Macromolecular components of tomato fruit pectin

Chelate and alkaline-soluble pectin extracted from cell walls of pericarp tissue from mature green, turning, and red ripe (Lycopersicon esculentum Mill.) fruit (cv. Rutgers), were studied by high-performance size-exclusion chromatography. Computer-aided curve fitting of the chromatograms to a series of Gaussian-shaped components revealed that pectin from all fractions was composed of a linear combination of five macromolecular-sized species. The relative sizes of these macromolecules as obtained from their radii of gyration were 1:2:4:8:16. Dialysis against 0.05 M NaCl induced partial dissociation of the biopolymers. Apparently, the weight fraction of smaller sized species increased at the expense of larger ones. Also, the dissociation produced low-molecular-weight fragments. Behavior in the presence of 0.05 M NaCl led to the conclusion that cell wall pectin acted as if it were an aggregated mosaic, held together at least partially through noncovalent interactions.     

Volatile flavour components of mango fruit

An essence of fresh Venezuelan mango fruit obtained by well-established procedures possessed the characteristic aroma of the fruit. It was analysed by GC/MS using both EI and Cl. The fruit produced a relatively small quantity of aroma volatiles (ca 60 μg/kg fresh fruit), less than that obtained from many similar tropical fruits. Terpene hydrocarbons comprised ca 68% of the sample, eight monoterpenes contributing ca 54% and four sesquiterpenes contributing ca 14%. Important constituents included α-pinene, car-3-ene, limonene, γ-terpinene, α-humulene, β-selinene, acetophenone, benzaldehyde and a dimethylstyrene. Car-3-ene (26%) was the major constituent, and on odour evaluation of separated components at an odour port during GC, the peak due to this compound was described as having an aroma of mango leaves. This compound has not previously been detected among mango volatiles. The only other component providing mango aroma was a dimethylstyrene, and this too is a new mango volatile.     

Application of PSX biocontrol preparation confers root-knot nematode management and increased fruit quality in tomato under field conditions

PSX is a combination of biocontrol bacteria that can potentially prevent and control soil-borne diseases for a variety of crop cultivars. In this study, we investigated the utility of PSX in controlling root-knot nematodes in tomato under field conditions. The application of PSX reduced the severity of disease caused from Meloidogyne incognita by 63–69% and increased tomato yield by 31.5–39%. Furthermore, to investigate the effect of PSX treatment on tomato fruit quality, we quantified the soluble sugar, titratable acid, soluble solids, and vitamin C contents in fruit postharvest. We demonstrated that PSX treatment improved tomato fruit quality. Finally, we also showed that the total nitrogen (N), available N, potassium, and organic matter contents in the soil increased after PSX treatment. PSX is a promising biocontrol preparation that can provide beneficial effects to tomato growers, including biological control of root-knot disease, plant growth promotion, enhanced tomato fruit quality, and increased levels of organic fertilisers in the soil.     

Competition for assimilates and fruit position affect fruit set in indeterminate greenhouse tomato

Localization and characterization of fruit set in winter tomato crops was investigated to determine the main internal and external controlling factors and to establish a quantitative relationship between fruit set and competition for assimilates. Individual fruit growth and development was assessed on a beef tomato cultivar during the reproductive period (first nine inflorescences). A non-destructive photograph technique was used to measure fruit growth from very early stages of their development and then calliper measurements were made on big fruits. From these measurements we determined the precise developmental stage at which fruit growth stopped. Fruit potential growth, which is defined as the growth achieved in non-limiting conditions for assimilate supply, was also assessed by this method on plants thinned to one flower per inflorescence. The latter was used to calculate the ratio between actual and potential growth, which was found to be a good index of the competition for assimilates. Time lags of fruit set were observed mainly on distal organs. When more than three flowers were left on each inflorescence, distal organs developed at the same time as proximal organs of the following inflorescence. Consequently they were submitted to a double competition within one inflorescence and among inflorescences. It was shown that, what is commonly named 'fruit set failure', is not an irreversible death of the organ and that a small fruit could resume growth after a delay of several weeks as soon as the first fruits ripened and thus ceased to compete for assimilates. In that case proximal fruits resumed growth before distal ones. The delayed fruits contained only few seeds but a germination test confirmed that fertilization took place before fruit set failed. Competition for assimilates was calculated during plant development by the ratio between actual and potential fruit growth. Potential growth of proximal fruits was strongly dependent on the position of the inflorescence on the stem, whereas potential growth of distal fruits was lower than or equal to that of proximal fruits of the same inflorescence and it was independent on the inflorescence position. We took into account both inflorescence and fruit positions to establish a quantitative relationship between fruit set of individual inflorescences and the ratio between actual and potential fruit growth.     

Growth,yield and reproduction of dwarf tomato grown under simulated microgravity conditions

Abstract

A closed hydroponic system combined with a horizontal uniaxial clinostat has been used to grow tomato plants (Solanum lycopersicum L.) under simulated microgravity conditions. The study was carried out to evaluate the quanti-qualitative traits (growth, yield and quality) of the dwarf tomato variety ‘Micro-Tom’ grown under simulated microgravity conditions and to determine if tomato plants would complete their life cycle (‘seed-to-seed’). Morphological and growth characteristics of ‘Micro-Tom’ were modified during clinorotation treatment. The ‘Micro-Tom’ plants grown under simulated microgravity exhibited a spreading growth and an increasing of the internode length. Total fruit yield, small fruit yield, leaf area, leaf dry weight, fruit dry weight, total dry weight and shoot – root ratio were lower in the clinorotated tomato plants than those grown in the control treatment. Foliar amount of carotenoids, and chlorophyll a and b were also substantially reduced under simulated microgravity conditions. Quality parameters (total soluble solids and fruit dry matter) of tomato plants were also negatively affected by clinorotation. The number of flowers per plant was increased by 32% in clinorotated plants versus controls. Fruit setting was reduced by 46% under clinorotation, while no significant difference was recorded for the pollen fertility and the seed number in small and large fruits. Clinorotation-exposed and control seeds were used in a germination trial in order to evaluate whether the seeds so formed were viable and if subsequent generations might be obtained in microgravity. Seeds formed under simulated microgravity proved to be biologically and functionally complete (germination = 78.6%) showing that ‘Micro-Tom’ plants could realize complete ontogenesis, from seed to seed in microgravity.     

Vesicular-arbuscular mycorrhizae of epiphytic and terrestrial Piperaceae under field and greenhouse conditions

We examined the roots of 27 epiphytic and terrestrial species of Piperaceae collected in primary and secondary habitats in Monteverde, Costa Rica. Terrestrial roots of only two of the nine Peperomia species, two of eight Piper species, and of Pothomorphe umbellatum contained internal vesicles and/or arbuscules. We did not find internal vesicles and/or arbuscules in 3024 cm of fine roots of epiphytic Piperaceae, even though 15% of these root segments had associated external typical glomalean hyphae. Glomus and Acaulospora spores, and Gigaspora auxiliary cells occurred in both canopy and terrestrial habitats. After inoculation of a low nutrient substrate, the facultatively epiphytic Peperomia costaricensis averaged 23% mycorrhizal root length. Relatively high atmospheric inputs of dissolved inorganic nutrients that alleviate the requirement for mycorrhizae, and heterogeneity of mycorrhiza inocula in the canopy may explain the absence of mycorrhizae from epiphytic Piperaceae. We suggest that the Piperaceae comprises predominantly facultatively mycotrophic species, and that facultative mycotrophism facilitates their radiation to the canopy.     

Photosynthetic and respiratory characterization of field grown tomato

The photosynthetic responses of tomato (Lycopersicum esculentum Mill.) leaves to environmental and ontogenetic factors were determined on plants grown in the field under high radiation and high nitrogen fertilization. Response curves showed net photosynthesis to only approach light saturation at a photosynthetic photon flux density (PPFD) of 2200 mol m^-2 s^-1, with rates of approx. 40 mol CO₂ m^-2 s^-1. A broad temperature optimum was observed between 25° and 35°C, with 50% of the photosynthetic rates remaining even at 47°C. The high rate, the lack of saturation at the equivalent of full sunlight, and the tolerance to high temperature of tomato were unusual in light of the literature on this C₃ species. Apparently, acclimation to the field environment of high radiation and hot daytime temperature, coupled with the high nitrogen nutrition, made possible the high photosynthetic performance normally associated with C₄ species.Photosynthetic ability of the leaf reached a maximum near the time of its full expansion and declined steadily thereafter, regardless of the time of leaf initiation. Leaf nitrogen content showed a similar decline with leaf ontogeny. Photosynthesis was linearly correlated with nitrogen content, whether the nitrogen variation was due to leaf age or rates of nitrogen fertilization. Internal CO₂ concentrations (C_i) of the leaf indicated that stomatal function was well coordinated with photosynthetic capacity as leaf age and fluence rate varied down to a PPFD of 500 mol m^-2 s^-1. As PPFD decreased further, there was less stomatal control and C_i increased to as high as 320 bar bar^-1.Dark respiration was highest for expanding leaves and increased nearly exponentially with temperature. Respiration was also highest for young and expanding fruits, and next highest for fruits just turning pink. Fruit respiration increased approximately linearly with temperature, and was estimated to be an important component of the CO₂ flux of the plant near maturity because of the heavy fruit load and low leaf photosynthesis at that time. The results are significant for model simulation of tomato productivity in the field.     

Resistance of transgenic tomato to cucumber mosaic cucumovirus under field conditions

Since the summer of 1993, transgenic tomato plants expressing the coat protein (CP) genes of cucumber mosaic cucumovirus have been tested under field conditions to assess the level of resistance and agronomic performance. Trials were performed in different areas in Italy and the target virus in the majority of tests was spread naturally by the indigenous aphid populations. Twenty-three homozygous lines of variety UC82B, transformed to contain four different CP genes of CMV, were evaluated. The lines were preselected for CP expression, single gene copy, and virus resistance in growth chamber experiments. In general, CMV resistance was confirmed under field conditions though resistance in the field was less effective than what was observed in growth chamber experiments. The resistance observed in multi-year and multi-location experiments is of commercial value for several of the most resistant lines. Engineered resistance upon transfer to Italian varieties by breeding or direct transformation will be used in tomato production in Italy or elsewhere. This revised version was published online in June 2006 with corrections to the Cover Date.     

Purification and characterization of two ribonucleases from developing tomato fruit

Two neutral ribonucleases have been purified from developing tomato fruit. Their activity is maximal 5 days after anthesis, declines during maturation, and then increases slightly in the mature green through breaker stages. The ribonucleases Tf1 and Tf2 have molecular weights of 59 and 29 K, respectively, based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and are glycoproteins. The reduced and denatured Tf1 is composed of two subunits, 30 and 29 K, of which only the 30-K subunit displays ribonuclease activity after renaturation. Reduced and denatured Tf2 is a single 29-K polypeptide that is renaturable to an active ribonuclease. Only the 30-K, active subunit of Tf1 is immunologically cross-reactive with Tf2. Both ribonucleases are cyclyzing endoribonucleases with a strong preference for cleavage at pyrimidine residues, thus generating oligonucleotide products ending with pyrimidine 2',3'-cyclic phosphate. These tomato fruit ribonucleases share a number of properties in common with the S-glycoprotein ribonucleases that are involved in self-incompatibility reactions in some solanaceous plants.     

Diversity of endophytic bacterial communities in poplar grown under field conditions

Bacterial endophytes may be important for plant health and other ecologically relevant functions of poplar trees. The composition of endophytic bacteria colonizing the aerial parts of poplar was studied using a multiphasic approach. The terminal restriction fragment length polymorphism analysis of 16S rRNA genes demonstrated the impact of different hybrid poplar clones on the endophytic community structure. Detailed analysis of endophytic bacteria using cultivation methods in combination with cloning of 16S rRNA genes amplified from plant tissue revealed a high phylogenetic diversity of endophytic bacteria with a total of 53 taxa at the genus level that included Proteobacteria, Actinobacteria, Firmicutes and Bacteroidetes. The community structure displayed clear differences in terms of the presence and relative proportions of bacterial taxa between the four poplar clones studied. The results showed that the genetic background of the hybrid poplar clones corresponded well with the endophytic community structure. Out of the 513 isolates and 209 clones identified, Actinobacteria, in particular the family Microbacteriaceae, made up the largest fraction of the isolates, whereas the clone library was dominated by Alpha- and Betaproteobacteria. The most abundant genera among the isolates were Pseudomonas and Curtobacterium, while Sphingomonas prevailed among the clones.     

Photosynthetic characteristics and quality of five passion fruit varieties under field conditions

Due to photosynthetic mechanisms respond very quickly to most stressors and due to strong concerns regarding the impact of climate change on future plant productivity, the purpose of this study was to perform a comparative analysis of in vivo photosynthetic efficiencies and fruit quality of five cultivars of passion fruit (Passiflora edulis Sims. f. flavicarpa Degener). The experiments were conducted in the northern region of Espírito Santo State using cultivars FB 200, FB 300, BRS Gigante Amarelo, BRS Sol do Cerrado, and BRS Ouro Vermelho. Analyses were performed 6 months after planting, when the plants were beginning reproduction and were repeated two times during the next 4 months until fruit ripening. Chlorophyll a fluorescence transient, total chlorophyll content, and gas exchange were measured in the leaves. Physical and chemical fruit attributes were also assessed. The lowest fluorescence rates were identified in the FB 300, BRS Sol do Cerrado, and BRS Ouro Vermelho cultivars, which exhibited better capacities for quinone A (Q_A) reoxidation and better electron transfer efficiencies from Photosystem II to Photosystem I acceptors. Better photochemical performances (PI_total) and CO₂ assimilations (A) resulted in higher fruit pulp yields, demonstrating the superior quality of the FB 300, BRS Sol do Cerrado, and BRS Ouro Vermelho cultivars.     

Root traits and nitrogen fertilizer recovery efficiency of corn grown in biochar-amended soil under greenhouse conditions

Plant and Soil - The Oxalate-Carbonate Pathway (OCP) is a biogeochemical process that transfers atmospheric CO2 into the geologic reservoir as CaCO3; however, until now all investigations on this...     

Relationship between tomato fruit growth and fruit osmotic potential under salinity

To investigate the relationship between fruit growth and fruit osmotic potential (Ψ_s) in salty conditions, a sensitive tomato cultivar (Lycopersicon esculentum Mill.) and a tolerant accession of the wild species Lycopersicon pimpinellifolium Mill. were grown in a greenhouse with 0 and 70 mM NaCl, and the growth of the fruit studied from 15 to 70 days after anthesis (DAA). L. pimpinellifolium did not reduce significantly fruit weight in salty conditions throughout the growth period, whereas L. esculentum fruit weights decreased significantly with salinity from 45 DAA. L. esculentum fruit fresh weight reductions resulted from both less dry matter and water accumulation, although the fruit water content was affected by salinity before the fruit weight. In both species, fruit osmotic potential (Ψ_s) decreased significantly with salinity during the rapid fruit growth phase, although the changes were different. Thus, fruits from L. pimpinellifolium salt treated plants showed a Ψ_s reduction at the beginning (15 DAA) twice as high as that found in L. esculentum. As the advanced growth stage (from 15 to 55 DAA), the Ψ_s reduction percentages induced by salinity were quite similar in L. pimpinellifolium fruits, while increased in L. esculentum. Under saline conditions, the solutes contributing to reduce the fruit Ψ_s during the first 55 DAA were the inorganic solutes in both species, while in the ripe fruits they were hexoses. L. esculentum fruits accumulated K⁺ as the main osmoticum in salty conditions, while L. pimpinellifolium fruits were able to use not only K⁺ but also the Na⁺ provided by the salt.     

基于双作物系数法估算不同水分条件下温室番茄蒸发蒸腾量

2015—2016年在中国农业科学院新乡综合试验基地,以华北地区典型日光温室滴灌番茄为研究对象,分析2种灌溉水平[参考20 cm标准蒸发皿的累积蒸发量(E_p),设置2种灌溉水平(高水: 0.9E_p;低水:0.5E_p)]下番茄不同生育期土壤蒸发(E)、作物蒸腾(T)、蒸发蒸腾(ET)和土壤蒸发占蒸发蒸腾比值(E/ET)的变化,探讨水分亏缺对作物系数(K_c)的影响以及水分胁迫系数(K_s)在全生育期的动态变化.采用双作物系数法分别估算E、T和ET,并与实测结果进行对比分析.结果表明: 2015和2016年全生育期高水处理的E分别比低水处理高21.5%和20.4%, 占总蒸发蒸腾量的24.0%和25.0%,E/ET在生育初期最大、中期最小;高水处理的K_c值在生育初期、发育期、生育中期和生育后期分别为0.45、0.89、1.06和0.93,低水处理下分别为0.45、0.89、0.87和0.41;低水处理的K_s值在0.32～1.0,生育初期、发育期、生育中期和生育后期分别为0.98、0.93、0.78和0.39.双作物系数法可较精确地估算不同水分处理的ET,其平均绝对误差(MAE)为0.36～0.48 mm·d^-1,均方根误差(RMSE)为0.44～0.65 mm·d^-1;该方法也可精确地估算E和T,其MAE分别为0.15～0.19和0.26～0.56 mm·d^-1,RMSE分别为0.20～0.24和0.33～0.72 mm·d^-1.     

Differential acclimation capacity to frost in sugarcane varieties grown under field conditions

In certain sugarcane (Saccharum spp. hybrids) production regions of the world, including South Africa, frost frequently occurs. Great demand exists for frost tolerant sugarcane varieties as production in these areas could become more profitable. Two Louisiana (USA) varieties, known to yield high sugar even when immature (LCP 85-384 and HOCP 96-540), and two South African varieties (N21 and N36) were evaluated in a field trial for frost tolerance. O–J–I–P chlorophyll a fluorescence transients were recorded in youngest fully-expanded leaves of these varieties on several occasions before and following exposure to frost. Analysis of these transients revealed that varieties N36 and LCP 85-384 were capable of cold acclimation following the first frost, while N21 and HOCP 96-540 lacked similar capability. Exposure to further frosts altered the fluorescence transients in a variety-specific fashion, with recovery in N36 and LCP 85-384 towards baseline kinetics, but with further deterioration in N21 and HOCP 96-540. Between the first frost and harvest, estimated recoverable crystal (ERC) content values in cane stalks of N36 and LCP 85-384 increased by 26 and 20 % respectively, while in N21 and HOCP 96-540 ERC content values only increased by 8 and 11 % respectively. Consequently, N36 and LCP 85-384 ultimately achieved the highest ERC yields (tons/hectare). The ability to maintain high ERC accumulation capacity for longer following frost could be an important factor determining sugarcane yield performance in frost-prone areas. In addition, O–J–I–P fluorescence rise kinetics show promise as a rapid screening tool for assessment of cold acclimation potential in sugarcane.     

Genetically modified parthenocarpic eggplants: improved fruit productivity under both greenhouse and open field cultivation.

Background  

Parthenocarpy, or fruit development in the absence of fertilization, has been genetically engineered in eggplant and in other horticultural species by using the DefH9-iaaM gene. The iaaM gene codes for tryptophan monoxygenase and confers auxin synthesis, while the DefH9 controlling regions drive expression of the gene specifically in the ovules and placenta. A previous greenhouse trial for winter production of genetically engineered (GM) parthenocarpic eggplants demonstrated a significant increase (an average of 33% increase) in fruit production concomitant with a reduction in cultivation costs.     

Relative growth rates of leaves from soybean grown under drought-stressed and irrigated field conditions

Abstract. The relative growth rates and leaf area were graphed against leaf area, normalized with respect to final leaf area, to assess the applicability of the Lockhart cell wall expansion equation to soybean, Glycine max (L.) Merr., leaf development under field conditions. For leaves that had completed more than 20% of their growth, relative growth rates decreased linearly with an increase in the normalized leaf area, indicating that these leaves were undergoing strictly expansive growth. Drought stress significantly decreased the relative growth rate of these larger leaves. Small leaves which had completed less than 20% of their growth, were found to have highly variable relative growth rates. The large variability in relative growth rates indicated that the Lockhart cell wall expansion equation was inadequate to evaluate the growth of these young leaves. Drought stress had virtually no influence on the relative growth rates observed in the small leaves.     

Estimating tomato water consumption by sap flow measurement in response to water stress under greenhouse conditions

This research was conducted to determine the water consumption of tomato plants, the effects of water stress on stem sap flow (SF) and its response to climatic factors. SFs in 100% irrigation (T₁), 75% (T₂) and 50% (T₃) of irrigation amount of T₁ were monitored using Dynagage sensors. Compared to T₁, the difference in SF was observed under deficit irrigation in the same climatic conditions on sunny days although there was no apparent difference between T₁ and T₂ on cloudy days. Under T₁, the correlation and regression relationships between SF and climatic factors were analyzed at daytime (6:00–22:00), morning (6:00–14:00) and afternoon (14:00–22:00). Considering daytime, the order of sensitive indicators to SF was VPD?>?LI?>?Ta and LI?>?VPD?>?Ta for the Fall-Winter sunny days and Spring-Summer season, respectively. The water uptake over SFs measured for Fall-Winter and Spring-Summer periods were calculated as 168.65 and 229.18?mm, respectively.