Samples were taken from grapefruit Citrus paradise Macf. cv. Marsh, Valencia orange Citrus sinenesis L. Osbeck, and lemon Citrus limetta, ‘Risso’ trees growing in the field in the Citrus Research Center, Riverside, California. Quantitation of 17 protein and 18 nonprotein amino acids of citrus leaves were evaluated for comparative effects of sample drying-methods on the 3 citrus species.
Freeze-dried leaves contained significantly higher amounts of nonprotein, and lower amounts of protein amino acids, than the analogous leaves that were oven-dried. This indicates that citrus leaves must be enzymatically deactivated immediately after sampling and kept in a frozen condition in preparation for analysis. Otherwise, accurate assessment of amino acids in the leaves at sampling would not be obtained.
Grapefruit and ‘Valencia’ orange leaves contained higher concentrations of glutamic acid, aspartic acid, leucine, lysine, and arginine than of other protein amino acids. Lemon leaves contained more substantial amounts of glutamic acid, arginine, aspartic acid, leucine, and glycine.
The nonprotein amino acids proline, serine, alanine, and aspartic acid were found in more substantive amounts in grapefruit and ‘Valencia’ orange leaves, 77 and 69 percent, respectively, of the sum of nonprotein amino acids determined. In lemon leaves, proline, arginine, lysine, serine, and alanine were found to be more concentrated. These 5 nonprotein amino acids constituted 79% of the total of those determined. Proportionally, lemon leaves contained a larger fraction of nonprotein amino acids than grapefruit or ‘Valencia’ orange leaves.
Three-year-old ‘Cardinal’ and ‘Pinot noir’ vines were grown from véraison to fruit maturity in a stationary and rotating phytotron at high (30°C) and low (20°C) day temperatures in combination with both high (>2,500 ft-c) and low (< 1,200 ft-c) average light intensities. Night temperature (6 PM to 6 AM) was 15°C in all treatments. Berries were collected at weekly intervals and analyzed for various constituents.
Low temperature usually resulted in increased berry weight, total acidity, and malate, and in decreased pH, arginine, proline, and total N in the berry juices, as compared to fruits grown at high temperature. The concentrations of total soluble solids and tartrate in the fruits generally did not significantly differ with temperature. Low light intensity at both high and low temperatures generally resulted in reduced berry weight, total soluble solids, pH, and proline, and in increased levels of total acidity, malate, arginine, and total N in the berry juices compared to grapes grown at high light intensity at the same room temperature. The concentration of arginine was highly correlated with the level of total N in the fruits of both cultivars.
Desiccation tolerance of somatic embryos is a key factor for production of dry synthetic seeds. In celery (Apium graveolens L.) desiccation tolerance can be enhanced by optimization of culture duration, ABA application, or sucrose concentration in the embryo production medium. Morphologically mature embryos cultured for 10 days have shown higher desiccation tolerance then those cultured for 8 days, indicating that biochemical changes occur without any noticeable morphological changes. Application of ABA (1 μM) for the last two days of the embryo production cycle was critical for inducing desiccation tolerance; ABA application for the last four days had some additional beneficial effect. Desiccation tolerance was further enhanced by increasing the sucrose concentration of the embryo production media from 3% to 7% for the last two days. Increased desiccation tolerance achieved with optimal harvest timing and ABA application were associated with increased endogenous proline and aminobutyrate, and reduced glutamine.
Physiological, biochemical and anatomical indexes were investigated for rose hardiness. It was found that bound/free water ratio, proline accumulation, photosynthetic rate, palisade/spongy tissue ratio, and lignification of winter-acclimated stems were heavily influenced by the temperature causing stem browning. Spongy cell volume and stem tenderness were inversely related to winter hardiness. Data generated from this research demonstrated that catalase stability, TTC reduction rate at 0°C, total photosynthetic rate, stem pith ray number, and leaf wax thickness are good indicators for rose hardiness to freezing temperatures. Two compound indexes were developed through the main component analysis. Based on the results obtained from 12 tested cultivars, these indexes are ideal to quantify hardiness of rose germplasm.
Shoot tip culture of Ficus benjamina L. `Variegata' produced multiple shoots on Murashige and Skoog (MS) medium with 1 μm 2,4-dichlorophenoxy acetic acid (2,4-D), 1 μm napthalene acetic acid (NAA), 1 μm benzylaminopurine (BAP), l-proline at 2 mg·liter–1, and l-glutamine at 1 mg·liter–1 without previously producing callus. Multiple shoots were more profuse on one-half MS medium with 4.44 μm BAP. Single shoot of multiple shoots produced roots on one-half MS medium with NAA at 2.69 μm. Leaf culture of the plant produced profuse calli on same media without plant regeneration. Calli subcultured on one-half MS or MS media with 1.7 μm indole-3-acetic acid (IAA) and 150 μm 6-(y,y-dimethylallylamino)-purine (2iP) did not induce plant regeneration.
Rough lemon seedlings [Citrus limon (L)] were hydroponically-cultured in complete Shive's nutrient solution (+K) or in Shive's nutrient solution with potassium omitted (-K) for a period of eight months. Fresh and dry weight of whole -K plants were reduced 4-fold (P<0.01). Nitrogen metabolism was monitored during this period in young, fully expanded leaves. Results showed that leaves of -K plants accumulated 2.5-fold more NH3-NH4 + than +K plants (P<0.01) and exhibited a concomitant increase in both activity of the de novo arginine biosynthetic pathway (2.5-fold) and free-arginine concentration (3.5-fold; P<0.001). Leaf proline content of -K plants increased 1.6-fold (P<0.05), while putrescine content increased 10-fold. Arginine decarboxylase activity was accelerated in -K plants.
Postharvest discoloration of cultivated mushrooms (Agaricus.bisporus [Lange] Sing., ‘tan strain’) was significantly retarded by treatment with succinic acid-2,2-dimethylhydrazide (SADH). The optimum SADH concn was 100 ppm. The effect, however, lasted no longer than 3 days after which time all SADH treatments discolored at rates equal to or greater than controls. The decrease in discoloration was correlated with a decrease in o-diphenol oxidase (o-DPO) activity. Protease activity was higher in SADH treated mushrooms suggesting that reduction in browning was due to degradation of o-DPO rather than direct inhibition of o-DPO by SADH. In vitro SADH competes with proline for quinones produced by enzymatic or non-enzymatic oxidation of diphenols. It is proposed that in vivo SADH exerts a dual effect in reducing mushroom discoloration: first SADH induces degradation of o-DPO through an increase in proteolytic activity, and second it binds to quinones thereby removing intermediates which lead to pigment formation.
Tracheal sap was extracted from stem and root segments of ‘Troyer’ (Poncirus trifoliata × Citrus sinensis), ‘Volkamer’ lemon (C. volkameriana), and sour orange (C. aurantium L.). Thirty to 100 μl of sap were used for determination of amino acids, cytokinins, and gibberellins. Proline, γ-aminobutyric and aspartic acid, arginine, and serine were the main (90–94%) amino acids found in sap of ‘Troyer’ and ‘Volkameriana’. Cytokinin-like activity was higher in orange (C. sinensis Osb.) trees on ‘Volkamer’ lemon than on ‘Troyer’ rootstock. Gibberellin activity in alternate-bearing ‘Wilking’ [‘King’ × ‘Willowleaf’ (C. reticulata Blanco × C. sinensis) × C. reticulata] sap was higher in fruiting shoots late in the on-year than in nonfruiting shoots late in the off-year.
The amino acid, organic acid, and free sugar contents as determined by gas-liquid chromatography, of ‘Wolcott’ fruit were not influenced quantitatively or qualitatively by different ratios of NH4-N and NO3-N applied in nutrient solution via a constant-flow gravity drip system to blueberries planted in sand. The amino acids detected in order of decreasing concn in the ‘Wolcott’ fruit were: tyrosine, glutamine, lysine, glutamic acid, tryptophane, gamma-aminobutyric acid, histidine, arginine, aspartic acid, alanine, serine, leucine, cysteine, threonine, isoleucine, valine, proline, and glycine. Citric acid was the predominant organic acid accompanied by lesser concn of shikimic and quinic acids. Fructose was the free sugar present in greatest concn in the fruit followed by beta-glucose and alpha-glucose. Sucrose was present at extremely low concn. The sugar/acid ratio of the ‘Wolcott’ fruit was not influenced by the N nutrient treatment.
Potted citrus trees, 1-yr-old ‘Valencia’ orange (Citrus sinensis (L.) Osbeck) on 1.5-yr-old Rusk citrange (C. sinensis (L.) Osbeck × Poncirus trifoliata) rootstocks were maintained for 6 consecutive 7-day periods in a controlled environment to induce cold hardiness with cold-hardening temperatures 10 ± 1°C, illumination 500 μeinsteins/m2 per sec (photosynthetically active radiation = PAR), relative humidity, 60 ± 5%. Trees progressively cold hardened as a result of the above conditions and, after 5 weeks, would tolerate −6.7° for 4 hours without apparent injury. Leaves sustained injury up to 5 weeks and stems up to 3 weeks of cold hardening. Solutes increased most rapidly in leaves during the first week as a result of carbohydrate accumulation.
Proline, glutamic acid and valine increased, whereas other amino acids decreased. Water potentials in the leaves of hardened trees averaged −19.5 bars after 6 weeks of cold hardening compared to −5 bars in leaves of unhardened trees.