Effect of atmospheres combining high oxygen and carbon dioxide levels on microbial spoilage and sensory quality of fresh-cut pineapple

Fresh-cut fruit such as pineapple have a very limited shelf-life. The study aims at prolonging the shelf-life of fresh-cut pineapple by means of modified atmospheres (MAs). The effect of MAs combining high O₂ (21–70%) and CO₂ (21–50%) levels on microbial spoilage and sensory quality of fresh-cut pineapple was therefore evaluated. In the first part of the study, the behaviour of two spoilage yeasts (Candida sake and Candida argentea) and one lactic acid bacterium (Leuconostoc citreum), which had previously been isolated from spoiled commercial fresh-cut pineapple cubes, were monitored on pineapple agar separately. In the second part of the study, the shelf-life of commercial fresh-cut pineapple cubes packaged in selected MAs was evaluated at 7 °C. The results showed that MAs combining high O₂ and high CO₂ levels had a large inhibitory effect on the growth and volatile metabolite production of C. sake and C. argentea on pineapple agar. A MA with 50% O₂ and 50% CO₂ was in both cases the most inhibitive. Although MAs induced the production of ethyl acetate by the yeasts, the quantity of ethyl acetate was much lower in high O₂ and high CO₂ than that in air due to lower yeast population density in MAs. With regards to growth, L. citreum was not sensitive to high O₂ and CO₂ levels. The fresh-cut pineapple packaged in air had deteriorated and were not acceptable any more by day 7, while those packaged in 50% O₂ combined with 50% CO₂, which also retarded the growth of aerobes and yeasts on pineapple cubes during storage, were still acceptable. It can be concluded that a MA with 50% O₂ and 50% CO₂ shows the best potential for extension of the shelf-life of fresh-cut pineapple.     

Low oxygen levels and light exposure affect quality of fresh-cut Romaine lettuce

Modified atmosphere packaging (MAP) has the potential to extend the shelf-life of fresh-cut lettuce mainly by limiting the oxidation processes. However, exposure to light conditions has been described as causing browning and quality loss. The influence of O₂ partial pressures (pO₂) and light exposure during storage on the shelf-life of fresh-cut Romaine lettuce was studied. Fresh-cut lettuce was exposed daily during storage to different light conditions: light (24 h), darkness (24 h) and photoperiod (12 h light + 12 h darkness). Changes in respiration rate, headspace gas composition, sensory quality, colour, electrolyte leakage, stomatal opening, water loss, texture and compositional constituents related to browning such as vitamin C and individual and total phenolic compounds were evaluated. Different weight samples (75–275 g), packaged with an initial pO₂ of 0.5–2.0 kPa balanced with N₂, reached pO₂ from 0.1 to 1.5 at the steady-state. Atmospheres with low pO₂ (0.2–0.5) at the steady-state preserved lettuce quality by the control of browning and the prevention of off-odours and off-flavours. Light exposure during storage positively influenced the number of open stomata (74% in light vs 24% in darkness) which contributed slightly to weight loss. Consumption of O₂ in samples exposed to light differed significantly from those stored in photoperiod or darkness (10.6 ± 7.0, 18.3 ± 3.5 and 25.8 ± 8.6 nmol O₂ kg^?1 s^?1, respectively). Packages exposed to light showed higher pO₂ compared with packages stored in darkness while those exposed to photoperiod had intermediate values. Moreover, location of the packages in the shelves affected package headspace gas composition and thus, packages near the front of the shelves showed higher pO₂ than those at the back. The different light conditions did not influence the content of vitamin C or the individual and total phenolic compounds. This study shows that under light conditions respiration activity was compensated by photosynthesis resulting in a higher pO₂. Thus, browning of fresh-cut Romaine lettuce can be promoted by light exposure during storage as it increases headspace pO₂.     

High oxygen combined with high carbon dioxide improvesmicrobial and sensory quality of fresh-cut peppers

The effects of high O₂ and high CO₂ throughout storage on the microbial and sensory quality of fresh-cut bell peppers from two commercial ‘California’ cultivars grown under different climatic conditions were studied. The ‘Meteor’ cultivar was minimally processed in Leuven (Belgium) and the ‘Requena’ cultivar in Cartagena (Murcia, Spain). The storage conditions were (kPa O₂/kPa CO₂/kPa N₂) 100/0/0, 80/15/5, 60/0/40, 50/15/35, 20/15/65 and 21/0.03/≅79 as control. Bell peppers freshly-cut in cubes were stored at 5 °C up to 9–10 days. Changes in total counts of mesophilic, psychrotrophic, yeasts and mould as well as Enterobacteriaceae were monitored. Individual and total sugars and organic acids contents, visual appearance, color, shriveling, off-aroma, crunchiness, flavor and overall quality were also evaluated. The results in both experiments showed that 80 or 50 kPa O₂ combined with 15 kPa CO₂ maintained the main sensory quality attributes and inhibited growth of the spoilage microorganisms and Enterobacteriaceae in minimally processed bell peppers.     

High carbon dioxide and low oxygen storage effects on reactive oxygen species metabolism in Pleurotus eryngii

This study addressed the influence of high carbon dioxide and low oxygen levels on Pleurotus eryngii samples, stored at 20–25 °C and 90–95% RH for 5 d. Evaluations of sensory characteristics, malondialdehyde (MDA) content, superoxide anion (O₂⁻) production rate and the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and cytochrome c oxidase (CCO) were made in the mushrooms in response to high carbon dioxide and low oxygen treatments. The results showed that 2% O₂ + 30% CO₂ significantly prolonged mushroom shelf-life when compared to the control. The 2% O₂ + 30% CO₂ mixture was better suited to maintaining mushroom sensory characteristics and delaying the MDA increase and O₂⁻ production rate during storage. The activities of SOD, POD, and CAT in 2% O₂ + 30% CO₂-treated mushrooms were significantly higher than those of the control. However, the CCO activity was not affected by the atmospheric treatment (2% O₂ + 30% CO₂). These results indicated that the 2% O₂ + 30% CO₂ treatment could alleviate lipid peroxidation and enhance antioxidant enzyme activities, but it exerted little influence on the CCO activity of Pleurotus eryngii.     

The kinetics of acetaldehyde and ethanol accumulation in ‘Hass’ avocado fruit during induction and recovery from low oxygen and high carbon dioxide conditions

The kinetics of acetaldehyde (AA) and ethanol (EtOH) accumulation and pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) activities were studied in pre-climacteric ‘Hass’ avocado fruit flesh during induction and recovery from hypoxic conditions at 6 °C. Oxygen levels <0.5% resulted in a rapid accumulation of AA and EtOH. The pattern of AA and EtOH accumulation could be described by a hyperbolic model, although the initial 96 h of EtOH accumulation was linear. The accumulation of EtOH and AA was coincident with a doubling of the extractable ADH and PDC activities after 120 h exposure. Exposure of the fruit to up to 20% CO₂ concentrations resulted in an increase in tissue levels of AA, but not EtOH. The pattern of AA accumulation under high CO₂ was similar to that under low O₂, with the level of AA being higher at higher CO₂ concentrations.The AA and EtOH induced by low O₂ declined to basal levels in an exponential manner when O₂ was increased from ≤0.5 to ≥2%. The longer the duration of hypoxic induction, the longer the time required for AA and EtOH to decline to basal levels. When low O₂ induction was 48 h or less, the time required for AA and EtOH to decline to basal levels was not affected by O₂ concentrations >2%. However, after 96 h induction, the initial rate of decline in AA or EtOH was slower at lower O₂ concentrations. Including 20% CO₂ in the recovery atmosphere decreased the initial rapid rate of AA and EtOH decline, affecting EtOH levels more than AA, although both compounds reached pre-induction levels at approximately the same time. The rate of decline of ADH and PDC activity following low O₂ induction was accelerated by the presence of CO₂ in the atmosphere.Based on the rapid induction of AA and EtOH in response to low O₂ stress, and the comparable rapid recovery to basal levels after removal of the stress atmosphere, together with a seemingly high tolerance to O₂ atmospheres <2% and the similar but relatively smaller effect of CO₂ compared with O₂, it is concluded that preclimacteric ‘Hass’ avocados are physiologically well suited to dynamic CA storage.     

Responses of 1-MCP application in plums stored under air and controlled atmospheres

The potential of 1-MCP for controlling ripening in ‘Angeleno’ plum fruit under air and controlled atmosphere (CA) storage was explored, and the possibility that 1-MCP can inhibit development of brown rot caused by Monilinia laxa and internal breakdown in ‘Fortune’ and ‘Angeleno’ plums tested. After harvest, fruit were exposed to 300 and 500 nl l⁻¹ (in 2003) and 500 nl l⁻¹ 1-MCP (in 2004) at low temperatures (0–3 °C) for 24 h. After treatment the plums were stored in air at 0 °C and ‘Angeleno’ fruit were also stored in CA storage (1.8% O₂ + 2.5% CO₂). Following storage, fruit were kept at 20 °C. In ‘Angeleno’ fruit, 1-MCP was effective in delaying the loss of firmness and colour changes during holding at 20 °C. 1-MCP reduced brown rot in fruit stored in CA but no significant reduction was found in air storage. Internal breakdown, a major physiological storage disorder in plums, was inhibited by 1-MCP treatment. Furthermore, since 1-MCP applied in air storage showed better results than the control in CA conditions, an application of 1-MCP before air storage could be the best way to reduce the ripening process for short or medium storage periods (40 and 60 days). CA storage plus 1-MCP treatment could be used for long periods (80 days).     

Identification of respiration rate and water activity change in fresh-cut carrots using biospeckle laser and frequency approach

For consumers, fresh-cut fruits and vegetables are a convenient product and a healthy source of fresh food that has nutritional and sensory characteristics similar to those of intact products. In this paper, a non-destructive method for analyzing fresh-cut fruit and vegetables is described. The biospeckle laser technique is based on the optical phenomenon of interference generated by a coherent light interacting with biological materials or dynamical systems. Although many publications on this technique's biological applications have reported that biospeckle activity corresponds to the activity of biological samples, there is some difficulty in determining the correlation between a particular phenomenon and the activity observed. In this study, we evaluated the use of biospeckle data for measuring the physiological properties of fresh-cut carrots stored at two temperatures (0 and 10 °C). In conjunction with the biospeckle activity, the moisture content, respiration rate, water activity, and mass loss changes were monitored using traditional analytical methods to evaluate the possible correlation of the biospeckle data with any of these phenomena with or without the use of frequency signatures. The results showed that the manifestation of water in the monitored activity was isolated only by removing these high frequencies, thus allowing the activity manifested in the material to be linked to a specific phenomenon, such as respiration. Therefore, we were able to monitor the respiration process in fresh-cut carrots and assign a spectral signature to their water content and respiration.     

Inheritance of net photosynthesis,dark respiration,stomatal resistance and related characters in tomato (Lycopersicon esculentum Mill.) under low energy conditions

Summary Inheritance of net photosynthesis, dark respiration, specific leaf fresh weight, and stomatal resistance was studied in a diallel cross without reciprocals with 15 tomato genotypes. The plants were grown under low light intensity (24 Wm^-2), short days (8 h) and low temperature (19 °C/10 °C day/night temperature). Significant f-values for GCA were observed for all characters. Smaller, but for most characters also significant f-values for SCA were found. This indicated that the characters were mainly controlled by additive gene action. The relationships between the physiological characters and breeding aspects are discussed.     

不同耐低氮性玉米品种的花后碳氮积累与转运特征

为了探明不同耐低氮性玉米品种生育后期碳、氮物质积累与转运特性及其对氮肥响应的差异,以期为品种高效施氮技术的制定提供理论依据。以耐低氮品种‘正红311’(Zhenghong311,ZH311)和低氮敏感品种‘先玉508’(Xianyu 508, XY508)为材料,设置4个氮肥用量(0、150、300和450 kg hm–2),于2017—2019年研究氮肥水平对不同耐低氮性玉米品种生育后期物质,包括干物质、全氮和非结构性碳水化合物(non-structural carbohydrate, NSC)积累和转运的影响。结果表明,供氮不足时,玉米通过增加花前贮存碳、氮物质对籽粒的转运以保证产量。增施氮肥能够提高玉米花后干物质和碳水化合物生产及其对籽粒质量的贡献率。与低氮敏感品种先玉508相比,在低氮条件下,耐低氮品种正红311在花前、花后均保持较高的植株干物质、NSC和氮素量,花后物质积累量及其对籽粒质量的贡献率更高,从而拥有更高的籽粒产量;品种间花前物质转运率及其对籽粒质量的贡献率差异不大。面对低氮胁迫,正红311既保证了花前贮存物质充分向籽粒运输,同时维持着较高的同化物积累能力来影响其产量形成。     

Growth and senescence characteristics associated with tolerance of wheat-alien amphiploids to high temperature under controlled conditions

Tolerance of wheat (Triticum aestivumL.) to high temperature might be improved by introducing alien genes from amphiploids. Our objectives were to determine responses of synthetic hexaploid and octaploid amphiploid wheats to high temperature and evaluate their potential usefulness for developing improved cultivars. Thirty synthetic hexaploids from durum wheat (T. turgidum L.) × Aegilops tauschii Cos. Accessions and four octaploid amphiploids from Chinese Spring wheat × different grasses were grown at 20/15 and 30/25 ^°C day/night during maturation. Tolerance was ascertained by two measures of senescence, leaf chlorophyll content and grain filling duration, plus grain yield and its components. Leaf chlorophyll was measured after 10 and 15 days of treatment, and grain yield was determined at maturity to calculate the heat susceptibility index(HSI), a gauge of the reduction in yield at high temperature of each line relative to all other lines. Chlorophyll content, grain filling duration, yield, and kernel weight were highly negatively correlated with HIS of the hexaploid amphiploids at30/25 ^°C, but grain yield was positively correlated with HSI at20/15 ^°C. The hexaploid lines might be useful for improving wheat for regions where stress from high temperature occurs frequently. Chlorophyll content and grain filling duration also were highly negatively correlated with HSI of the octaploid lines, but they would be less directly useful for improving wheat because the kernel number was reduced greatly due to unbalanced meiotic chromosomal segregation. This revised version was published online in August 2006 with corrections to the Cover Date.     

Changes of starch composition by postflowering environmental conditions in kernels of maize hybrids with different endosperm hardness

Starch composition of maize grains is of great importance when used in animal feed and many processing industries. Maize production involves hybrids with different kernel composition and hardness, sown at areas that range from subtropical to temperate cold climates. Therefore, it is relevant to understand how the environment influences starch composition. The objective of this work was to analyze the effect of location and sowing date on starch composition of maize grains. Field experiments were carried out at five locations across the argentinean maize-production area during two growing seasons. At each location, two sowing dates and three hybrids differing in endosperm hardness (i.e. semi-dent, a semi-flint and flint) were evaluated. Late sowing dates reduced amylose percentage and amylose/starch ratio. This last variable increased as latitude decreased. Minimum temperature during effective grain filling period explained those latitude and sowing date effects. This finding would be helpful to estimate starch composition of maize kernels to be expected in order to satisfy specific end uses.     

Comparison of bread wheat varieties with different breeding origin under organic and low input management

In recent years needs have increased to investigate the necessity of breeding cereals for organic agriculture. The aims of this study were (1) to compare 37 bread wheat (Triticum aestivum L.) varieties with different breeding origin under low input conventional and certified organic farming conditions in Austria and Hungary for 3 years, (2) to identify traits highly sensitive to management systems that could be separated according to their suggested selecting environments and (3) to find evidence for the distinctness of organic wheat breeding. According to the results, seven out of the 15 traits assessed during this study showed significant management × genotype interaction meaning that these traits could be the basis of selection for different management systems. Heading date, sensitivity to leaf rust and powdery mildew had high repeatabilities. For economic reasons, it is therefore reasonable to select for these traits in conventional fields even if the selection target is organic agriculture. However, the present study suggests that selection for the other four traits (grain yield, test weight, leaf-inclination and vigorous growth during booting) should be done later in the target environment. The study compared groups of varieties developed by different breeding strategies (organic, conventional and combined strategies). The results of multivariate analyses showed that the organic breeding was distinct from the other two breeding strategies, but the combined and conventional breeding resulted in similar groupings. It is concluded that the selecting environment has measurable effects on the performance of bread wheat varieties under organic and low input growing conditions.     

No-tillage permanent bed planting and controlled traffic in a maize-cotton irrigated system under Mediterranean conditions: Effects on soil compaction,crop performance and carbon sequestration

Under irrigated Mediterranean conditions, no-tillage permanent bed planting (PB) is a promising agriculture system for improving soil protection and for soil carbon sequestration. However, soil compaction may increase with time up to levels that reduce crop yield. The aim of this study was to evaluate the mid-term effects of PB on soil compaction, root growth, crop yield and carbon sequestration compared with conventionally tilled bed planting (CB) and with a variant of PB that had partial subsoiling (DPB) in a Typic Xerofluvents soil (Soil Survey Staff, 2010) in southern Spain. Traffic was controlled during the whole study and beds, and furrows with (F + T) and without traffic (F − T), were spatially distinguished during measurements. Comparisons were made during a crop sequence of maize (Zea mays L.)—cotton (Gossypium hirsutum L.)—maize, corresponding to years 4–6 since trial establishment. After six years, soil compaction was higher in PB than in CB, particularly under the bed (44 and 27% higher in top 0.3- and 0.6-m soil layers, respectively). Around this time, maize root density at early grain filling was 17% lower in PB than in CB in the top 0.6-m layer. In DPB, the subsoiling operation was not effective in increasing root density. Nevertheless, root density appeared to maintain above-ground growth and yield in both PB and DPB compared to CB. Furthermore, at the end of the study, more soil organic carbon was stocked in PB than in CB and the difference increased significantly with a depth down to 0.5 m (5.7 Mg ha⁻¹ increment for the top 0.5-m soil layer). Residues tended to accumulate on furrows, and this resulted in spatial and temporal differences in superficial soil organic carbon concentration (SOC) in the permanent planting systems. In PB, SOC in the top 0.05-m layer increased with time faster in furrows than on beds, and reached higher stable values (1.67 vs. 1.09% values, respectively). In CB, tillage homogenized the soil and reduced SOC in the top 0.05-m layer (average stable value of 0.96% on average for beds and furrows).     

Changes in allele frequencies in landraces, old and modern barley cultivars of marker loci close to QTL for grain yield under high and low input conditions

Changes in alleles frequencies of marker loci linked to yield quantitative trait loci (QTL) were studied in 188 barley entries (landraces, old and modern cultivars) grown in six trials representing low and high yielding conditions in Spain (2004) and Syria (2004, 2005). A genome wise association analysis was performed per trial, using 811 DArT^® markers of known map position. At the first stage of analysis, spatially adjusted genotypic means were created per trial by fitting mixed models. At the second stage, single QTL models were fitted with correction for population substructure, using regression models. Finally, multiple QTL models were constructed by backward selection from a regression model containing all significant markers from the single QTL analyses. In addition to the association analyses per trial, genotype by environment interaction was investigated across the six trials. Landraces seemed best adapted to low yielding environments, while old and modern entries adapted better to high yielding environments. The number of QTL and the magnitude of their effects were comparable for low and high input conditions. However, none of the QTL were found within a given bin at any chromosome in more than two of the six trials. Changes in allele frequencies of marker loci close to QTL for grain yield in landraces, old and modern barley cultivars could be attributed to selection exercised in breeding, suggesting that modern breeding may have increased frequencies of marker alleles close to QTL that favour production particularly under high yield potential environments. Moreover, these results also indicate that there may be scope for improving yield under low input systems, as breeding so far has hardly changed allele frequencies at marker loci close to QTL for low yielding conditions.     

绿色低碳约束下重庆能源DEA效率实证分析

客观评价重庆能源投入产出效益,探究环境污染、能源消费和经济增长之间的关系,进行能源结构优化,是当前重庆能源消耗走向绿色低碳方向发展面临的重大问题,也是重庆制定节能减排政策、能源发展战略和经济规划的重要基础。本文将能源投入和经济社会等产出因子科学分组,运用数据包络分析技术（DEA）,通过构建的能源需求结构方程以及DEA模型,对重庆能源消费进行了一系列DEA实证研究,得到了重庆能源投入产出规模效率在不同历史时期、不同阶段的变化规律,获取了能源冗余投入（径向改进和松驰改进）值、规模效应值、综合技术效率值和纯技术效率值,确定了DEA弱有效、DEA强有效、DEA完全有效的生产前沿面,并在此基础上对2016-2020年重庆能源结构进行了优化。研究成果可以为确定重庆能源绿色低碳发展方向、优化“十三五”重庆能源消费结构提供科学依据。     

不同降水状况下旱地玉米生长与产量对施氮量的响应

水分不足是旱地玉米生长主要限制因素,渭北旱塬雨养玉米种植区降水季节波动大,干旱频繁发生,已严重影响春玉米正常生长发育及产量稳定性。于2016—2018年在渭北旱塬合阳县进行旱地玉米施氮量定位试验,设置5个施氮量处理, 2016—2017年包括0、75、150、270、360 kg hm~(–2) (分别以N0、N75、N150、N270、N360表示), 2018年施氮量处理为0、90、180、270、360kgNhm~(–2) (分别以N0、N90、N180、N270、N360表示),供试品种为郑单958(ZD958)和陕单8806(SD8806)。分析了不同降水分布年份施氮量对春玉米生育期土壤水分变化动态、干物质积累动态、产量构成、经济效益及水分利用效率(WUE)的影响。结果表明,试验年份降水分布可分为穗期多雨、粒期干旱型(2016年和2018年)和穗期干旱、粒期多雨型(2017年)。生长季降水量及其分布显著影响土壤蓄水量和玉米地上部干物质积累,从而影响玉米产量及其构成因素,穗期干旱显著降低地上部干物质积累量和穗粒数,粒期干旱会明显降低粒重。不同降水分布年份施氮处理较N0增产6.72%～91.23%不等,施氮量对玉米产量、水分利用效率(WUE)影响呈现二次曲线关系,穗期多雨、粒期干旱型以N270处理籽粒产量和WUE最高,而穗期干旱、粒期多雨型以N150处理产量和WUE最好。籽粒产量与"休闲至抽雄期降水(FP2)"、"播前土壤蓄水量+播种至抽雄期降水(SP2)"相关性较强(FP2:R2=0.839**; SP2:R2=0.837**)。根据产量、水分利用和经济收益综合评价,渭北旱地玉米最适施氮方案为基施氮肥150kghm~(–2),再根据休闲至抽雄期降水量或播前土壤蓄水量与播种至抽雄期降水量之和预测产量,估算并及时追施适宜施氮量。     

Relationship of IAD index to internal quality attributes of apples treated with 1-methylcyclopropene and stored in air or controlled atmospheres

The research was conducted to evaluate the relationship between I_AD index (index of absorption difference between 670 and 720 nm) values and internal quality attributes of apples treated with 1-methylcyclopropene (1-MCP) and stored in air and controlled atmospheres (CA). Apples of ‘8S6923’ (Aurora Golden Gala™), ‘Fuji’ and ‘Royal Gala’ were tested. The results with Aurora Golden Gala™ show that I_AD index values were maintained at higher levels if the fruit were stored in CA and that 1-MCP had no significant effect on retaining at-harvest values. The I_AD values correlated with chlorophyll a content in the peel (R² = 0.95, P < 0.0001), but not with chlorophyll b content, internal ethylene levels, firmness or titratable acidity. ‘Royal Gala’ apples showed a similar response to Aurora Golden Gala™ apples, showing no correlation between I_AD index values and internal quality attributes of those apples when treated with 1-MCP and/or CA. In contrast, ‘Fuji’ apples showed a relationship between I_AD index value changes and internal ethylene concentrations (R² = 0.67, P < 0.05) and titratable acidity changes (R² = 0.89, P < 0.01), but not firmness. These results suggest that when 1-MCP and/or CA are applied to apples after harvest, that I_AD index values do not consistently correlate to any internal quality attributes other than peel chlorophyll a content.     

氮肥运筹对寒地粳稻淀粉合成关键酶活性及淀粉积累的影响

选用寒地粳稻松粳9号和松粳6号,在一定的施肥量下采用不同氮肥运筹处理,对水稻开花后淀粉积累、淀粉合成关键酶活性及其之间的关系进行研究。结果表明,合理减少基肥施氮比例、增加穗粒肥施氮比例可以促进籽粒灌浆、增加总淀粉含量,同时还可适当提高稻米支链淀粉含量。适当减小基肥施氮比例、增加穗粒肥施氮比例有利于提高灌浆后期籽粒中ADPG焦磷酸化酶和淀粉分支酶(Q酶)的活性,而在灌浆前期淀粉合酶(SSS)活性随着基蘖肥比例的减小而降低。通过相关分析可知,ADPG焦磷酸化酶、Q酶和SSS与淀粉及其淀粉组分密切的相关,对淀粉及淀粉组分含量变化均有同等重要的作用。因此: 合理的基肥、蘖肥、穗肥、粒肥配比(5∶3∶1∶1)能够调控灌浆过程中淀粉合成关键酶活性,从而增加淀粉及淀粉组分含量。     

Effect of free air carbon dioxide enrichment combined with two nitrogen levels on growth,yield and yield quality of sugar beet: Evidence for a sink limitation of beet growth under elevated CO2

The increase in atmospheric CO₂ concentration [CO₂] has been demonstrated to stimulate the growth of C₃ crops. However, little information exists about the effect of elevated [CO₂] on biomass production of sugar beet, and data from field experiments are lacking. In this study, sugar beet was grown within a crop rotation over two rotation cycles (2001, 2004) at present and elevated [CO₂] (375 μl l^?1 and 550 μl l^?1) in a free air CO₂ enrichment (FACE) system and at two levels of nitrogen supply [high (N2), and 50% of high (N1)], in Braunschweig, Germany. The objective of the present study was to determine the CO₂ effect on seasonal changes of leaf growth and on final biomass and sugar yield. Shading treatment was included to test whether sugar beet growth is sink limited under elevated [CO₂]. CO₂ elevation did not affect leaf number but increased individual leaf size in early summer resulting in a faster row closure under both N levels. In late summer CO₂ enrichment increased the fraction of senescent leaves under high but not low N supply, which contributed to a negative CO₂ effect on leaf area index and canopy chlorophyll content under high N at final harvest. Petioles contained up to 40% water-soluble carbohydrates, which were hardly affected by CO₂ but increased by N supply. More N increased biomass production by 21% and 12% in 2001 and 2004, respectively, while beet and sugar yield was not influenced. Concentration of α-amino N in the beet fresh weight was increased under low N and decreased under high N by CO₂ enrichment. The CO₂ response of total biomass, beet yield and white sugar yield was unaffected by N supply. Averaged over both N levels elevated [CO₂] increased total biomass by 7% and 12% in 2001 and 2004, respectively, and white sugar yield by 12% and 13%. The shading treatment in 2004 prevented the decrease in leaf area index under elevated [CO₂] and high N in September. Moreover, the CO₂ effect on total biomass (24%) and white sugar yield (28%) was doubled as compared to the unshaded conditions. It is concluded that the growth of the storage root of sugar beet is not source but sink limited under elevated [CO₂], which minimizes the potential CO₂ effect on photosynthesis and beet yield.     

The effect of skips on the grain yield of the adjacent hills in trials with maize hybrids under different conditions

Experiments were carried out with maize during the years 1959, 1960, and 1961 with the purpose of studying the effect of skips on the adjoining hills and some factors which may have some influence on this effect. Among the factors studied are the size and shape of skips, the type of stand, the amount of nitrogen applied, the hybrids used and the climatic conditions during the years considered. Under the conditions of the Netherlands the following results were obtained:

1. 1.
   There was an increase in the yield of the hills adjoining a skip in the same row and in the adjacent rows while the effect of a skip on the direct neighbour in the row (A) was very high.