Postharvest physiology of Corchorus olitorius baby leaf growing with different nutrient solutions

The storage at 4°C in darkness of Corchorus olitorius L. baby leaf as a ready-to-eat (RTE) vegetable has been studied for the first time. C. olitorius was cultivated in a floating system with different nutrient solutions: standard (NS100%) or halved (NS50%). Several quality factors of this produce were evaluated during season (spring, summer, autumn) considering treatments and days of storage in order to understand the interactions. During storage, sucrose, total and reducing sugars, nitrate, phenolic compounds, anthocyanins, chlorophylls, and carotenoids were measured. Results showed that chlorophylls decreased by 20–30% for both treatments and the changes were statistically different during spring. Carotenoid content did not change until the end of the storage and values ranged from 0.60 g kg^?1 to 0.75 g kg^?1 fresh weight depending on the season. Phenols and anthocyanins decreased within 10 days: ?40% of phenols and ?50% of anthocyanins, respectively. No interaction between nutrient solutions and storage behaviour was reported. Thus, C. olitorius resulted to be a good source of nutraceutical compounds and it is able to maintain these components during storage. Moreover, the public interest in regards to nutritional and healthy food is rapidly increasing, promoting the discovery of new vegetables, like C. olitorius, for RTE commercialisation.     

Nickel supplementation effect on the growth,urease activity and urea and nitrate concentrations in lettuce supplied with different nitrogen sources

Effect of nickel (Ni) in the nutrient solution on yield, N metabolism, and nitrate content of leafy vegetables is poorly understood. The aim of this nutrient solution culture experiment was to investigate the effects of Ni supplementation on the nitrogen (N) metabolism and growth of lettuce (Lactuca sativa L. cv. Baker) with either urea or nitrate as the N source. Nickel supplement at 0.04 μM reduced urea toxicity to the urea-fed plants. Addition of Ni to the nutrient solution significantly increased the leaves and root growth of the urea-fed lettuce plants while it increased the growth of lettuce plants fed with nitrate only at N level of 20 mM. At N level of 20 mM, the leaves fresh weight of the urea-fed plants promoted by Ni supplement was comparable with the nitrate-fed plants untreated with Ni. Nickel supplementation increased the leaf total N concentrations in the urea-fed plants, although the nitrate-fed plants accumulated greater N in their leaves compared with urea treated plants at without Ni treatment. Nickel addition decreased the concentrations of leaf urea-N in the urea-fed plants and NO₃-N in the nitrate-fed plants. Nickel addition enhanced urease activity in the leaves of urea-fed plants. The results indicated Ni supplementation enhances the growth of the urea-fed lettuce plants while it has role in decreasing leaf nitrate concentration and thus, improving the health quality of the nitrate-fed plants.     

水培营养液配方对不同叶菜产量和品质的影响

为了研究不同水培营养液对不同类型绿叶蔬菜产量和品质的影响,寻求适合华南地区叶菜生长的营养液配方,采用穴槽无土栽培种植方式,比较了日本园试配方与霍格兰配方对苋菜、芥菜、菜心、生菜、油麦菜生长情况、产量和品质的影响。结果表明,在所有供试蔬菜种类中,使用日本园试配方的蔬菜产量显著高于霍格兰配方,株高、茎粗、叶宽、叶长等外观品质多数较霍格兰配方更具优势,且日本园试配方处理下油麦菜、菜心和苋菜的VC含量较高。因此,日本园试配方更适合华南地区小型蔬菜生产企业实际生产中单一配肥池培养多种叶菜的生产模式。     

Effects of cultural cycles and nutrient solutions on plant growth,yield and fruit quality of alpine strawberry (Fragaria vesca L.) grown in hydroponics

Alpine strawberry (Fragaria vesca L.) was grown in hydroponics with the nutrient film technique, in order to evaluate the effects of four buffer concentrations (1.3, 1.6, 1.9, 2.2 mS cm⁻¹) and two cultural cycles (summer-spring versus autumn-spring) in terms of growth, yield and fruit quality (dry and optical residues, sugars, acids, antioxidants, mineral composition). The longer summer-spring cycle gave a correspondingly higher yield than the autumn-spring one. The 1.3 mS cm⁻¹ nutrient solution was the most effective in terms of overall and spring production. However, the autumn and winter yields were not affected by the buffer EC. Fruit quality did not change with the cultural cycle, but the berries harvested in the spring had higher vitamin C and sucrose content and lower nitrate content compared with berries picked up in the winter. Fruit quality was also improved when the nutrient solution concentration increased. From the productive point of view, the cultural cycle choice should be made considering that 71% of the yield of the more productive summer-spring cycle derived from the spring harvest. Moreover, as regards the nutrient solution strength, 1.3 mS cm⁻¹ EC should be preferred during the spring season, whereas the 2.2 mS cm⁻¹ EC proved to be best in the winter in terms of fruit quality.     

The influence of growing season on fruit yield and quality of greenhouse melon (Cucumis melo L.) grown in nutrient film technique in a Mediterranean climate

Summary

The influence of growing season on some physiological and biochemical variates related to fruit yield and quality was investigated in melon (Cucumis melo L.) plants cultivated in nutrient film technique in a greenhouse located at Pisa, Central Italy, from mid-March to mid-June, or from mid-July to mid-September. Compared with spring, the plants grown in summer exhibited faster growth and development, but produced fewer fruits of larger size and poorer quality due to reduced sucrose content. Growing season did not affect total leaf area, but dry-matter production and partitioning to the fruits was significantly lower in summer than in spring. Summer fruit ripened within 30–35 d after anthesis, about 14 d fewer than in spring. Higher average temperature was presumably responsible for earlier fruit maturation in summer, as in both seasons all melons were harvested after 450–500 degree-days (base temperature of 12°C) from anthesis. Fruit swelling did not account for the reduction of sucrose content in summer-grown fruits, which instead was due to shortage of photoassimilate supply and inadequate sucrose synthesis, as suggested by the rate of leaf gas exchange and the activity of sucrose phosphate synthase in the fruit flesh, as determined during the final stages of fruit development. Lower solar radiation was presumably responsible for the reduced leaf carbon assimilation in summer, as growing season did not affect leaf turgor, stomatal conductance, mineral status and chlorophyll content.     

Effect of nitrogen form and radiation on growth and mineral concentration of two Brassica species

Three greenhouse experiments were carried out to determine the growth, yield, nitrate, total N and S concentration in shoots, and water uptake of hydroponically grown Brassica rapa L. subsp. nipposinica var. chinoleifera and Brassica juncea L. In each experiment, daily photosynthetically active radiation (PAR) level was 5.0 mol m⁻² (low), 6.8 mol m⁻² (medium) or 9.0 mol m⁻² (high). Plants were supplied with nutrient solutions having equal N concentrations of 11 mM in different forms: 100% NH₄, 50% NH₄ + 50% NO₃, and 100% NO₃. Nitrogen supplied as 100% NH₄ reduced fresh and dry shoot biomass, leaf area, and leaf number in both Brassica species, especially at low and medium PAR levels. In both Brassica species, S concentrations were highest, while nitrate concentrations were lowest in leaves of plants grown at N supplied as 100% NH₄. No differences in leaf nitrate concentrations were observed between 50% NH₄ + 50% NO₃ and 100% NO₃ treatments. Low and high PAR levels increased the nitrate concentrations and decreased the N/S ratio in leaves of both crops compared to medium PAR level. Fresh shoot biomass was maximized in Brassica rapa when PAR level was above the medium value and nitrate was supplied in the nutrient solution as NO₃ or as a mixture of 50% NO₃ and 50% NH₄. The highest fresh shoot biomass of Brassica juncea was observed in all nutrient solution treatments at high PAR level.     

家庭阳台蔬菜种植方式的初步探索

以适合阳台栽植的菜心、白菜和芥菜3种叶菜的9个品种为材料,在施肥处理上采用常规管理与水肥一体化两种模式,初步探索了阳台蔬菜在两种栽培模式下的生长和发育状况。试验结果表明,在相同施肥管理栽培模式下,不仅菜心、白菜与芥菜3种蔬菜间的产量存在差异,且相同蔬菜的不同品种的地上部鲜质量也存在差异,但是菜心、白菜和芥菜均一致表现出在水肥一体化栽培模式下的植株地上部鲜质量高于常规管理模式,增幅分别为13.83%~51.60%、34.26%~35.24%、16.36%~26.70%,植株收获期根冠比则均低于常规管理模式。     

EM发酵有机肥对油菜生物性状及重金属含量的影响

采用盆栽定位试验的方法研究了EM菌剂发酵有机肥料与化肥配施对油菜生长及硝酸盐、VC及重金属铅、汞含量的影响。结果表明:在试验范围内,EM菌剂发酵有机肥料与化肥配施,油菜的生物量比对照增加132.0%,VC含量较对照增加36.4%;硝酸盐含量降低20.9%,铅、汞含量分别降低37.4%和36.8%。EM菌剂发酵有机肥料与化肥配施,可以协调土壤生态肥力,降低油菜对重金属和硝酸盐的吸收,改善油菜生长与品质。     

Inhibition of postharvest senescence of green leafy vegetables by exogenous D-cysteine and L-cysteine as precursors of hydrogen sulphide

Hydrogen sulphide (H₂S) inhibits senescence in harvested fruit and vegetables but presents logistical, safety and regulatory issues to become a commercial treatment. D-cysteine and L-cysteine are semi-essential amino acids that are metabolised to hydrogen sulphide by plant tissues albeit by different pathways. This paper examines the effect of cysteine on postharvest senescence of three green leafy vegetables. Spraying pak choy leaves with 10 mmol D-cysteine, L-cysteine or DL-cysteine inhibited leaf senescence through a delayed loss of green colour expressed as market life, reduced respiration rate and reduced ethylene production. The beneficial effects of cysteine were similar to those achieved by fumigation with hydrogen sulphide. L-cysteine sprays on parsley and peppermint leaves also showed reduced leaf colour loss and respiration compared to untreated leaves. Cysteine, either as the racemate or individual enantiomers, is considered to have commercial potential for green leafy vegetables as it provides the beneficial effect of hydrogen sulphide but should be easier to register for commercial use due to the GRAS status of L-cysteine.     

Effects of different organic apple production systems on seasonal nutrient variations of soil and leaf

An organic apple (Malus × domestica Borkh.) orchard was established to study the interaction effects of ground cover management systems (GMS) and nutrient sources (NS) on soil and tree nutrients in the Southern U.S.A. GMS mulches as follows: green compost (GC), wood chips (WC), shredded paper (SP), and mow-and-blow (MB). Across GMS, one of three NS treatments was applied: commercial organic fertilizer (CF), poultry litter (PL), and no fertilizer (NF). GC-treated plots had greater soil solution nitrate concentrations in year 3. GC plots also maintained greater seasonal soil organic matter and macronutrient concentrations during 3 years compared with the other GMS. Seasonal foliar nutrient concentrations grown under GMS in year 3 tended to follow nutrient concentration patterns similar to those observed in conventional apple orchards. GC and WC trees had overall greater leaf area, dry weight, and total foliar nutrient contents in year 3 than the SP and MB trees.     

African nightshades: genetic,biochemical and metabolite diversity of an underutilised indigenous leafy vegetable and its potential for plant breeding

African nightshades are becoming more important as leafy vegetables in sub-Saharan Africa. Previously considered as food for the poor, their cultivation is now being promoted, and some cultivars are commercialised; however, most farmers use self-produced seeds, leading to low and varying yields. Improvement through conventional breeding depends on the available genetic diversity, the possible breeding systems, and the nutritional value of the accessions. Therefore, we review the information on these topics with the following main outcomes: the most commonly discussed species, S. nigrum, S. scabrum, S. villosum, and S. americanum, could be differentiated using molecular markers, but further sub-clustering was rarely possible, and statistical support often missing. S. nigrum and S. scabrum seem to be most closely related to each other. The mainly self-pollinating African nightshades form a polyploidy series with diploid (2n = 2x = 24) to hexaploid taxa. Interploidy hybridisations between diploids and tetraploids are possible, whereas the hexaploid S. nigrum and S. scabrum could not be crossed to genotypes of lower ploidies. Solanine, solamargine, solasonine, and chaconine are the major steroidal alkaloid glucosides in African nightshades. Amounts are age and environment dependant. Mineral and vitamin contents in leaves are at least as high as in Brassica oleracea or Spinacia oleracea, underlining their relevance as local vegetables.     

The effects of alternatives to soil residual herbicides on weed control,yield and quality of hops

Summary

Several non-chemical methods of weed control in hops (Humulus lupulus) were evaluated in a three-year study. The results show that the use of cultivation, grass and winter rye cover crops, straw and plastic mulches all gave satisfactory weed control in both alleyways and hop rows. Data are presented on the effects of the main treatment groups, on the yield, alpha-acid content and alpha yield of hops. The effects on other hop cone quality criteria are also reported. Cultivation to control weeds had to be timely, and by the end of the study, numbers of weeds germinating in the spring were increasing. The use of a winter rye cover crop was successful in reducing over-wintering weed populations in cultivated plots. Grass reduced yield but raised the alpha-acid content of the cones, resulting in no overall loss in yield of alpha-acid. Yield reductions were overcome by adding extra nitrogen as an early spring top dressing, but this tended to reduce alpha-acid content to give similar alpha yields. Analysis of soil mineral nitrogen contents of soils to 90 cm depth in spring and autumn indicated that extra spring nitrogen was readily taken up by grass swards, helping to overcome its competitive effect on the hop plants. Winter rye reduced soil mineral nitrogen levels although this failed to reach statistical significance (P>0.05) but this nitrogen was returned to the soil when the cover was cultivated out in spring. Straw mulches tended to raise alpha-acid levels enough to raise alpha yield one year by 5% compared with conventional residual herbicide, although this failed to reach statistical significance (P>0.05). The implications of the results to growers of hops are discussed.     

Nutritional quality of greenhouse lettuce at harvest and after storage in relation to N application and cultivation season

The effect of five levels of nitrogen fertilization on the growth and nutritional quality of Cos lettuce (Lactuca sativa L. cv. Parris Island) at harvest and after storage was studied during autumn and winter in South-West Greece. Plants were cultivated hydroponically in a greenhouse and the nitrate, chlorophyll and ascorbic acid (vitamin C) concentrations within the plant tissues were measured at harvest and following storage at 5 or 10 °C for 10 days. Nitrate accumulated in the leaves with increasing amounts of N within the nutrient solution and was higher in the winter than in the autumn. At the lowest N level (20 mg L⁻¹), the inner leaves accumulated more nitrate than the outer leaves, whereas at higher N levels (140, 200 or 260 mg L⁻¹) nitrate accumulation was higher in the outer leaves. Overall, the highest nitrate concentrations were detected in the petiole and the proximal end of the leaf, but at the lowest N application rate (20 mg L⁻¹) nitrate accumulated in the distal region of the leaf too. Although the nitrate concentrations within the leaves did not change significantly during 10 days storage at 5 or 10 °C, the chlorophyll and vitamin C concentrations decreased. Chlorophyll loss was higher in lettuce that was grown under low N levels and was higher at 10 °C than at 5 °C, but was reduced by enclosure of the lettuce in polyethylene film. It is concluded that the optimum N application rate for Cos lettuce grown hydroponically under cover during autumn and winter in South-West Greece, and in other areas with a similar climate, is 200 mg N L⁻¹ because at this N rate yield is satisfactory and leaf nitrate concentrations are below the maximum acceptable level for human consumption. Nutritional value (vitamin C concentration) and market quality (chlorophyll content) are highest at harvest and decrease during storage, but quality in terms of nitrate concentration does not change.     

Quality changes in hydroponic lettuce grown under pre-harvest short-duration continuous light of different intensities

Summary

The effect of pre-harvest light intensity on the quality of hydroponically-grown lettuce (Lactuca sativa var. capitata L.) was studied by growing lettuce under 48 h of continuous illumination delivered by red- or blue-light-emitting diodes (LEDs) with a red:blue ratio of 4.0. Four light intensity treatments (50, 100, 150, or 200 µmol m^–2 s^–1) were applied. The results showed that the nitrate concentrations in lettuce shoots decreased significantly after treatment with 48 h of continuous light, while the contents of soluble sugars and vitamin C increased substantially. It was observed that the effect of pre-harvest short-duration continuous light (PSCL) on improving lettuce quality was significantly influenced by the intensity of the light. The decrease in nitrate concentration and the increases in soluble sugars and vitamin C contents were relatively low at a light intensity of 50 µmol m^–2 s^–1, but increased gradually as the light intensity increased from 50 µmol m^–2 s^–1 to 200 µmol m^–2 s^–1. However, the marginal benefit of increased light intensity in lowering nitrate concentration and increaseing vitamin C content declined rapidly when the light intensity increased beyond 100 µmol m^–2 s^–1. In conclusion, PSCL offers an effective method by which to improve the quality of lettuce, and a light intensity of between 100 µmol m^–2 s^–1 – 150 µmol m^–2 s^–1 is the economic optimum.     

Effect of aeration of the nutrient solution on the growth and quality of purslane (Portulaca oleracea)

Summary

The aim of this work was to assess the influence of three levels of aeration of the nutrient solution (high, low, or no aeration) on the growth and quality of two cultivars of purslane (Portulaca oleracea L.): the commercial cultivar, ‘Golden Purslane’, and a local Spanish accession, C-215. Both were grown in a floating system over four crop cycles. Our results showed purslane to be a crop that exhibited little sensitivity to oxygen depletion in the rooting medium, since it was able to adapt to a gradual reduction in oxygen content. Under such conditions, purslane plants created an aerenchyma tissue (equivalent to approx. 10% of root sections in the non-aerated treatments in both cultivars) that helped to maintain growth. Under conditions in which no aeration was provided, there was a slight decrease in plant growth. The final quality of the product was improved because leaf nitrate concentrations were reduced (by more than 1,300 mg kg^–1 FW) compared with the high aeration treatment, and the content of functional phytochemicals and SPAD values (chlorophyll contents) were increased.     

The influence of irrigation system and nutrient solution concentration on potted geranium production under various conditions of radiation and temperature

Zonal geranium (Pelargonium × hortorum ‘Real Mintaka’) were grown in closed soilless systems to evaluate the effects of irrigation system (drip and subirrigation) and nutrient solution concentration (half and full) under various conditions of radiation and temperature (winter and summer) in terms of substrate electrical conductivity (EC_s), growth, quality, crop evapotranspiration (ET_c) and growth index water use efficiency (WUE_GI) and nutrient uptake. At he end of the cultural cycle the highest EC_s in the upper and lower layers were recorded in the spring season on plants grown in subirrigation using a full nutrient solution concentration. The highest shoot biomass, leaf area, plant growth index, and quality index were recorded in the winter season on plants grown in both drip-irrigation and subirrigation using half and full nutrient solution concentration, whereas the lowest value was observed in the spring season on plants grown with subirrigation using the full nutrient solution concentration. The highest maximum air temperature recorded during the first 20 days after transplanting in the spring growing season was presumably responsible for the reduction in shoot biomass production, growth and quality index, and in time of geranium flowering compared to the plants grown in the winter season. The ET_c was 44% higher in spring than in winter season treatment, while the effect of the irrigation system was less pronounced with an increase in 11% in the subirrigation treatment compared with the drip-irrigation system. WUE_GI was not stable and showed a seasonal variability. Solar radiaton (R_s), air temperature (T_a) and vapour pressure deficit (VPD) were greatly higher in the spring season, which influenced WUE_GI negatively. The WUE_GI improved especially when R_s, T_a and VPD were below 12 MJ m², 20 °C and 0.6 kPa, respectively. The highest N, and Mg uptake were recorded in the winter season, especially on plants grown with subirrigation at 2 dS m⁻¹. The highest P, K, and Ca uptake values were measured during winter season using subirrigation system, and on plants grown under full strength nutrient solution. The variation of the nitrate concentration and EC in the nutrient solution during the spring growing cycle was less pronounced in the subirrigation than with a drip-irrigation system which represents an important aspect for the simplification of the closed loop management of the nutrient solution.     

微生物肥料及有机肥对菜心可食部分产量及品质的影响

探讨了微生物肥料、鸡粪、猪粪以及微生物肥料与有机肥的配合施用对蔗渣基质栽培菜心的产量及品质的影响。结果表明:与施用等氮量的无机肥(对照)相比,鸡粪、猪粪及微生物有机肥的菜心,其可食部分硝酸盐含量为517.6～725.1 mg/kg FW,比对照低47.7%～66.9%,达到国家规定的叶菜类硝酸盐含量标准(≤3 000 mg/kg)(GB-15401)和世界卫生组织、联合国粮农组织规定标准(≤750 mg/kg);微生物肥料显著增加可食部分的产量,有机肥处理及有机肥+微生物肥的处理的产量相当于对照的85.1%～106.7%;微生物肥料及有机肥均能提高菜心可食部分的VC及水溶性蛋白质的含量;微生物肥料与鸡粪的配合施用的菜心可食部分产量较高,而硝酸盐含量最低。     

营养液浓度对秸秆基质栽培黄瓜生长和产量的影响

以津优2号黄瓜为试验材料,研究了不同浓度的营养液对小麦秸秆基质栽培黄瓜的生长势、叶片光合特征、产量的影响.结果表明,以50%秸秆 50%蛭石为基质,浇l倍营养液黄瓜的株高、茎粗、叶片数、叶面积、叶片叶绿素含量、光合速率、蒸腾速率、产量最高.     

Closed cycle subirrigation with low concentration nutrient solution can be used for soilless tomato production in saline conditions

Closed cycle soilless techniques can be adopted to minimize water and fertilizer losses in greenhouse cultivation. There is a general lack of information regarding the soilless cultivation of vegetables with closed cycle subirrigation techniques, specifically when using saline water. In this study, a trough bench subirrigation system (SUB), with two fertilizer concentrations (“100%”, containing 9.8 mol m⁻³ N-NO₃, 1.6 mol m⁻³ P-H₂PO₄, 8.7 mol m⁻³ K⁺, 2.8 mol m⁻³ Ca⁺, 1.8 mol m⁻³ Mg⁺, 4 mol m⁻³ S-SO₄, and “70%”, containing 70% of the macronutrient concentration) in the nutrient solution (NS), was compared with open cycle drip-irrigation (DRIP with “100%” NS). For all the three treatments, NS was prepared using rain water (0.05 dS m⁻¹) and adding NaCl (1 g L⁻¹), in order to simulate moderate saline irrigation water. The effect of the treatments on tomato (Solanum lycopersicum L.) plant growth, yield, fruit quality, water use efficiency (WUE) and fertilizer consumption was evaluated. Substrate and recirculating NS composition were also studied. Subirrigation, regardless of NS concentration, reduced plant height (by 30 cm), leaf area (by 1411 cm²), total fresh and dry weight (by 429 and 48.5 g plant⁻¹, respectively) but not dry matter percentage of the whole plant, with respect to DRIP. Yield was reduced when plants were subirrigated with the higher concentrated NS, but no differences with open cycle DRIP were recorded when the lower NS concentration was used in SUB. Fruit quality was not affected by irrigation system or NS concentration. The higher WUE was obtained with subirrigation. NaCl accumulated similarly over the crop cycle in recirculating NS of both SUB treatments and in growing substrates of all the three treatments. Higher salt concentration was found in subirrigated substrates, in particular in the upper part of the substrate profile. Fertilizers accumulated in the subirrigated substrates when the higher NS concentration was used, but not when the NS concentration was reduced by 30%. The results of this study indicate that tomato can be grown successfully in a closed cycle subirrigation system, using saline water, by reducing the fertilizer NS concentration normally used with traditional open cycle systems.     

Nitrogen accumulation and nitrate reductase activity in MM. 106 apple trees as affected by nitrate supply

The effect of nitrate supply in the nutrient solution on N accumulation was investigated in various organs of MM.106 apple trees (Malus domestica Borkh.). Increasing nitrate supply increased the concentration and amount of total N in leaves and stems, but there was a saturation point of total N accumulation in response to the nitrate supply. The increased accumulation of total N in leaves and stems with increasing nitrate supply were due to increases in reduced N, since nitrate N remained relatively constant. Reduced N contents of trunk bark and trunk wood were significantly decreased when low nitrate was supplied, whereas that of roots was changed insignificantly. Most organs contained only a small portion of their total N as nitrate. The activities of nitrate reductase (NR) were measured using an in vivo assay either with or without nitrate for estimating reduced N accumulation. The in vivo —N03^- NR assay may be a better way to estimate the accumulation of reduced N than the in vivo +N03^- NR assay since the in vivo +N03^- nitrate reductase activity (NRA) was not related to the changes in the reduced N concentration with the differential nitrate supplies. Increasing nitrate supply significant increased in vivo —N03^- NRA of all organs. The rate of increase of the in vivo —N03^- leaf NRA was greater than those of stems and roots with increasing nitrate supply. Consequently, the proportion of leaf NRA to the total activity increased as the nitrate supply increased. The roots exhibited higher NRA than leaves and stems. The stem also contributed considerably to the total NRA. It can therefore be concluded that the reduction of nitrate can occur in various organs of MM. 106 apple trees as long as nitrate is available.