Antioxidant response of bitter gourd (Momordica charantia L.) seedlings to interactive effect of dimethoate and UV-B irradiation

Bitter gourd (Momordica charantia L.) seedlings treated with elevated concentrations of dimethoate (100 and 200 ppm) and fixed ultraviolet-B (0.4 Wm⁻²/30 min) irradiation showed stunted growth and less photosynthetic pigments chlorophylls (Chl) content. The synergistic effects of both the stresses were more pronounced than the individual effect. However, dimethoate at low concentration (50 ppm) stimulated growth and pigmentation but with UV-B it showed slight inhibition. Reactive oxygen species (ROS) accumulated considerably in leaves due to UV-B and high concentrations of dimethoate. Combined exposure further increased the ROS leading to lipid peroxidation and electrolyte leakage. Both the stresses alone and together also caused the increase activity of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD). High concentration of dimethoate and UV-B accelerated the accumulation of ROS particularly H₂O₂ in leaves, causing heavy damage to photosynthetic pigments and growth of bitter gourd seedlings. Simultaneous exposure of UV-B and dimethoate inhibit the growth, photosynthetic pigment and enhanced the accumulation of ROS more severely than the individual exposure. Interestingly, low concentration (50 ppm) of dimethoate significantly reduced the effects of UV-B. The results suggested synergistic effect of dimethoate and UV-B on plant growth as a function of decreased photosynthetic pigments despite increase in the activities of the antioxidant enzyme.     

增强UV-B辐射对达乌里胡枝子紫外吸收物质和渗透调节物质含量的影响

以盆栽达乌里胡枝子为试材,研究在0(CK)、1.944(T1)和3.002kJ.m-2.d-1(T2)3种UV-B辐射强度下,达乌里胡枝子叶片内紫外吸收物质和渗透调节物质含量的动态响应。结果表明:增强UV-B辐射下达乌里胡枝子叶片内类黄酮、总酚、花青素含量以及苯丙氨酸转氨酶活性均呈现先增加后降低的趋势,且大部分情况显著(P0.05)高于对照组。不同剂量的UV-B辐射所引起的效应也略有不同,3.002kJ.m-2.d-1强度处理紫外吸收物质(花青素除外)和苯丙氨酸转氨酶活性在紫外辐射前期显著(P0.05)高于1.944kJ.m-2.d-1强度处理。可溶性蛋白含量在UV-B辐射下大幅度下降,最终极显著(P0.01)低于CK,且随着UV-B辐射强度的增加而降低。游离脯氨酸含量只有在1.944kJ.m-2.d-1处理第6天时显著(P0.05)高于对照组,其余情况下均未显著高于对照组。表明增强UV-B辐射主要促进达乌里胡枝子叶片内紫外吸收物质含量的增加,但是抑制了渗透调节物质的合成,尤其是抑制可溶性蛋白。     

Effect of enhanced ultraviolet-B on allelopathic potential of Zanthoxylum bungeanum

The effect of enhanced ultraviolet-B on allelopathic potential of Zanthoxylum bungeanum was investigated. A significant inhibitory effect on germination rate of crop seeds under bioassay was observed at 25 g l⁻¹ and 50 g l⁻¹ by extracts from Zanthoxylum leaf both treated with enhanced ultraviolet-B radiation and untreated control. Medicago sativa and lettuce were more sensitive than radish to the extract from Zanthoxylum leaf treated with enhanced UV-B radiation, as the germination rates of M. sativa and lettuce were significantly reduced compared to control at 25 g l⁻¹ and 50 g l⁻¹, and so did alfalfa at 12.5 g l⁻¹. However, as for radish (Raphanus sativus) there was no significant reduction in germination rate at any concentration under bioassay compared to control. Content of UV-B absorbing compounds and total phenols in Zanthoxylum seedlings responded positively to enhanced UV-B radiation. The results suggest that the allelopathic potential of Z. bungeanum was generally improved under enhanced UV-B radiation.     

NaHSO3 对UV-B辐射增强下菠菜幼苗光合作用的影响

 研究了NaHSO₃对不同强度UV2B辐射下菠菜幼苗光合速率、Hill反应速率、叶片色素含量以及叶绿素荧光参数的影响。结果表明, UV2B辐射降低了叶片光合色素含量、净光合速率( P_n) 、原初光能转化效率( F_v /F_m ) 、光化学猝灭系数( q_P ) 、非光化学猝灭系数(q_N) 、实际光化学效率(ΦPSⅡ ) 及Hill反应速率; 提高了叶绿素a与b (Chl. a /b) 和类胡萝卜素与叶绿素(Car. /Chl. ) 的比值; 在UV-B辐射胁迫和NaHSO₃复合作用下, NaHSO₃降低了重度UV-B辐射胁迫下上述指标的变化幅度, 而轻度UV-B辐射胁迫下变化无显著差异。分析认为, 随着UV2B辐射胁迫剂量的累积, NaHSO3的正效应可以减轻UV-B辐射对菠菜的负效应。复合处理下叶片Chl. a含量、Hill反应速率、原初光能转化效率( Fv/Fm ) 及ΦPSⅡ的升高是NaHSO₃提高UV-B胁迫下Pn的内在原因。     

UV-B radiation and photosynthetic irradiance acclimate eggplant for outdoor exposure

Treatment of greenhouse-grown eggplant (Solanum melongena L. var. esculentum Nees. 'Burpee's Black Beauty') seedlings with supplemental photosynthetically active radiation from cool-white fluorescent lamps increased growth of plants subsequently transferred outdoors relative to growth of plants that received no supplemental radiation or were shaded to 45% of solar irradiation in the greenhouse before transfer outdoors. Eggplant seedlings transferred outdoors were placed under plastic tarps either to provide relative protection from solar ultraviolet-B (UV-B) radiation (280-315 nm) using Mylar film or to allow exposure to UV-B using cellulose acetate. Protection of seedlings from UV-B radiation resulted in greater leaf expansion than for UV-B-exposed seedlings, but no change in leaf or shoot dry weight occurred after 9 days of treatment. Specific leaf weight increased in response to UV-B exposure outdoors. Exposure of eggplant to UV-B radiation from fluorescent sunlamps in the greenhouse also decreased leaf expansion and leaf and shoot dry weight gain after 5 days of treatment. However, there were no differences in leaf or shoot dry weight relative to control plants after 12 days of UV-B treatment, indicating that UV-B treated plants had acclimated to the treatment and actually had caught up with non-UV-B-irradiated plants in terms of growth.     

60Co-γ辐射对茭白叶片光合特性和荧光参数的影响

分别以50,75和100Gy剂量水平的60Co-γ射线对3叶期的茭白(Zizania latifolia)幼苗进行辐射处理,通过测定其叶绿素含量、光合气体交换指标和叶绿素荧光参数来探讨γ射线辐射对茭白植株光合和荧光生理特性的影响.试验结果表明,75 Gy剂量处理茭白的叶绿素a、叶绿素b和总叶绿素含量降低显著;不同剂量的...     

Modulation of manganese toxicity in Pisum sativum L. seedlings by kinetin

In the present study, the effects of kinetin (KN; 10 and 100 μM) application under manganese toxicity (Mn; 50, 100 and 250 μM) were investigated, on growth, photosynthetic pigments, total protein, total nitrogen, ammonium (NH₄⁺) content, NH₄⁺ assimilating enzymes and antioxidant system in pea seedlings. The exposure of pea seedlings to Mn and 100 μM of KN alone and in combination, caused decrease in growth, photosynthetic pigments, total protein and total nitrogen contents, and an increase in NH₄⁺ content. However, application of 10 μM of KN together with Mn reduced the Mn toxicity symptoms, promoted the growth of seedlings and led to the decrease in NH₄⁺ content compared to Mn treatments alone. The root and shoot activities of glutamine synthetase (GS), glutamate oxoglutarate aminotransferase (GOGAT) and catalase (CAT) were decreased while glutathione reductase (GR) and dehydroascorbate reductase (DHAR) activities exhibited differential responses when pea seedlings were exposed to Mn and 100 μM of KN. However, under similar treatments, activities of glutamate dehydrogenase (GDH), superoxide dismutase (SOD) and ascorbate peroxidase (APX) in root and shoot were increased. It was noticed that addition of 10 μM of KN together with Mn, caused significant stimulation in activities of enzymes of NH₄⁺ assimilation and antioxidant defense system even over their respective control values. Non-enzymatic antioxidants (ascorbate and glutathione) in root and shoot of pea seedlings exposed to Mn stress were significantly increased by the addition of 10 μM of KN. Therefore, ameliorative effect of 10 μM of KN against Mn toxicity was observed. This study thus suggests that 10 μM of KN appreciably improves Mn tolerance of pea seedlings under Mn toxicity while reverse effects were exhibited by 100 μM of KN.     

Evaluation of the sensitivity to ionising γ-radiation of a Cymbidium hybrid

Gamma-rays are an important mutagenic agent that can induce new, useful genetic variations in plants. However, γ-irradiation can also cause damage that negatively affects the use of such mutagens in plant breeding. The aim of the present study was to investigate the effects and damage caused by γ-radiation in a Cymbidium hybrid, RB001. The relative growth rate of protocorm-like bodies (PLBs) was reduced by 50% at a γ-ray dose of approximately 40 Gy. Malondialdehyde concentrations increased significantly with increasing radiation dose. However, almost no difference was observed between untreated control PLBs and PLBs treated with 200 Gy 8 weeks after γ-irradiation. The activities of several antioxidant defence enzymes increased gradually with increasing γ-ray dose, 24 h after irradiation. These enzymes showed different responses between 1 and 4 weeks, but no difference 8 weeks after irradiation. The ‘comet assay’ and flow cytometry were performed. Clear differences in radiation-induced damage were observed between control and 200 Gy-treated PLBs at 24 h. However, PLBs had a tendency to recover from 4 weeks after irradiation, and the integrity of their DNA was similar in samples treated with 10–200 Gy. These results indicated that γ-rays caused little DNA damage and the plants could recover. This demonstrated the feasibility of using physiological responses, the ‘comet assay’, and flow cytometry to detect DNA damage after γ-irradiation.     

Modification of chilling susceptibility in seedlings of cucumber and zucchini squash by the bioregulator paclobutrazol (PP333)

Application of paclobutrazol at 1, 5 or 10 mg 1^?1 by soil drench inhibited growth and increased chlorophyll content of leaf discs of cucumber and zucchini squash. The treatments also significantly postponed symptoms of chilling injury of seedlings at 5°C. The degree of protection from injury sustained at low temperature increased with increasing duration of the paclobutrazol treatment. Cucumber seedlings were more sensitive to chilling injury and were more responsive to the paclobutrazol treatment than seedlings of zucchini squash.     

外源NO诱导辣椒对UV-B胁迫的生理响应

以果期辣椒为试材,研究不同浓度外源NO供体硝普钠(SNP)对UV-B胁迫下辣椒的生理响应,旨在为辣椒栽培生产提供科学参考依据。结果表明:喷施SNP(3 mmol·L^-1)显著提高了UV-B胁迫下辣椒叶片的光合色素含量,光合荧光参数Fv/Fm,抗氧化酶活性(SOD、POD、CAT)和可溶性糖含量;光合荧光参数Fo、丙二醛(MDA)含量显著降低,从而降低了UV-B胁迫对果期辣椒的伤害。综上所述,外源NO参与了辣椒对UV-B胁迫的应答与防御,提高了辣椒对UV-B胁迫的抗性。     

Amelioration of chilling stress by paclobutrazol in watermelon seedlings

Paclobutrazol (PBZ) is a member of the triazole plant-growth inhibitor group that is responsible for inducing tolerance to number of biotic and abiotic stresses. An experiment was, therefore, conducted to test whether PBZ application at various concentrations (0, 25, 50 and 75 mg L⁻¹) through seed soaking or foliar spray would protect watermelon (Citrullus lanatus) seedlings, subjected to chilling stress. Thirty-five-day old plants were exposed to chilling 5 h/day at 4 °C for 5 days. PBZ improved growth rate of watermelon seedling subjected to chilling stress and increased relative leaf chlorophyll content (RLCC) and chlorophyll fluorescence ratio (Fv/Fm) compared with the control at the end of chilling stress. PBZ ameliorated the injury caused by chilling stress by inhibiting increases in proline and leaf electrolyte leakage, which suggested that PBZ ameliorated the negative effect of chilling stress. PBZ was most effective in increased chilling tolerance of watermelon seedling when applied using the seed soak method than as a foliar spray. The best protection appeared to be obtained from seedlings seed soaked with PBZ at 50 and 75 mg L⁻¹.     

Effect of different light intensities on the photosynthate distribution in cherry tomato seedlings

To investigate the effect of varying the light intensity on the photosynthate distribution, cherry tomato (Solanum lycopersicum L.) seedlings were grown under different light intensities. It was found that the seedlings under 300 μmol m^–2 s^–1 had a significantly higher dry weight and health index (Health index = Stem diameter/Stem height × Dry weight) than seedlings receiving other light treatments. On the contrary, the biomass, specific leaf mass and health index values of seedlings exposed to 50 μmol m^–2 s^–1 and 550 μmol m^–2 s^–1 were the lowest among all of the treatments. In terms of ¹⁴C-labelled photosynthate translocation, the seedlings under 300 μmol m^–2 s^–1 had lower remaining ¹⁴C-labelled photosynthate (31.45%) compared with other treatments, after ¹⁴CO₂ was supplied for 2 days. The seedlings under 150 μmol m^–2 s^–1 had 36.97% of ¹⁴C-labelled photosynthate in the labelled leaves and transported the obviously higher ¹⁴C-labelled photosynthate to new shoot than others. Together, our results indicate that the photosynthate distribution was the most rational in cherry tomato seedlings at 300 μmol m^–2 s^–1, which enhanced leaf photosynthesis and plant growth.     

LED光质补光对黄瓜幼苗生长和光合特性的影响

采用发光二极管（light emitting diode,LED）精确调制光谱能量分布,以单色光质（红光、蓝光、UV-B）和组合光质（红/蓝1∶1）进行每天4 h补光,以未补光组为对照,研究LED光质补光对黄瓜幼苗生长和光合特性的影响。结果表明：与未补光组相比,LED光质补光处理显著促进了黄瓜幼苗的生长;不同光质对黄瓜幼苗生长和光合特性的影响具有一定的差异性。其中,UV-B处理显著提高了黄瓜幼苗叶片单位鲜质量的叶绿素a、叶绿素b和类胡萝卜素含量,但显著降低了Fv/Fm;红光处理显著提高了黄瓜幼苗的真叶数、叶面积、株高、干鲜质量、壮苗指数、根系活力、SOD活性和可溶性蛋白含量。总体而言,红光有利于培育壮苗,较适合作为黄瓜育苗的补光光质。     

Morphology,yield and quality of ashwagandha (Withania somnifera L. Dunal) roots and its cultivation economics as influenced by tillage depth and plant population density

Summary

Ashwagandha (Withania somnifera L. Dunal; Solanaceae) is being cultivated around the world mainly for its root which has rejuvenative properties. Field experiments during 1999–2001 under semi-arid tropical conditions of Hyderabad, India studied the effect of tillage depths (15 and 30 cm) and plant population densities (20, 40, 60 and 80 plants m^–2) on root morphology, yield and quality and cultivation economics of ashwagandha. Preparatory tillage to 30 cm depth in combination with a density of 60 plants m^–2 gave the highest root yield of 1.2 t ha^–1 which was 50% higher than that following 15 cm tillage depth and the same density. This is attributed to the favourable effect of the former treatment leading to 33, 37 and 21% increases in plant height, number of branches per plant and shoot biomass yield, respectively. Further, this treatment produced most (68%) best quality root pieces. Main root length, length of lateral roots and diameter of lateral roots were significantly increased, while the diameter of main root and the number of laterals decreased. Furthermore, increase in plant density from 20–80 plants m^–2 increased production of best quality roots from 42% to 59% under shallow tillage and from 53% to 71% of root yield under deep tillage. The implications of change in root morphology are discussed in the light of production of different grades of roots, their market preferences and economics. Deep tillage was equally advantageous for seed production, but plant population density for maximum seed yield (211 kg ha^–1) was lower at 40 than at 60 plants m^–2 for maximum root yield. Maximum gross and net returns and benefit-cost ratio occurred following the highest root yield.     

The influence of wax emulsion,morphactin and gibberellic acid on the storage behaviour of indian gooseberry fruits

Qualities of Indian gooseberry fruits (Phyllanthus emblica L.) were determined after dip-treatment with wax emulsion (WE) with or without morphactin (Mor) and gibberellic acid (GA₃). Dip-treatments with 100–500 mg l^?1 Mor reduced marketability by inducing browning and high weight loss, but loss in ascorbic acid was checked and phenols increased. 10 mg l^?1 Mor maintained marketability at par with control, effectively controlled loss in ascorbic acid, and increased acidity and reducing sugars. GA₃, although failing to control the loss of ascorbic acid, was effective in checking browning and thereby increased the market value of fruits as compared with controls and Mor-treated fruits.WE with or without Mor (10 mg l^?1) controlled browning, accumulation of phenols and losses in weight and moisture as compared with 10 mg l^?1 Mor, 100 mg l^?1 GA₃, or control, but could not retain ascorbic acid in comparison to 10 mg l^?1 Mor-treated fruits. Marketability of fruits having had treatment with either WE or GA₃ was the same. Fruits having had combined treatment with WE and 10 mg l^?1 Mor had maximum marketability. Minimum marketability was observed in fruits subjected to a combined treatment of WE + 100 mg l^?1 GA₃ due to maximum infection with Aspergillus spp. and Penicillium spp.     

Growth and nutrient partitioning of containerized Cercis siliquastrum L. under two fertilizer regimes

Lebanon's native flora is threatened by loss of natural habitat to rural and urban development and the increased demand of plant materials for landscaping. Despite Lebanon's floristic richness, most taxa used for landscaping are non-native. This study was done to determine if Cercis siliquastrum (L.) is amenable to container production. Therefore, six open pollinated seeds sources native to Lebanon were grown under two fertilizer rates to study growth, N, P, K uptake efficiency, and partitioning. Two-year-old seedlings were planted in 11 L containers in a 3:1 pine bark:compost substrate. Seedlings within each seed source or mother tree were grown at either 25 or 100 mg N L⁻¹ from 21N–3.1P–5.9K water-soluble fertilizer. Seedlings of all sources grown under 25 mg N L⁻¹ had greater dry weight than those grown at 100 mg. Nutrient loading occurred in plants under the high fertilizer rate, although total plant N, P, and K content were not affected by fertilizer rate. There were significant differences in mineral nutrient uptake and nutrient use efficiencies among the seed sources. The results show that C. siliquastrum is amenable to container production. The great variation in growth rate and nutrient use efficiency among the limited number of seed sources studied suggest that significant improvement can be made through mother tree selection and/or clonal propagation of superior individual plants within a source.     

Effects of nitrogen and phosphorus nutrition on the growth of asparagus seedlings

N was applied at 50, 100 or 150 mg l^?1 in factorial combination with P at 7.5, 15 or 22.5 mg l^?1 to asparagus seedlings. There were 6 successional harvests. N and P increased shoot dry weight by increasing mean dry weight and number of shoots. Increasing P had no effect on shoot growth at 50 mg l^?1 N. N increased root dry weight (crown and roots) by increasing root number, whereas P decreased root dry weight due to a decrease in mean root dry weight. N increased total plant dry weight, but P had no effect. N and P increased the partitioning of dry weight to the shoots, while partitioning to the roots increased with time. Plant analysis revealed that 2.6–2.7% N and 0.29–0.36% P, on a dry-weight basis, were present in the shoots at the later harvests with the higher concentrations of N and P. 100–150 mg 1^?1 N in combination with 15 mg l^?1 P produced a seedling suitable for transplanting into commercial fields at 6 weeks from emergence.     

Studies on the Maturity of Apples.: Respiration Progress Curves for Cox’s Orange Pippin Apples for a Number of Consecutive Seasons

Summary

The effect of UV-B irradiation at 10°C and 20°C on the quercetin glycosides procyanidins, chlorogenic acid and anthocyanin levels in the skin of detached fruit of five apple cultivars was investigated. UV-B responsiveness was compared between sides of the fruit that were outwardly facing (exposed) and inwardly facing (shaded) when on the tree. There were no common effects of UV-B irradiation and temperature across all cultivars. UV-B irradiation increased the quercetin glycoside levels in the shaded side of ‘Gala’, ‘Royal Gala’ and ‘Braeburn’ fruit and only at 20°C. UV-B irradiation of the exposed sides of the five cultivars, of either side at 10°C, and of ‘Pacific Rose’ and ‘Aurora’ at either 10°C or 20°C had no significant effect on quercetin glycoside levels. There was no effect of UV-B irradiation on procyanidin levels at any combination of treatments. However, levels of chlorogenic acid, although one tenth of those of quercetin glycosides and procyanidins, increased markedly with UV-B irradiation. Both exposed and shaded sides of fruit of all cultivars increased in chlorogenic acid levels at 10°C and 20°C after UV-B irradiation. UV-B irradiation increased anthocyanin levels in exposed and shaded sides of fruit of all cultivars at 20°C, and on ‘Braeburn’, and ‘Aurora’ at both 20°C and 10°C. UV-B irradiation at either temperature had no significant effect on either the relative proportions of the glycosides of quercetin (galactoside, rhamnoglucoside, glucoside, xyloside, arabinoside and rhamnoside) or the relative proportions of the procyanidins (Procyanidins B2, B5, epicatechin and catechin). The effect of UV-B irradiation was variable, depending on cultivar, previous light exposure, temperature and class of flavonoids examined.     

Effect of Seed Coat Removal Treatments on Seed Germination and Seedling Attributes in Mango Varieties

A field experiment was carried out at the Indian Institute of Horticultural Research, Bengaluru during 2011–12 to study the effect of seed coat removal on seed germination and vigor of polyembryonic mango seedlings. In seed coat removal, the cultivar Muvandan recorded the maximum germination percent (85.4%), extent of polyembryony (2.76), and maximum number of leaves (10.3), whereas Bappakkai recorded maximum plant height (22.4 cm), stem girth (0.64 cm), leaf area (249.2 cm²), fresh weight (18.5 g) and dry weight (8.4 g), vigor index-I (1831.5 cm), and vigor index-II (685.7 g). With respect to treatments, seed coat removal was superior in all of the parameters, namely, initiation of germination (16.7 days), germination percent (78.3%), extent of polyembryony (2.50), plant height (19.5 cm), stem girth (0.62 cm), number of leaves per plant (8.7), leaf area (288.3 cm²), fresh weight (16.2 g) and dry weight (7.3 g), vigor index-I (1559.0 cm), and vigor index-II (581.8 g) compared to seed coat intact. There were no significant differences among the interactions of different treatments and cultivars.     

Synergistic effects of modified atmosphere and minimal processing on the keeping quality of pre-cut papaya (Carica papaya L.)

Summary

Pre-cut papaya is a highly perishable product and requires suitable pre-treatment and storage protocols for commercial utilisation. Papaya was peeled, cut into slices (5 cm 0.6 cm 0.7 cm) and surface sanitised with chlorinated water (0.1 g l^–1). The slices were then subjected to minimal processing pre-treatments with a tissue firming agent (1 g l^–1 CaCl₂) for 10 min, anti-microbials (0.4 g l^–1 potassium sorbate and 0.4 g l^–1 sodium benzoate) and anti-browning agents (0.2 g l^–1 ascorbic acid) for 30 min, followed by acidification (7.0 g l^–1 citric acid) for 2 min. The pre-treated slices were kept under UV light (2.5 kJ m^–2 for 10 min) and subsequently packed in a modified atmosphere (3% O₂ + 6% CO₂ + 91% N₂) under partial vacuum (30 kPa), or in air, in polyethylene (PE) pouches (12 cm 10 cm; 25 µm thick; 100 g fill-weight) or in polyethylene terephthalate (PET) bottles (2 l; 500 g fill-weight) with a 2.25 cm² silicone membrane diffusion window. Samples were stored at 6° ± 1°C and analysed for changes in their physico-chemical, microbiological and sensory attributes, along with their head-space gaseous composition. The pre-treatments acted synergistically with the modified atmospheres to stabilise the papaya slices, physiologically, as well as restricting the proliferation of microbes (e.g., total plate counts of coliforms, yeasts and moulds). Physiological stability was characterised by a significant (P < 0.05) reduction in respiration rate, reduced losses of texture and ascorbic acid, delayed increases in electrical conductivity and in colour co-ordinates, without impeding the sensory quality of the product. Pre-treated papaya slices, kept under different modified atmospheres, had storage lives of 44 – 60 d at 6° ± 1°C, which may facilitate bulk storage and long-distance transportation.