强光下高温与干旱胁迫对花生光系统的伤害机制

为探讨高温和干旱胁迫对花生光合系统的不同影响机制,以鲁花14为试材进行高温(42 ℃)强光(1200 μmol · m^-2 · s^-1)(HH)、干旱(PEG6000,30%)强光(1200 μmol · m^-2 · s^-1)(DH)和强光(1200 μmol · m^-2 · s^-1)胁迫(NH)处理,以未处理为对照(CK)的实验。与CK及NH处理相比,HH和DH的最大光化学效率(Fv/Fm)和820 nm光吸收大幅下降,叶绿素荧光动力学曲线上J点相对荧光(Vj)上升,单位面积内吸收的光量子(ABS/CSm)、单位面积内反应中心捕获的光量子(TRo/CSm)和单位面积内有活性的反应中心的数目(RC/CSm)均出现大幅下降,而PSⅡ的关闭程度(1-qP)明显升高,依赖于叶黄素循环的非辐射能量耗散(NPQ)升高,同时超氧化物歧化酶(SOD)活性出现下降,丙二醛(MDA)和膜透性增加,这些结果表明,HH和DH胁迫引起了花生叶片的严重光抑制,但快速叶绿素荧光诱导动力学曲线中均没有出现K点,表明花生叶片光合系统放氧复合体(OEC)对高温和干旱胁迫不敏感,光合系统Ⅱ(PSⅡ)反应中心的受体侧更容易受到高温和干旱的影响,而对花生光系统造成严重破坏的主要原因则是过剩光能的积累,一方面虽然叶黄素循环可以耗散部分能量,但不是全部;另一方面水-水循环受到高温和干旱的影响不能有效起到能量消耗的作用,造成活性氧的大量积累。HH和DH处理对花生光系统造成的伤害相似,但DH处理对花生光系统的伤害程度大一些,强光下,高温和干旱对花生叶片的伤害位点及破坏机制却较为相似。     

In sacco degradation kinetics of fresh and field-cured peanut (Arachis hypogaea L.) forage harvested at different maturities

There is interest in growing peanut (Arachis hypogaea L.) for forage, but little is known about the nutritive value and forage quality of modern cultivars. The objective of this study was to compare the chemical composition and in sacco degradation kinetics of three cultivars of peanuts (cv. ‘C99-R’, ‘Georgia-01R’, and ‘York’) at either stage 2 or 8 maturities when fresh and field-cured. Herbage yield was at least 3000 kg DM/ha for all cultivars at both maturities. Crude protein (CP) was greater (P < 0.0001) at R2 stage than at R8 stage; whereas, neutral detergent fiber (aNDF), acid detergent fiber, and Lignin (sa) were greater (P < 0.01) at R8 than R2 maturity stages. Water soluble carbohydrate and acid detergent insoluble nitrogen was not different (P > 0.07) among cultivars, maturity stage, or harvest forms. In vitro true digestibility was greatest (P < 0.02) for C99-R and least for York. Undegradable intake protein concentration was greatest (P < 0.04) in York and least for C99-R. Maturity had a greater effect on the degradation kinetics than harvest form or cultivar. The dry matter (DM) and CP in the soluble wash fraction (A) and insoluble but degradable fraction (B) and the effective ruminal degradability were greater among all cultivars and both harvest forms of the R2 maturity stage than the R8. The undegradable DM, aNDF, and CP in the undegradable fraction were greatest (P < 0.002) for all three cultivars at R8 maturity. The rate of degradation of DM and CP in the B fraction was faster (P < 0.001) at R2 stage than at R8 stage; whereas, rate of aNDF degradation was not different (P > 0.09) among treatments. Lag of DM, aNDF, or CP degradation was not different (P > 0.1) among treatments. The cultivars C99-R and Georgia-01R are recommended for further feeding trials.     

三种根系分泌脂肪酸对花生生长和土壤酶活性的影响

为了探讨花生连作后土壤中脂肪酸类物质的累积与花生连作障碍间的关系,为花生连作障碍机理的研究提供新的理论依据,以田间土壤为介质,采用盆栽试验的方法研究了花生根系分泌物中3种长链脂肪酸,即:豆蔻酸、软脂酸和硬脂酸的混合物,对花生植株生长、产量和土壤酶活性的影响。结果表明,当土壤中脂肪酸的初始含量较低时(80 mg/kg土),对花生植株的生长和产量有微弱的促进作用(P>0.05),当土壤中脂肪酸的初始含量较高时(160 mg/kg土和240 mg/kg土),显著抑制了花生植株的生长和产量(P<0.05)。叶片叶绿素含量、根系活力、土壤酶(蔗糖酶、脲酶、磷酸酶)活性在低脂肪酸含量处理下升高,在高脂肪酸含量处理下显著降低(P<0.001)。光合产物、根际有效养分的减少和根系养分吸收能力的降低,可能是导致花生植株生长和产量降低的原因之一。花生连作土壤中豆蔻酸、软脂酸和硬脂酸的累积与花生的连作障碍有着密切关系。     

Ectopic over-expression of peroxisomal ascorbate peroxidase (SbpAPX) gene confers salt stress tolerance in transgenic peanut (Arachis hypogaea)

Peroxisomal ascorbate peroxidase gene (SbpAPX) of an extreme halophyte Salicornia brachiata imparts abiotic stress endurance and plays a key role in the protection against oxidative stress. The cloned SbpAPX gene was transformed to local variety of peanut and about 100 transgenic plants were developed using optimized in vitro regeneration and Agrobacterium mediated genetic transformation method. The T₀ transgenic plants were confirmed for the gene integration; grown under controlled condition in containment green house facility; seeds were harvested and T₁ plants were raised. Transgenic plants (T₁) were further confirmed by PCR using gene specific primers and histochemical GUS assay. About 40 transgenic plants (T₁) were selected randomly and subjected for salt stress tolerance study. Transgenic plants remained green however non-transgenic plants showed bleaching and yellowish leaves under salt stress conditions. Under stress condition, transgenic plants continued normal growth and completed their life cycle. Transgenic peanut plants exhibited adequate tolerance under salt stress condition and thus could be explored for the cultivation in salt affected areas for the sustainable agriculture.     

Heme enzymes in a chlorina hybrid of ground nut (Arachis hypogaea) and its parents

Chlorophyll biosynthesis in the Chlorina hybrid was affected due to the lower levels of the enzyme δ-amino levulinate dehydratase responsible for the synthesis of porphobilinogen. A comparison of the amounts of different heme containing enzymes from the etiolated and green seedlings of the Chlorina and its parents suggested that the chlorophyll and heme moiety of catalase share the same pool of porphobilinogen and that this pool is different to the one shared by peroxidase and indole acetic acid oxidase. The enzyme δ-amino levulinate dehydratase possesses two isoenzyme bands. These isoenzymes may be spatially separated and responsible for the synthesis of two pools of porphobilinogen.     

Role of biotechnological interventions in the improvement of castor (Ricinus communis L.) and Jatropha curcas L

Castor and Jatropha belong to the Euphorbiaceae family. This review highlights the role of biotechnological tools in the genetic improvement of castor and jatropha. Castor is monotypic and breeding programmes have mostly relied on the variability available in the primary gene pool. The major constraints limiting profitable cultivation are: vulnerability to insect pests and diseases, and the press cake is toxic which restrict its use as cattle feed. Conventional breeding techniques have limited scope in improvement of resistance to biotic stresses and in quality improvement owing to low genetic variability for these traits. Genetic diversity was assessed using protein based markers while use of molecular markers is at infancy. In vitro studies in castor have been successful in shoot proliferation from meristematic explants, but not callus-mediated regeneration. Genetic transformation experiments have been initiated for development of insect resistant and ricin-free transgenics with very low transformation frequency. In tropical and subtropical countries jatropha is viewed as a potential biofuel crop. The limitations in available germplasm include; lack of knowledge of the genetic base, poor yields, low genetic diversity and vulnerability to a wide array of insects and diseases. Great scope exists for genetic improvement through conventional methods, induced mutations, interspecific hybridization and genetic transformation. Reliable and highly efficient tissue culture protocols for direct and callus-mediated shoot regeneration and somatic embryogenesis are established for jatropha which indicates potential for widening the genetic base through biotechnological tools. Assessment of genetic diversity using molecular markers disclosed low interaccessional variability in local Jatropha curcas germplasm. The current status and future prospects of in vitro regeneration, genetic transformation and the role of molecular tools in the genetic enhancement of the two-oilseed crops are discussed.     

Early generation intermating for yield improvement in groundnut (Arachis hypogaea L.)

Summary Seeds of 4 crosses of groundnut (Arachis hypogaea L.), Robut 33-1 x Chico, Robut 33-1 x NC Ac 17090, Robut 33-1 x PI 298115 and MK 374 x GAUG 1, were irradiated with 30 kR. In the F₁, some branches of each plant were intermated with other plants at random and others selfed in each cross to produce S₂ and F₂ seeds. They were evaluated for pod yield, shelling percentage and 100-kernel weight. The frequency of plants superior to F[in1] was much higher in S₂ than in F₂, which was, in general, true for the values of yield and its components. The S₂ and F₂ were advanced to third generation by selfing. The families descending from S₂ showed clear superiority over those from F₂. The reason for such superiority was suggested to be the recombination of genes from the upper and lower ends of the genotypic distribution under intermating.     

Halopriming of seeds imparts tolerance to NaCl and PEG induced stress in Vigna radiata (L.) Wilczek varieties

The investigation was carried out to study the effect of halopriming on NaCl and polyethylene glycol-6000 (PEG-6000) induced stress tolerance potential of three Vigna radiata (L.) Wilczek varieties, with varied abiotic stress tolerance potential. Halopriming is a seed priming technique in which the seeds were soaked in various salt solutions (in this study NaCl was used). The results of the study indicated that the application of stresses (both NaCl and PEG) induced retardation of growth attributes (measured in terms of shoot length, fresh weight, dry weight) and decrease in physiological attributes like total chlorophyll content, metabolites, photosynthetic and mitochondrial activity of the seedlings in all three V. radiata (L.) varieties. However, halopriming of the seeds could reduce the extent of decrease in these biological attributes. NaCl and PEG stress also caused increase in MDA content (a product of membrane lipid peroxidation) in all the varieties studied and this increase was significantly minimized under halopriming. From the present investigation it was evident that among the green gram varieties studied, Pusa Vishal, a NaCl tolerant variety showed enhanced tolerance to NaCl and PEG induced stress, when the seeds were subjected to halopriming followed by Pusa Ratna (stress sensitive variety). Pusa 9531 (drought tolerant variety) also showed positive halopriming effects but it was less significant when compared to other two varieties. It could be concluded that halopriming improved the drought and salinity stress tolerance potential of all varieties and it was significantly higher in the Pusa Vishal as compared to Pusa 9531 and Pusa Ratna.     

Plant regeneration and Agrobacterium-mediated transformation of cotyledon explants of Citrullus colocynthis (L.) Schrad.

The effect of 6-benzylaminopurine (6-BA) alone or in combination with naphthaleneacetic acid or indoleacetic acid on the morphogenetic response of cotyledon explants of Citrullus colocynthis (L.) Schrad. was tested. The best results were obtained with a medium containing 25 μm 6-BA, which yielded organogenic calli at a frequency of 81.8%. When these organogenic calli were transferred to elongation medium (basal medium supplemented with 0.5 μm 6-BA), 80% produced well-developed shoots. These shoots rooted normally when cultured on rooting medium containing indolebutyric acid at 2.5 or 5.0 μm. Plants grew to maturity under greenhouse conditions and gave normal fruits. Cotyledon explants were transformed by cocultivation with Agrobacterium tumefaciens LBA4404 carrying the binary vector pBI121 which bears the reporter gene β-glucuronidase (gus) and the marker gene neomycin phosphotransferase (nptII). Transformants were selected for growth capacity on medium with 100 mgl^–1 of kanamycin. On the basis of β-glucuronidase expression, the transformation frequency was 14.2%. Molecular characterization by polymerase chain reaction confirmed the presence of the two genes transferred (gus, nptII) in the transgenic plants. Sexual transmission of both genes was also confirmed by studying their expression in progenies from several transgenic plants. Received: 9 May 1996 / Revision received: 3 December 1996 / Accepted: 20 January 1997     

Salicylic acid changes morpho-physiological attributes of feverfew (Tanacetum parthenium L.) under salinity stress

Feverfew (Tanacetum parthenium) (TP) is a valuable medicinal plant from Asteraceae family with various pharmaceutical and therapeutic properties. A pot experiment was conducted to evaluate the effect of salicylic acid (SA) on the physiological and morphological responses of TP under salinity stress. Salinity was induced by NaCl and CaCl₂ (2:1) at 30, 60, 90, 120, 150 and 180 mM levels. SA was applied as foliar application at 0, 200 and 300 ppm concentrations. Plant height, leaf and shoot number, fresh and dry weight and essential oil, starch, sugar, protein, proline, catalase (CAT), peroxidase (POD), and ascorbic peroxidase (APX) contents were as measured morpho-physiological traits. The results showed that SA significantly (P ≤ 0.05) improved the measured traits and caused higher tolerance in TP plants under salinity stress. The essential oil content increased with increasing the salinity level up to 90 mM, which was more significant when combined with SA application. All of the measured traits except proline content, antioxidant enzymes, essential oil and sugar decreased at high salinity levels.     

Evaluation and selection of reliable reference genes for gene expression under abiotic stress in cotton (Gossypium hirsutum L.)

Reference genes are critical for normalization of the gene expression level of target genes. The widely used housekeeping genes may change their expression levels at different tissue under different treatment or stress conditions. Therefore, systematical evaluation on the housekeeping genes is required for gene expression analysis. Up to date, no work was performed to evaluate the housekeeping genes in cotton under stress treatment. In this study, we chose 10 housekeeping genes to systematically assess their expression levels at two different tissues (leaves and roots) under two different abiotic stresses (salt and drought) with three different concentrations. Our results show that there is no best reference gene for all tissues at all stress conditions. The reliable reference gene should be selected based on a specific condition. For example, under salt stress, UBQ7, GAPDH and EF1A8 are better reference genes in leaves; TUA10, UBQ7, CYP1, GAPDH and EF1A8 were better in roots. Under drought stress, UBQ7, EF1A8, TUA10, and GAPDH showed less variety of expression level in leaves and roots. Thus, it is better to identify reliable reference genes first before performing any gene expression analysis. However, using a combination of housekeeping genes as reference gene may provide a new strategy for normalization of gene expression. In this study, we found that combination of four housekeeping genes worked well as reference genes under all the stress conditions.     

Influence of abiotic factors on bacterial proliferation and anoxic survival of the sea mussel Mytilus edulis L.

The effect of several abiotic factors (salinity, temperature and pH) on bacterial proliferation and survival time of the sea mussel Mytilus edulis L. were studied under anoxic incubations. In addition, the presence in the incubation media of ammonium and the volatile fatty acids propionate and acetate, both excreted fermentation products of the bivalve, was tested.Anoxic incubations with seawater diluted with demineralised water showed at the lowest salinity (50% seawater, SW) a significant increase in the capacity of M. edulis to survive anoxia as compared to both 75% SW and control [100% SW, corresponding to 32 practical salinity units (psu)]. Formation of biotic sulphide and ammonium occurred in all incubations. However, bacterial proliferation was postponed by 2-3 days at lowest salinity and accordingly, concentrations of both compounds were lower. Anoxic survival profiles of mussels collected from different habitats in the Dutch Scheldt area, characterised by differences in salinity (range from 17 to 31 psu), corresponded with the above salinity effect. Walsoorden mussels (17 psu) showed the longest (P<0.001) survival time under anoxia (LT₅₀=17.2 days) as compared with Paulina (27 psu) and Wemeldinge (31 psu) mussels (LT₅₀=12.8 and 9.8 days, respectively). Condition index (ratio of soft body weight to shell volume) was not correlated with anoxic survival time in untreated mussels, although this was clearly the case when the antibiotic chloramphenicol was added to the anoxic seawater.Acidification of the anoxic incubation medium had a positive effect on survival time. LT₅₀ values significantly (P<0.001) increased from 10.2 days at pH 8.1 to 11.6 and 11.5 days at pH 7.3 and 6.5, respectively. Biotic sulphide and ammonium accumulation as well as bacterial numbers were significantly lower at pH 7.3 and 6.5 as compared with pH 8.1. Anoxic incubations at 10 °C (LT₅₀=12.0 days) strongly increased survival time as compared to 18 °C (LT₅₀=5.9 days). The benefit of antibiotic addition was also stronger at lower temperature (10 °C).Addition of both propionate and acetate (0.5 mM) displayed no effect on mortality of mussels under anoxia, but ammonium (0.5 mM) caused a negative effect (P<0.001). Biotic sulphide and ammonium concentrations measured in both volatile fatty acid incubations were lower than the control situation, as well as total bacterial numbers.This study shows that environmental factors play a significant role in determining the course of bacterial infection and death of bivalves exposed to anoxia.     

Physiological responses of groundnut (Arachis hypogea L.) to drought stress and its amelioration: a critical review

Groundnut (Arachis hypogea L.), is an important legume cash crop for the tropical farmers and its seeds contain high amounts of edible oil (43–55%) and protein (25–28%). Even though it is a fairly drought-tolerant, production fluctuates considerably as a result of rainfall variability. To develop a water stress response function in groundnut, research works have been done to improve the performance under varying degrees of stress at various physiological stages of crop growth. This review summarizes recent information on drought resistance characteristics of groundnut with a view toward developing appropriate genetic enhancement strategies for water-limited environments. It is suggested that there are considerable gains to be made in increasing yield and stabilizing the yield in environments characterized by terminal drought stress and by shortening crop duration. Many traits conferring dehydration avoidance and dehydration tolerance are available, but integrated traits, expressing at a high level of organization are suggested to be more useful in crop improvement programs. Possible genetic improvement strategies are outlined, ranging from empirical selection for yield in drought environments to a physiological–genetic approach. It was also suggested that in view of recent advances in understanding drought resistance mechanisms, the later strategy is becoming more feasible. It is summarized that application of knowledge into practice in a systematic manner can lead to significant gains in yield and yield stability of the worlds groundnuts production. Research is needed to develop transferable technology to help farmers of arid and semi-arid regions. Increasing soil moisture storage by soil profile management and nutrient management for quick recovery from drought are some of the areas that need to be explored further.     

甘薯基因组 TCP转录因子鉴定与逆境胁迫表达分析

基于甘薯( Ipomoea batatas ( L.) Lam.)全基因组序列, 利用生物信息学方法鉴定筛选了全基因组中的TCP( teosinte branched1/cincinnata/proliferating cell factor)转录因子, 并分析了甘薯苗期在蔓割病菌胁迫及块根储藏期低温胁迫下TCP基因的...     

Spatial distribution of Crinum americanum L. in tropical blind estuary: Hydrologic, edaphic and biotic drivers

The competitive abilities of a given species are inversely proportional to its tolerance to environmental stress. Thus, in estuaries, vegetation is generally controlled by salinity and flooding in their lower limits, and by biotic drivers in their upper limits. Crinum americanum L. is vastly distributed over flooded regions of American seacoast, frequently associated with stressful habitats. We aimed to explain the role of hydrologic, edaphic, and biotic drivers in the distribution of this species on the Massaguaçu River estuary, Southeastern Brazil (23°37′20″S and 54°21′25″W). We sampled randomly 400 plots in the estuary, and registered covering of all species, the height of the C. americanum individuals, and the relative height of the plots. We collected soil samples from every five plots. We measured the estuary level daily for two years. We used Correspondence Analysis, Simple and Canonical, and graphic analysis. The salinity has explained the major part of the observed pattern, and the C. americanum population was positively related to it. The estuary level was also important. C. americanum has presented higher densities in intermediary flooding classes than in the extremes of the gradient. Species reduction in regions of low salinity or its absence has probably been due to the highly competitive environment, and not to the lack of salt per se.