Mild salinity improves sugar beet (Beta vulgaris L.) quality

Abstract

Sugar beet (Beta vulgaris L.) is cultivated mainly on saline soils. Low levels of salinity stimulate growth of this crop plant possibly due to production of broader leaves as sources of assimilates. In this work, six cultivars were studied under mild salinity (EC = 5.5 dS m^?1) in a field experiment to analyse its effect on growth parameters and yield of storage root and sugar accumulation. An attempt was also made to determine the contributing role of photosynthetic gas exchange in response of sugar beet plants to salinity. Production of greater leaf area in salinized plants occurred only transitionally in the early growth period; in progression of the growing season it was decreased, and at 3rd harvest (100 days after treatment) it was significantly lower compared with control plants without cultivar differences. Leaf chlorophyll fluorescence, net photosynthesis rate, and stomatal conductance did not change by salinity significantly. Although, at the end of growth season, leaf area and potential photosynthesizing component of salinized plants on the basis of leaf area (LAR) or weight (LWR) were significantly lower than for control plants, weight of storage root and sugar content were up to 90 and 37% higher than in control plants, respectively. Consequently, a considerable higher yield under mild salinity conditions in sugar beet is not attributable to higher leaf area or, therefore, higher photosynthetic capacity of whole plants. Indeed, the storage roots benefit from lower dry matter and surface production of shoot during the late growing season (because of lower nitrogen assimilation and a slight drought stress of salinized plants) and a change in dry-matter partitioning in favor of roots takes place. However, a possible special effect of Na on carbon allocation for storage and structure and involvement of growth regulators in the change of root-shoot allometry could not be excluded.     

Effect of soil type on the time-course of changes in sugar beet (Beta vulgaris L.) productivity in Tokachi District,Hokkaido, Japan

Abstract

To clarify the effect of soil type on changes in sugar beet (Beta vulgaris L.) productivity since 1980 in Tokachi District (Hokkaido, Japan), we analyzed yield data from 121 settlements from 1980 to 2002 using maps of parent materials and surface organic matter contents in a geographical information system. The soil types were Brown Lowland soils, Andosols with an alluvial subsoil, Wet Andosols and Andosols. The sugar beet yields were highest in the Andosols and moderate in Andosols with an alluvial subsoil. Yields in Brown Lowland soils in the 1980s were similar to those in Andosols, but decreased below the yields in the Andosols by the 1990s. The yields in Wet Andosols were the lowest in the 1980s, but have been similar to those in Andosols with an alluvial subsoil since 1990. Thus, productivity appears to have varied over time in Brown Lowland soils and Wet Andosols. The correlation coefficients between yields and cumulative daily mean temperature from late April to mid-July since 1990 were highest in the Andosols (r = 0.67), lowest in the Brown Lowland soils (r = 0.50) and intermediate in the other soil types (r = 0.54–0.60). However, the magnitude of the correlation between the yield and the cumulative precipitation since 1990 was lowest in the Andosols (r = –0.22), highest in the Brown Lowland soils (r = –0.58) and intermediate in the other soil types (r = –0.44 to –0.45). These results suggest that the present soil water environment in the Andosols is superior to that in the other soil types.     

Interactive effect of lithium on concentration of alkali cations in sugar beet (Beta vulgaris L.) under saline conditions

Background and aims

Increasing demand for lithium (Li⁺) for portable energy storage is leading to a global risk of Li⁺ pollution from the manufacture, use, and disposal of Li⁺-containing products. Although Li⁺, a reactive alkali metal, has no essential function in plants, they readily take it up and accumulate it in large amounts in their tissues. The underlying mechanisms for this Li⁺ uptake and accumulation are, however, not well described. Our aim has been to investigate the effects of other alkali metals with similar physicochemical properties on the uptake, accumulation, and toxicity of Li⁺ at low and high osmolarity.

Methods

To determine the way in which Li⁺ affects the accumulation of other cations under saline conditions, sugar beet plants were grown in hydroponic culture with equimolar amounts of Li⁺, potassium (K⁺), and sodium (Na⁺) at low and high concentrations in various combinations.

Results

Sugar beet plants tolerated high Li⁺ concentrations in the leaf and petiole. Low Li⁺ concentrations had no impact on plant growth but induced stomata closure. The presence of other monovalent cations at equimolar concentrations did not affect Li⁺ accumulation, but Li⁺ application altered the ratio of monovalent and divalent cations in leaves. Plants treated with high Li⁺ in combination with Na⁺ or K⁺ showed reduced plant growth and leaf necrosis, indicating the severe stress caused by Li⁺ toxicity.

Conclusion

The presence of cations with similar physicochemical properties to those of Li⁺ cannot mitigate its toxicity.     

氮肥施用量对高产甜菜纤维根系分布及活力的影响

为了解施N肥对甜菜生长的影响规律。在田间条件下,研究了不同施N量（0、90、180、270、360 kg/hm2）对甜菜（KWS2409）纤维根系生长、分布和活力变化的影响。结果表明,施N比对照增加浅层侧根数、外层和深层纤维根干重及100 cm土层纤维根总干重,并提高各生育期侧根和主根活力。其中,100 cm土层最大纤维根干重施N 比对照增加了60.4%～168.4%,最大侧根数增加了22.7%～75.1%,且以0—20 cm和40—60 cm深的外土层及80—100 cm深的内土层纤维根系增加较大,分别比对照增加了129.6%～266.8%、71.0%～234.0%和101.5%～202.8%。主根伤流液量和侧根的活力分别比对照增加了56.2%～89.9%、23.7%～63.4%。N 180 kg/hm2处理0—100 cm土层中纤维根总量、各土层中根量最大,各生育时期主根和侧根活力最强,块根产量（82609.63 kg/hm2）和产糖量（13892.64 kg/hm2）均最高,而含糖率（16.83%）较N0处理（18.34%）略降。说明合理施N量有利于甜菜纤维根系生长和提高产糖量。     

低磷胁迫对不同基因型甜菜抗性生理特征的效应

选用对低磷胁迫抗性各异的3个甜菜品种:品20、品17和品14,在人工培养室内采用沙培试验法,研究了甜菜抗耐低磷胁迫的生理机制。结果表明,低磷胁迫限制了甜菜对磷的吸收,导致植株含磷量和生物产量显著下降;不同品种间差异显著,品14降幅最大,品17次之,品20最小。与足磷处理(P 100μmol/L)相比,低磷胁迫后甜菜品种间体内抗性生理特征差异显著。其中,品14和品17的丙二醛含量、脯氨酸含量、过氧化物酶活性均显著增加;品20的丙二醛含量、脯氨酸含量极显著下降,而过氧化物酶活性变化不显著。叶片中Mg2+-ATPase活性降低,不同品种降幅各异,从小到大依次为品20品17品14,其中品20与后两者间的差异均达显著。品20和品17体内的钙调素(CaM)含量显著增加,而品14变化不明显,其相对值从大到小依次为品20品17品14,差异显著,与品种自身抗磷胁迫能力顺序一致。不同磷素营养条件对甜菜抵御外界不良环境有较大影响,叶片在受到热伤害时,抗磷胁迫能力较弱的品14和品17在低磷胁迫时质膜损伤率显著增加;而抗磷胁迫能力较强的品20叶片质膜的损伤率显著下降,抗热能力得到改善。     

灌溉制度对膜下滴灌甜菜产量及水分利用效率的影响

为制定新疆合理的甜菜膜下滴灌制度,设置3个灌水次数(8、9和10次)和2个灌水定额(45和60mm)两因素全组合试验,于2016—2017年在新疆玛纳斯县农科院甜菜改良中心开展田间试验。结果表明,灌水次数增加时甜菜叶面积指数与产量增加,含糖率降低,对甜菜的水分利用效率、耗水量无明显影响(P0.05),甜菜叶绿素值随灌水次数与定额增加呈下降趋势;在灌水次数与定额交互作用下,灌水8次时由于土壤相对含水率低于50%,甜菜会减产;当灌水9次,灌水定额为45 mm时,增加15 mm灌水定额土壤相对含水率达50%以上,此时甜菜增产7.4%～7.7%,糖产增加9.4%～9.7%;而继续增加灌水次数时,会导致甜菜含糖率降低而降低糖产。因此针对新疆膜下滴灌甜菜以60 mm灌水定额灌水9次为宜,可获得高产与糖产,较传统新疆膜下滴灌甜菜制度节水10%。该研究对指导新疆膜下滴灌甜菜灌溉制度具有一定意义。     

Base cations ameliorate Zn toxicity but not Cu toxicity in sugar beet (Beta vulgaris)

Seedlings of sugar beet (Beta vulgaris) were grown in nutrient solutions containing a range of Cu and Zn concentrations. Based on measurements of shoot and root length and dry weight, copper was found to be already toxic at 10 μM, while Zn became toxic at 100 μM. At Cu and Zn levels found to induce a similar level of growth inhibiton, the influence of increasing the supply of K, Ca and Mg was investigated. Increasing the concentration of both Ca and Mg in the nutrient solution attenuated the degree of inhibition of root growth by Zn, but not Cu. Potassium did not affect the toxicity of either Cu or Zn. An increase in Ca decreased the level of both Cu and Zn in roots. Magnesium ameliorated the toxicity effects of Zn without effecting the Zn concentration in the roots. Treatment with Zn significantly decreased the concentration of Mg in the roots. An increased supply of Mg lowered the percentage decrease in root Mg concentration due to Zn toxicity. The maintenance of an adequate Mg level in the roots may be critical to prevent Zn induced inhibition of root growth.     

滴施改良剂对新疆盐碱土改良及甜菜产量的影响

为了明确滴施化学改良剂对新疆盐碱土盐碱指标的影响,合理选用化学改良剂,选择4种滴灌专用盐碱改良剂类产品(酸碱平衡护理剂、酸酸肥霸、肽能氮、生物有机菌肥),以不施化学改良剂为对照,对施用前后土壤盐分、pH值、钠吸附比、总碱度、碱化度指标变化和甜菜锤度、产量的差异进行分析。结果表明:与不施化学改良剂相比,酸碱平衡护理剂处理和生物有机菌肥处理使土壤pH值分别降低了0.67和1.03个单位,达到显著水平(P0.05)。除施用酸酸肥霸处理的土壤盐分上升外,其余3种改良剂处理的土壤盐分均下降,施用生物菌肥使土壤盐分下降1.19 g/kg,达到显著水平(P0.05)。施用改良剂使土壤CO_3~(2-)和HCO_3~-的降幅达2.00%~80.00%,酸碱平衡护理剂和肽能氮主要降低土壤中CO_3~(2-)的含量,分别降低了49.50%和30.00%;酸酸肥霸降低HCO_3~-的效应优于CO_3~(2-);生物菌肥对HCO_3~-和CO_3~(2-)均有显著的降低作用,分别下降了60.40%和80.00%。4种盐渍土改良剂均能够有效地降低土壤耕层总碱度和pH值,以生物有机菌肥效果最显著;肽能氮和生物有机菌肥可同时降低土壤钠吸附比和碱化度,显著提高了甜菜的产量,但酸酸肥霸和酸碱平衡护理剂处理的甜菜产量与对照相比差异不显著。     

Nitrogen requirement of fodder and sugar beet (Beta vulgaris L.) cultivars under high-yielding conditions of northwestern Europe

This study provides current data on plant nitrogen (N) uptake required for maximum sugar yield (PNUp_max) and the corresponding fertilizer N dose (ND) (optimum N dose [ND_opt]) for high-yielding beet crops (sugar yield up to 20 Mg ha^?1). In 2010 and 2011, field experiments were conducted with four cultivars from Beta genus differing in dry matter composition, and six mineral NDs (0–200 kg N ha^?1) at three sites (The Netherlands, Germany, Denmark). Differences between cultivars in PNUp_max and ND_opt were small; however, environments (defined as combination of site and year) substantially differed from each other: highest PNUp_max and lowest ND_opt occurred at environments supplying high amounts of N from soil resources, and vice versa. The level of maximum sugar yield (SY_max) was related neither to PNUp_max (200–270 kg N ha^?1) nor to ND_opt. However, N dose and plant N uptake required for 95% of maximum sugar yield was 50–80 kg N ha^?1 lower than for maximum sugar yield. To conclude, accepting a slight reduction in sugar yield might allow for a substantial decrease in the ND. Cultivar choice and yield level need not to be taken into account at present.     

Potassium substitution by sodium in sugar beet (Beta vulgaris) nutrition on K‐fixing soils

Alluvial soils with illite and vermiculite clay minerals are highly potassium (K)‐fixing. Such soils have been reported to require a huge amount of K fertilization for optimum plant growth. For halophytic plants such as sugar beet, sodium (Na) can be an alternative to K under such conditions. This study was conducted to investigate the possible substitution of K by Na fertilization with reference to K‐fixing soils. Three soils, i.e., Kleinlinden (subsoil), Giessen (alluvial), and Trebur (alluvial), differing in K‐fixing capacities, were selected, and sugar beet plants were grown in Ahr pots with 15 kg soil pot^–1. Three treatments (no K and Na, K equal to K‐fixing capacity of soil, and Na equivalent to regular K fertilization) were applied. In a second experiment, containers (90 cm × 40 cm × 40 cm) were used with 170 kg Kleinlinden soil each, and one sugar beet plant per container was grown. In both experiments, plants were grown till beet maturity, and beets were analyzed for sucrose concentration and other quality parameters such as α‐amino nitrogen to calculate white‐sugar yield with the New Brunswick formula. The results showed that growth and quality of sugar beet were not affected by Na application, and ultimately there was no decrease in white‐sugar yield. Moreover, the soils with more K‐fixing capacity were more suitable for K substitution by Na. It is concluded that Na can substitute K in sugar beet nutrition to a high degree and soils with high K‐fixing capacity have more potential for this substitution.     

甜菜谷氨酸合成酶活性与块根产量、含糖率的相关性分析

采用双丰16(偏丰产型)和甜单1号(偏高糖型)两个甜菜(Beta vulgaris L.)品种作为试材,在5个氮素水平(0、60、120、180和240 kg.hm-2)下,研究甜菜功能叶片与块根中谷氨酸合成酶(glutamate syn-thase,GOGAT)在生育进程中的活性变化动态及其与块根产量、含糖率和产糖量的关系。结果表明:在不同氮素水平下,两个品种功能叶片和块根的GOGAT活性均呈双峰曲线变化,两峰值分别出现在6月下旬和8月下旬,其中,功能叶GOGAT前一峰值高于后一峰值;块根GOGAT则与之相反。在不同氮素水平下,功能叶片GOGAT活性表现为N180>N120>N240>N60>N0,块根GOGAT表现为N120>N180>N240>N60>N0。GOGAT的活性与块根产量及含糖率关系紧密,块根产量随GOGAT活性的增加而提高,但是GOGAT活性过高反而降低了块根含糖率,进而导致甜菜产糖量的降低。     

Diagnosis of sugar beet (Beta vulgaris L.) nutrient imbalance by DRIS and CND-clr methods at two stages during early growth

High yield of sugar beet require adequate mineral nutrition. To be diagnosed across interacting nutrients using appropriate interpretation models, the plant must be sampled at a critical physiological stage. This study aimed to develop and validate norms at the 7-leaf and well-developed rosette stages, for diagnostic purposes using the Diagnosis and Recommended Integrated System (DRIS) and Compositional Nutrient Diagnosis based on centered log ratios (CND-clr). Data on nutrient concentrations and plant performance were obtained from 409 plots in West-Central Poland. With respect to the growth stages, for physiological and practical reasons, the 7-leaf stage is preferable for diagnostic purposes. At this growth stage, the high-yield subpopulation characterized by higher concentration of potassium and sodium compared to other nutrients. CND-clr indices were closely related to DRIS indices (R² > 0.93). The CND-clr indices, however, better explained the differences in the white sugar yield within the validated dataset than the DRIS indices.     

Prediction of nitrogen uptake by sugar beet (Beta vulgaris L.) by scoring organic matter and nitrogen management (N-score), in Hokkaido,Japan

Studies were carried out on the interaction between potato scab, soil pH and exchangeable calcium in two different fields, one consisting of volcanic ash soil and the other, of red-yellow soil. Severity of potato scab in the field with red-yellow soil was correlated with the soil pH, unlike in the field with volcanic ash soil. The amount of exchangeable calcium in both soils was positively correlated with the scab index of potato tuber, when the content of exchangeable calcium in soil exceeded 150 mg per 100 g soil. From these results, it was concluded that the content of exchangeable calcium is as a more reliable parameter than the soil pH to evaluate the severity of potato scab.     

Nutrients management strategies to improve yield and quality of sugar beet in semi-arid regions

The objective of this study was to evaluate the effects of organic and inorganic fertilizers on the yield and quality of sugar beet genotypes (Beta vulgaris L.). Therefore, a field trial was carried out in Peshawar, Pakistan, during the winters in 2012–2013. The field experiment was conducted in a randomized complete block design with split plots, having three replications. Fertilizer treatments (control, composted manure Higo Organic Plus at 5 t ha^?1, Maxicrop Sea Gold seaweed extract at 5 L ha^?1, farm yard manure at 10 t ha^?1, inorganic nitrogen–phosphorus (NP) at 90:60 kg ha^?1, NP at 120:90 kg ha^?1 and NP at 150:120 kg ha^?1) were allotted to main plots, while genotypes (Sandrina, Serenada and Kawe Terma) were allotted to the sub-plots. Plots treated with the application of NP at 120:90 kg ha^?1 produced the highest beet yield (76.4 t ha^?1) and sugar yield (11.1 t ha^?1), and had the second highest polarizable sugar content (14.52%) and more economic return (Rs. 553,000 per hectare) as compared to control plots. Sugar beet genotype Serenada had significantly higher beet yield (55.5 t ha^?1) and sugar yield (7.9 t ha^?1) and a higher economic return (Rs. 380,000 per hectare) than the other genotypes. Sugar beet genotype Serenada supplied with NP at 120:90 kg ha^?1is recommended for the general cultivation in the agro-climatic conditions of Peshawar valley.     

Sugar beet (Beta vulgaris L.) response to diammonium phosphate and potassium sulphate under saline–sodic conditions

Salinity and sodicity are prime threats to land resources resulting in huge economic and associated social consequences in several countries. Nutrient deficiencies reduce crop productivity in salt‐affected regions. Soil fertility has not been sustainably managed in salt‐affected arid regions. Few researchers investigated the crop responses to phosphorus and potassium interactions especially in saline–sodic soils. A research study was carried out to explore the effect of diammonium phosphorus (DAP) and potassium sulphate (K₂SO₄) on sugar beet (Beta vulgaris L.) grown in a saline–sodic field located in Kohat district of Pakistan. The crop was irrigated with ground water with EC_iw value of 2.17–3.0 dS/m. Three levels each of K₂O (0, 75 and 150 kg/ha) as K₂SO₄ and P₂O₅ (0, 60 and 120 kg/ha) as DAP were applied. The application of P significantly affected fresh beet and shoot yield while K fertilizers had significant effect on fresh beet yield and ratio of beet:shoot, while non‐significant effects on the fresh shoot were observed. The application of K₁ and K₂ promoted sugar beet shoot yield by 49.2 and 49.2% at P₁ and 64.4 and 59.7% at P₂, respectively over controls. In comparison with controls, fresh beet yield was increased (%) by 15 and 51, 45 and 84, and 50 and 58 for corresponding K₁ and K₂ at P₀, P₁ and P₂, respectively. Addition of P₁ and P₂ increased beet yield by 37 and 47% over control. The shoot [P] (mmol/kg) were achieved as 55.2, 73.6 and 84.3 at P₀, P₁ and P₂, respectively. The shoot [Mg] and [SO₄] tended to decrease with increasing P levels, while [SO₄] was markedly reduced at P₂. The effect of P on leaf [Na] was non‐significant, but increasing levels of K decreased [Na] substantially at P₀ and P₁, but there was no difference in the effect of K level on [Na] at P₂. Consequently, K application reduced leaf Na:K ratios. Fresh shoot yield was weakly associated with leaf [P] (R² = 0.53). The leaf Na:K ratio showed a negative relationship (R² = 0.90) with leaf [K]. A strongly positive relationship (R² = 0.75) was observed between leaf [K] and fresh beet yield. The addition of K₂SO₄ also enhanced [SO₄] and SO₄:P ratios in leaf tissues. The ratio of Na:K in the shoot decreased with increasing K application. These results demonstrated that interactions of K and P could mitigate the adverse effects of salinity and sodicity in soils. This would contribute to the efficient management of soil fertility system in arid‐climate agriculture.     

有机无机复混肥优化化肥养分利用的效应与机理研究Ⅰ. 有机物料与尿素复混对玉米产量及肥料养分吸收利用的影响

本研究采用团粒法工艺,利用味精厂制糖形成的糖渣（A）作为有机原料,与尿素复混制成有机无机复混氮肥,运用土柱栽培试验研究等尿素氮投入条件下（设置低、中、高3个施氮水平）不同有机无机比例的有机无机复混氮肥对玉米产量和养分吸收利用的影响。主要结果为, 1）低氮、中氮和高氮水平下,有机无机复混氮肥处理平均玉米子粒产量比单施尿素处理的分别提高12.4%、4.8%和5.4%;低氮、中氮和高氮水平下,有机无机复混氮肥比对应的有机物料处理的增产幅度均大于尿素处理比对应的不施氮肥（CK）处理的增产幅度,有机物料与尿素复混,明显提高了尿素的增产效果。2）有机物料与化学氮肥复混具有优化化学肥料养分利用和提高化肥利用率的效果。低氮、中氮和高氮水平下,有机无机复混氮肥处理玉米植株氮素吸收量比尿素处理的分别提高29.0%、21.6%和18.9%;低氮、中氮和高氮水平下,有机无机复混氮肥处理化肥氮（尿素N）的表观利用率比尿素处理（尿素N）的氮肥表观利用率分别提高了33.5、11.6和13.0个百分点。     

Analysis of morphological variation in wild beet (Beta vulgaris L.) from Sicily

Summary In this paper the variation pattern of the Sicilian Beta germplasm collection is analysed. Accessions from Sicily were grown under controlled conditions and were evaluated morphometrically. Geographical distribution patterns of morphological characters are identified and the putative classification of the collection into coastal and inland populations is reassessed. Between adjacent populations significant variation was found for Petiole length, Leaf length, Leaf width and Biomass, however no one variable unambiguously reflected a geographical pattern. Overall differences between coastal and inland populations were small. Petiole length and rate of generative development were found to be important for distinguishing between these groups. Interferences are drawn on how the collection from Sicily could be rationalized to avoid excessive duplication.     

生物有机无机复混肥对番茄产量、品质及土壤的影响

研究了不同肥料对大棚番茄及其土壤的影响。结果表明:生物有机无机复混肥对番茄产量、品质和土壤养分有重要的作用。与NPK无机复混肥、常规施肥相比,生物有机无机复混肥可使番茄产量增加7 34%～13 64%,果实可溶性糖、有机酸、维生素C、糖酸比分别提高18 2%～23 2%、8 3%～15 6%、13 2%～15 1%、9 1%～12 6%,果实中硝酸盐(NO3-)含量下降22 9%～23 8%。土壤耕层有机质、碱解氮、速效磷、速效钾含量分别增加8 25%～10 48%、9 43%～14 71%、11 29%～15 00%、13 60%～18 34%。根际土壤中细菌、真菌、放线菌的数量依次增加45 45%～60 00%、14 29%～33 33%、44 19%～100 00%,细菌与真菌数量比值提高19 98%～37 27%。     

不同氮素水平对甜菜硝酸还原酶和亚硝酸还原酶活性的影响

以当前甜菜（Beta Vulgaris L.）生产主栽品种KWS0143为试材,设立4个氮素水平（N 0、60、120、180 kg/hm2）,研究硝态氮肥对甜菜硝酸还原酶（nitrate reductase, NR）和亚硝酸还原酶（nitrite reductase, NiR）活性以及光合速率与叶绿素总含量的影响,探讨了氮素水平与NR及NiRA之间的关系。结果表明:在甜菜生育期间,光合速率呈单峰曲线变化,NR、NiR活性及叶绿素总含量基本呈双峰曲线变化,叶绿素变化曲线的高峰期早于NR活性,NR活性早于NiR活性。氮肥用量在N 120 kg/hm2时显著提高了甜菜光合速率、叶绿素总含量、NR活性和NiR活性。相比于N 120 kg/hm2,N 180 kg/hm2时光合速率及叶绿素总含量没有明显变化,NR与NiR活性则有一定的提高。本试验中,甜菜产量随氮水平的增加而提高;含糖率则相反,随氮水平的增加而降低,N 120 kg/hm2水平下产糖量最高。     

Boron stress inhibits beet (Beta vulgaris L.) growth through influencing endogenous hormones and oxidative stress response

Objective: This study aimed to evaluate the pleiotropic effects of boron stress on beet (Beta vulgaris L.) growth.

Methods: Beet seedlings were treated with varying concentrations of H₃BO₃ (0.05, 0.5, 2, and 30 mg/L) for 30 d for evaluation of diverse morphological parameters related to shoot and root growth. Transverse sections of beet leaves were observed under a microscope, and the leaf thickness was measured. Photosynthesis in beet was evaluated by measuring the photosynthetic rate, intercellular carbon dioxide concentration, and chlorophyll content; chloroplast morphology was observed by transmission electron microscopy. In addition, the levels of diverse endogenous hormones, as well as oxidative stress parameters, were also analyzed in beet leaves.

Results: We found that boron accumulated in different beet tissues but was observed mainly in mature leaves, followed by young leaves, mature petioles, young petioles, and roots. Boron stress (boron toxicity, 30 mg/L; boron deficiency, 0.05 mg/L) significantly inhibited beet shoot, root growth, and leaf expansion while promoting leaf thickening. Additionally, the levels of indole-3-acetic acid, gibberellin A3, and zeatin in beet leaves decreased significantly under boron stress, whereas the level of abscisic acid increased. Moreover, the levels of superoxide dismutase, peroxidase, catalase, malondialdehyde, and proline in beet leaves increased significantly under boron stress.

Conclusion: Together, our results indicate that boron stress significantly inhibited normal beet growth via the influence of endogenous hormone levels and oxidative stress responses.