This means that even a small section of the plant contains the blueprint to produce a complete, genetically identical plant.
Dedifferentiation is the process by which mature, specialized plant cells can revert to an undifferentiated, meristematic (growth) state, allowing them to form a new growing point. These undifferentiated cells, capable of rapid division, then develop into a complete plant structure. Together, the two processes allow the production of true-to-type plants with predictable traits. It also aids transfers non-additive genetic variance (traits beyond simple gene inheritance) to the next generation, offering greater genetic gain than sexual propagation.
How stem cuttings work?
Stem cutting propagation works by harnessing the natural regenerative abilities of a tree or a plant to induce adventitious root formation. Adventitious roots are the roots that form from non-root tissues. They are the plant’s normal response to stress or injury. Cutting is extracted from healthy branch of the parent tree ensuring it includes nodes.
Normally, the lower leaves are removed from cuttings to reduce transpiration and prevent rot, and focus energy on root development. The lower part of the cutting is deprived of water and nutrients that it normally receives from the roots. In response, the cells near the cut site, particularly around nodes and the cambium layer, dedifferentiate and proliferate to form a callus.
The callus, under the influence of rooting hormone auxin that is usually applied externally in liquid or powder form, develops root primordia that eventually grow into adventitious roots. The totipotency enables the production of a true-to-type copy of the parent tree. The cutting is placed in a moist, aerated medium to promote rooting. After 90 days or more, rooted cuttings are hardened outdoors before field planting.
Can all type of tree cuttings be used for propagation?
Stem cuttings are classified as hardwood, semi-hardwood, softwood and herbaceous. Hardwood cuttings are made from mature, lignified shoots after the leaves have fallen while semi-hardwood are made from stems that are partially hardened and woody, but not fully mature.
Softwood cuttings are made from soft, succulent new growth of woody plants, just as it begins to harden and herbaceous cutting are made from soft, non-woody stems of herbaceous plants. Mostly in forestry herbaceous cuttings are not used. Regeneration can be done easily and cheaply by using hardwood cuttings. Semi-hardwood cuttings are employed for broad-leaved evergreen species while hardwood cuttings are typically used for deciduous species.
What factors results in cutting success?
The cutting’s ability to take root differs from species to species. In the case of poplar, eucalyptus, willow the technique has been successful while cuttings from oak and other conifers are difficult to root. The development of callus in the vegetative propagules’ basal area is crucial for cell differentiation since it is directly related to the induction of adventitious roots.
The factors that impact rooting of the cuttings are both internal and external. Internal factors include genetic make-up, physiological state, sugar content etc, while the external factors are season, temperature, humidity, edaphic conditions and air-circulation; normally these factors are manipulated by keeping the cuttings into man-made mist chamber. Other factors include tree age, cutting position etc.
Why cutting based propagation is still relevant?
Despite advancements in biotechnology and micropropagation, stem cutting propagation remains relevant as it combines simplicity, cost-effectiveness, and predictability. It enables farmers and nurseries to mass-produce genetically identical plants, preserving superior traits without sophisticated equipment or high costs. This method is especially crucial for species with high genetic variability, low seed viability or dormancy issues, and for ensuring uniformity in timber plantations where consistency in wood quality is essential.
Also, in resource-limited settings or remote areas, stem cutting propagation offers a practical solution that can be implemented with basic tools and knowledge. As global demand for wood reforestation efforts continues to grow, this age-old method remains a linchpin of sustainable tree propagation.
(Author is PhD, Forestry from Forest Research Institute, Dehradun. Email: [email protected])
