Low conductances for CO2 diffusion from stomata to the sites of carboxylation in leaves of woody species

Concurrent measurements of leaf gas exchange and on-line ¹³C discrimination were used to evaluate the CO₂ conductance to diffusion from the stomatal cavity to the sites of carboxylation within the chloroplast (internal conductance; g_i). When photon irradiance was varied it appeared that g_i and/or the discrimination accompanying carboxylation also varied. Despite this problem, g_i, was estimated for leaves of peach (Prunus persica), grapefruit (Citrus paradisi), lemon (C. limon) and macadamia (Macadamia integrifolia) at saturating photon irradiance. Estimates for leaves of C. paradisi, C. limon and M. integrifolia were considerably lower than those previously reported for well-nourished herbaceous plants and ranged from 1.1 to2.2μmol CO₂ m^?2 s^?1 Pa^?1, whilst P. persica had a mean value of 3.5 μmol CO₂ m^?2 s^?1 Pa^?1. At an ambient CO₂ partial pressure of 33Pa, estimates of chloroplastic partial pressure of CO₂ (C_c) using measurements of CO₂ assimilation rate (A) and calculated values of g_i, and of partial pressure of CO₂ in the stomatal cavity (C_st) were as low as 11.2 Pa for C. limon and as high as 17.8Pa for peach. In vivo maximum rubisco activities (V_max) were also determined from estimates of C_c. This calculation showed that for a given leaf nitrogen concentration (area basis) C. paradisi and C. limon leaves had a lower V_max than P. persica, with C. paradisi and C. limon estimated to have only 10% of leaf nitrogen present as rubisco. Therefore, low CO₂ assimilation rates despite high leaf nitrogen concentrations in leaves of the evergreen species examined were explained not only by a low C_c but also by a relatively low proportion of leaf nitrogen being used for photosynthesis. We also show that simple one-dimensional equations describing the relationship between leaf internal conductance from stomatal cavities to the sites of carboxylation and carbon isotope discrimination (Δ) can lead to errors in the estimate of g_i. Potential effects of heterogeneity in stomatal aperture on carbon isotope discrimination may be particularly important and may lead to a dependence of g_i upon CO₂ assimilation rate. It is shown that for any concurrent measurement of A and Δ, the estimate of C_c is an overestimate of the correct photosynthetic capacity-weighted value, but this error is probably less than 1.0 Pa.     

Alterations in lipid peroxidation,lipid profile,insulin sensitivity,and hepatic histopathological changes in diabetic rats following the treatment with Salvadora persica

We examined the effects of various partitions of Salvadora persica extract on lipid profile (LP), lipid peroxidation, and insulin sensitivity (IS) of diabetic rats. The rats were divided into normal control, diabetic control (DC), standard, sham, and test groups. The test groups were treated with an oral dose of 200, 400, and 600 mg/kg of crude, aqueous, and ethyl acetate partition of S. persica extract. After 21 days of experiment, the fasting blood glucose (FBS), LPs, lipid peroxidation, IS, liver enzymes levels, liver histopathology, and body weight alteration were evaluated. A significant decrease in FBS and lipid profile (except HDL) were observed in rats treated with various dose of extract compared with the DC rats ( P < 0.05). Treating diabetic rats with various extracts of S. persica meaningfully decreased the level of malondialdehyde ( P < 0.05). Animals treated with various dose of aqueous extract showed better results ( P < 0.01). On the basis of used indirect indexes to determine IS, all partitions of extracts showed anti-insulin resistance effects in diabetic rats. On the basis of our statistical analyzing, treating diabetic rats with all of the three extracts of S. persica decreased the elevated levels of alanine phosphatase, aspartate aminotransferase, and alanine transferase. Also, pathological changes in the liver tissue were reduced following treatment with the S. persica. In conclusion, our results give evidence that the S. persica extract, especially aqueous partition, has a healing effect on diabetes and can be considered as an alternative therapy for this disease.     

Phenylethanoids, iridoids and a spirostanol saponin from Veronica turrilliana

From the aerial parts of Veronica turrilliana two phenylethanoid glycosides, turrilliosides A and B and a steroidal saponin, turrillianoside were isolated and their structures elucidated as beta-(3,4-dihydroxyphenyl)ethyl-4-O-E-caffeoyl-O-[beta-glucopyranosyl-(1-->4)-alpha-rhamnopyranosyl-(1-->6)]-beta-glucopyranoside, beta-(3,4-dihydroxyphenyl)ethyl-4-O-E-caffeoyl-[6-O-E-feruloyl-beta-glucopyranosyl-(1-->4)-alpha-rhamnopyranosyl-(1-->6)]-beta-glucopyranoside and (23S,25S)-12beta,23-dihydroxyspirost-5-en-3beta-yl O-alpha-rhamnopyranosyl-(1-->4)-beta-glucopyranoside, respectively. Furthermore, eight known glucosides are reported namely, catalpol, catalposide, verproside, amphicoside, isovanilloylcatalpol, aucubin, arbutin, and 6-O-E-caffeoylarbutin, the latter two for the first time in the genus Veronica. The two phenylethanoid glycosides were found to be potent DPPH radical scavengers. All of the tested compounds were inactive against the representative species of fungi and bacteria.     

桃果实成熟前后细胞壁成分和降解酶活性的变化及其与果实硬度的关系

比较桃品种‘双久红’和‘川中岛白桃’果实成熟前后20 d内果肉硬度、细胞壁成分和细胞壁降解酶活性变化的结果表明,桃果实成熟5 d后,‘双久红’桃果实的硬度、纤维素含量和原果胶含量均极显著高于‘川中岛白桃’:从成熟前15 d开始,‘双久红’的水溶性果胶含量、多聚半乳糖醛酸酶活性和纤维素酶活性均极显著低于‘川中岛白桃’;整个成熟期间,‘双久红’的果胶甲酯酶活性明显低于‘川中岛白桃’。相关分析表明,果实硬度与原果胶、纤维素含量呈极显著正相关,而与可溶性果胶含量、多聚半乳糖醛酸酶活性和纤维素酶活性呈极显著负相关。     

Evaluation of the biocidal effects of Brassica seed meal on Armillaria mellea

The antifungal properties of isothiocyanates released from the hydrolysis of the glucosinolate sinigrin were assessed on an Armillaria mellea strain in Petri dishes. The fumigation with sinigrin at 100 µM showed a fungicidal effect, while lower rates determined a temporary fungistatic effect. The application of increasing rates of solid and liquid biofumigant formulations on A. mellea inoculated potted peach plants showed an increase of soil nitrate concentration, basal respiration, microbial biomass, leaf nitrogen and chlorophyll concentration. These effects indicated a stimulating effect of Brassicaceae derivatives on soil biological activity and plant growth. The application of a rate of meal higher than 6.42 g kg^?1 soil caused a stunted growth and the death of some plants showing a clear phytotoxic effect of the treatments. The inhibition of A. mellea growth observed in in vitro trials was not evidenced in in vivo experiments due to the lack of infection symptoms in experimentally inoculated potted trees.     

Systematic significance of seed morphology in the genus Veronica (Plantaginaceae), with special reference to the Egyptian taxa

Seed morphology of 29 taxa including 9 subgenera belonging to the genus Veronica was compared using scanning electron microscopy to assess their diagnostic value for systematic studies. Subgenus Beccabunga is the largest in this study represented by nine taxa. Seed surface often varies from ridged reticulate or verrucose/granulate reticulate to rugose-reticulate. Seed color and size have limited taxonomic significance as their variation is uninformative. Thereagainst, seed shape and seed coat ornamentation present informative characters that can be used efficiently in distinguishing the studied taxa. Our seed features support the DNA sequence data in showing close relationships between V. biloba and V. campylopoda, and between V. fruticans and V. fruticulosa. The present study indicates thatV. anagallis-aquatica, V. anagalloides, V. comosa, and V. catenata have more or less the same seed features; consequently, these four former species are most likely representing a single species as reported by earlier studies. Furthermore, V. polita and V. persica are very similar in terms of seed characteristics. Our results justify placement of V. peregina within subgenus Beccabunga and support the monophyly of the subgenus Veronica.     

Anatomical and biochemical studies in persisting and shedding seeds during the development of peach fruits

ABSTRACT

Peach fruits were collected in the period between anthesis and harvest. The relationship between histological structure, free abscisic acid (ABA) and carbohydrate content was investigated in control seeds (class A) and in the seeds of fruit that were affected by fruit-drop and that were not yet abscised from the plant (class B). The results of the histological analysis showed that seeds from class A generally showed a normal embryogenesis, whereas we did not detect any embryo and endosperm in seeds of class B because they were undergoing degeneration. The ABA level reached a positive peak during the first 75 days after anthesis in seeds of class A, whereas the seeds of class B showed a negative peak in the same period. Carbohydrate content followed a similar trend to that of ABA. Results are discussed in relation to the development of the fruits.     

Diurnal patterns of stem extension growth in peach (Prunus persica): Temperature and fluctuations in water status determine growth rate

Field measurements of stem extension growth rate in peach ( Prunus persica [L.] Batsch) exhibited a consistent diurnal pattern. Stem extension rate was lowest in the early morning and increased throughout the day. In the late afternoon, 2–3-fold increases in extension rate occurred and were sustained for 2 to 4 h. After this growth surge, rates precipitously declined and remained low during the night. The temperature response of stem growth rate at constant water potential was determined using potted trees in a dark growth chamber. Under such conditions, stem growth rate was strongly dependent on air temperature. In the field, the observed stem growth rate deviated from that predicted on the basis of temperature. These deviations were proportional to the rate of change in stem water potential. A model was constructed to predict diurnal patterns of stem extension rate using temperature and water potential data. The model was tested using data from undisturbed trees and from trees in which water potential was artificially manipulated. Growth patterns predicted by the model were in general agreement with observed rates.