Boron deficiency increases putrescine levels in tobacco plants

Polyamine concentrations were determined in leaves and roots of tobacco plants (Nicotiana tabacum L.) subjected to a short-term boron deficiency. A decrease in the growth of shoots and, especially, roots was found under this mineral deficiency. Boron deficiency did not lead to a significant decrease in leaf or root ion concentrations when compared to control treatment; however, as expected, leaf boron concentration was lower in boron-deficient plants in comparison to the control. In leaves, the levels of free putrescine and spermidine were similar in both treatments. In roots, a short-term boron deficiency caused an increase in free putrescine. Moreover, boron-deficient plants had higher conjugated polyamine concentration than boron-sufficient plants, which was especially evident for conjugated putrescine in leaves. A possible link between boron and polyamine levels is proposed and discussed.     

缺硫对脐橙叶片光合特性和叶绿素荧光参数的影响

采用营养液培养的方法,对缺硫脐橙叶片的光合特性进行了研究。结果表明,在缺硫情况下,脐橙叶片的净光合速率(Pn)、光呼吸速率(Pr)、光合色素含量、可溶性蛋白质含量、初始荧光(Fo)、光化学效率(Fv/Fm)、最大荧光(Fm)和电子传递速率(ETR)显著下降,而光呼吸/光合比(Pr/Pn)显著升高。缺硫脐橙植株的光合能力降低,可能是叶绿体发育不全或特性功能蛋白含量不足所致。     

Boron deficiency causes accumulation of chlorogenic acid and caffeoyl polyamine conjugates in tobacco leaves

The effects of boron (B) deficiency on carbohydrate concentrations and the pattern of phenolic compounds were studied in leaves of tobacco plants (Nicotiana tabacum L.). Plants grown under B deficiency showed a notable increase in leaf carbohydrates and total phenolic compounds when compared to controls. The qualitative composition of phenolics was analyzed by HPLC-mass spectrometry. The level of caffeate conjugates (i.e., chlorogenic acid) increased in B-deficient plants. In addition, the accumulation of two caffeic acid amides (N-caffeoylputrescine and putative dicaffeoylspermidine) was observed.     

缺硼导致柑橘叶脉和果实导管分子形态畸形的观察

缺硼可导致柑橘叶片变厚而脆、发生木栓化、"猴头果"等现象,其原因是植物组织内部起运输作用的维管组织受到损坏。导管是维管组织重要组成部分,本实验以‘纽荷尔’脐橙(Citrus sinensis Osbeck ‘Newhall’)和HB柚[Citrus maxima (Burm.) Merr.‘HB You’]叶片、HB柚果实中果皮为材料,利用离析方法将导管分离,观察缺硼导管分子形态的变化。结果表明:(1)缺硼使纽荷尔脐橙叶脉中的孔纹导管数量增多;(2)缺硼使HB柚叶片和果实中果皮的孔纹导管大量增生,梯纹导管和网纹导管数量减少;(3)正常导管圆润饱满,而缺硼导管变形干瘪,且有侧壁穿孔现象;(4)缺硼导管变得短而窄,细胞壁变薄,无尾率增加,使维管组织功能丧失。(5)缺硼维管束受损,运输效率降低,是发生叶脉木栓化和"猴头果"现象的源头。     

Mineral nutrient deficiency increases the sensitivity of photosynthesis to sulphur dioxide in needles of a coniferous tree,Abies nordmanniana

Summary Abies nordmanniana (Stev.) Spach was cultivated in rooting media either rich in nutrients (control) or low in magnesium (low Mg) or low in magnesium and nitrogen (low Mg-N), respectively. Intact, attached needles were exposed, in the light (460 mol photons m^-2 s^-1), to an atmosphere containing 1 ppm SO₂ for 5 h. Measurements of light- and CO₂-saturated rates of photosynthetic O₂ evolution, A _max, were performed before and after SO₂ treatments. In needles from well fertilized plants, A _max was high (about 50 mol m^-2 s^-1) and was not affected by SO₂. Needles from low-Mg and low-Mg-N plants had lower photosynthetic rates and showed a marked decline in A _max in response to the SO₂ treatment. Stomatal conductance was similar in the three groups of plants during SO₂ treatments.Abbreviations A _max photosynthetic capacity (CO₂- and light-saturated rate of O₂ evolution) - DW dry weight - F_o yield of dark level fluorescence - F_M maximum yield of fluorescence, induced in a pulse of saturating light - F_v yield of variable fluorescence (= F_M–F_O) - FW fresh weight; g, conductance to water vapor transfer     

Combined effects of enhanced UV-B radiation and nitrogen deficiency on the growth,composition and photosynthesis of rye (Secale cereale)

The interactive effects of N-deficiency and enhanced UV-B radiation on growth, photosynthesis and pigmentation of rye were studied. The plants were grown for 5 weeks in growth chambers with high (700 mol m^-2 s^-2) irradiance levels. A 30% difference in UV-B at plant level was achieved by using different thicknesses of UV-B transparent Plexiglass. One half of the plants received optimal N nutrition, while the other received half of this dose. Both enhanced UV-B and N deficiency strongly decreased production (from 24–33%). The combined effect was additive (no interaction) on most parameters, including total dry weight production which was 52% lower than in the control series. Significant interaction was found on the root/shoot ratio. While reduced N supply induced an increase in the ratio at normal UV-B irradiation, under the increased UV-B, N deficiency had no effect on the root/shoot ratio. The reduced biomass due to UV-B was clearly correlated to a reduction in photosynthesis. At optimal N supply the plants increased the production of protective pigments in response to UV-B, but at reduced N supply this response was lacking. The increased N content of the high UV-B/high N plants could be a result of increased flavonoid production as well as changes in light penetration in the canopy.     

Salt-induced modulation in growth,photosynthesis and antioxidant system in two varieties of Brassica juncea

The present study was carried out to examine salt-induced modulation in growth, photosynthetic characteristics and antioxidant system in two cultivars of Brassica juncea Czern and Coss varieties (Varuna and RH-30). The surface sterilized seeds of these varieties were sown in the soil amended with different levels (2.8, 4.2 or 5.6 dsm⁻¹) of sodium chloride under a simple randomized block design. The salt treatment significantly decreased growth, net photosynthetic rate and its related attributes, chlorophyll fluorescence, SPAD value of chlorophyll, leaf carbonic anhydrase activity and leaf water potential, whereas electrolyte leakage, proline content, and activity of catalase, peroxidase and superoxide dismutase enzymes increased in both the varieties at 30 d stage of growth. The variety Varuna was found more resistant than RH-30 to the salt stress and possessed higher values for growth, photosynthetic attributes and antioxidant enzymes. Out of the graded concentrations (2.8, 4.2 or 5.6 dsm⁻¹) of sodium chloride, 2.8 sm⁻¹ was least toxic and 5.6 dsm⁻¹ was most harmful. The variation in the responses of these two varieties to salt stress is attributed to their differential photosynthetic traits, SPAD chlorophyll value and antioxidant capacity, which can be used as potential markers for screening mustard plants for salt tolerance.     

Magnesium deficiency treatment causes reductions in photosynthesis of well-nourished Norway spruce

In order to investigate effects of magnesium deficiency on Norway spruce [Picea abies (L.) Karst.] photosynthesis, 100 well-nourished 5-year-old spruce trees were grown in sand culture, individually supplied with circulating nutrient solutions. Mineral nutrients were added to the nutrient solutions in optimal quantities and optimal relations to nitrogen. Magnesium was supplied at 0.203, 0.041 and 0.005 mM in order to simulate optimal nutrition, moderate deficiency and severe deficiency. Parameters of photosynthetic gas exchange, chlorophyll, magnesium and starch concentrations were determined in current-year and 1-year-old needles during one growing season. By mid May — 6 months after onset of the Mg deficiency treatments in late autumn — CO₂-assimilation rates of 1-year-old needles were significantly decreased independent of the severity of the deficiency treatment, whereas the chlorophyll concentrations did not differ from the controls. The occurrence of yellowing symptoms during July did not further influence the Mg deficiency effect on photosynthesis. In contrast to 1-year-old needles, significant reductions of photosynthesis and chlorophyll in current-year needles were only caused by severely deficient Mg supply. Mg deficiency affected carboxylation efficiency but not light use efficiency. From the accumulation of starch in the needles, up to 30-fold of the controls, the conclusion has been drawn that reactions of CO₂-fixation were affected by reduced carbohydrate export. The light-dependent pigment reduction, leading to the typical tipyellowing of needles, clearly reflects a secondary effect of Mg deficiency.     

The movement and distribution of citrus tristeza virus and citrus exocortis viroid in citrus seedlings1

The systemic movement of citrus tristeza virus (CTV) in sour orange (Citrus aurantium) seedlings and of citrus exocortis viroid (CEVd) in Etrog citron (C. medica) seedlings was studied. The movement of the two pathogens was analysed by detection in sections of roots and stems at different time intervals. Both pathogens were detected initially in the basal parts and the roots and subsequently spread to the shoot. CTV and CEVd moved in young citrus seedlings at similar rates. The findings are consistent with long distance phloem transport of the virus and the viroid. The practical implications of the pattern of systemic movement for diagnosis of infected trees are discussed.     

Proteomic analysis of Arabidopsis thaliana leaves in response to acute boron deficiency and toxicity reveals effects on photosynthesis,carbohydrate metabolism,and protein synthesis

Boron (B) stress (deficiency and toxicity) is common in plants, but as the functions of this essential micronutrient are incompletely understood, so too are the effects of B stress. To investigate mechanisms underlying B stress, we examined protein profiles in leaves of Arabidopsis thaliana plants grown under normal B (30 μM), compared to plants transferred for 60 and 84 h (i.e., before and after initial visible symptoms) in deficient (0 μM) or toxic (3 mM) levels of B. B-responsive polypeptides were sequenced by mass spectrometry, following 2D gel electrophoresis, and 1D gels and immunoblotting were used to confirm the B-responsiveness of some of these proteins. Fourteen B-responsive proteins were identified, including: 9 chloroplast proteins, 6 proteins of photosynthetic/carbohydrate metabolism (rubisco activase, OEC23, photosystem I reaction center subunit II-1, ATPase δ-subunit, glycolate oxidase, fructose bisphosphate aldolase), 6 stress proteins, and 3 proteins involved in protein synthesis (note that the 14 proteins may fall into multiple categories). Most (8) of the B-responsive proteins decreased under both B deficiency and toxicity; only 3 increased with B stress. Boron stress decreased, or had no effect on, 3 of 4 oxidative stress proteins examined, and did not affect total protein. Hence, our results indicate relatively early specific effects of B stress on chloroplasts and protein synthesis.     

Boron deficiency inPinus radiata D. Don and the effect of applied boron on height growth and nutrient uptake

Summary Severe dieback observed inP. radiata D. Don plantations during dry years in Southeastern Australia was found to be due to boron deficiency. Borax applied in spring (August 1982) at rates of 50, 100 and 150 kg ha^–1 resulted in a marked increase in foliar B and an alleviation of B deficiency symptoms. During the dry summer following the application of borax no further dieback was observed and height growth of fertilized trees was significantly improved. Correction of B deficiency enhanced the uptake of P by the trees.     

Boron deprivation decreases liver S-adenosylmethionine and spermidine and increases plasma homocysteine and cysteine in rats

Two experiments were conducted with weanling Sprague–Dawley rats to determine whether changes in S-adenosylmethionine utilization or metabolism contribute to the diverse responses to boron deprivation. In both experiments, four treatment groups of 15 male rats were fed ground corn-casein based diets that contained an average of 0.05 mg (experiment 1) or 0.15 mg (experiment 2) boron/kg. In experiment 2, some ground corn was replaced by sucrose and fructose to increase oxidative stress. The dietary variables were supplemental 0 (boron-deprived) or 3 (boron-adequate) mg boron/kg and different fat sources (can affect the response to boron) of 75 g corn oil/kg or 65 g fish (menhaden) oil/kg plus 10 linoleic acid/kg. When euthanized at age 20 (experiment 1) and 18 (experiment 2) weeks, rats fed the low-boron diet were considered boron-deprived because they had decreased boron concentrations in femur and kidney. Boron deprivation regardless of dietary oil increased plasma cysteine and homocysteine and decreased liver S-adenosylmethionine, S-adenosylhomocysteine, and spermidine. Plasma concentration of 8-iso-prostaglandin F_2α (indicator of oxidative stress) was not affected by boron, but was decreased by feeding fish oil instead of corn oil. Fish oil instead of corn oil decreased S-adenosylmethionine, increased spermidine, and did not affect S-adenosylhomocysteine concentrations in liver. Additionally, fish oil versus corn oil did not affect plasma homocysteine in experiment 1, and slightly increased it in experiment 2. The findings suggest that boron is bioactive through affecting the formation or utilization of S-adenosylmethionine. Dietary fatty acid composition also affects S-adenosylmethionine formation or utilization, but apparently through a mechanism different from that of boron.     

The relationship between phosphate status and photosynthesis in leaves

Spinach (Spinacia oleracea L.) and barley (Hordeum vulgare L.) were grown in hydroponic culture with varying levels of orthophosphate (Pi). When leaves were fed with 20 mmol·l^–1 Pi at low CO₂ concentrations, a temporary increase of CO₂ uptake was observed in Pi-deficient leaves but not in those from plants grown at 1 mmol·l^–1 Pi. At high concentrations of CO₂ (at 21% or 2% O₂) the Pi-induced stimulation of CO₂ uptake was pronounced in the Pi-deficient leaves. The contents of phosphorylated metabolites in the leaves decreased as a result of Pi deficiency but were restored by Pi feeding. These results demonstrate that there is an appreciable capacity for rapid Pi uptake by leaf mesophyll cells and show that the effects of long-term phosphate deficiency on photosynthesis may be reversed (at least temporarily) within minutes by feeding with Pi.Abbreviation Pi orthophosphate     

Zinc deficiency, carbonic anhydrase, and photosynthesis in leaves of spinach

A shortage in the zinc supply to spinach (Spinacia oleracea L.) drastically reduced carbonic anhydrase levels with little effect on net CO₂ uptake per unit leaf area, except with the most severe zinc stresses. Under these conditions, carbonic anhydrase was below 10% and photosynthesis 60 to 70% of the control levels. When photosynthesis was measured at a range of CO₂ supply levels, zinc-deficient leaves were less efficient at 300 to 350 microliters per liter CO₂ and above, but the same as controls at lower CO₂ levels. This suggests that carbonic anhydrase does not affect the diffusion of CO₂, and that the effect of zinc deficiency was on the photosynthetic process itself. Our evidence does not support the hypothesis that carbonic anhydrase has some role in facilitating the supply of CO₂ to the sites of carboxylation within the chloroplast.     

Seasonal fluctuations of photosynthesis and its pigments in 1-year mycorrhized spruce seedlings

Specimens of spruce Picea abies (L.) Karsten were inoculated with the fungi Laccaria laccata, Pisolithus tinctorius and Lactarius piperatus in a nursery at the time of sowing. The 1-year seedlings were then tested in two growth periods for their photosynthesis, chlorophyll and carotenoid levels, and water potential; their roots were examined with a scanning electron microscope. Increased photosynthetic activity was determined at the start of the growth season in only those seedlings inoculated with the fungus Laccaria laccata. The levels of chlorophyll and carotenoids measured in September in the needles of all three mycorrhized groups of plants were higher than in the controls.     

Midday depression of photosynthesis and effects of mist spray in citrus

Diurnal variations of gas exchange, chlorophyll a fluorescence and some related biochemical characteristics in sun-acclimated mature citrus leaves of mist-sprayed (treatment) and unsprayed (control) trees were compared on sunny days during summer to identify the environmental and physiological factors limiting carbon gain in citrus tree canopies. At midday, net photosynthesis and maximal photochemical efficiency of photosystem II ( F _v/ F _m) in citrus leaves decreased significantly under control conditions, but the decrease was mitigated by mist spraying. Although the content of malondialdehyde, hydrogen peroxide and activities of antioxidant enzymes increased at midday in both mist-sprayed and control leaves, they were much higher in control leaves than in mist-sprayed leaves. The level of D1 protein decreased significantly in control leaves at midday and then was partly recovered later, while that in treated leaves changed to a much lesser extent because of alleviation of photoinhibition by mist spraying. Both the fast and the slow phases of millisecond-delayed light emissions in treated citrus leaves were higher than those in control leaves, indicating that mist spraying protects the normal operation of the photosynthetic apparatus in leaves. Mist spraying also reduced leaf temperatures and the ratio of air to leaf vapour pressure deficit (ALVPD), leading to increases in stomatal conductance ( g _s) and alleviation of photoinhibition at midday. It is concluded that the decline of leaf g _s under high-ALVPD conditions in summer is an important factor contributing to midday depression of photosynthesis in citrus, and mist spraying is effective in alleviating midday depression of photosynthesis in citrus leaves.     

Rhythms during extended dark periods determine rates of net photosynthesis and accumulation of starch and soluble sugars in subsequent light periods in leaves of Sorghum

Photosynthesis and photosynthate partitioning in leaves of Sorghum bicolor (L.) Moench exhibited a cyclic dependence on the duration (10–62 h) of dark periods inserted prior to bright light test periods (550 mol·s^-1·m^-2, photosynthetic photon flux). Maximum rates of net photosynthesis and of accumulation of starch and soluble sugars were, in the order given, two-, three- and fourfold greater than minimum values. Between 14 and 53% of photosynthate was retained in leaves depending on the length of the dark period. These changes were sufficient to account for the previously described stimulatory effect of short daylengths (i.e., long nights) on carbohydrate accumulation in leaves (N.J. Chatterton and J.E. Silvius, 1980, Physiol. Plant. 49, 141–144). The freerunning periods for the rhythmic dependence on darkness, determined either directly or by curve fitting, were about 24 h for net photosynthesis, 23 h for starch accumulation, and 26 h for solublesugar cccumulation. The deviation from period lengths of 24 h for carbohydrate accumulation indicates that these rhythms are probably endogenous and circadian. Initial maxima were observed after 14 h of darkness for photosynthesis, after 18–22 h for starch, and after 26 h for soluble sugars. The differences in period length and phase indicate that at least three separate rhythms underlie the dependence of photosynthate partitioning in Sorghum on darkness. Periods of low leaf dry-matter accumulation coincided approximately with periods of high net photosynthesis. As a result, maximum photoassimination and maximum export were synchronized and, furthermore, occurred at about the same time as expected light periods.Abbreviations and symbols DD (the nth h of) continuous darkness - LT Iocal time of day - free-running period length This paper is dedicated to Professor Wilhelm Nultsch on his 60 th birthdayMention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the United States Department of Agriculture and does not imply its approval to the exclusion of other products that may also be suitable