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Boron deficiency is a widespread problem for field crop production where large losses of yield occur annually both quantitatively (e.g. in southeast China over 40% yield reductions may occur in oilseed rape: Wei et al. 1998), as well as qualitatively (Stephenson and Gallagher 1987; Ram et al. 1989; Bell et al. 1990; Nyomora et al. 1997). Significant losses of yield or quality resulting from boron deficiency may occur as well in vegetable crops (e.g. Kotur 1991). Even eucalyptus trees in large areas of southern China (Dell and Malajczuk 1994), and pine trees in southeast Australia (Hopmans and Flinn 1984) may be severely affected by boron deficiency in both growth and quality.

Historical accounts of possible B roles in the protection of tree and horticulture species against frost damage were reported as early as 1950s, with more field observations and experimental evidence since then. Although the initial reports (Anon 1958; Beltram 1958) were no more than anecdotal evidence due to the lack of proper comparative control experiments, later field and glasshouse studies have provided more reliable evidence about the involvement of B in the protection against frost damage – decreased frost-induced shoot-tip dieback or increased flowering and fruit yield, for example: in subtropical eucalypts Eucalyptus grandis (Cooling 1967; Cooling and Jones 1970) and Eucalyptus grandis x Eucalyptus urophylla (Lu and Huang 2003); apple, pear and blueberry (Blevins et al. 1996; Hanson and Breen 1985; Milovankic et al. 1990) and in birch, Scots pine, and Norway spruce (Braekke 1983). Frost-induced “white top” (bleached young leaves) has been observed in low temperature-sensitive E. urophylla and E. grandis in south China (Xu Daping, pers. comm.) where B deficient soils are common (Dell and Malajczuk 1994). Field observations have also suggested a link between low canopy temperature and enhanced leaf tissue damage (bleached patches) in oilseed rape grown in low B soil in south-east China (Ye et al. 1997).

Very little is known about the mechanisms that drive xylogenesis. In conifers, xylogenesis incorporates cambial cell division, subsequent xylem cell differentiation and culminates in cell death, marking the formation of a mature tracheid. Many researchers suggest that boron availability plays a critical role in the regulation of cell development. In particular, boron may be involved in maintaining the strength and integrity of the cell wall matrix, as well as the production and deposition of cell wall material (Hu 1994). We have a particular interest in the role of boron in xylogenesis and xylem cell development.

Root border cells possess special physiological properties and biological significance, being distinct from the root cap cells. This cell population detaches from root tips and rapidly suspends in water once the root tips are immersed. They can survive in a wide range of osmotic pressure including distilled water for a relatively long time without bursting or any visible damage (Brigham et al. 1995). These unusual cells form a biological interface between root tip surface and soil. Most tested plant species produce root border cells, and usually over 90% of them remain viable when detached (Brigham et al. 1995).

Root border cells are released from the root apices of most plant species, and function crucially in the rhizosphere through their ability to modify its chemical and physical properties. After detachment from the root cap, root border cells have already served several functions. They can dramatically alter the behavior of populations of rhizosphere microflora (Hawes and Brigham 1992; Hawes et al. 1998; Hawes et al. 2000). These detached cells can reduce the mechanicalfriction of the growing root under some conditions (Hawes et al. 1998; Iijima et al. 2004) and protect the tip by repelling bacteria.

Boron has been proved an essential element for higher plants growth since 1923 (Warington 1923), but its primary physiological function in plants is yet unclear. Increasing number of experiments supported the idea that boron play an important role in plasma membrane integrity by binding membrane compounds containing cis-diol groups, or affecting activities of some enzymes related to membrane function or structure, or participating phenolics metabolism (Blevins and Lukaszewski 1998, Brown et al. 2002, Goldbach et al. 2002). Cakmak et al. (1997) reported that the major defense system of cells against toxic active oxygen was reduced in response to boron deficiency. It is possible that supplied boron might protect plasma membranes against peroxidative damage by the toxic active oxygen.

Boron presents a challenge to agronomists. Management of boron in soil is made difficult by its high mobility, being easily leached under high rainfall conditions, leading to deficiencies in plants that grow there. Under low rainfall conditions, the opposite is often true, that it is not sufficiently leached and therefore may accumulate to levels that become toxic to plant growth. This is often exacerbated by irrigation to compensate for the low rainfall, because of the high boron concentrations that characterise many irrigation waters. As will be discussed in more detail in this paper, it is also the nutrient for which the plant has the least control over uptake. All essential plant nutrients except boron are acquired as ionised solutes (except perhaps N supplied as urea), which limits their membrane permeability, and allows a high degree of control by the activation, induction or repression of membrane transporters. To use the vernacular, boron is a ‘slippery customer’ which understand its physiology, agronomic attempts to improve plant performance on B-deficient and B-toxic soils, and molecular attempts to engineer plants that are able to tame boron.

In the past 30 years, research on plant boron (B) nutrition has progressed significantly and the application of B fertilizer has become a standard measure in many B deficient regions. In China, this promoted the development of agriculture, especially the production of cotton and oilseed rape. In this paper, we will review the respective progress and report about the Chinese studies on the physiological function of B, diagnosis of B status of plants and techniques of B fertilizer application.

Rice ( L.), the world’s leading staple food, is grown on 2.3 M ha alluvial, calcareous, low organic matter soils of Pakistan, giving an average paddy yield of 2.000 t ha (GOP 2004). As fertilizer use in rice predominantly pertains to nitrogen (N), and to a lesser extent to phosphorus (P) and zinc (Zn) (Rashid et al. 2000), one major cause of low farm-level productivity compared with much higher potential yields (i.e. 4.00–4.50 t ha, M. Akram, personal communication) is inadequate and imbalanced nutrient management

India is a predominantly vegetarian country but per capita vegetable consumption is not up to the desired national standards due to low productivity. Though introduction of F-1 hybrids in recent times has resulted in substantial yield increase, the full genetic yield potential could not be realized, due to several yield limiting factors including nutrient deficiencies. Though cauliflower is temperate in its climate requirement, introduction of heat tolerant tropical cauliflower F1 hybrids have transformed periurban cauliflower production around Bangalore, situated in semi arid tropics of India. But the yield and quality are not optimum due to nutrient deficiencies especially. B Visible deficiency symptoms (like browning of curds, hollow stem) and yield response to B have been recorded in local varieties (Kotur 1994) in traditionally B deficient regions like Chotanagpur and Assam in North India (high rainfall, coarse soils with high humidity) but not in semi arid regions of southern India like Bangalore. But yields are low at 10-15 t ha and quality of the curds (compactness and color) is affected resulting in low market acceptability. Since sub clinical deficiency or hidden hunger is a major problem in a comparatively low input field crop production in developing countries like India (Wallace 1982) identifying them is a challenge. Nutrient deficiency expression is genotype dependent and in some crops like wheat and barley plants result in total sterility due to copper and Manganese deficiencies without visible expression of any symptoms. Hence breeding nutrient efficient varieties is a better way of solving the hidden hunger (Graham, 1984). Since breeding for such nutrient efficiency is a very time consuming task, correction of the probable deficiencies by properly standardized input is necessary. Since Cauliflower is known to be highly susceptible to B deficiency a study was undertaken in the field to evaluate different sources and methods of B correction of B for eliminating hidden hunger for high yield and quality in F1 hybrids. Since the F1 hybrids have a fast, growth pattern (Srinivas and Bhatt 1994) the established soil and plant critical levels of nutrients for the low yielding open pollinated varieties (not F1 hybrids) is redundant. Hence there is a need to follow new critical levels for these F1 hybrids (Anonymous 1989). Hence in this study though the available B (hot water soluble B) is at 0.48 mgkg which is nearer to the critical level of 0.5 mgkg, the response study was initiated so that the full yield potential and best quality can be realized.