桃综合贮藏保鲜技术研究 Ⅱ.适宜的贮藏条件

研究了大久保、京玉和燕红桃在不同贮藏温度（自然温度、３～４℃、０～２℃）和不同贮藏方式（冷藏、塑料袋小包装贮藏和人工气调贮藏）下的贮藏效果。结果表明,在０～２℃下,将桃果实装入０．０３ｍｍ厚的聚乙烯塑料薄膜保鲜袋中,并加入乙烯吸收剂进行塑料袋小包装贮藏,其效果最好。在这一贮藏条件下,保鲜袋中的Ｏ２为１４．５％～１５．９％,ＣＯ２为３．７％～４．１％。这一条件可明显延长贮藏期并能保持桃的品质,减少腐烂和褐变程度,增加商品果率。同时果实的硬度、淀粉、糖、有机酸和Ｖｃ的保存率也比冷藏对照高。     

桃综合贮藏保鲜技术研究

研究了大久保、京玉和燕红桃在不同贮藏温度和不同贮藏方式下的贮藏效果。结果表明,在０－２℃下,将桃果实装入０．０３ｍｍ厚的聚乙烯塑料薄膜保鲜袋中,并加入乙烯吸收剂进行塑料袋小包装贮藏,其效果最好。在这一贮藏条件,保鲜袋中的Ｏ２为１４．５－１５．９％,Ｃ炎３．７－４．１％。这一条件可明显延长贮藏期并保持桃的品质,减少腐烂和褐变程度,增加商品果率,同时果实的硬度、淀粉、糖、有机酸和ＶＣ的保存率也比冷藏对     

'八月脆'桃果实气调贮藏过程中品质及相关酶活性的变化

为寻求减轻桃低温冷害的有效方法和提高桃贮藏保鲜效果的措施,以'八月脆'桃为试材,研究气调贮藏(0～1 ℃,10%O2 10%CO2)和冷藏(O～1℃)条件下果实品质特性及几种酶活性的变化.结果表明;与冷藏相比,气调贮藏能延迟'八月脆'桃果实出现褐变的时间并降低果实的褐变程度,显著提高可溶性糖含量和过氧化氢酶(CAT)活性,降低果实组织细胞膜的透性,同时在贮藏的后半期多酚氧化酶(PPO)活性显著提高,而过氧化物酶(POD)的活性受到明显的抑制.气调贮藏的效果显著好于冷藏对照.     

冷害桃果实品质劣变及其控制措施

概述了在贮藏期间,桃果实受到冷害后其色泽、质地和风味等品质劣变机理及控制冷害的措施。桃果实的低温褐变主要是酶促褐变,但对不同的品种来说,决定褐变的主导因子则不尽相同。在产生絮败的果实中,果胶物质发生了代谢异常,不溶性果胶明显增加,果胶质代谢异常与PE和PG的活性变化密切相关。桃果实的糖分主要是蔗糖,当冷害出现时桃果实中蔗糖含量迅速下降,可滴定酸含量在贮藏期间也显著下降。目前已从桃果实中分离到近百种芳香成分,冷害桃果实的重要表现之一是原有桃香气变淡或丧失,甚至产生异味。品种与采收成熟度、采前或采后的化学处理、低温锻炼、热调处理和气调均能够不同程度地减轻桃果实的冷害。     

低温贮藏对黄藤笋品质的影响

在3℃、7℃、11℃-1125℃4种贮藏温度下,测定了黄藤笋外观品质、笋心的色度、硬度、失重率和相对电导率的变化。结果表明,贮藏于3℃和7℃的黄藤笋分别会在第14天、第2l天发生冷害现象,说明黄藤笋属于冷敏性蔬莱。低温可以显著抑制黄藤笋心腐烂的发生,延缓失重率的下降,贮藏28天失重率≤4．5％。随着时间的延长,低温下贮藏的黄藤笋心,其硬度和相对电导率总体呈上升趋势;而25℃下贮藏的黄藤心,硬度在14天前也呈上升趋势,但随后缓慢下降,在第21～28天急剧下降,电导率在第28天时已无法测定,因为部分笋心已腐烂。综合结果分析认为,11℃是黄藤笋适宜的贮藏温度。     

不同成熟度水蜜桃果实软化的影响因素

摘后桃果局部软化现象较为普遍,且极易产生呼吸跃变,因而较难贮运。为给桃树栽培和桃果贮藏加工提供理论依据,以"湖景蜜露"水蜜桃为试材,研究了冷藏期间不同成熟度桃果实软化相关影响因素的变化规律。观测结果表明:果实中缝线处果实硬度下降速率均高于中缝线两侧果实硬度,且成熟度愈高,差异愈显著;不同成熟度桃果实与桃果核同一时间出现呼吸高峰,说明采后果实软化与种子的呼吸密切相关;九成熟果实采后硬度下降速率、可滴定酸含量、丙二醛含量及果肉色差L*值的变化均显著高于七、八成熟果实,其可溶性固形物含量变化的差异不显著。试验结果表明:桃果核在桃果采后软化过程中起着重要的作用,七、八成熟为长途运输及冷藏适宜的采收成熟度。     

低温保鲜处理对东魁杨梅果实的影响

以东魁杨梅果实为研究对象,采用冷藏控温技术,在室温、2、4、8℃条件下对不同成熟度的东魁杨梅果实进行贮藏处理,测定采摘当日、贮藏2、4、6、8、10、12 d的东魁杨梅的呼吸速率、可溶性固形物含量、总酸度和好果率,探究东魁杨梅果实成熟度、贮藏温度和贮藏时间对杨梅果实品质的影响。结果表明,东魁杨梅最佳的低温贮藏方法是:九成熟时采摘,并及时在2℃低温条件下进行分类、装箱和运输,可以使东魁杨梅果实保鲜期由室温下的4 d提高到10~12 d。     

贮藏板栗休眠与萌芽的温度调控

本文研究了板栗贮藏过程中呼吸作用变化和内源激素含量与贮藏温度的关系,确定了板栗的休眠时期,并探讨了通过贮藏温度调控板栗休眠和萌芽的措施。研究结果表明,板栗休眠期长短与贮藏温度有密切关系,在室温（２０℃～２２℃）贮藏条件下板栗的休眠期为２个月左右,在冷藏（０℃～２℃）条件下的休眠期为３个月左右。说明虽然冷藏较室温贮藏能延长板栗的休眠期,但不能完全控制休眠。板栗休眠解除后,在生理上表现为呼吸作用上升和内源激素（ＩＡＡ、ＧＡ３、ＺＲ）含量增加,外观上表现为胚芽萌动生根。冷藏板栗在休眠解除前将贮藏温度降至临界低温（－２℃～－４℃）,可有效地抑制呼吸回升和内源激素的合成,使休眠不被解除,从而在整个贮藏过程中不萌芽。经临界低温贮藏的板栗,仍较好地保持种子活力,出库后品质和萌芽正常,未造成低温伤害。     

采前不同浓度钙喷施对‘沪油’018贮藏品质的影响

为了探讨采前喷钙对桃果实硬度、糖度、腐烂率等品质指标的影响情况,于果实采收之前以浓度分别为0.05%、0.10%、0.20%和0.30%的钙Ca(NO3)2钙喷施‘沪油’018树体(树冠及果实),以不作任何处理的树体果实作为对照(CK),将不同浓度钙处理的果实放置在温度为(0±0.5)℃、相对湿度为80%~85%的冷库中贮藏,就采前不同浓度的钙处理对采摘时和贮藏期间果实品质的影响情况进行了试验。结果表明:适量喷钙处理可显著提高采收时的果实硬度、可滴定酸、可溶性蛋白含量和果实表面亮度,但对其总糖含量却无显著性影响;在整个冷藏期间,采前适宜浓度的钙处理可显著抑制果实的软化及其可滴定酸含量的降低,能缓解因糖酸比急剧上升而导致的果实原有风味的失调;显著降低了贮藏期间果实的腐烂率,增强了贮藏期间果实的蛋白合成能力,并保持了果皮原有的色泽,有效延缓了果实衰老进程。试验结果表明:从5月27日(盛花期后第55天)起每隔5天对整个树体(树冠及果实)喷施浓度为0.10%的Ca(NO3)2,共计喷施5次,可使果实贮藏期延长至30 d,果实腐烂率降低至5%以下,且能较好地保持果实原有的风味和品质。     

桃综合贮藏保鲜技术研究Ⅰ.采收成熟度及采前处理对贮藏效果的影响

桃的采收成熟度与果实的耐藏性有较密切的关系。在７～８成熟时的绿熟期采收,经贮藏后果面新鲜,果实硬而脆,褐变和腐烂少;采收过晚则果实易软化,容易褐变和腐烂。采前１个月用１００ｍｇ／ｋｇＧＡ３处理有利于提高桃果实的耐藏性,贮藏后处理果的硬度比对照高１倍;采前１～２ｄ用５００ｍｇ／ｋｇ朴海因处理大久保、京玉和燕红桃,贮藏好果率分别增加２２．８％,２２．９％和１８．３％;采前用混合液（ＧＡ３５０ｍｇ／ｋｇ,２,４－Ｄ５０ｍｇ／ｋｇ,多菌灵２０００倍）处理可减慢桃果实在贮藏期间的生理代谢,并能较好地保持品质,腐烂和褐变指数分别比对照降低７．７％和４．０％。     

Browsing Damage on Pine (Pinus sylvestris and P. contorta) by a migrating moose (Alces alces) Population in Winter: Relation to Habitat Composition and Road Barriers

In Scandinavia, moose (Alces alces L.) sometimes cause severe browsing damage to economically-important pine. Moose-vehicle accidents have spurred construction of fences along roads, and these may interfere with moose migration between summer and winter ranges, or the road alone may be a barrier. If this happens and moose build up along roads, landowners may suffer economically. Therefore, this study investigated whether roads, fences or other factors influence the use of young pine stands by moose. Eighty stands along roads in northern Sweden were evaluated in which individually-browsed branches were counted on 9972 pines. Moose browsing was not significantly related to birch (Betula pendula Roth, B. pubescens Ehrh.) density, nor did it differ between pines (Pinus contorta Douglas or P. sylvestris L.). However, increased pine density, site productivity and proximity to a highway were associated with increased browsing. Further large-scale studies are needed to understand moose habitat selection and the effects of roads.     

Effects of Root Freezing on the Physiology and Growth of Picea glauca,Picea mariana and Pinus banksiana Seedlings Under Different Soil Moisture Regimes

The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO 2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage.     

Decomposition and nutrient loss from prunings of different contour hedgerow species in tea plantations in the sloping highlands of Sri Lanka

Contour hedgerows of multipurpose tree species in the sloping tea lands of Sri Lanka are expected to reduce soil erosion and also add significant amounts of plant nutrients to the soil via periodic prunings. The objective of this experiment was to characterize the biomass decomposition pattern and quantify the amount of nutrients added through prunings of six tree species (Calliandra calothyrsus, Senna spectabilis, Euphatorium innulifolium, Flemingia congesta, Gliricidia sepium and Tithonia diversifolia) currently being used in hedgerows associated with tea. Withered leaf and stem prunings (50 g) were enclosed in 2-mm litter bags, placed at 5-cm depth and retrieved after one, three, six, nine and 12 weeks. Loss of initial dry weight, N, P and K was measured. Single exponential decay function adequately described both dry weight and nutrient loss. Tree species differed significantly in their rate of breakdown with decomposition constants (k) varying from 0.0299 to 0.2006 week⁻¹ for leaves and from 0.0225 to 0.0633 week⁻¹ for stems. Gliricidia showed the highest k for leaves with the rest in the following descending order: Senna > Tithonia ≥ Euphatorium > Calliandra > Flemingia. A similar pattern was observed for loss of all nutrients with Calliandra and Flemingia always having lower k values than the rest. Although N immobilization was not observed, immobilization of P and K was observed during the first week of incubation in some species, particularly in stem prunings. Annual biomass of prunings differed significantly between tree species in the following descending order: Calliandra > Senna > Flemingia > Tithonia > Gliricidia > Euphatorium. Calliandra added the greatest amount of nutrients annually to the soil with Euphatorium adding the least. Calliandra prunings provided the annual total K requirement and 49% of the N requirement of mature tea. However, none of the species provided more than 5% of the P requirement. It is concluded that among the tree species tested, Calliandra and Flemingia are the most suitable for contour hedgerows in tea plantations of this agroclimatic region because of their higher soil nutrient enrichment capacity and slower decomposition rates which would minimize leaching losses. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effects of Seed Weight and Seed Type on Early Seedling Growth of Pinus sylvestris under Harsh and Optimal Conditions

The effects of seed weight and seed type on seedling growth of Pinus sylvestris (L.) were studied by seeding individually weighed orchard and stand seed in different mixtures under harsh (direct seeding in field) and optimal (seeding in nursery) conditions. In the nursery experiment an increase in the seed weight from 3 to 7 mg increased the seedling height by 10-27% and total weight by 27-113%, and decreased the height/diameter ratio by 5-6% after 2 yrs. With elimination of seed weight effects, orchard seedlings were 2% taller than stand seedlings in year 2. Without elimination of seed weight effects, orchard seedlings were 7-13% taller. In the field experiment an increase in the seed weight from 3 to 7 mg increased seedling height by 18-65%, stem volume by 81-274% and the number of top-buds by 23-34% in year 5. After elimination of seed weight effects, orchard seedlings were 7-13% taller than stand seedlings and without elimination of seed weight effects 20-21% taller after 5 yrs. Even after elimination of both seed weight and genetic effects orchard seedlings were 3-9% larger than stand seedlings in the field experiment. In conclusion, the influence of seed weight and seed type on growth traits and slenderness is highly significant and the influence seems to be greater in harsh conditions.     

Potential to harness superior nutritional qualities of exotic baobabs if local adaptation can be conferred through grafting

Baobab leaves form an important part of the local diet in Sahel countries and elsewhere in Africa. Existing leaf nutritional data and agroforestry performance information are based solely on Adansonia digitata L., the baobab of continental Africa. The introduction potential of Adansonia species from the center of diversity in Madagascar and from Australia remains untapped. To assess this potential, the mineral contents and B₁ and B₂ vitamin levels of dried baobab leaves were determined for five-year old trees of A. digitata, A. gibbosa (A. Cunn.) Guymer ex D. Baum, A. rubrostipa Jum. & H. Perrier (syn. A. fony Baill.), A. perrieri Capuron and A. za Baill. grown in an introduction trial in Mali. Nutritional data were evaluated against survival and vigor to identify promising germplasm. Leaf vitamin and crude protein contents were highest in the Madagascar species, especially A. rubrostipa (B₁ 88 mg 100 g⁻¹, B₂ 187 mg 100 g⁻¹, protein 20.7% dry weight). However, the local species far outperformed the introductions in survival, tree height, basal diameter and resistance to termites. We suggest grafting as a way of harnessing the vigor of well-adapted local baobab varieties to the superior nutritional profiles of A. rubrostipa and others. Cross-species grafting tests in Adansonia were successful, thus creating new agroforestry possibilities with different scion/rootstock combinations.     

Modelling of adequate pretwist for obtaining straight timber

Abstract

Wood in general and wooden studs in particular are often distorted owing to uneven shrinkage during the drying process in the sawmill. Twist is often the most detrimental of all types of distortion, and it is caused by spiral grain in combination with variations in moisture content. For sawmills, the objective is to produce dried, straight boards, and one method of dealing with boards with excessive spiral grain is to sort them out and then dry them in a pretwisted position to obtain straight boards after drying. A model using the finite element (FE) method for the simulation of drying twist distortions was first calibrated against laboratory experiments in which boards were dried with and without restraints and pretwists. After the calibration, the FE results were compared with industrial test results for boards that were dried without restraints or with restraints with zero pretwist, i.e. straight restraints. The FE model used an elastic–ideally plastic material model to obtain permanent deformations. The calibration was to set the yield stresses so that there was a good match between FE results and results from the laboratory experiments. The comparison between the industrial test results and the FE results showed that the FE model is capable of realistic simulations of drying boards with and without restraints and presumably also pretwists.     

Growth of Phlebiopsis gigantea in wood of seven conifer species

Heterobasidion parviporum and Heterobasidion annosum are widely distributed root‐rot fungi that infect conifers throughout Europe. Infection of conifer stumps by spores of these pathogens can be controlled by treating fresh stumps with a competing non‐pathogenic fungus, Phlebiopsis gigantea. In this study, growth of three Latvian strains of P. gigantea and the biological control agent ‘Rotstop’ strain was evaluated in stem pieces of Norway spruce, Scots pine, lodgepole pine, Douglas‐fir, Weymouth pine, Siberian larch and Sitka spruce. The growth rates of one H. parviporum and one H. annosum isolate were also measured in the same stem pieces. The growth rate of P. gigantea varied greatly in wood of different conifer species. It was higher in the three pine species, lower in Norway spruce and lowest in Sitka spruce and Siberian larch, and in Douglas‐fir, this fungus did not grow. The largest area of wood occupied by P. gigantea was in lodgepole pine. Growth of Latvian isolates of P. gigantea in the wood of Pinus and Picea species was comparable to that of the Rotstop isolate. Consequently, stump treatment with local P. gigantea isolates should be recommended. However, our results suggest that Douglas‐fir stump treatment against Heterobasidion by P. gigantea may be ineffective and other stump treatment methods should be considered.     

Stand Structure in Pine,Spruce and Deciduous Forests: A Comparison Between Finnish and Russian Karelia

This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland.     

Growth and Terminal Bud Formation in Picea abies Seedlings Grown with Alternating Diurnal Temperature and Different Light Qualities

The root collar diameter and the height:diameter ratio are of particular importance in container-grown seedlings where a high density in the containers may produce spindly seedlings. Temperature regimes and light quality are known to affect plant growth. The aim of this study was to identify responses in Picea abies (L.) Karst. seedlings grown with light providing different red:far-red ratios and under temperature regimes with alternating day (DT) and night temperature (NT) from negative (DT < NT) to positive (DT > NT) difference (DIF) between DT and NT. Experiments were conducted in controlled environment chambers and in a daylight phytotron. Only limited thermoperiodic responses appeared in P . abies seedlings with respect to seedling height and dry weight accumulation. The formation of terminal buds, however, was clearly delayed in seedlings grown at negative DIF. The results indicate a requirement for day extension light that is high in far-red, to prevent terminal bud formation under natural short-day conditions. An extended study should be conducted to clarify the minimum level of light intensity and the optimal light quality needed to prevent terminal bud formation under natural short-day conditions.     

CAD与建筑设计的关系

本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。