Effects Of Boron Deficiency Research Articles

Boron deficiency affects root vessel anatomy and mineral nutrient allocation of Poncirus trifoliata (L.) Raf.

Citrus plants are frequently exposed to boron (B) deficiency, which has reduced citrus production worldwide. The effects of boron deficiency on citrus rootstock mineral absorption and allocation, and cell and vessel element anatomy are very important in understanding the nutrient absorbing mechanisms and resolving the boron deficiency problems of citrus production. Poncirus trifoliata seedlings were grown in Hoagland’s solution, which contained 0.25 µM H3BO3 (moderate B) and 0 µM H3BO3 (B deficiency). Seedling growth, root tip cell and vessel anatomy, and nutrient contents were investigated 30 days after treatment. B deficiency significantly inhibited the growth of Poncirus trifoliata seedlings, significantly decreased the mean lateral root length and root number, and significantly increased the root diameter and lateral root primordial (LRP) density. Ultrathin section micrographs showed a thickened root tip cell wall and more attachments on the cell wall in the boron-deficient treatment. The vessel wall of all root orders was markedly thickened and the inner vessel diameter decreased in the boron-deficient treatment. The boron and calcium contents in the leaf, stem and root were significantly decreased, and the phosphorus content decreased significantly in the leaf but not in stem or root in the boron-deficient treatment. The changes in root morphology and vessel element anatomical characteristics completely inhibited mineral nutrient absorption and transportation, resulting in a limited nutrient supply and reduced growth of Poncirus trifoliata in the boron-deficient treatment.

Effects of boron deficiency on major metabolites, key enzymes and gas exchange in leaves and roots of Citrus sinensis seedlings.

Boron (B) deficiency is a widespread problem in many crops, including Citrus. The effects of B-deficiency on gas exchange, carbohydrates, organic acids, amino acids, total soluble proteins and phenolics, and the activities of key enzymes involved in organic acid and amino acid metabolism in 'Xuegan' [Citrus sinensis (L.) Osbeck] leaves and roots were investigated. Boron-deficient leaves displayed excessive accumulation of nonstructural carbohydrates and much lower CO2 assimilation, demonstrating feedback inhibition of photosynthesis. Dark respiration, concentrations of most organic acids [i.e., malate, citrate, oxaloacetate (OAA), pyruvate and phosphoenolpyruvate] and activities of enzymes [i.e., phosphoenolpyruvate carboxylase (PEPC), NAD-malate dehydrogenase, NAD-malic enzyme (NAD-ME), NADP-ME, pyruvate kinase (PK), phosphoenolpyruvate phosphatase (PEPP), citrate synthase (CS), aconitase (ACO), NADP-isocitrate dehydrogenase (NADP-IDH) and hexokinase] involved in glycolysis, the tricarboxylic acid (TCA) cycle and the anapleurotic reaction were higher in B-deficient leaves than in controls. Also, total free amino acid (TFAA) concentration and related enzyme [i.e., NADH-dependent glutamate 2-oxoglutarate aminotransferase (NADH-GOGAT) and glutamate OAA transaminase (GOT)] activities were enhanced in B-deficient leaves. By contrast, respiration, concentrations of nonstructural carbohydrates and three organic acids (malate, citrate and pyruvate), and activities of most enzymes [i.e., PEPC, NADP-ME, PK, PEPP, CS, ACO, NAD-isocitrate dehydrogenase, NADP-IDH and hexokinase] involved in glycolysis, the TCA cycle and the anapleurotic reaction, as well as concentration of TFAA and activities of related enzymes (i.e., nitrate reductase, NADH-GOGAT, glutamate pyruvate transaminase and glutamine synthetase) were lower in B-deficient roots than in controls. Interestingly, leaf and root concentration of total phenolics increased, whereas that of total soluble protein decreased, in response to B-deficiency. In conclusion, respiration, organic acid (i.e., glycolysis and the TCA cycle) metabolism, the anapleurotic pathway and amino acid biosynthesis were upregulated in B-deficient leaves with excessive accumulation of carbohydrates to 'consume' the excessive carbon available, but downregulated in B-deficient roots with less accumulation of carbohydrates to maintain the net carbon balance.

Effects of boron-deficiency on anatomical structures in the leaf main vein and fruit mesocarp of pummelo [Citrus grandis (L.) Osbeck

SummaryBoron (B)-deficiency is a nutritional problem in the citrus industry worldwide. Under B-deficient conditions, symptoms such as corky split veins, small fruit, low tree vigour, and low fruit yield appear. In this study, we investigated the anatomical responses of mature leaves and the albedo of mature fruit of HB pummelo [Citrus grandis (L.) Osbeck] to B-deficiency. Under B-deficient conditions, the numbers of parenchyma cells in the vascular bundles of the leaf and fruit mesocarp increased significantly. The ratio of the area of the phloem to the area of the vascular bundle also increased, while the ratio of the area of the xylem to the area of the vascular bundle decreased in both tissues. Moreover, we observed alterations in the xylem elements under B-deficient conditions. The average lengths of xylem vessels were 216.7 µm and 175.4 µm in leaf main veins and in fruit mesocarp, respectively, both significantly lower than the corresponding values in B-sufficient control plants. However, B-deficiency reduced the average diameter of xylem vessels only in leaf main veins. On the other hand, B-deficiency increased the numbers of pitted vessels to 63 and 59 among 100 xylem vessels sampled at random in leaf main veins and in the fruit mesocarp of B-deficient pummelos, respectively, while the corresponding numbers were 43 and 35, respectively, under B-sufficient conditions. B-deficiency also decreased the numbers of scalariform and reticulated vessels. Possible mechanisms for these anatomical modifications under B-deficient conditions are discussed.

Effects of Boron Deficiency on Geranium Grown under Different Nonphotoinhibitory Light Levels

Apart from a role in cell wall structure, specific functions for boron (B) in plants are unclear; hence, responses and adaptations to B stress are incompletely understood. We tested hypotheses that net photosynthesis (Pn) decreases with B deficiency before visible foliar symptoms and that higher nonphotoinhibitory light levels enhance soluble carbohydrate status and therefore mitigate B deficiency. Geranium (Pelargonium ×hortorum L.H. Bailey cv. Nittany Lion Red) plants were grown hydroponically and were then exposed to normal (45 μm) or deficient (0 μm) B at two light levels [100 or 300 μmol·m−2·s−1 photosynthetically active radiation (PAR)]. Photosynthesis [net CO2 uptake, carboxylation, and photosystem II (PSII) efficiency] was monitored for 5 days, as were concentrations of B, chlorophyll, soluble sugars, total protein, and several photosynthetic and stress proteins [ribulose 1,5-bisphospate carboxylase oxygenase (rubisco), rubisco activase, oxygen-evolving complex-23 (OEC23), Cu/Zn-superoxide dismutase (SOD), Mn-SOD, and eukaryotic translation initiation factor 5A-2 (eIF5A-2)]. Biomass and sugar concentration were greater in high light, and mass was decreased by B deficiency only in leaves in high light. Boron deficiency decreased [B] in all tissues, especially in new leaves. Carboxylation efficiency and Pn decreased within 1 day of B deficiency in low light, but not until 5 days in high light. Chlorophyll concentration decreased, and Mn-SOD increased transiently, with B deficiency in both light levels, but no other effects of low B were observed. Protection of Pn by higher light was confirmed in a different cultivar (Maverick White) grown at 100, 300, and 500 μmol·m−2·s−1 PAR. Thus, in geranium, photosynthesis is affected by B deficiency before effects on leaf growth, and higher light can at least temporarily ameliorate B deficiency, perhaps partly due to enhanced carbohydrate status.

Effects of boron deficiency in cell suspension cultures of Populus alba L.

Cell suspension cultures of Populus alba L. (original cells) require at least 10 microM boron for appropriate growth. Using original cells we established a cell line, T-5B, which can grow in a medium containing low levels of boron (5 microM). The level of boron localized in the cell walls of T-5B cells was one-half that found in the cell walls of original cells maintained in medium containing 100 microM boron, and the level of the rhamnogalacturonan II dimer, cross-linked by a borate ester, also decreased in the former. The sugar composition of whole cell walls of the T-5B cell line was similar that of the original cells, however pectic polysaccharides composed of arabinose or galacturonic acid were easily extracted from T-5B cell walls with 50 mM trans-1,2-cyclohexanediamine-N,N,N',N'-tetraacetic acid. Our results suggest that boron deficiency causes a weakening of the interaction among pectic polysaccharides due to a decrease in boron-rhamnogalacturonanII cross-linkage.

Effects of Boron Deficiency on Anther Development and Floret Fertility in Wheat (Triticum aestivum L. ‘Wilgoyne’)

Boron (B) deficiency limits reproductive growth more than vegetative growth in cereals such as wheat. The purpose of the present study was to identify the critical stages of anther development of wheat (‘Wilgoyne’) during which B deficiency causes a significant and irreversible decrease of floret fertility in order to formulate timely measures for correcting or preventing this problem. Withdrawing B from the rooting medium for 3 d between premeiotic interphase through meiosis to late tetrad, limited anther elongation and resulted in the loss of pollen viability. The negative effects of B withdrawal on anther length suggest that the role of B in reproductive cell walls is similar to that in vegetative ones. The results indicated that as more florets reached meiosis within the period of B withdrawal, the lower was floret fertility and the number of grains set in a whole ear. For the whole ear, the critical period during which B deficiency causes maximal and irreversible damage to floret fertility was about 7 d, extending from the early emergence of the flag leaf to 2–3 d after its full emergence. The results suggest that there are two phases of pollen development sensitive to boron deficiency: the period from premeiotic interphase through meiosis to late tetrad was the most sensitive stage of microsporogenesis in wheat while the period from mitosis-I to II during which starch accumulation occurred in pollen grains was less sensitive.

Boron Stress and Mitochondrial Quinone Accumulation in Zea mays Seedlings

Summary The effects of boron deficiency (-B) and boron doses of five and ten times the optimal concentration (X5B and X10B) on the activities of ATPases and oxidative phosphorylation, and on the accumulation of mitochondrial quinones in Zea mays L. seedlings, were investigated for 12 days. The specific activities of the respiratory enzymes as well as the level of quinones were enhanced under the deficiency and one supraoptimal concentration (MB), the increase being greater in the former group of seedlings. The other supraoptimal concentration (X10B), however, elicited a decrease in these parameters relative to the control seedlings in full nutrient solution (FN). It is suggested that enhancement of the quinone levels in the -B and X5B seedlings when compared with the FN regime may be due, at least partially, to the increase in ATP levels in these Zea mays seedling regimes.

INTERACTIVE EFFECT OF BORON AND PHOSPHORUS ON GROWTH AND METABOLISM OF MAIZE GROWN IN REFINED SAND

Boron-phosphorus interaction was observed in maize (Zea mays L. ’Ganga 2’) when grown in refined sand at three levels of boron, deficient (0.0033 mg L−1), normal (0.33 mg L−1) and excess (3.3 mg L−1), each at three levels of phosphorus, deficient (0.17 m mol L−1), normal (1.5 mmol L−1) and excess (4 m mol L−1). The effects of phosphorus deficiency (i.e., reduction in dry matter, soluble protein, DNA, activity of ribonuclease and increase in the activities of peroxidase, acid phosphatase and polyphenol oxidase) were intensified by a combined deficiency of boron and phosphorus. The effects of boron deficiency (i.e., reduction in dry weight, leaf boron and DNA and increase in starch content and in the activities of starch phosphorylase, peroxidase and polyphenol oxidase) become more intense in the treatment-deficient B-excess P. The decreases caused by excess phosphorus (i.e., dry weight, starch and sugar content, DNA, RNA and activity of ribonuclease) were aggravated by combined excess of boron and phosphorus.Key words: Zea mays, maize, boron and phosphorus nutrition

Effects of boron deficiency and calcium supply on the calcium metabolism in tomato plant

Tomato plants were grown in water-culture with a different supply of Ca (10, 100 ppm) and B (0, 0.2 ppm), and the effects of B deficiency on the translocation and subcellular distribution of Ca in tomato plants were studied by using45CaCl2 as a carrier of Ca. Boron deficiency slight increased the total Ca uptake by the plant and inhibited the Ca translocation to the upper leaves. The incorporation of45Ca into the cell wall in the upper leaves was increased by B deficiency at both Ca levels. As Ca supply decreased, the distribution of45Ca in the 1N NaCl fraction of the cell wall increased only at 0.2 ppm B. As B supply decreased, the distribution of45Ca in the 0.6N HCl fraction increased at both Ca levels. These results suggest that B deficiency inhibit the translocation of Ca, and induce the abnormal changes of the Ca metabolism in the cell wall.

Effects of Boron Deficiency on Mitosis and Incorporation of Tritiated Thymidine into Nuclei of Sunflower Root Tips

Boron deprivation has multiple effects upon root growth within 6 hr after this essential micronutrient is withheld. Root elongation is inhibited and this response has been attributed to a cessation of mitosis and DNA synthesis. Our preliminary results using an autoradiographic analysis of sunflower roots labeled with [3H]-thymidine demonstrated no difference in label distribution between +/-B root tips. We found that mitosis in inhibited in -B roots but does not completely cease. Scintillation counting of whole root tips shows that boron-deficient roots up to 72 hr of treatment incorporate radioactive label at a level comparable to that of the controls. Because mitosis and presumably DNA synthesis are affected by prolonged boron deficiency, these results may be brought about by a change in membrane integrity or permeability. We propose that effects of boron deprivation on DNA synthesis and mitosis in sunflower are secondary and that primary events involve alterations in cellular membranes.

ARE THERE INTER‐RELATIONS BETWEEN THE METABOLIC ROLE OF BORON, SYNTHESIS OF PHENOLIC PHYTOALEXINS AND THE GERMINATION OF POLLEN?

SUMMARYThe similarities between the effects of wounding, microbial infection and boron deficiency in bringing about alterations in phenolic and hormone metabolism in vascular plants are emphasized and attention drawn to gaps in available information. It is proposed that the similarities are due to induction of localized or systemic sequestration of endogenous borate by β‐l,3 glucans or other carbohydrates including glycoproteins (microbial elicitors and wound callose). In view of the morphological, physiological and biochemical parallels between fungal infection and pollination, it is further argued that there are common metabolic links between the effects of boron deficiency, wounding and infection and the presence of callose in pollen grains and tubes, the stigmatic deposition of callose in response to some incompatible pollinations and the boron requirement for the germination of pollen. A highly speculative but experimentally testable scheme is proposed.

Effects of Boron Deficiency on the Chemical Composition of a Marine Diatom

Effects of Boron Deficiency on the Chemical Composition of a Marine Diatom

Anatomical responses of root tips to boron deficiency I. Effects of boron deficiency on elongation of root tips and their morphological characteristics

Abstract Effects of boron deficiency on the elongation of root tips of tomato and sunflower seedlings were investigated and the morphological responses of root tips were discussed. The primary effect of boron deficiency was the rapid cessation of root elongation followed by browning and some morphological changes in the root tips, such as abnormal enlargement and dense appearance of lateral roots. Root elongation was extremely inhibited within 3 hr after the plants were placed in boron-free media and the lack of boron in the nutrient solution for 72 hr or more caused the root tips to suffer necrosis. The rapid cessation of root elongation was characteristic in boron deficiency and calcium deficiency among several essential element deficiencies which were tested. Differences between boron and calcium deficiency symptoms were discussed in relation to the morphological characteristics of the root tips.

RESPONSE TO BORON DEFICIENCY: A COMPARISON WITH RESPONSES PRODUCED BY CHEMICAL METHODS OF RETARDING ROOT ELONGATION

SummarySeedlings of Vicia faba L. were subjected to treatments with IAA, 2,4‐D, tri‐iodobenzoic acid, kinetin, 2‐chloroethanephosphonic acid as well as those designed to prevent normal division in the primary meristem. Where division was inhibited with colchicine, trifluralin, dinitramine or surgical excision, a radial expansion of the root tip occurred. However, the anatomical aspects of the responses and their effects on phosphate absorption and incorporation were quite distinct from the effects produced in both boron deficiency and excess auxin treatments. Kinetin gave similar effects to mitotic inhibitors. The possibility that boron deficiency is associated with an excess level of endogenous auxin was examined. The effects of boron deficiency were compared with those associated with the presence of excess auxin.