Effect of electrical conductivity and transpiration on production of greenhouse tomato (Lycopersicon esculentum L.)

We investigated the hypothesis that manipulating water out-flow of a plant through the shoot environment (potential transpiration, ET₀) in a glasshouse could modulate the effect of salinity/osmotic potential in the root environment upon yield of tomatoes. Contrasting root-zone salinity treatments were combined with two climate treatments — a reference (high transpiration, HET₀) and a “depressed” transpiration (low transpiration, LET₀). The salinity treatments, characterised by their electrical conductivity (EC) were 6.5, 8 and 9.5 dS m⁻¹, were always coupled with a reference treatment of EC=2 dS m⁻¹. In another experiment, concentrated nutrients (Nutrients) and nutrients with sodium chloride (NaCl) at the same EC of 9 dS m⁻¹ were compared.Marketable fresh-yield production efficiency decreased by 5.1% for each dS m⁻¹ in excess of 2 dS m⁻¹. The number of harvested fruits was not affected; yield loss resulted from reduced fruit weight (3.8% per dS m⁻¹) and an increased fraction of unmarketable harvest. At the LET₀ treatments, yield loss was only 3.4% per dS m⁻¹ in accordance with the reduction in fruit weight. Low transpiration did increase fruit fresh yield by 8% in both NaCl and Nutrients treatments at an EC=9 dS m⁻¹. Neither EC nor ET₀ affected individual fruit dry weight. Accordingly, fruit dry matter content was significantly higher at high EC than in the reference (4% per each EC unit in excess of 2 dS m⁻¹) and responded to ET₀ to a minor extent. Control of the shoot environment in a greenhouse to manipulate the fresh weight of the product may mitigate the effects of poor quality irrigation water without affecting product quality.     

Effect of electrical conductivity,fruit pruning,and truss position on quality in greenhouse tomato fruit

Summary

The combined effects of electrical conductivity (an EC of 2.5 dS m^–1 or 8 dS m^–1 in the root zone) and fruit pruning (three or six fruit per truss) on tomato fruit quality were studied in a greenhouse experiment, planted in January 2005. Taste-related attributes [dry matter content (DM), total soluble solids content (SSC), titratable acidity (TA), glucose, fructose and citric acid content] and health-promoting attributes (lycopene, βcarotene, vitamin C, and total anti-oxidant activity) of tomato fruits harvested on the vine from the fifth or tenth truss positions were determined. The quality of tomato fruits was improved by high EC. A high EC in the root zone increased the DM content, total SSC, TA, as well as glucose, fructose and citric acid contents. A significantly higher lycopene and βcarotene content was also observed [on a fresh weight (FW) and dry weight (DW) basis] with a high EC in the root zone. The accumulation of different compounds that determine tomato fruit quality differed between the fifth and tenth truss. In particular, the lycopene content was reduced, whereas the βcarotene content was increased in the tenth truss with respect to the fifth truss, most likely because of higher temperatures during ripening of the tenth truss. Fruit pruning increased fruit FW by 42% and positively influenced the DM content and total anti-oxidant activity, while a negative effect was observed on lycopene and citric acid contents (on a FW and DW basis). EC and fruit pruning both had a strong effect on fruit size; however, EC had a much stronger impact on taste and health-related fruit quality attributes. A small interaction between EC and fruit pruning was found for marketable yield, fructose and glucose content, fruit firmness, and P and Ca concentrations in fruits.     

Morphological responses of bedding plants to three greenhouse temperature regimes

Seedling crops of gazania, geranium, marigold, mimulus, pansy, verbena and vinca were grown to 60% anthesis in three greenhouse temperature regimes: (a) 26 °C day/6 ± 3 °C night (LT), with a 16.5 °C mean daily temperature (MDT), (b) 26 °C day/17 ± 4 °C night, with a 21 °C MDT, and (c) variable day/night temperatures in response to heating and cooling by a phase change material energy storage module (PCM) with an 8 ± 2 °C night and a 16 °C MDT. Crops bloomed from 2 to 17 days earlier in the 26 °C/17 °C greenhouse. The morphological characteristics of all cultivars of gazania, mimulus, pansy and verbena, geranium and vinca were similar regardless of greenhouse temperature regime. Marigold diploid and triploid cultivars and mimulus were morphologically more variable than the other bedding plant species. Crops grown in the PCM and LT greenhouses had virtually identical morphological characteristics and bloomed in about the same number of days. Plant height was not affected by DIF environments in the greenhouses. The PCM and LT greenhouses had a similar MDT, but the distribution of numbers of hours of mean daily temperatures was different.     

Physiological responses and adaptive strategies of tomato plants to salt and alkali stresses

In this study, seedlings of tomato were treated with salt stress or alkali stress. The growth, photosynthesis and concentrations of solutes and inorganic ions in tissue sap of stressed seedlings were measured to investigate the physiological adaptive mechanisms by which tomato tolerates alkali stress. The alkali stress clearly inhibited growth and photosynthesis. With increasing salinity, the Na⁺ concentration and Na⁺/K⁺ ratio in leaves increased, with greater degrees of increase under alkali than under salt stress. This indicated that high-pH caused by alkali stress might affect the control of roots on Na⁺ uptake and increased the intracellular Na⁺ to a toxic level, which might be the main cause of reductions of stomatal conductance and net photosynthetic rates under alkali stress. Under salt stress, organic acids (OAs), Na⁺, K⁺ and Cl⁻ were the main osmolytes in both roots and leaves. Under alkali stress, roots and leaves revealed different mechanisms of ion balance and osmotic regulation. Under alkali stress, in roots, OAs and Na⁺ were the main osmolytes, and the osmotic role of K⁺ was small; however, in leaves, OAs, Na⁺ and K⁺ all played important osmotic roles. The mechanisms governing ionic balance under both stresses were different. Under salt stress, the contribution of inorganic ions to keep ion balance was greater than that of OAs. However, under alkali stress, Cl⁻, H₂PO₄⁻ and SO₄²⁻ concentrations decreased, and tomato might have enhanced OA synthesis to compensate for the shortage of inorganic anions.     

设施菜地土壤基础养分含量分析

为了给设施蔬菜减量施肥提供依据,结合设施蔬菜种植户施肥调研结果,以及室内土壤样品测定结果,研究了新乡市牧野区设施蔬菜地土壤基础养分含量和施肥中存在的主要问题。结果表明,该区土壤质地良好,磷钾丰富,氮含量中等,有机质缺乏,pH值约为6.5,为非盐渍化土壤。除类金属总砷含量有部分地块超标外,土壤中其余金属元素含量均未超标。选择优质商品有机肥和微生物菌肥做为底肥的种植户只占到10%,而选择生粪的占65%以上。每茬作物化肥施用量可达250 kg·667 m-2。因此,建议该地区设施蔬菜种植施用优质商品有机肥1 200 kg·667 m-2,并逐渐降低化学肥料追肥次数和数量,不断增加生物菌肥和有机水溶肥的施用。     

Response of tomato plants to saline water as affected by carbon dioxide supplementation. II. Physiological responses

Summary

Photosynthesis of tomato plants (Lycopersicon esculentum (L.) Mill. cv. F144) was studied under conditions of CO₂ supplementation and salinity. The purpose of the study was to elucidate the mechanisms underlying the effects of salinity on the acclimation of tomato plants to CO₂ supplementation. Plants were grown under either low (355.mmol mol^–1) or elevated (1200.6.50 mmol mol^–1) CO₂ and were irrigated with low concentrations of mixed salts. The highest salinity level (E.C. 7 dS m–1) was that used to produce quality tomatoes in the Negev highlands, in Israel. During early development (three weeks after planting), the net photosynthetic rate of the leaves was much higher under elevated CO₂, and other than a slight decrease in quantum yield efficiency as measured by fluorescence (DF/F 9 ^m ), no signs of acclimation to high levels of CO₂ were apparent. Clear acclimation to high CO₂ concentration was evide t ten weeks after planting when the net photosynthetic rate, photosynthetic capacity, and carboxylation efficiency of leaves of non-salinized plants were strongly suppressed under elevated CO₂. This was accompanied by reductions in carboxylation efficiency, Rubisco activity and PSII quantum yield, and an increased accumulation of leaf soluble sugars. The reduction in photosynthetic capacity in the high CO₂ plants was less in plants grown at the highest salinity level. This was correlated with an increase in the PSII quantum yield parameters (F_v/F_m) and DF/F 9 m ) but not with Rubisco activity which was affected by the CO₂ treatments only. These results explain the effects of high CO₂ on yields in tomatoes grown at high levels of salt (Li et al., 1999).     

Physiological responses associated to substrate water availability of Rosa ‘Eurored’ plants grown in soilless greenhouse conditions

The aim of the present study was to provide a better insight into the adaptive processes to water deficit of Rosa hybrid plants grown in soilless cultivation. Rose plants were grown in a greenhouse under two water regimes, corresponding to 100% and 67% of the irrigation needs. Watering was stopped for 0, 72, and 96 h (dry-down period) and photosynthetic parameters, water relations, chlorophyll fluorescence, carbohydrate and ion content were determined.     

Growth responses of some greenhouse plants to environment. I. Experimental techniques

A system for continuous measurement of net photosynthesis of small stands of greenhouse plants in an almost air-tight cabinet is described. The accuracy of control of the CO₂ concentration in the cabinet is within ± 1% of the desired value. The control of air temperature is within ± 0.2°C and the relative humidity within ± 2% from the adjusted value. The amount of CO₂ used in photosynthesis is measured by the number of injections of controlled volumes of CO₂ in a specific time interval.A system for soil temperature regulation is described. In the range from 5 to 35°C, the accuracy of control of the soil temperature is usually within ± 0.5°C from the desired value. At high solar irradiance, however, the temperature may rise about 2°C at the lower, and somewhat less at the higher, soil temperatures.Results from preliminary experiments with roses and chrysanthemums are presented.     

Growth responses of some greenhouse plants to environment. II. The effect of soil temperature on Chrysanthemum morifolium Ramat

The effect of a wide range of soil temperatures (6–26°C) on growth and flowering of Chrysanthemum morifolium Ram. ‘Horim’ were studied at the favourable air temperature of 18°C. Shoot growth was severely reduced at soil temperatures below 10°C which may be explained by poor root growth, while flowering was enhanced by approximately 2 days compared to higher soil temperatures. Increasing the soil temperature to 18°C was beneficial. Further increase had no positive effect on growth. Measurements of net photosynthetic rates revealed no effect of lowering soil temperatures from 18 to 6°C.Mother plants grown at 18°C air temperature revealed no effect of soil temperatures ranging from 13 to 21°C on number and fresh weight of the cuttings. Neither did mother plants grown at the less favourable air temperatures of 12 or 15°C. Cutting production was, however, affected by air temperature.     

有机复混肥替代化肥减施对日光温室番茄生长及土壤环境的影响

为探讨日光温室栽培番茄化肥减量施用技术,通过有机复混肥替代化肥减施不同比例氮,研究其对日光温室番茄植株生长、果实品质、产量、土壤酶活性、土壤微生物数量等各项指标的影响。结果表明,与对照CK(鸡粪2 000 kg·667 m~(-2)+常规化肥量333 kg·667 m~(-2))相比,有机复混肥替代化肥的减氮施肥处理可不同程度地促进番茄生长,增加产量,改善土壤环境。其中T3(鸡粪2 000 kg·667 m~(-2)+有机复混肥46.88 kg·667 m~(-2)+化肥283 kg·667 m~(-2))处理,即有机复混肥替代减施氮含量15%的化肥,效果显著,番茄植株生长状况最好,产量品质最佳。     

Evaluation and modelling of greenhouse cucumber-crop transpiration under high and low radiation conditions

The main objective of this study was to analyse the transpiration time course of soilless culture cucumber plants (Cucumis sativus L.) during two cycles, at low (up to 9 MJ m⁻² d⁻¹) and high (up to 20 MJ m⁻² d⁻¹) radiation levels, and their relationship with greenhouse climate parameters (incident radiation and vapour pressure deficit, VPD) and canopy development. The coefficients of the simplified Penman–Monteith formula were calibrated in order to calculate the transpiration rate of the crop, to help improve irrigation management in substrate cultivation. The transpiration rate per ground surface area was measured by weighing plants with an electronic balance.At high radiation levels, the diurnal canopy transpiration rate was four times higher than at low radiation levels and the night transpiration rate reached values between 120 and 200 g m⁻² d⁻¹ in both cases. The leaf transpiration rate decreased during crop ontogeny and was higher in the afternoon than in the morning for the same value of radiation, whereas a linear relationship with the VPD was found even for values greater than 3 kPa. The results showed that the fitted simplified Penman–Monteith formula accounted for more than 90% of the measured hourly canopy transpiration rate, signifying that this formula could be used to predict water requirements of crops under Mediterranean conditions and improve irrigation control in a substrate culture. However, the model coefficients will have to be adjusted for specific climate and crop conditions.     

The influence of container volume,solution concentration,pH and aeration on dry matter partition by tomato plants in water culture

When containers, each holding a single tomato plant, were continuously supplied with nutrient solution from a common reservoir, the volume of the containers (from 0.65 to 6.00 1) had little influence on the partition of dry matter between cotyledons, roots, stem and leaves, regardless of the time of the year or the frequency of renewal of the solution. Partition was also unaffected by solution pH (between 4 and 8 inclusive) or by the aeration of the solution, although both these factors affected total dry matter. Reducing the solution concentration, however, reduced the proportion of the total dry matter in the roots during the first two weeks of seedling growth but subsequently increased it slightly.     

Growth responses of some greenhouse plants to environment. III. Design and function of a growth chamber prototype

Growth chambers for the study of effects of temperature, air humidity and CO₂-concentration on plant growth, with or without supplementary artificial light, are described. Each chamber has a volume of 1080 1. The mean airflow at plant level is 0.22 m s^?1. The temperature is controlled within ± 0.5°C in the range from 10°C lower to 20°C higher than the ambient temperature at low solar radiation. In direct sunshine, the temperature may rise 1°C at floor level and the gradient from the floor to the upper part of the chamber may be about 2°C.The relative humidity is generally controlled within ± 4%, in the range from 50 to 95%.The CO₂-concentration is controlled within ± 5% of the desired value. The number of air changes in the chambers may be controlled from 0 to 20 h^?1.Tests revealed no significant difference between the chambers with respect to fresh weight production of lettuce, rose or chrysanthemum. There was, however, a significant effect from the position within the chambers.     

A comparison of winter-sown tomato plants grown with restricted and unlimited water supply

The morphology, anatomy and physiology of winter-sown tomato plants grown with a restricted water supply (producing ‘hard’ plants) were compared with those of plants given an unlimited water supply (‘soft’ plants). The stressed plants had smaller and fewer leaves on thinner stems; the reduction in leaf area was largely due to smaller cell size. The leaves and stems also had a higher percentage dry matter; in the stems this was associated with many more and larger starch grains. It is suggested that the improvement in earliness and in fruit quality found in stressed plants originates from this increase in stored carbohydrate.

Rates of photosynthesis per unit leaf area were the same in both groups of plants when measured under laboratory conditions. The leaf cell sap had the same osmotic potential but there was a greater proportion of apoplastic water in the leaves of the stressed plants. Transpiration rates in the glasshouse were lower in the stressed plants. Possibilities for the control of plant water status to optimize early yield quantity and quality are considered.     

Root zone soil nitrogen management to maintain high tomato yields and minimum nitrogen losses to the environment

Greenhouse field experiments on tomato were carried out at Shouguang, Shandong province, over four double cropping seasons between 2004 and 2008 in order to understand the effects of manipulating root zone N management (RN) on fruit yields, N savings and N losses under conventional furrow irrigation. About 72% of the chemical N fertilizer used in conventional treatment (CN) inputs could be saved using the RN treatment without loss of yield. The cumulative fruit yields were significantly higher in the RN treatment than in the CN treatment. Average seasonal N from irrigation water (118 kg N ha⁻¹), about 59% of shoot N uptake, was the main nitrogen source in treatments with organic manure application (MN) and without organic manure or nitrogen fertilizer (NN). N losses in the RN treatment were lowered by 54% compared with the CN treatment. Lower N losses were found in the MN and NN treatments due to excessive inputs of organic manure and fruit yields were consequently substantially affected in the NN treatment. The critical threshold of N_min supply level in the root zone (0–30 cm) should be around 150 kg N ha⁻¹ for sustainable production. April to May in the winter–spring season and September to October in the autumn–winter season are the critical periods for root zone N manipulation during crop growth. However, control of organic manure inputs is another key factor to further reduce surplus N in the future.     

Effects of high electrical conductivity of nutrient solution and its application timing on lycopene,chlorophyll and sugar concentrations of hydroponic tomatoes during ripening

Tomato (cv. Durinta) plants were grown hydroponically under two electrical conductivities (EC, 2.3 and 4.5 dS m⁻¹) of nutrient solution inside a greenhouse. The high EC treatment was initiated either immediately after anthesis (high EC treatment) or 4 weeks after anthesis (delayed high EC treatment). Fruits were harvested weekly beginning 2 weeks after anthesis, until all fruits reached the red stage (8 weeks after anthesis). Lycopene, chlorophyll, sugar and total soluble solid (TSS) concentrations of fruits were measured every week for all harvested tomatoes from the different ripeness stages. The results showed that lycopene concentration, fructose and glucose concentrations and TSS of red ripe tomato fruits were enhanced by both high EC and delayed high EC treatments compared to those in the low EC treatment. The lycopene concentration of red ripe tomato fruits in the high EC and the delayed high EC treatments showed an increase of 30–40% (1.29–1.39 mg g⁻¹ dry matter) compared to those in the low EC treatment (0.99 mg g⁻¹); however, there was no significant difference in the lycopene concentration between the high EC and delayed high EC treatments. TSS of red ripe tomato fruits grown in the high EC treatment was 6.1%, significantly greater than those grown in the delayed high EC treatment (5.7%). Weekly change in lycopene concentration indicated that lycopene synthesis was enhanced by the high EC treatment, regardless of the application timing. Regardless of EC treatment, chlorophyll concentration in fruit declined linearly during fruit development and ripening and reached non-detectable levels 7 weeks after anthesis. Our results indicated that: (1) accumulation of sugars and TSS in fruit was due to reduced water flux to the fruit under high EC as previously reported, and (2) lycopene synthesis was promoted by, but chlorophyll degradation was independent from, the osmotic and/or salt stress caused by the high EC.     

Effects of night-time humidity and nutrient solution concentration on the calcium content of tomato fruit

Calcium intake into tomato fruits was greater when nights were humid rather than dry and nutrient solutions dilute rather than concentrated.The concentration of calcium in the wall tissue of the distal segment of fruits damaged by blossom-end rot was 0.03% of dry matter, but was 2- to 3-fold greater in the most favourable conditions of humidity and solution concentration, when fruits were undamaged.Adding extra calcium to the nutrient solution increased the calcium concentration in the proximal, but not in the middle or distal, segments of the fruit.The results support the hypothesis that a positive root pressure at night promotes transport of calcium into tissues and organs that have restricted transpiration.     

Diurnal variations in the oxygen content and acid requirement of recirculating nutrient solutions and in the uptake of water and potassium by cucumber and tomato plants

The oxygen content of recirculating nutrient solutions was measured in July and August, together with the amounts of acid required to maintain a constant pH in the solution and the rates of uptake of water and potassium. The oxygen content of the solutions declined to a minimum during the brightest part of the day. The oxygen deficit was highly correlated with both the temperature and the amount of acid required to maintain the pH of the nutrient solution. Under similar environmental conditions, the oxygen content of the solution was reduced to lower concentrations by cucumber (2.7 mg l^?1; 34% saturation) than by tomato plants (6.7 mg l^?1; 84% saturation), reflecting the thicker root mat formed by cucumber.     

Response of young hydroponically grown tomato plants to phenolic acids

Phenolic acids—excreted both as root exudates and by microorganisms—are of interest in cultivation systems of different horticultural crops since they have been claimed to accumulate in closed hydroponic growing systems. The aim of the present investigation was to assess the phytotoxic effects when hydroponically grown tomato plants are exposed to phenolic acids in the root environment. The tomato plants were grown in static aerated culture and exposed to benzoic, caffeic, chlorogenic, ferulic, p-hydroxybenzoic, salicylic and vanillic acid at concentrations of 50, 100, 150, 200 and 400 μM in the fresh nutrient solution. The highest concentration of all tested compounds significantly reduced fresh and dry weights. Salicylic and ferulic acid affected plants already at 150 and 200 μM while effects were less pronounced for p-hydroxybenzoic and chlorogenic acid. Chlorophyll fluorescence analysis did not result in any significant difference between any of the tested acids or concentrations. No clear dose-related pattern was obtained with respect to number of leaves and plant length. Visual assessment showed that the most deleterious effects appeared on the roots, which were discoloured and/or had slimy coatings when exposed to the phenolic acids. The uptake of several mineral nutrients was influenced at the highest concentration of all studied compounds. Significantly more bacteria were enumerated in the nutrient solution treated with phenolic acids compared to the controls. Most of the phenolic acids were degraded after 2 days during the start of the trial and within 1 day at the end of the trial. Concentrations phytotoxic to small tomato plants were 1000-fold higher than the natural concentrations measured before. Instead of potentially harmful, the relevance of certain phenolic acids as antimicrobial substances should be considered.