This PPT deals with the physiology of dwarfism in fruit trees, explaining why and how dwarf growth occurs and how it can be deliberately induced and managed for efficient fruit production. It begins with the concept of dwarfism, defining dwarf fruit trees as plants that attain smaller size at full maturity due to genetic factors or horticultural manipulations. The presentation emphasizes the importance of dwarf trees in modern fruit cultivation, particularly for maximizing the use of vertical and horizontal space and increasing productivity per unit area and time.
The PPT explains that the physiology of dwarfism involves complex anatomical, physiological, and biochemical alterations that modify normal growth patterns. Various theories and postulations explaining dwarfing mechanisms are discussed. A major focus is placed on the role of dwarfing rootstocks, interstocks, and scion–stock interactions, which influence water and nutrient uptake, hydraulic conductivity, carbohydrate partitioning, canopy development, and hormonal balance.
Key physiological processes associated with dwarfing include reduced xylem vessel size, higher bark-to-wood ratio, restricted root systems, partial blockage at graft unions, and depletion of minerals and solutes in xylem sap. The role of phytohormones, especially reduced auxin transport, altered ABA:IAA ratio, reduced gibberellin activity, and variations in cytokinin levels, is explained in detail. Dwarfing is also associated with reduced net assimilation rate, early and heavy fruiting at the expense of vegetative growth, and restricted canopy architecture.
The PPT further discusses methods to achieve dwarfism, including the use of dwarfing and incompatible rootstocks, plant growth regulators (such as paclobutrazol and gibberellin inhibitors), pruning and training systems, nutrient management, phenolic compounds, in vitro techniques, viral induction, genetic engineering, and induced mutations. Each method is supported by physiological explanations and research findings.
Advantages of dwarf fruit trees highlighted include suitability for high-density planting (HDP), ultra-high-density planting (UHDP), and meadow orcharding, ease of management, reduced wind damage, early bearing, and improved fruit quality. Disadvantages such as shorter lifespan, higher technical requirements, and increased pest and disease pressure in intensive systems are also discussed.
The PPT concludes with extensive case studies demonstrating dwarfing effects of rootstocks, interstocks, training systems, growth retardants, virus inoculation, and in vitro techniques across fruit crops like apple, pear, citrus, mango, plum, and mandarin. Overall, the presentation provides a comprehensive understanding of the physiological basis of dwarfism and its practical application in modern orchard systems