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Boron (B) deficiency is an agricultural problem that causes significant yield losses in many countries. B transporters (BORs) are responsible for B uptake and distribution and play important roles in yield formation. A comprehensive analysis of the BOR family members in common wheat is still lacking. In the present study, to clarify the molecular characterization and response to B status, genome-wide TaBOR genes and expression patterns were investigated. Fourteen TaBOR genes were identified in common wheat by a homology search. The corresponding phylogenetic tree indicated that 14 TaBOR genes were separately classified into subfamilies of TaBOR1, TaBOR3, and TaBOR4. All TaBOR genes had 12-14 extrons and 11-13 introns. Most TaBOR proteins contained 10 conserved motifs, and motifs 1, 2, 3, 4, and 6 constituted the conserved bicarbonate (HCO3-) domain. Fourteen TaBOR genes were mapped on 13 chromosomes mainly distributed in the first, third, fifth, and seventh homologous groups. The promoters of TaBOR genes consisted of phytohormones, light responses, and stress-related cis-elements. GO analysis indicated that TaBOR genes were enriched in terms of transmembrane transport and ion homeostasis. TaBOR genes showed diverse expression profiles in different tissues. The members of the TaBOR1 subfamily showed high expression in grains, leaves, roots, stems, and spikes, but members of the TaBOR4 subfamily were highly expressed only in spikes and grains. RT--qPCR indicated that TaBOR1-5A, TaBOR1-5B, and TaBOR1-5D were induced by low B concentrations and had much higher expression in roots than in shoots. TaBOR3-3A, TaBOR3-3B, TaBOR3-3D, TaBOR4-1A, TaBOR4-1B, TaBOR4-1D, and TaBOR3-4B were induced by low and high B concentrations and had high expression in roots and shoots. TaBOR3-4D and TaBOR3-7B were upregulated by low and high B concentrations, respectively, but had expression only in roots. Our results provide basic information on the TaBOR family, which is beneficial for elucidating the functions of TaBOR genes to overcome the problem of B deficiency. [ABSTRACT FROM AUTHOR]

For many years after the discovery of the two stable isotopes of B (10B,11B) in 1920 it was not used routinely as a tracer in the biological sciences until the development of inductively coupled plasma mass spectrometry in the early 1980s. This development provided an impetus to the study of the role of B in plant nutrition, although many seminal discoveries were made beforehand without the aid of isotopes. Thus, much information on the mobility and physiological function of B in plants is post-1985. Boron is unusual in plant nutrition in that it is taken up by plants through roots or foliage as undissociated boric acid, unlike other essential elements that are taken up in ionic form. The within-plant mobility of B in species important in agriculture and horticulture is examined in the present review including the role of sugar alcohols in xylem to phloem transfer. The molecular basis of its movement at the cellular level via transporters as revealed through the strategic application of enriched 11B and 10B is addressed. Few studies have been carried out on B use efficiency by crops and results show great variability. Suggestions for future applications of tracing with 10B and 11B are provided. [ABSTRACT FROM AUTHOR]

Although boron (B) is an element that has long been assumed to be an essential plant micronutrient, this assumption has been recently questioned. Cumulative evidence has demonstrated that the players associated with B uptake and translocation by plant roots include a sophisticated set of proteins used to cope with B levels in the soil solution. Here, we summarize compelling evidence supporting the essential role of B in mediating plant developmental programs. Overall, most plant species studied to date have exhibited specific B transporters with tight genetic coordination in response to B levels in the soil. These transporters can uptake B from the soil, which is a highly uncommon occurrence for toxic elements. Moreover, the current tools available to determine B levels cannot precisely determine B translocation dynamics. We posit that B plays a key role in plant metabolic activities. Its importance in the regulation of development of the root and shoot meristem is associated with plant developmental phase transitions, which are crucial processes in the completion of their life cycle. We provide further evidence that plants need to acquire sufficient amounts of B while protecting themselves from its toxic effects. Thus, the development of in vitro and in vivo approaches is required to accurately determine B levels, and subsequently, to define unambiguously the function of B in terrestrial plants.

Abstract Background Boron (B) deficiency is an agricultural problem that causes significant losses of crop yield in many areas of the world. However, systematic analysis of BOR family genes for B transport in rapeseed is still lacking. We aimed to identify and characterize BOR transporters in Brassica napus and the potential role of these transporters in B homeostasis in response to B deficiency. Results Here, we identified 20 BOR transporters from the Brassica napus genome, which were classified into six distinct groups that represent clear orthologous relationships to their family members in Arabidopsis. qRT-PCR revealed distinct expression profiles for BnBORs in different tissues and in response to external B levels. The B-efficient cultivar QY10 accumulated more B in shoots than the B-inefficient cultivar W10, and overexpression of BnaBOR1;1c could alleviate shoot B-deficiency symptoms in W10 by distributing more B from roots to shoots. Additionally, BnBOR1;1c expression was up-regulated by B deficiency, and the induction of BnBOR1;1c was more intense in QY10. Moreover, two conserved InDels were found in the promoter regions of BnBOR1;1c within different B-efficient genotypes. Conclusions Overall, the molecular characterization of the BnBOR genes of two B-efficient cultivars and their responses to B deficiency highlights the diversity of the family members in B. napus, and BnaC4.BOR1;1c has potential as a candidate gene for improving B nutrition.

Although boron (B) is an element that has long been assumed to be an essential plant micronutrient, this assumption has been recently questioned. Cumulative evidence has demonstrated that the players associated with B uptake and translocation by plant roots include a sophisticated set of proteins used to cope with B levels in the soil solution. Here, we summarize compelling evidence supporting the essential role of B in mediating plant developmental programs. Overall, most plant species studied to date have exhibited specific B transporters with tight genetic coordination in response to B levels in the soil. These transporters can uptake B from the soil, which is a highly uncommon occurrence for toxic elements. Moreover, the current tools available to determine B levels cannot precisely determine B translocation dynamics. We posit that B plays a key role in plant metabolic activities. Its importance in the regulation of development of the root and shoot meristem is associated with plant developmental phase transitions, which are crucial processes in the completion of their life cycle. We provide further evidence that plants need to acquire sufficient amounts of B while protecting themselves from its toxic effects. Thus, the development of in vitro and in vivo approaches is required to accurately determine B levels, and subsequently, to define unambiguously the function of B in terrestrial plants. [ABSTRACT FROM AUTHOR]

Our current understanding of boron’s roles in plants is still limited to the formation of B-rhamnogalacturonan-crosslinks in the cell wall, but deficiency symptoms in plants and animals point to additional functions of boron (B) in cell membranes. However, no membrane-bound molecules interacting with B have been isolated so far.In the present study we address the hypothesis that boron exerts a physiological function at membranes by crosslinking membrane-bound proteins.Boron-interacting membrane proteins were isolated from root microsomal preparations of arabidopsis (Arabidopsis thaliana) and maize (Zea mays) using phenylboronate affinity chromatography, subsequently separated by two-dimensional gel electrophoresis and identified using MALDI-TOF peptide mass fingerprinting.A relatively large number of B-binding membrane proteins was detected, of which sixteen (A. thaliana) and nine (Z. mays) were identified. Common to both species were the beta subunit of mitochondrial ATP synthase, several beta-glucosidases, a luminal binding protein and fructose bisphosphate aldolase. Binding of these proteins to B was significantly reduced after 5 days of B deprivation in A. thaliana. Plants grown under B deficiency also exhibited an altered protein composition of membrane microdomains. This combined with the fact that many of the B-binding proteins are components of membrane rafts, supports the hypothesis that B may indeed play a function in plant membranes by crosslinking glycoproteins, and may be involved in their recruiting to membrane microdomains.

Plant reproduction has higher boron (B) requirements than vegetative growth and generally reproductive plant parts contain more B, but the form and function of the extra B remains unexplained. In this paper we review the literature on B in plant reproductive development and add to it recent results on B distribution and forms in reproductive parts (silks, pollen) and vegetative parts (youngest open leaves) of maize grown in B-buffered solution culture. Cell wall binding of B in the silk and pollen of maize does not explain the higher B concentrations in reproductive than vegetative tissue. Given the rather high proportion of B present in the non-cell wall fraction in pollen and silk, the high B requirement for plant reproduction suggests an additional role for B other than in cell wall formation. The identity of non-cell wall B binding substrates in pollen and carpel tissue awaits further study. The higher sensitivity of plant reproduction to B deficiency is also related to weaker B transport into floral organs, especially where transpiration is suppressed in reproductive plant parts by enclosure of sheaths (e.g. wheat ear) or husks (e.g. maize ear) during the critical stage of development.

Since the essentiality of boron (B) to plant growth was reported nearly one century ago, the implication of B in physiological performance, productivity and quality of agricultural products, and the morphogenesis of apical meristem in plants has widely been studied. B stresses (B deficiency and toxicity), which lead to atrophy of canopy and deterioration of Citrus fruits, have long been discovered in citrus orchards. This paper reviews the research progress of B stresses on Citrus growth, photosynthesis, light use efficiency, nutrient absorption, organic acid metabolism, sugar metabolism and relocation, and antioxidant system. Moreover, the beneficial effects of B on plant stress tolerance and further research in this area were also discussed.

Boron (B) is essential for normal plant growth, including pollen tube growth. B deficiency influences various physiological and metabolic processes in plants. However, the underlying mechanism of B deficiency in pollen tube growth is not sufficiently understood. In the present research, the influence of B deficiency on apple (Malus domestica) pollen tube growth was studied and the possible regulatory mechanism evaluated.Apple pollen grains were cultured under different concentrations of B. Scanning ion‐selective electrode technique, fluorescence labelling and Fourier‐transform infrared (FTIR) analysis were used to detect calcium ion flux, cytosolic Ca2+ concentration ([Ca2+]cyt), actin filaments and cell wall components of pollen tubes.B deficiency inhibited apple pollen germination and induced retardation of tube growth. B deficiency increased extracellular Ca2+ influx and thus led to increased [Ca2+]cyt in the pollen tube tip. In addition, B deficiency modified actin filament arrangement at the pollen tube apex. B deficiency also altered the deposition of pollen tube wall components. Clear differences were not observed in the distribution patterns of cellulose and callose between control and B deficiency treated pollen tubes. However, B deficiency affected distribution patterns of pectin and arabinogalactan proteins (AGP). Clear ring‐like signals of pectins and AGP on control pollen tubes varied according to B deficiency. B deficiency further decreased acid pectins, esterified pectins and AGP content at the tip of the pollen tube, which were supported by changes in chemical composition of the tube walls.B appears to have an active role in pollen tube growth by affecting [Ca2+]cyt, actin filament assembly and pectin and AGP deposition in the pollen tube. These findings provide valuable information that enhances our current understanding of the mechanism regulating pollen tube growth. [ABSTRACT FROM AUTHOR]

Vinte plantas de abacaxi "Pérola" foram cultivadas em vasos de plástico de 10 L, em casa de vegetação, com o objetivo de caracterizar os sintomas visuais de deficiência de B nas plantas e nos frutos. Os vasos continham areia de rio lavada cinco vezes com água comum e depois duas vezes com água desionizada. Dez plantas foram irrigadas com solução completa e, de outras dez, o B foi suprimido da solução cinco meses após o plantio. As plantas apresentaram crescimento vegetativo normal e formaram frutos normais. Após a colheita dos frutos, acompanhou-se a formação das mudas do tipo rebento e rebentão basal, onde se observou que as plantas cultivadas sem B formaram mais mudas do tipo rebento do que as plantas cultivadas com B. Na formação das mudas do tipo rebentão basal, não se observou o efeito da supressão do B. No cultivo da planta-soca e em rebentões basais, cultivados em solução nutritiva sem B, observaram-se sintomas de deficiência de B somente no período reprodutivo. Os sintomas de deficiência de B se caracterizaram por: frutos deformados e menores, com formação de excrescência cortiçosa ou secreção de goma entre os frutilhos, rachaduras entre estes preenchidas com excrescência cortiçosa. As mudas tipo filhote formadas nas plantas-soca apresentaram folhas com falhas na borda e pontas secas.Twenty pineapple "Pérola" plants were cultivated in 10L plastic pots in a greenhouse, with the objective of characterizing the visual symptoms of boron deficiency in the pineapple leaves and fruit. The pots contained river sand that was washed five times with common water and two times with deionized water. Ten plants were irrigated five months after planting with a complete nutrient solution and the other ten, without B in the solution. The plants presented regular vegetative growth and fruit formation. After the harvest of the fruit, the formation of shoot and suckers seedling types were accompanied, where it was possible to observe that plants were grown without B produced more seedling from the shoot type than from those ones grown with B. The formation of suckers was not affected by the suppression of B from the nutrient solution. Symptoms of boron deficiency were observed only in the fruiting period in plants in the second cycle of growth. Symptoms of B deficiency were characterized by deformed and smaller fruit, with formation of cork tissue or gum secretion among the fruitlets and cracks filled out with of cork tissue. Slip formed in second cycle plants had leaves with uneven borders and dry tips.

The impact of soil (1, 2 kg ha−1) and foliar (100, 200 mg L−1) boron (B) with control (no B) was evaluated on phenology and yield formation ofCamelinaeach applied at stem elongation and flowering stages. Foliar (200 mg L−1) or soil B (2 kg ha−1) resulted in earlier flowering and maturity, increased fruit bearing branches (19.68%), number of siliqua, seeds per siliqua (4.6%), biological yield (15%), seed yield (24%), harvest index (11.4%) and oil contents (23%) than no B. Increased fruit bearing branches, seed filled siliqua or seed numbers, harvest index and oil quality can be attributed to changes in dry matter accumulated of stem with simultaneous increase in siliqua dry weight with foliar or soil applied B. In crux, foliar (200 mg L−1) or soil applied (2 kg ha−1) B seems promising to improve seed and oil yield, harvest index ofCamelina sativaunder B deficient condition. [ABSTRACT FROM AUTHOR]

Boron (B) deficiency is prevalent in the soils of tea growing regions of India. In order to investigate the physico-chemical alterations associated with B deficiency in tea (( Camellia sinensis (L.) O. Kuntze, cv. T-78) plants, young plantlets were treated with boric acid (HBO) at 0, 2.5, and 5 μM for 8 weeks. B-scarcity decreased the photosynthetic rate ( P), stomatal conductance ( g), and transpiration ( E) alongside chlorophyll a (Chl a), chlorophyll b (Chl b), and carotenoids (Car). Superoxide anion (O), malondialdehyde (MDA), hydrogen peroxide (HO) generation and electrolyte leakage were elevated in B-deprived plants. The activities of ascorbate peroxidase (APX; EC 1.11.1.11), catalase (CAT; EC 1.11.1.6), peroxidase (POD; EC 1.11.1.7), and superoxide dismutase (SOD; EC 1.15.1.1) were increased in B-deficient plants. Simultaneously, transcripts of the antioxidant enzymes were up-regulated under B deficiency. By and large, the results suggest that B deficiency intensifies ROS generation but the antioxidant system does not provide for an adequate protection from oxidative damage. [ABSTRACT FROM AUTHOR]

Aims: Variation in boron (B) efficiency in citrus in different rootstock genotypes is expressed as large differences in the occurrence of leaf symptoms and dry mass production under low B conditions, but the mechanisms responsible for such differences are unknown. This paper aims to determine whether differences in B uptake, cellular B allocation, and pectin content can explain genotype differences in B efficiency between B-efficient citrange ( Citrus sinensis (L.) Osb. × Poncirus trifoliata (L.) Raf.) and B-inefficient trifoliate orange ( Poncirus trifoliata (L.) Raf.) citrus rootstock. Methods: Plants were grown hydroponically in a nutrient solution supplemented with 5 μ M B for 14 days and then transferred to a B-free medium (0 μ M B) or control medium (5 μ M B) for 35 days. Boron uptake and allocation and cell wall pectin contents were examined. Results: After 35 days under B deprivation, shoot dry mass in trifoliate orange decreased by 28 %, but shoot dry mass of citrange was not significantly affected. Root growth of both types of rootstock seedlings was inhibited, but the trifoliate orange was affected more than the citrange. In comparison with B concentrations in plants prior to the commencement of B treatments, B deprivation for 35 days decreased B concentration in various parts of citrange plants, and the reduction was much greater in trifoliate orange plants. Trifoliate orange seedlings contained higher B concentration and total B in cell wall on a dry leaf basis than citrange subject to 5 μ M B treatment. However, the proportion of leaf B allocated in cell wall was higher in citrange than trifoliate orange when B supply was deficient in the nutrient. The changes in pectin composition in cell wall due to B deprivation differed between citrange and trifoliate orange. The decreased uronic acid (UA) content in the NaCO-soluble pectin was observed in both rootstock, but the increased UA content in CDTA-soluble pectin was observed only in citrange. Conclusions: These results demonstrated that a combination of greater B uptake ability, greater B accumulation in cell walls, as well as the increased CDTA-soluble pectin, under limited external B supply, contribute to the integrity of cell walls in citrange and therefore increased tolerance to B deficiency. [ABSTRACT FROM AUTHOR]

Modification in the metabolism of phenolic compounds under boron (B) deficiency conditions was studied in tea plants. Plants were grown from seed, treated with low B in hydroponic medium under environmentally controlled conditions for six weeks. Dry matter production and B content of plants were significantly declined under B deficiency conditions. Boron starvation resulted in rising phenylalanine ammonia lyase activity in the young leaves and declining polyphenol oxidase activity in the roots. Soluble phenolics fraction was increased up to 3.4-fold in the young leaves while did not influence by B nutrition in the old leaves and roots. Cell wall (CW) bound phenolics and lignin content was lower in B-deficient plants compared with B-sufficient ones. Boron deficiency increased significantly activity of soluble per-oxidase (POD) only in the leaves. Activity of ionically bound POD was decreased in the old leaf and roots while it increased in the young leaves upon B deprivation. Activity of covalently bound POD decreased in the roots and leaves of different age in low B plants. Our results suggested that tea plant is highly tolerant species to B deficiency and CW tightening and accumulation of oxidized phenolics are not mechanisms for growth inhibition under B deficiency conditions. [ABSTRACT FROM AUTHOR]

Boron (B) is an essential microelement, which is necessary for reproductive organs including pollen tube formation in wheat (Triticum aestivumL.), and flowering and boll formation in cotton (Gossypium hirsutumL.) The study was associated with wheat-cotton rotation in 80 farm fields, belonging to different soil series, in four districts of cotton belt of Punjab, Pakistan to assess concentrations of extractable B in soils [0.05 M hydrochloric acid (HCl) extractable B], and added fertilizer B and their relationship to some soil physico-chemical properties [pH, organic matter (OM), calcium carbonate (CaCO3) and clay content], yields and total B concentrations in wheat and cotton plants. All soils had alkaline pH (7.45 to 8.55), high CaCO3content (2.14 to 8.65%), less than 1.0% OM (0.33 to 0.99%), low plant available-P (Olsen P less than 8 mg kg−1soil) and medium ammonium acetate extractable potassium (K) (< 200 mg K kg−1soil). Of the 80 soil samples, 65 samples (81%) were low in available B (<0.45 mg B kg−1, ranging from 0.11 to 0.43 mg B kg−1) Of the corresponding 80 plant samples, leaves B concentrations were below critical levels (<10 mg B kg−1for wheat; <30 mg B kg−1for cotton) for all the tested samples for wheat and cotton. The regression analysis between plant total B concentrations and soil extractable B concentrations showed strong linear positive relationships for both wheat (R2= 0.509***, significant atP<0.001) and cotton (R2= 0.525***, significant atP<0.001). Further regression analysis between extractable soil B and wheat grain yield as well as between wheat leaves total B and wheat grain yield also depicted strong linear relationships (R2= 0.76 and 0.42, respectively). Boron fertilizer demonstration plots laid out at farmers’ fields low in extractable B, in each district not only enhanced grain yields of wheat crop but also contributed a significant increase towards seed cotton yield of succeeding cotton crop through residual B effect. In conclusion, the findings suggest that many soils in the cotton belt of Punjab may be low in extractable B for wheat and cotton, especially when these crops are grown on low OM soils with high CaCO3content. [ABSTRACT FROM PUBLISHER]

Boron (B) deficiency is an agricultural problem that causes significant yield losses in many countries. B transporters ( BOR s) are responsible for B uptake and distribution and play important roles in yield formation. A comprehensive analysis of the BOR family members in common wheat is still lacking. In the present study, to clarify the molecular characterization and response to B status, genome-wide TaBOR genes and expression patterns were investigated. Fourteen TaBOR genes were identified in common wheat by a homology search. The corresponding phylogenetic tree indicated that 14 TaBOR genes were separately classified into subfamilies of TaBOR1 , TaBOR3 , and TaBOR4 . All TaBOR genes had 12-14 extrons and 11-13 introns. Most TaBOR proteins contained 10 conserved motifs, and motifs 1, 2, 3, 4, and 6 constituted the conserved bicarbonate (HCO 3 - ) domain. Fourteen TaBOR genes were mapped on 13 chromosomes mainly distributed in the first, third, fifth, and seventh homologous groups. The promoters of TaBOR genes consisted of phytohormones, light responses, and stress-related cis-elements. GO analysis indicated that TaBOR genes were enriched in terms of transmembrane transport and ion homeostasis. TaBOR genes showed diverse expression profiles in different tissues. The members of the TaBOR1 subfamily showed high expression in grains, leaves, roots, stems, and spikes, but members of the TaBOR4 subfamily were highly expressed only in spikes and grains. RT-qPCR indicated that TaBOR1-5A , TaBOR1-5B , and TaBOR1-5D were induced by low B concentrations and had much higher expression in roots than in shoots. TaBOR3-3A , TaBOR3-3B , TaBOR3-3D , TaBOR4-1A , TaBOR4-1B , TaBOR4-1D , and TaBOR3-4B were induced by low and high B concentrations and had high expression in roots and shoots. TaBOR3-4D and TaBOR3-7B were upregulated by low and high B concentrations, respectively, but had expression only in roots. Our results provide basic information on the TaBOR genes to overcome the problem of B deficiency.TaBOR genes to overcome the problem of B deficiency., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Wang, Niu, Hu, Wu, Yang, Hao, Zhou, Yang, Dong, Liu and Ru.)

In the present study (i) the impact of plant Boron (B) status on foliar B absorption and (ii) the effect of B complexation with polyols (sorbitol or mannitol) on B absorption and translocation was investigated. Soybean ( Glycine max (L.) Meer.) plants grown in nutrient solution containing 0 μ M, 10 μ M, 30 μ M or 100 μ MB labelled boric acid (BA) were treated with 50 m MB labelled BA applied to the basal parts of two leaflets of one leaf, either pure or in combination with 500 m M sorbitol or mannitol. After one week, B concentrations in different plant parts were determined. In B deficient leaves (0 μ MB), B absorption was significantly lower than in all other treatments (9.7% of the applied dose vs. 26%-32%). The application of BA in combination with polyols increased absorption by 18-25% as compared to pure BA. The absolute amount of applied B moving out of the application zone was lowest in plants with 0 μ MB supply (1.1% of the applied dose) and highest in those grown in 100 μ MB (2.8%). The presence of sorbitol significantly decreased the share of mobile B in relation to the amount absorbed. The results suggest that B deficiency reduces the permeability of the leaf surface for BA. The addition of polyols may increase B absorption, but did not improve B distribution within the plant, which was even hindered when applied a sorbitol complex. [ABSTRACT FROM AUTHOR]

This report is on a 22-year-old male vegetarian with acute polyneuropathy secondary to vitamin B deficiency. He presented with weakness and numbness of the distal limbs and absent deep tendon reflex in all four extremities. Nerve conduction study (NCS) showed an axonal type sensori-motor polyneuropathy. Serum biochemical studies revealed vitamin B level of 119 pg/mL (reference range 185-710 pg/mL), with elevated creatine kinase (CK) (719 U/L) and homocysteine (Hcy) (24.04 μmol/L) levels. Anti-parietal cell antibody test was positive. The patient received both oral and intramuscular injection of vitamin B. The amplitude of the median and ulnar motor NCS increased 2.5 months later, while muscle power of the ankle plantar flexion and dorsiflexion recovered after 3.5 and 5.5 months, respectively. Follow-up NCS after 14.5 months showed response in sural NCS, but not the peroneal NCS. Follow-up also showed decreased serum Hcy and CK to 9.6 μmol/L and 198 U/L, respectively, and increasing amplitude of response. Recovery sequence involved muscle power of the proximal muscles, hands, plantar flexion, and dorsiflexion of the feet, and followed by sensory conduction. [ABSTRACT FROM AUTHOR]

The aim of the study was to induce B deficiency symptoms and to relate the generation of reactive oxygen species (ROS) and altered cellular redox environment with the effects of B deficiency in mulberry (Morus alba L.) cv. Kanva-2 plants. Study was undertaken on antioxidant responses, malondialdehyde (MDA) content as an indicator of oxidative damage and ratio of dehydroascorbate (DHA) to ascorbic acid (AsA) as an index of cellular redox environment in B-deficient (0.0 µM) and B-supraoptimal (33 µM) mulberry plants. B deficiency symptoms appeared as upward cupping of the young emerging leaves. Later on, B-deficient plants developed lenticels like cracks on major vein, petiole and stem. B-deficient leaves had higher water potential (Ψ) and relative water content (RWC), contained a lower concentration of B, less chloroplastic pigments and high tissue Fe, Mn and Zn concentrations compared to the controls. Hydrogen peroxide was accumulated in leaves of B-deficient and B-supraoptimal plants. B-supraoptimal plants also showed an increased DHA/AsA ratio. The activities of superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), peroxidase (POD, EC 1.11.1.7) and ascorbate peroxidase (APX, EC 1.11.1.11) were increased in B-deficient leaves. The activities of SOD and POD were decreased in B-supraoptimal plants. The results suggest that B deficiency aggravates oxidative stress through enhanced generation of ROS in mulberry plants. [ABSTRACT FROM AUTHOR]

Summary: It has previously been shown that boron (B) deficiency inhibits growth of the plant apex, which consequently results in a relatively weak apical dominance, and a subsequent sprouting of lateral buds. Auxin and cytokinins (CKs) are the two most important phytohormones involved in the regulation of apical dominance. In this study, the possible involvement of these two hormones in B-deficiency-induced changes in apical dominance was investigated by applying B or the synthetic CK CPPU to the shoot apex of pea plants grown in nutrient solution without B supply. Export of IAA out of the shoot apex, as well as the level of IAA, Z/ZR and isopentenyl-adenine/isopentenyl-adenosine (i-Ade/i-Ado) in the shoot apex were assayed. In addition, polar IAA transport capacity was measured in two internodes of different ages using 3H-IAA. In B-deficient plants, both the level of auxin and CKs were reduced, and the export of auxin from the shoot apex was considerably decreased relative to plants well supplied with B. Application of B to the shoot apex restored the endogenous Z/ZR and IAA level to control levels and increased the export of IAA from the shoot apex, as well as the 3H-IAA transport capacity in the newly developed internodes. Further, B application to the shoot apex inhibited lateral bud growth and stimulated lateral root formation, presumably by stimulated polar IAA transport. Applying CPPU to the shoot apex, a treatment that stimulates IAA export under adequate B supply, considerably reduced the endogenous Z/ZR concentration in the shoot apex, but had no stimulatory effect on IAA concentration and transport in B-deficient plants. A similar situation appeared to exist in lateral buds of B-deficient plants as, in contrast to plants well supplied with B, application of CKs to these plants did not stimulate lateral bud growth. In contrast to the changes of Z/ZR levels in the shoot apex, which occurred after application of B or CPPU, the levels of i-Ade/i-Ado stayed more or less constant. These results suggest that there is a complex interaction between B supply and plant hormones, with a B-deficiency-induced inhibition of IAA export from the shoot apex as one of the earliest measurable events. [Copyright &y& Elsevier]

Mung bean (Phaseolus aureus Roxb.) was grown in solution culture to study the effect of boron (B) deficiency on leaf expansion and intercellular airspaces. Different B concentrations were supplied just after initiation of the second trifoliate leaf because this is the first leaf whose growth depends on the exogenous B supply. The central leaflet of the second trifoliate was employed in this study. When plants were grown in 0.2 µmol L-1 B, leaf expansion was limited compared with that of plants supplied with 50 µmol L-1 B. During the progress of leaf development, plants grown in 0.2 µmol L-1 B were transferred to medium with 50 µmol L-1 B medium at days 2, 4, 6, and 8. The final leaf area of plants transferred on day 2 was half that of plants raised in 50 µmol L-1 B solution. Plants transferred on days 6 and 8 produced a leaf area similar to that of plants grown in 0.2 µmol L-1 B. Uptake experiments with 10B-enriched boric acid showed that there was enough B present at the sites of cell expansion after 50 µmol L-1 B was supplied for two days. The failure of deficient leaves to resume elongation may therefore have been due either to a lack of incorporation of B into the cell wall or boron or to a requirement for B early in leaf development to enable future cell wall expansion. In addition to the reduced leaf expansion resulting from B deficiency, the formation of intercellular airspaces was also depressed. The proportion of the spongy mesophyll region comprising airspaces in B-deficient leaves was less than 50% of that observed in leaves of plants supplied with sufficient B. [ABSTRACT FROM AUTHOR]

Since the essentiality of boron (B) to plant growth was reported nearly one century ago, the implication of B in physiological performance, productivity and quality of agricultural products, and the morphogenesis of apical meristem in plants has widely been studied. B stresses (B deficiency and toxicity), which lead to atrophy of canopy and deterioration of Citrus fruits, have long been discovered in citrus orchards. This paper reviews the research progress of B stresses on Citrus growth, photosynthesis, light use efficiency, nutrient absorption, organic acid metabolism, sugar metabolism and relocation, and antioxidant system. Moreover, the beneficial effects of B on plant stress tolerance and further research in this area were also discussed. [ABSTRACT FROM AUTHOR]

Since the essentiality of boron (B) to plant growth was reported nearly one century ago, the implication of B in physiological performance, productivity and quality of agricultural products, and the morphogenesis of apical meristem in plants has widely been studied. B stresses (B deficiency and toxicity), which lead to atrophy of canopy and deterioration of Citrus fruits, have long been discovered in citrus orchards. This paper reviews the research progress of B stresses on Citrus growth, photosynthesis, light use efficiency, nutrient absorption, organic acid metabolism, sugar metabolism and relocation, and antioxidant system. Moreover, the beneficial effects of B on plant stress tolerance and further research in this area were also discussed.

Boron (B) is essential for normal plant growth, including pollen tube growth. B deficiency influences various physiological and metabolic processes in plants. However, the underlying mechanism of B deficiency in pollen tube growth is not sufficiently understood. In the present research, the influence of B deficiency on apple (Malus domestica) pollen tube growth was studied and the possible regulatory mechanism evaluated. Apple pollen grains were cultured under different concentrations of B. Scanning ion-selective electrode technique, fluorescence labelling and Fourier-transform infrared (FTIR) analysis were used to detect calcium ion flux, cytosolic Ca 2+ concentration ([Ca 2+ ]cyt), actin filaments and cell wall components of pollen tubes. B deficiency inhibited apple pollen germination and induced retardation of tube growth. B deficiency increased extracellular Ca 2+ influx and thus led to increased [Ca 2+ ]cyt in the pollen tube tip. In addition, B deficiency modified actin filament arrangement at the pollen tube apex. B deficiency also altered the deposition of pollen tube wall components. Clear differences were not observed in the distribution patterns of cellulose and callose between control and B deficiency treated pollen tubes. However, B deficiency affected distribution patterns of pectin and arabinogalactan proteins (AGP). Clear ring-like signals of pectins and AGP on control pollen tubes varied according to B deficiency. B deficiency further decreased acid pectins, esterified pectins and AGP content at the tip of the pollen tube, which were supported by changes in chemical composition of the tube walls. B appears to have an active role in pollen tube growth by affecting [Ca 2+ ]cyt, actin filament assembly and pectin and AGP deposition in the pollen tube. These findings provide valuable information that enhances our current understanding of the mechanism regulating pollen tube growth., (© 2018 German Society for Plant Sciences and The Royal Botanical Society of the Netherlands.)