Triacontanol stimulates nitrogen-fixation,enzyme activities,photosynthesis, crop productivity and quality of hyacinth bean (Lablab purpureus L.)

Hyacinth bean (Lablab purpureus L.) serves as a good source of vegetable proteins in human diet, and its seeds and pods contain as much as 20–28% protein. The bean contains tyrosinase enzyme, which has potential use for the treatment of hypertension. However, plant biological yield appears to be comparatively low in Aligarh soil in this region of India (Western Uttar Pradesh). A hypothesis was designed to address whether foliar application of triacontanol (TRIA) could enhance the crop productivity as well as crop quality. TRIA is known to be a potent plant growth promoting substance for many agricultural and horticultural crops. The hyacinth bean plants grown in soil containing pots, were sprayed with five concentrations of TRIA (10⁻⁰ (Control), 10⁻⁸, 10⁻⁷, 10⁻⁶ and 10⁻⁵ M) at 15-day intervals. The plant fresh and dry weights, leaf-area, number and dry weight of nodules per plant, total chlorophyll and carotenoid content, nitrate reductase activity, carbonic anhydrase activity, nodule-nitrogen content, leghemoglobin content and leaf N, P, K and Ca contents were analyzed at 60, 90 and 120 days after sowing (DAS). Net photosynthetic rate, transpiration rate and stomatal conductance were measured only at 90 DAS. The protein content plus carbohydrate and tyrosinase activity were analyzed in the seeds. Foliar spray of 10⁻⁶ M TRIA significantly stimulated most of the studied attributes. At the highest concentration (10⁻⁵ M TRIA), values of all attributes were significantly decreased at all three stages. For example, 10⁻⁶ M TRIA increased seed-yield and -protein content by 56.3 and 14.5%, respectively when compared to unsprayed plants. TRIA also stimulated the activity of tyrosinase when compared to the control plants.     

Zinc influence and salt stress on photosynthesis,water relations,and carbonic anhydrase activity in pistachio

A greenhouse study was conducted to evaluate the ameliorative effects of zinc (0, 5, 10 and 20 mg Zn kg⁻¹ soil) under saline (800, 1600, 2400 and 3200 mg NaCl kg⁻¹ soil) conditions on pistachio (Pistacia vera L. cv. Badami) seedlings’ photosynthetic parameters, carbonic anhydrase activity, protein and chlorophyll contents, and water relations. Zn deficiency resulted in a reduction of net photosynthetic rate and stomatal conductance. The quantum yield of photosystem II was reduced at zinc deficiency and salt stress. Zinc improved plant growth under salt-affected soil conditions. Increasing salinity in soil under Zn-deficient conditions, generally decreased carbonic anhydrase activity, protein, chlorophyll a and b contents. However, these adverse effects of salinity alleviated by increasing Zn levels up to 10 mg kg⁻¹ soil. Under increasing salinity, chlorophyll a/b ratio significantly increased. Zinc treatment influenced the relationship between relative water content and stomatal conductance, and between leaf water potential and stomatal conductance. It concluded that Zn may act as a scavenger of ROS for mitigating the injury on biomembranes under salt stress. Adequate Zn also prevents uptake and accumulation of Na in shoot, by increasing membrane integrity of root cells.     

Silicon mediates changes to some physiological and enzymatic parameters symptomatic for oxidative stress in spinach (Spinacia oleracea L.) grown under B toxicity

The effect of exogenous silicon (Si) on the growth, boron (B) uptake, stomatal conductance, lipid peroxidation (MDA), membrane permeability, lipoxygenase activity (LOX), proline and H₂O₂ accumulation, non-enzymatic antioxidant activity (AA) and the activities of major antioxidant enzymes (superoxide dismutase, SOD; catalase, CAT and ascorbate peroxidase, APX) of spinach were investigated under greenhouse conditions. Spinach plants were grown with 0 or 30 mg kg⁻¹ B combined with 0 and 150 mg kg⁻¹ Si. The severity of leaf symptoms of B toxicity was lower when the plants were grown with 150 mg kg⁻¹ Si. Silicon supplied to the soil with high B counteracted the deleterious effects of B on root and shoot growth. Application of B significantly increased B concentration in shoot and in root tissues. However, Si decreased B concentration in the shoots but increased it in the roots. Shoot tissues of spinach contained higher B than the roots in all treatments. Applied Si increased the Si concentration of the root and shoot. Stomatal conductance of the plants was decreased by B, but was increased by Si. The concentrations of H₂O₂ and proline were increased by B toxicity but were decreased by Si applied to plants. Boron toxicity increased the membrane permeability, MDA content and LOX activity of excised leaves of spinach. Applied Si ameliorated the membrane deterioration significantly. Compared with control plants, the activities of AA, SOD, CAT and APX in B-stressed plants without Si applied increased, and application of Si decreased their activities under toxic B conditions. Based on the present work, it can be concluded that Si alleviates B toxicity by preventing oxidative membrane damage and also translocation of B from root to shoots. To our knowledge, this is the first report on the effect of Si in improving B tolerance in spinach.     

High-frequency embryogenesis,regeneration of broccoli (Brassica oleracea var. italica) and analysis of genetic stability by RAPD

High-frequency somatic embryogenesis and shoot regeneration of broccoli (Brassica oleracea var. italica) were achieved. Cotyledon and hypocotyl explants from four varieties of broccoli were cultured on MS and modified MS media (mMS, supplemented with PG-96 organic components) with different combinations of growth regulator. The effects of genotypes, different explants, growth regulator combinations, organic components and AgNO₃ on induction of calli and shoots were evaluated. The optimal media for inducting calli/shoots and roots were mMS medium containing 3% (w/v) sucrose and 0.8% (w/v) agar supplemented with NAA at 0.5 mg l⁻¹, 6-BA at 3.0 mg l⁻¹, AgNO₃ at 4.0 mg l⁻¹ and MS medium containing 3% sucrose and 0.8% (w/v) agar supplemented with NAA at 0.2 mg l⁻¹, respectively. The callus induction percentages were over 90% in all four varieties; shoot induction percentage was 92.5% and the average number of shoot per explant was 4.1 from cotyledon explant in variety Bishan. In this study, we established high-efficient embryogenesis and shoot regeneration system of broccoli and analyzed genetic stability of regenerants at DNA level using RAPD molecular marker. Out of 62 arbitrary primers screened using PCR amplification, 79 polymorphic bands were amplified from 20 primers. The results demonstrated the genetic stability of regenerants from the same variety.     

Nitrogen best management practice for citrus trees: I. Fruit yield,quality, and leaf nutritional status

Elevated levels of nitrate-nitrogen (NO₃-N) in the surficial aquifer above the drinking water quality standard, i.e. maximum contaminant limit (MCL; 10 mg L⁻¹), have been reported in some part of central Florida citrus production regions. Soils in this region are very sandy (sand content >95%), hence are vulnerable to leaching of soluble nutrients and chemicals below the rooting depth of the trees. The objective of this research was to develop N and irrigation best management practices for citrus in sandy soils to maintain optimal crop yield and quality, and to minimize potential leaching of nitrate below the root zone. Six years of field experiment was conducted in a high productive (mean fruit yield > 80 Mg ha⁻¹yr⁻¹) >20-year-old ‘Hamlin’ orange trees [Citrus sinensis (L.) Osbeck] on ‘Cleopatra mandarin’ (Citrus reticulata Blanco) rootstock grown on a well drained Tavares fine sand (hyperthermic, uncoated, Typic Quartzipsamments) in Highland county, FL. Nitrogen rates ranged from 112 to 280 kg ha⁻¹ yr⁻¹ applied as fertigation (FRT), water soluble granular (WSG), 50:50 mix of FRT and WSG, and controlled-release fertilizer (CRF). Tensiometers were used to monitor the soil water content as a basis to schedule optimal irrigation. Fruit yield response over the entire range of N rates was greater for the FRT and WSG sources as compared to that for the WSG + FRT or CRF sources. Using the regression analysis of the fruit yield in relation to N rate, the optimum N rate appeared to be at 260 kg ha⁻¹ yr⁻¹. Based on fruit production response in this study, the N requirement for production of 1 Mg of fruit varied from 2.2 to 2.6 kg across four N sources. This study demonstrated an increased N uptake efficiency, as a result of best management of N and irrigation applications. The optimal N and K concentration in the 4–6-month-old spring flush leaves were 26–30, and 15–18 g kg⁻¹, respectively. However, fruit yield response showed no significant relationship with concentrations of P in the 4–6-month-old spring flush leaves over a range of 0.8–2.4 g kg⁻¹. The results of fate and transport of N in soil and in soil solution with application of different rates and sources of N, and components of citrus tree N budget, are reported in a companion paper.     

Growth and flowering of black iris (Iris nigricans Dinsm.) following treatment with plant growth regulators

The effects of application method and concentration of gibberellic acid (GA₃), paclobutrazol and chlormequat on black iris performance were assessed. Plants (10 cm high, 4 ± 1 leaves) were sprayed with 125, 250, 375 or 500 mg L⁻¹ or drenched with 0.25, 0.5, 1 or 2 mg L⁻¹ GA₃. In a second experiment, the plants were sprayed with 100, 250, 500 or 1000 mg L⁻¹ or drenched with 0.25, 0.5, 1 or 2 mg L⁻¹ paclobutrazol. Other plants were sprayed with 250, 500, 1000 or 1500 mg L⁻¹ or drenched with 100, 250, 375 or 550 mg L⁻¹ chlormequat. In each experiment, the control treatment consisted of untreated plants. Results indicated that the tallest plants (37.3 cm) in the GA₃ experiment were those sprayed with 250 mg L⁻¹. The most rapid flowering (160 days after planting) occurred when a 375 mg L⁻¹ GA₃ spray was used, whereas flowering was delayed to 200 days using 1 mg L⁻¹ GA₃ drench. Drenching with 1 mg L⁻¹ GA₃ increased height of the flower stalk by 7 cm compared to the control. Though relatively slow to flower, plants drenched with 1 mg L⁻¹ GA₃ had long and rigid stalks, which were suitable as cut flowers. Number and characteristics of the sprouts were not affected by GA₃. All paclobutrazol sprays resulted in leaf falcation. A 500 or 1000 mg L⁻¹ paclobutrazol spray resulted in severe and undesirable control of plant height, drastic reduction in stalk height and weight, and delayed flowering. Plants drenched with 0.25 or 1 mg L⁻¹ paclobutrazol were suitable as pot plants. Chlormequat reduced plant height only at the highest drench concentration, which also reduced flowering to 70%. No leaf falcation was observed with GA₃ or chlormequat. Chemical names: ( ± )-(R*,R*)-beta-((4-chlorophenyl)methyl)-alpha-(1,1,-dimethylethyl)-1H-1,2,4,-triazol-1-ethanol (paclobutrazol); (2-chloroethyl) trimethylammonium chloride (chlormequat).     

Chemical changes during myrtle (Myrtus communis L.) fruit development and ripening

The chemical composition of fruit belonging to ‘Barbara’ and ‘Daniela’ myrtle cultivars was monitored during development from fruit-set to an over-ripe stage (July–January), with the aim to identify a reliable maturity index. Acidity, pH, reducing and total sugars, phenols, tannins, anthocyans, carbon dioxide and ethylene production rates were monitored over two different year seasons. Titratable acidity decreased during maturation, with significant differences due to cultivar and year of observation. Reducing sugars increased in both cultivars approximately sevenfold from fruit set to complete maturation. Total sugar content increased similarly ranging from 1.43% and 1.41% at fruit set to 8.28% and 7.56% at maturation for ‘Barbara’ and ‘Daniela’, respectively. Total phenols and tannins occurred at high levels after fruit set and declined during development. Anthocyans levels increased, in both cultivars, according to a sigmoid curve. The pattern of respiration rate showed a gradual decline in both cultivars ranging from 365.81 and 396.42 mg kg⁻¹ h⁻¹ to 79.98 and 52.27 mg kg⁻¹ h⁻¹, respectively for ‘Barbara’ and ‘Daniela’ in 2006. A peak of variable size was observed in October–November period. Small increases in ethylene production have been detected during fruit development ranging from 130.57 and 269.14 μL kg⁻¹ h⁻¹ measured at the onset of development to 13.04 and 19.36 μL kg⁻¹ h⁻¹ measured at harvest for ‘Barbara’ and ‘Daniela’, respectively.     

Effect of organic and inorganic fertilizers applied during successive crop seasons on growth and nitrate accumulation in lettuce

A romaine-type lettuce (Lactuca sativa L.) cv. Corsica was cultivated during three successive crop seasons (late-spring, late-autumn and late-winter) in the same soil of an experimental greenhouse in S.W. Peloponnese, Greece. Seven long-term fertilization treatments were tested for their effect on plant growth and nitrate concentration in the external lettuce leaves. Treatments included: three different doses of organic fertilization (composted sheep manure) applied at the start of each crop season, three different doses of inorganic N fertilization applied via fertigation during each crop season, and a control treatment in which no fertilizer was applied. A drip irrigation system was used to water all plants. The highest nitrate levels were observed in the medium and maximum inorganic fertilization treatments (572–664 mg kg⁻¹) in all crop seasons. They were significantly higher compared to the respective organic fertilization treatments (253–435 mg kg⁻¹) and all other fertilization treatments (148–435 mg kg⁻¹). Crop season affected lettuce growth more than nitrate accumulation in the lettuce leaves: lettuce biomass production was the smallest and most uniform in the late-autumn season and did not respond to the fertilization treatments tested (ranging from 409 to 439 g plant⁻¹), while in the late-spring season biomass production was the highest and most variable (561–841 g plant⁻¹), it correlated with nitrate concentration in the leaves and in the medium and maximum inorganic fertilizer doses it significantly exceeded production from all other fertilization treatments (827–841 g plant⁻¹). Following the three crop seasons the residual availability of N, P and K was clearly enhanced in the soil receiving the organic compared to the inorganic fertilization. Nitrate concentration in lettuce leaves was far below the upper limits set by the European Commission in all fertilization treatments throughout the three crop seasons, a result attributed mainly to the sufficient level of light intensity and duration throughout the year in Southern Greece.     

Response of apple trees to boron fertilization under conditions of low soil boron availability

The aim of the study was to examine the effect of boron (B) fertilization on the vegetative and the reproductive responses of apple (Malus domestica Borkh.) trees grown at low soil B availability. The experiment was carried out in 2005 under a greenhouse on 5-year-old ‘Jonagold’ apple trees/M.9 EMLA planted singly in 50-L containers filled with a sandy loam soil with hot water-soluble B concentration of 0.32 mg kg⁻¹. The trees were fertilized with B as foliar or soil application. Foliar B sprays were applied at the stage of pink bud, beginning of flowering, petal fall, and 10 days after flowering, at a solution concentration of 0.03%. Soil B fertilization was done at the bud break stage at a rate of 2 g per tree (27 mg B kg⁻¹ soil). The trees untreated with B served as the control. The results showed that soil B fertilization improved root development and tree vigor. Leaves of trees supplied with B to the soil had higher B concentration and chlorophyll, net photosynthetic rate, stomatal conductance, and activity of catalase and glutathione reductase than those of the control plants. Boron fertilization, regardless of application mode, increased fruit yield; the efficiency of foliar B sprays was higher than soil B application. Apple fruits of trees fertilized with B to the soil were bigger, more colored, richer in B, and had higher soluble solids concentration, and titratable acidity compared to those of the control trees.     

An upper limit for elevated root zone dissolved oxygen concentration for tomato

It is well understood that insufficient oxygen within plant root zones can greatly diminish plant productivity. However, little is known about the effect of elevated root zone oxygen concentrations. Tomato (Lycopersicon lycopersicum Mill., cv. Trust) seedlings were grown in nutrient solutions containing dissolved oxygen (DO) concentration ranging from 5.3 to 40 mg L⁻¹ for 4 weeks. There were no visible symptoms observed on the leaves or stems in any of the treatments. Leaf chlorophyll content was higher in the 40 mg L⁻¹ treatment than with 20 and 30 mg L⁻¹ DO treatments. Two weeks from the start of the experiment, roots in the 40 mg L⁻¹ treatment exhibited stunted growth, became thicker, and had fewer side and fine roots compared to roots in the lower levels of DO treatment. Almost all the measured growth parameters (fresh and dry weights of root, stem, and leaf, leaf area, stem diameter) were significantly reduced in plants grown in the 40 mg L⁻¹ treatment compared to plants in the lower level of DO treatments, except that the plant height increased with the increasing DO concentration. Root respiration increased linearly with increasing DO concentration; however, there was no effect on leaf net CO₂ exchange rate. It is suggested that it was safe to enrich root zone DO to as high as 30 mg L⁻¹, although the growth benefit was minor by increasing DO from ambient air saturated level (∼8.5 mg L⁻¹) to 30 mg L⁻¹. Higher than 30 mg L⁻¹ could cause reduction in tomato plant growth.     

In vitro germination of walnut (Juglans regia L.) embryos

The present studies were undertaken with a view to standardize the medium and culture conditions for embryo culture of five cultivars of walnut viz., ACO 38853, Netar Akhrot, Gobind, Solding Selection and Blackmore. Embryos from mature fruits were aseptically excised and cultured on MS medium supplemented with different combinations of BAP, kinetin and GA₃. Best performing medium was MS with 0.5 mg l⁻¹ kinetin, 0.5 mg l⁻¹ BAP and 2 mg l⁻¹ GA₃ yielding 66.6% germination in Netar Akhrot after 12 days of culturing. Percent germination of excised embryos was higher when GA₃ and cold treatments were simultaneously applied as compared to those when applied separately. Netar Akhrot was found to be the best responding cultivar, which had a range of 25–66.6% embryo germination under different culture conditions. Plantlets with shoots and roots have been obtained in Netar Akhrot and ACO38853 and are transferred to soil after hardening.     

High frequency early flowering from in vitro seedlings of Dendrobium nobile

Dendrobium nobile Lindl. is a popular temperate Chinese orchid commonly marketed as a traditional medicinal plant. Seedlings of Dendrobium nobile Lindl. produced floral buds (33.3–34.8%) precociously on a defined basal medium (1/2 MS) containing paclobutrazol (PP₃₃₃) at 0.5 mg L⁻¹ or thidiazuron (TDZ) at 0.1 mg L⁻¹ within 4 months of culturing. The frequency of floral buds formation can be further increased to 95.6% by growing seedlings in a PN (PP₃₃₃ 0.3 mg L⁻¹ + NAA 0.5 mg L⁻¹)-containing medium followed by transfer onto 1/2 MS medium with PP₃₃₃ and TDZ (PP₃₃₃ + TDZ). However, flower developed was deformed under 25 °C but it developed fully when grown in a lower temperature regime (23 °C/18 °C, light/dark) for 45 days. Under optimal condition, in vitro flowering was observed about 6 months after seed sowing.     

Impact of exogenous salicylic acid on the growth,antioxidant activity and physiology of carrot plants subjected to combined salinity and boron toxicity

Previous studies have shown that salicylic acid (SA) plays a role in the response of plants to salt and osmotic stresses. Therefore, an experiment was conducted to investigate the impact of exogenous salicylic acid on the growth, physiology and antioxidant activity of carrot (Daucus carota L. cv. Nantes) grown under combined stress of salinity and boron toxicity. The treatments consisted of salt (control, NaCl, and Na₂SO₄), boron (−B: 0 and +B: 25 mg B kg⁻¹) and salicylic acid (−SA: 0 and +SA: 0.5 mmol SA kg⁻¹). The diameter of the storage root was increased by NaCl salinity in the absence of B toxicity, however, it was increased by Na₂SO₄ salinity under B toxicity. For the storage root yield, NaCl salinity was more toxic than Na₂SO₄ salinity. With its role in plant growth regulation, SA application positively affected the storage root dry weight, S concentration, carotenoids and anthocyanin content and increased the total antioxidant activity (AA) of the shoot and storage root. SA application regulated proline and toxic ion (B, Cl) accumulation in the storage root and shoot. This study reports the long term effects of SA under stress conditions and reveals that SA was not as effective as in alleviating abiotic stress as reported in the literature conducted with short-term studies. That means long-term effects of SA would be significantly different from its short-term effects.     

Direct plant regeneration from mature leaf explants of pistachio, Pistacia vera L.

A protocol was developed for direct shoot and plantlet regeneration from in vitro regenerated leaf explants of male Pistacia vera L. cv. ‘Atl?’. Leaves excised from axenic shoot cultures of pistachio were used to induce organogenesis on a Murashige and Skoog (MS) medium with Gamborg vitamins supplemented with combinations of different concentrations of BAP and IAA. The highest adventitious shoot regeneration in 35% of the explants, with the number of shoots ranging from 2 to 3 per explant, occurred in the explants cultured during the establishment phase in the medium with 1 mg l⁻¹ IAA and 2 mg l⁻¹ BAP. For shoot multiplication, the highest number of new microshoot/explants (5.76) was obtained in a culture medium supplemented with 1 mg l⁻¹ BAP, but it was not significantly different from the number obtained at 2 mg l⁻¹ BAP. A high rooting frequency (84%) for microshoots was recorded on a medium supplemented with 2 mg l⁻¹ IBA. In vitro rooted plantlets were transferred to pots filled with a mixture of soil, sand and peat (1:1:1). They were weaned in a growth room and finally moved to a greenhouse. This protocol could be utilized for in vitro clonal propagation of this economically important plant.     

Productivity and quality of statice (Limonium sinuatum cv. Soiree Mix) and cockscomb (Celosia argentea cv. Chief Mix) under organic and inorganic fertilization regiments

Very little information is available on organic specialty cut flower production, especially fertilization requirements. In order to better understand organic fertilization requirements of two specialty cut flower crops, Limonium sinuatum and Celosia argentea, we initiated a field and greenhouse experiment to study the effect of compost (organic) and conventional (inorganic) fertilization treatments on the growth and productivity of these crops. Optimum yields in the field, expressed as fresh weight per plot, were achieved at compost applications of 98.8 t ha⁻¹ for both Limonium and Celosia. However, when number of stems, height of the stems, and the environmental impacts of such compost applications are considered we concluded that the optimal organic fertilizer amounts were 12.4 and 24.7 t ha⁻¹, for Limonium and Celosia, respectively. Limonium and Celosia plants in the greenhouse experiment were fertilized with 100, 200, 300, and 400 mg L⁻¹ nitrogen, combined with 0, 5, 10, 20, 40, and 60 mg L⁻¹ phosphorus. The generation of response surfaces for total weight per pot, number of stems per pot, average weight per stem, and average stem length were attempted for each species. The results showed that nitrogen did not significantly contribute to any of the models, except for Celosia average weight and length per stem models. Total weights per pot on the other hand showed both a linear and quadratic relationship over the range of phosphorus applications we tested. Maximum number of stems and total weight per pot were observed between 30 and 46 mg L⁻¹ P in both Limonium and Celosia. Our results suggest that organic fertilizer recommendations, in the form of animal manure composts should be based on phosphorus content of the compost rather than nitrogen content especially for soils high in initial phosphorous content.     

Cultivation of beans (Phaseolus vulgaris L.) in limed or unlimed wastewater sludge,vermicompost or inorganic amended soil

Wastewater sludge can be vermicomposted to increase its nutrient content and reduce pathogens. The effect of vermicompost wastewater sludge on soil characteristics and growth of bean plants (Phaseolus vulgaris L.) was compared with that of inorganic fertilizer, untreated sludge or sludge treated with lime to pH 12. Plants cultivated in vermicompost amended soil developed best while those amended with inorganic fertilizer least. Bean plants grown in the unlimed amended soil had the highest total N content of 3.97 g kg⁻¹, but only 6 active and 8 total nodules. Plants cultivated in unamended soil and added with inorganic fertilizer had >20 active and total nodules, but ≤2.12 g N kg⁻¹ dry plant. It was found that limed and unlimed sludge stimulated development of bean plants to a larger extent than those cultivated in inorganic fertilized soil or unamended soil in the greenhouse, but less than those cultivated in vermicompost amended soil.     

Cercis siliquastrum L., Malus trilobata Schneid and Acer syriacum Boin and Gaill water use as affected by two fertilizer rates

There has been an increased demand for landscaping plants in Lebanon as a result of numerous reconstruction projects. Sustainable landscape regulations have created a need for regionally adapted taxa, especially those with low water requirements. Therefore, water use of container-grown plants and the impact of fertilization on water use were studied in the following native species: Cercis siliquastrum L. (six mother trees), Malus trilobata Schneid (two mother trees) and Acer syriacum Boin and Gaill (one tree). Two-year-old containerized seedlings were grown at The Ohio State University (Columbus, USA) under two fertilizer rates: 25 or 100 mg N L⁻¹ of 21 N–3.1 P–5.9 K water soluble fertilizer. Water use estimates were made by saturating the containers early in the morning, allowing them to drain for 1 h, weighing them and re-weighing approximately 5 h later. Although there were differences in seedling heights, those grown at 25 mg N L⁻¹ were taller than those at 100, there were few differences in water use per seedling. In August, Cercis seedlings grown under 100 mg N L⁻¹ had higher height adjusted water use (g water cm⁻¹ height h⁻¹, a method for standardizing water use among different sized plants) than those grown under 25 mg L⁻¹. However, there were no differences in height adjusted water use in September attributed to fertilizer rates. In September, Acer seedlings had higher water use cm⁻² leaf surface area under 25 than 100 mg N L⁻¹. There were no differences in water use among the progeny from the six Cercis mother trees. However, the seedlings from one Malus tree had higher water use cm⁻² leaf surface area than those from the other tree, even though the extant trees were separated by less than 20 m.     

Effects of post-harvest foliar boron and calcium applications on subsequent season's pollen germination and pollen tube growth of pear (Pyrus pyrifolia)

The primary objective of this study was to evaluate the effects of foliar boron and calcium application after harvest on the quantity and activity of pollen in the ‘Housui’ and ‘Wonwhang’ pears on a subsequent year. Pollen grains of the ‘Housui’ pear were cultured on germination medium, to which had been added boric acid (0, 25, 75, 100, 200, 300, 400, and 500 mg L⁻¹) and calcium nitrate (0, 10, 25, 50, 100, 150, 200, 250, 300, 400, and 500 mg L⁻¹). Boric acid, which was added to the germination media, exerted a significant stimulatory effect on both pollen germination and pollen tube growth, although pollen tube growth was inhibited at higher concentrations than 300 mg L⁻¹. Calcium nitrate addition stimulated pollen germination, except at concentration of 500 mg L⁻¹. However, pollen tube growth was significantly inhibited with increasing concentrations of calcium nitrate. In the orchard experiment, boron and calcium were sprayed at concentrations of 0, 100, 200, 500 or 1000 mg L⁻¹ onto leaves after harvest, respectively. Boron and calcium content in the tissues as well as pollen production and growth were determined after these treatments. The foliar application of boron mainly resulted in an increase of boron concentration in buds. It also induced an increase in the weight of the anther and pollen in the following year. On the other hand, the foliar application of calcium resulted in an increase of calcium concentration mainly in the leaves, but pollen weight was decreased at high concentration treatment in the following year. The germination rate and tube growth of collected pollen were highest in the trees which had received boron treatment at a concentration of 200 mg L⁻¹. In contrast, the germination rate and tube growth of collected pollen were decreased by calcium application at concentrations of 500 and 1000 mg L⁻¹ without significant increase at lower concentrations. Consequently, the accumulation of boron in the developed buds of pear trees subjected to post-harvest foliar boron application generated positive effects on both the quantity and quality of pollen in the following year.     

Evaluation of the effectiveness of soil-applied plant derivatives of Meliaceae species on nitrogen availability to peach trees

We assessed the effect of soil-applied derivatives of melia (Melia azedarach L.) and neem (Azadirachta indica A. Juss) on nitrogen (N) soil availability, root uptake and peach (Prunus persica L.) growth. First we evaluated the effectiveness of experimentally prepared amendments made with fresh ground melia leaves or commercial neem cake incorporated into the soil as nitrification inhibitors, then we evaluated the effect of fresh ground melia fruits and neem cake on growth and N root uptake of potted peach trees, and on soil microbial respiration. Soil-applied fresh ground melia leaves at 10 and 20 g kg⁻¹ of soil as well as commercial neem cake (10 g kg⁻¹) were ineffective in decreasing the level of mineral N after soil application of urea-N as a source of mineral N, rather they increased soil concentration of nitric N and ammonium N. The incorporation into the soil of fresh ground melia fruits (at 20 and 40 g kg⁻¹) and neem cake (at 10 and 20 g kg⁻¹) increased N concentration in leaves of GF677 peach × almond (Prunus amygdalus) hybrid rootstock alone or grafted with one-year-old variety Rome Star peach trees. An increase in microbial respiration, leaf green color and plant biomass compared to the control trees were also observed. The Meliaceae derivatives did not affect, in the short term (7 days), N root uptake efficiency, as demonstrated by the use of stable isotope ¹⁵N, rather they promoted in the long term an increase of soil N availability, N leaf concentration and plant growth.     

Compositional quality of virgin olive oils from cultivars introduced in Tunisian arid zones in comparison to Chemlali cultivars

This work is an evaluation of the quality of three introduced European olive cultivars Arbequina, Coratina, and Koroneiki grown under a biological agricultural system in the arid zone of Sfax in Tunisia compared to Chemlali cultivars. Various olive parameters were analyzed, such as ripening index, pulp/stone (P/S) ratio and oil content. We have considered the regulated physicochemical analytical parameters, fatty acids and minor compounds for olive oil. The most of the quality indices and fatty acid composition showed significant variations among olive cultivars. The Koroneiki, Coratina and Chemlali Zarzis cultivars had highest values of oleic acid (62.7%) (76.8%, 75.8% and 73.9%, respectively), Arbequina, had lowest value of oleic acid and similar to Chemlali Sfax. Coratina was noteworthy for its higher content of phenolic compounds (287.8 mg kg⁻¹), oil content (42.4%) and P/S ratio (4.7%). Although their low phenol contents, autochthonous cultivars presented high contents of α-tocopherol (577.8 and 434.6 mg kg⁻¹ for Chemlali Boughrara and Chemlali Zarzis, respectively) except for Chemlali Sfax. In conclusion, European cultivars seem to have adapted to the area studied according to their oil biochemical composition while the increase observed in their α-tocopherol levels. The cultivar Arbequina showed a similar composition of Chemlali Sfax.