Carnation (Dianthus caryophyllus L.) is immensely esteemed for its cut flower, due to its array of colours, keeping quality and extensive transportability. Carnation occupies the top slot in the global flower trade. Quality is one of the most important characters in the cut flower industry and this is influenced by application of nutrients. To reach out to the competitive international and domestic markets, quality plays a vital role. Carnations with good stem length, bud diameter, free from calyx splitting with better post harvest life command a greater price in the international market.

Integrated supply of micronutrients with macronutrients in adequate amounts and suitable proportions is one of the most important factors that control the plant growth in flower crops (Zende, 1996). Carnation being a nutrient exhaustive crop requires regular supply of nutrients in small doses that favours better growth and flower production. Boron is one amongst the micronutrients responsible for quality attributes in carnation. The inevitability of boron in plants is evident from the quote of Truog (1940) who postulated the importance of boron as, '..plants will not make growth without boron any more than... without phosphorus or potassium which they require in considerable amounts' and suggested, that no crop can reach its full potential without but adequate supply of boron.

IMPORTANCE OF BORON IN CROP PLANTS Boron, the non-metal compound plays an essential role in the growth and development of new cells in the plant meristem. Boron is a micronutrient of special importance, because of its role in the fertilization and flowering process. It has been known to be constituent of plants since 1857. The essentiality of boron as it affects the growth of maize was first reported by Maze (1914) in France. The function of boron in plant remained obscure prior to the mid 1950's. Facilitating pollination and fruit set is considered to be the most important function of boron besides its role in the synthesis of amino acids and protein metabolism. Boron increases the translocation of sugar in plants and increases the rate of transport of sugars (which are produced by photosynthesis in mature plant leaves) to actively growing regions (Gauch and Duggar, 1953). It is essential to maintain the structural integrity of plant membranes along with calcium and is involved in nucleic acid metabolism. It improves the solubility and mobility of calcium in plants and regulates the carbohydrate metabolism, besides helping in the absorption of nitrogen. Boron is an essential element found in the meristematic regions of plants such as root tips, emerging leaves and buds. Generally the concentration of boron in plants is comparatively higher in flower, anthers, ovary and stigma.

Boron, the nonmetal compound plays an essential role in the growth and development of new cells in the plant meristem. Boron is a micronutrient of special importance, because of its role in the fertilization and flowering process.

Boron also plays an essential role in the biosynthesis of auxins within the plant meristem. It is involved in regulating hormone levels in plants for growth and reproduction functions and for flower initiation, fruit development, cell wall and tissue formation and root elongation. Russel (1957) reported that boron is involved in nitrogen metabolism, hormone movement and action and also in cell division. The most important physiological effects of boron in plants are a structural role in cell walls, membrane function and a stimulation or inhibition of specific metabolic pathways. Boron plays an important role in both structural and functional integrity of plasma membranes. Integrity and functionality of plasma membranes are ensured with adequate supply of boron. Boron is involved in nitrogen fixation and it is required for growth and development of vascular tissues. It accelerates nitrogenase activity through effective nodule development for nitrogen fixation. Further, boron ensures healthy plant storage tissues and conductive tissues for the transport of water, nutrients and organic compounds to the actively growing portions in plants.

BORON FOR CALYX SPLIT CONTROL IN CARNATION
Calyx splitting is a major problem in carnation production and is quite a challenge for the growers. Occurrence of calyx splitting in carnation is associated with micronutrient deficiency, mainly boron in addition to environmental factors and varietal characteristics. Boron deficiency can aggravate the disorder up to 75 per cent. Calyx split resulting from deficiency of boron needs immediate attention, since the price of the flowers in the market gets slashed by about 75 per cent due to calyx split. In boron deficient carnation plants, the petals lose their structural integrity resulting in bending down of petals, which in turn leads to distortion of shape and structure of flowers due to calyx splitting. Brittle stems, cracking off near leaf joint when getting mature or easy stem breakage while harvesting are the symptoms which occur due to calyx split. High potassium also induces boron deficiency. The calyx split in carnation can be controlled by applying balanced nutrients and avoiding over fertilization as well as ensuring temperature control. In fertigation scheduling, boron can be added @ 1.0 g m2/ week.

Research done by TNAU under the ICAR sponsored National Agricultural Innovation Project in the Nilgiris for controlling calyx splitting in carnation indicated that foliar application of 0.1 per cent borax at fortnightly intervals till flower bud initiation and at weekly intervals thereafter could considerably reduced calyx splitting and enhance the yield and quality of flowers. The percentage of reduction over untreated plants is 32.63. In commercial carnation cultivation, it is essential to meet out the boron requirements of plants by application of the nutrient at appropriate levels, so as to prevent economic losses due to physiological disorders such as calyx split and flower malformation.