桃果实成熟前后细胞壁成分和降解酶活性的变化及其与果实硬度的关系

比较桃品种‘双久红’和‘川中岛白桃’果实成熟前后20 d内果肉硬度、细胞壁成分和细胞壁降解酶活性变化的结果表明,桃果实成熟5 d后,‘双久红’桃果实的硬度、纤维素含量和原果胶含量均极显著高于‘川中岛白桃’:从成熟前15 d开始,‘双久红’的水溶性果胶含量、多聚半乳糖醛酸酶活性和纤维素酶活性均极显著低于‘川中岛白桃’;整个成熟期间,‘双久红’的果胶甲酯酶活性明显低于‘川中岛白桃’。相关分析表明,果实硬度与原果胶、纤维素含量呈极显著正相关,而与可溶性果胶含量、多聚半乳糖醛酸酶活性和纤维素酶活性呈极显著负相关。     

不同类型甜瓜成熟过程中果肉质地及其细胞显微结构的变化

采用质地剖面分析(TPA)和穿刺方法,测定3种不同口感质地的5个甜瓜材料(梗硬果肉的P10和3-6、脆酥果肉的417和20-5以及软果肉的Charentais)不同成熟时期果肉硬度、咀嚼性和黏着性以及脆性和平均硬度,评价甜瓜果肉的质地特性;采用组织切片法观察果肉组织细胞的显微结构,并通过Image-pro plus 6.0软件测定细胞大小参数(细胞面积、周长、长度及宽度)和形状参数(细胞纵横比及圆度),明确不同果肉质地类型甜瓜果实成熟过程中果肉细胞显微结构的变化特征,探讨甜瓜细胞形态参数与果肉质地的关系,为甜瓜品质育种提供理论依据。结果显示:(1)梗硬果肉甜瓜(P10和3-6)的果肉细胞较小,排列紧密;脆酥果肉甜瓜(417和20-5)的细胞较大,排列较疏松;软果肉甜瓜(Charentais)的细胞最大,排列极不规则。(2)不同口感甜瓜果肉在成熟期的细胞面积和周长差异显著,与口感呈显著负相关关系;在成熟过程中,甜瓜果肉细胞面积、周长和长度等表现出不同程度的增大,而细胞纵横比和圆度总体表现为下降趋势,即细胞越来越圆。(3)甜瓜果肉的口感与质地及细胞大小参数呈显著或极显著相关关系;细胞大小与黏着性呈显著或极显著正相关关系(0.951*~0.983**),细胞面积与TPA硬度及脆性呈显著负相关关系(分别为-0.910*和-0.926*),长度和宽度与脆性呈显著负相关关系(分别为-0.884*和-0.894*);细胞形状参数中的圆度与黏着性具有显著相关性(0.936*)。研究表明,口感不同的甜瓜果肉具有显著不同的质地和细胞显微结构,且甜瓜果肉口感与其果肉质地及细胞大小密切相关,即细胞越小,甜瓜果肉质地越硬。     

枇杷冷藏过程中果肉木质化与细胞壁物质变化的关系

“大红袍”和“解放钟”枇杷果实在１℃下贮藏时,细胞壁物质代谢异常,果肉硬度升高而出汁率逐渐降低,果胶酯酶（ＰＥ）和多聚半乳糖醛酸酶（ＰＧ）活笥和水溶性果胶含量下降,原果胶含量、苯丙氨酸解氨酶（ＰＡＬ）活性及木质素和纤维含量不断增加。约经３周贮藏后,果实出现果皮难剥、果肉质地变硬、粗糙少汁的异常劣变现象。在１２℃下贮藏的枇杷果实,细胞壁物质代谢正常,果肉硬度增加少,ＰＥ和ＰＧ活性及水溶性果胶含量较遍     

枇杷冷藏过程中果肉木质化与细胞壁物质变化的关系

“大红袍”和“解放钟”枇杷果实在 1℃下贮藏时 ,细胞壁物质代谢异常 ,果肉硬度持续升高而出汁率逐渐降低 ,果胶酯酶 (PE)和多聚半乳糖醛酸酶 (PG)活性和水溶性果胶含量下降 ,原果胶含量、苯丙氨酸解氨酶(PAL)活性及木质素和纤维素含量不断增加。约经 3周贮藏后 ,果实出现果皮难剥、果肉质地变硬、粗糙少汁的异常劣变现象。在 12℃下贮藏的枇杷果实 ,细胞壁物质代谢正常 ,果肉硬度增加少 ,PE和PG活性及水溶性果胶含量较高 ,无原果胶增加现象 ,PAL活性呈下降趋势 ,木质素和纤维素含量变化不大 ,果实不出现木质化败坏。这些结果表明冷藏枇杷的木质化败坏可能是一种低温失调现象     

套袋苹果果实质地及其显微结构与果面裂纹的关系北大核心CSCD

以套白色单层纸袋的着色富士系‘天红2号’和短枝富士后代优系4-1-103,以及不着色姊妹系‘冀苹4号’和‘冀苹5号’4个苹果品种(系)为试验材料,利用质构仪整果穿刺和质地多面分析法(texture profile analysis,TPA)测定果实质地,光学显微镜观察果实显微结构,探讨苹果果实质地及其显微结构与果面裂纹的关系,为抗裂纹品种的选育和潜在裂纹机制提供理论依据。结果表明:(1)盛花后132~185 d,‘天红2号’和‘冀苹4号’裂纹率和裂纹指数始终高于4-1-103和‘冀苹5号’,其裂纹主要部位为果肩部。(2)‘天红2号’和‘冀苹4号’的果肉脆裂性、果肉硬度分别显著小于4-1-103和‘冀苹5号’。(3)‘天红2号’和‘冀苹4号’的表皮细胞密度显著小于4-1-103和‘冀苹5号’,其果肉细胞间隙率显著大于4-1-103和‘冀苹5号’,且其角质膜有“V”型凹陷,并发生龟裂,而4-1-103和‘冀苹5号’角质膜完整均一。(4)主成分和灰色关联度分析表明,果肉硬度、果皮果肉硬度比和果肉细胞间隙率是解释裂纹的主要指标。研究发现,果实角质膜完整均一、果肉硬度大、果肉细胞间隙率小的苹果品种不易发生果面裂纹。     

桃果实絮败与果胶质变化和细胞壁结构的关系

“白凤”桃果实在０ ℃下贮藏２０ ｄ 以后出现肉质发绵和干化的絮败现象。冷藏第１０ 天在１８ ℃下加温３８ ｈ 能有效减缓絮败的发生。连续冷藏１０ ｄ 以后,原果胶含量开始增多, 水溶性果胶含量变化不大。中途加温的果实原果胶含量变化不多,但水溶性果胶却不断增加。絮败果的果胶质粘度明显高于正常果。果肉出汁率是测定果实絮败程度的理想指标。絮败果肉细胞壁的明显特征是： 伴随胞间层的分解和胞间隙的扩大,出现大量凝胶状物质的沉积,初生壁结构变化不明显, 也没有细胞壁次生加厚的迹象。     

苦瓜果实不同发育时期细胞壁组分及相关酶活性的差异分析

为了解苦瓜(Momordica charantia)果实品质差异的原因，以厚肉型种质‘LX1-3’和薄肉型种质‘ZK54’为材料，对果实发育过程中细胞壁组分含量及相关酶活性进行了分析。结果表明，花后17 d，‘LX1-3’果实的横径(FD)、腔径(FLD)、果肉厚度(PT)、单瓜鲜质量(FFW)和干质量(FDW)均超过‘ZK54’。细胞壁组分和酶活性表现品种间差异，水溶性果胶含量整体水平表现为厚肉型高于薄肉型，且与PT、FFW和FDW呈显著正相关；花后17~23 d ‘LX1-3’的半纤维素(HCE)和纤维素(CE)含量均高于‘ZK54’；花后3 d，两种质的β-半乳糖苷酶(β-Gal)和β-木糖苷酶(β-Xyl)活性显著高于其他3个时期，多聚半乳糖醛酸酶(PG)、β-Gal和果胶酶变化趋势与离子型果胶和共价型果胶含量的变化一致。β-Gal、β-Xyl和纤维素酶活性与5个生长性状间呈极显著/显著负相关，PG与FD、FLD和PT呈极显著/显著负相关。因此，细胞壁组分和酶活性与果实发育密切相关，β-Xyl和β-Gal在苦瓜早期发育中发挥主要效应，而HCE和CE对果实中后期发育影响较大。     

亚硫酸钠处理对与采后竹笋木质化作用有关的细胞壁物质及酶活性的影响

研究了Na2SO3处理对与采后竹笋木质化作用相关的细胞壁物质及其酶活性的影响.结果表明1%Na2SO3处理能显著延缓竹笋组织中多聚半乳糖醛酸酶活性的降低和抑制苯丙氨酸解氨酶活性的上升,因此水溶性果胶含量显著高于对照,硬度、木质素和原果胶含量显著低于对照.但1%Na2SO3处理对纤维素酶、果胶甲酯酶活性和纤维素含量无显著影响.     

水分胁迫对柑橘果皮细胞壁结构与代谢的影响

研究水分胁迫下,盆栽'暗柳橙(Citrus Sinensis Osbeck cv. Anliu)'的果实成熟期果皮细胞壁超微结构、细胞壁物质成分、细胞壁代谢相关酶活性的变化规律及其之间关系.结果表明,在果实发育成熟期,果皮细胞壁代谢相关水解酶果胶酶、纤维素酶、果胶甲酯酶的活性随着水分胁迫的加强而增加,多酚氧化酶活性与果胶酶活性变化趋势相反,果皮细胞壁代谢相关成分离子结合型果胶、共价结合型果胶、半纤维素、纤维素的含量随着水分胁迫的加强而降低,水溶性果胶含量随着水分胁迫的加强而增加,果皮细胞壁超微结构随着水分胁迫的加强而加速解体.     

亚硫酸钠处理对与采后竹笋木质化作用有关的细胞壁物质及酶活性的影响

研究了Na2SO3处理对与采后竹笋与木质化作用相关的细胞壁物质及其酶活性的影响。结果表明：1％Na2SO3处理能显著延缓竹笋组织中多聚半乳糖醛酸酶活性的降低和抑制苯丙氨酸解氨酶活性的上升,因此水溶性果胶含量显著高于对照,硬度、木质素和原果胶含量显著低于对照。但1％Na2SO3处理对纤维素酶、果胶甲酯酶活性和纤维素含量无显著影响。     

Intercellular separation forces generated by intracellular pressure

Turgor pressure tends to force plant cells towards a spherical form, thus separating them at the angles from adjacent cells. In cooked vegetables containing starch, the swelling pressure of starch gelatinization generates analogous cell separation forces. A theoretical analysis of the relationship between internal pressure and cell separation forces is presented. Apart from the effect of internal pressure, cell separation forces increase with the diameter of the cell and decrease with the number of cell sides. Cell separation forces are reduced by the introduction of intercellular spaces and decrease further as these expand. The relationship between intracellular pressure and cell separation forces provides a basis upon which the strength of intercellular adhesion can be measured by experiment.     

Tracing cellulose microfibril orientation in inner primary cell walls

Summary By quantitative analysis of cellulose microfibril orientation at different levels in the primary cell wall of a number of cell types, the development of wall texture was studied. Meristematic, isodiametric and cylindrical parenchyma cells and cells of a suspension culture were used. Within the newly deposited microfibril population, various orientations were recognized on the micrographs. Within subpopulations the orientation of undercrossing and overcrossing microfibrils were measured. These measurements showed a gradual shift in cellulose microfibril orientation in the different levels. Microfibrils showed predominant orientations at particular levels but microfibrils of intermediate orientation also occurred, although at a much lower density. As cellulose microfibrils of intermediate orientation were not closely packed, lamellae were not formed. Interwoven microfibrils were occasionally present, indicating that differently orientated microfibrils are occasionally deposited simultaneously. Also gradual changes in orientation over the entire inner cell wall surface were observed. From these observations it was inferred that microfibril deposition occurs with a small but regular and progressive change in orientation, the rotational motion, related to that of a helicoidal system.Dedicated to Professor Dr. M. M. A. Sassen on the occasion of his 65th birthday     

Intercellular adhesion and cell separation in plants

Adhesion between plant cells is a fundamental feature of plant growth and development, and an essential part of the strategy by which growing plants achieve mechanical strength. Turgor pressure provides non‐woody plant tissues with mechanical rigidity and the driving force for growth, but at the same time it generates large forces tending to separate cells. These are resisted by reinforcing zones located precisely at the points of maximum stress. In dicots the reinforcing zones are occupied by networks of specific pectic polymers. The mechanisms by which these networks cohere vary and are not fully understood. In the Poaceae their place is taken by phenolic cross‐linking of arabinoxylans. Whatever the reinforcing polymers, a targeting mechanism is necessary to ensure that they become immobilized at the appropriate location, and there are secretory mutants that appear to have defects in this mechanism and hence are defective in cell adhesion. At the outer surface of most plant parts, the tendency of cells to cohere is blocked, apparently by the cuticle. Mutants with lesions in the biosynthesis of cuticular lipids show aberrant surface adhesion and other developmental abnormalities. When plant cells separate, the polymer networks that join them are locally dismantled with surgical precision. This occurs during the development of intercellular spaces; during the abscission of leaves and floral organs; during the release of seeds and pollen; during differentiation of root cap cells; and during fruit ripening. Each of these cell separation processes has its own distinctive features. Cell separation can also be induced during cooking or processing of fruit and vegetables, and the degree to which it occurs is a significant quality characteristic in potatoes, pulses, tomatoes, apples and other fruit. Control over these technological characteristics will be facilitated by understanding the role of cell adhesion and separation in the life of plants.     

Winding threads around plant cells: a geometrical model for microfibril deposition

In this paper, a geometrical model is put forward to account for the deposition orientation of plant cell wall microfibrils (CMFs). The model presupposes the insertion in the plasma membrane of CMF initiation complexes, which, once inserted, are moved through the fluid plane of the plasma membrane by the kinetic force of CMF synthesis, leaving CMFs in their wake. Deposition occurs in a limited space and the CMFs are linked to wall matrix molecules. CMF orientation is governed by the laws of geometry and, taking space-limiting conditions into account, therefore depends on (1) cell geometry, (2) the other wall molecules linked to the CMFs, and (3) the number of CMF initiation complexes inserted into the plasma membrane. The model does not exclude the idea that cortical microtubules may determine initial CMF orientation after cell division by determining the cell elongation direction.     

Pectin engineering to modify product quality in potato

Although processed potato tuber texture is an important trait that influences consumer preference, a detailed understanding of tuber textural properties at the molecular level is lacking. Previous work has identified tuber pectin methyl esterase (PME) activity as a potential factor impacting on textural properties, and the expression of a gene encoding an isoform of PME (PEST1) was associated with cooked tuber textural properties. In this study, a transgenic approach was undertaken to investigate further the impact of the PEST1 gene. Antisense and over-expressing potato lines were generated. In over-expressing lines, tuber PME activity was enhanced by up to 2.3-fold; whereas in antisense lines, PME activity was decreased by up to 62%. PME isoform analysis indicated that the PEST1 gene encoded one isoform of PME. Analysis of cell walls from tubers from the over-expressing lines indicated that the changes in PME activity resulted in a decrease in pectin methylation. Analysis of processed tuber texture demonstrated that the reduced level of pectin methylation in the over-expressing transgenic lines was associated with a firmer processed texture. Thus, there is a clear link between PME activity, pectin methylation and processed tuber textural properties.     

基于质构仪质地多面分析法对香菇质地评价

香菇Lentinula edodes质地是影响其食味品质和货架期的一系列重要品质指标.本研究首次基于质构仪质地多面分析法(TPA),结合传统感官评级对ZX6(浙香6号)和Lsm9两个香菇亲本及其2个杂交菌株(L1*11和L4*6)子实体的不同部位(菌柄P1、菌盖顶部P2、菌盖中心P3和菌盖侧边P4)的7个质地指标和2个...     

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Bioturbate texture is still the venerable senior synonym of ‘ichno‐fabric’     

Distribution of Selected Plant Parasitic Nematodes Relative to Vegetation and Edaphic Factors

The occurrence of selected plant-parasitic nematodes in the hemlock-hardwood-white pine, boreal forest, tundra, and oak-hickory associations in some northern states was compared. Helicotylenchus platyurus and Xiphinema americanum were not found in the boreal forest and tundra, and occurred infrequently in the hemlock-hardwood-white pine areas. They were found frequently, however, in the oak-hickory forest of Iowa. It is questioned that vegetational differences among the areas account directly for the major differences in nematode occurrence. Presence and absence of nematodes and their numbers in the oak-hickory association were clustered by similarity coefficients by sites and correlated with soil pH, percentage organic matter, percentage sand-silt-clay, and field capacity. Of the soil factors measured, pH gave the strongest correlations with nematode numbers. Xiphinema chambersi was found only in soils with a pH between 4.5 and 6.4 while the largest numbers of H. platyurus, H. pseudorobustus, and X. americanum occurred in soil above pH 6.0.