Coronatine Alleviates Water Deficiency Stress on Winter Wheat Seedlings

With the aim to determine whether coronatine(COR) alleviates drought stress on wheat,two winter wheat(Triticum aestivum L.) cultivars,ChangWu134(drought-tolerant) and Shan253(drought-sensitive) were studied under hydroponic conditions.Seedlings at the three-leaf stage were cultured in a Hoagland solution containing COR at 0.1 μM for 24 h,and then exposed to 20% polyethylene glycol 6000(PEG6000).Under simulated drought(SD),COR increased the dry weight of shoots and roots of the two cultivars significantly;the root/shoot ratio also increased by 30% for Shan253 and 40% for ChangWu134.Both cultivars treated with COR under SD(0.1COR+PEG) maintained significantly higher relative water content,photosynthesis,transpiration,intercellular concentration of CO2 and stomatal conductance in leaves than those not treated with PEG.Under drought,COR significantly decreased the relative conductivity and malondialdehyde production,and the loss of 1,1-diphenyl-2-picrylhydrazyl scavenging activity in leaves was significantly alleviated in COR-treated plants.The activity of peroxidase,catalase,glutathione reductase and ascorbate peroxidase were adversely affected by drought.Leaves of plants treated with COR under drought produced less abscisic acid(ABA) than those not treated.Thus,COR might alleviate drought effects on wheat by reducing active oxygen species production,activating antioxidant enzymes and changing the ABA level.     

The Transport of Water from Soil to Shoot in Wheat Seedlings

A technique is described for precisely measuring the drop inwater potential, , between the soil and the leaf xylem of wheatseedlings. The technique was used to explore the relation betweentranspiration rate and at various times during the monotonicdrying of the soil in which the plants were growing. When thesoil was wet, the relation was linear, but, as the soil dried,nonlinearities appeared which were, in the main, explicablein terms of simple soil physical models describing the flowof water through the soil to the roots. There was no sign ofthe major hydraulic resistance at the root: soil interface thatother people have recently found.     

水分胁迫对小麦幼苗叶片多胺含量的影响

水分胁迫下小麦幼苗叶片多胺含量变化的研究表明,聚乙二醇(PEG)的渗透胁迫明显提高了抗旱性强的周麦系列幼苗叶片游离态Put、Spd和Spm的含量和抗旱性弱的温麦6号的Put含量。外源Spd显著提高了水分胁迫下温麦6号的Spd的含量,对其抗性也有所改善。外源MGBG(Spd和Spm生物合成抑制剂)可提高水分胁迫下周麦12号Put的含量,但降低了Spd和Spm的含量和幼苗的抗性。     

Comparative Effects of Benzoic Acid and Water Stress on Wheat Seedlings

In the present study, we compared the effects of allelochemical, water stress (WS) and their combinations on seedling growth, biochemical parameters and responses of antioxidative enzymes in Triticum aestivum L. The wheat seedlings were treated with 0.5, 1.0 and 1.5 mM concentrations of benzoic acid (BA), with and without water stress. Leaf water status, photosynthetic pigments, protein content, amount of proline and activities of nitrate reductase and antioxidant enzymes were examined. Allelopathic stress resulted in reduction of seedling height. Height of water stressed seedlings greatly decreased. The combined treatments, BA + WS further decreased the seedling height. BA treatment with and without water stress caused significant reduction in dry weight of the seedlings. BA and water stress decreased relative water content, pigments and protein content. Total soluble sugar content and nitrate reductase activity were variedly affected under all treatments. Proline content and lipid peroxidation increased in treatments with BA and water stress. Activity of superoxide dismutase increased significantly (P < 0.05) while catalase activity decreased in all treatments. Ascorbate peroxidase and guaiacol peroxidase activities were higher as compared with catalase which seems to protect wheat seedlings from oxidative stress. Water stress elevated the toxic effect of allelochemical.     

Resistance to Water Flow in the Seminal Roots of Wheat

Water uptake by the seminal root system of wheat is describedby a model which incorporates radial and axial resistance toflow in the root and the resistance to flow in the soil. Inan experiment where wheat plants were dependent on subsoil waterextracted from below 45 cm by one, three, or five seminal roots,calculations indicated that the axial resistance was the dominantresistance within the soil-root system and that flow rate changedpredictably with changing axial resistance. The model also indicatedthat the observed shape of the metaxylem vessel in the seminalaxes has important effects on the pattern of water uptake.     

小麦幼芽水分胁迫诱导蛋白的特征

水分胁迫（－1．2MPaPEG-6000）处理萌动的小麦种子,24h后诱导小麦幼芽产生41．5kD蛋白,其含量随着胁迫时间延长明显增加,48h时含量最高,到72h后不再变化。复水后,该蛋白消失;再胁迫48h时则又出现,其含量与处理24h时相当。41．5kD诱导蛋白主要位于细胞器膜上,细胞质中几乎不存在。41．5kD蛋白主要溶于10％NaCl提取液中,其等电点为pl5．65。该蛋白的氨基酸组成中,脯氨酸含量最高,其次为丙氨酸、天冬氨酸、谷氨酸、甘氨酸,没有发现半胱氨酸和组氨酸。     

He-Ne激光对水分胁迫下小麦幼苗生理特性的影响

用He-Ne激光(5.23×10-3W.mm-2)处理经不同浓度PEG6000胁迫的小麦幼苗,研究水分胁迫条件下激光辐照对小麦幼苗生理特性的影响。结果表明,He-Ne激光辐照可显著提高水分胁迫下小麦幼苗的根系活力以及抗坏血酸过氧化物酶(APX)和谷胱甘肽还原酶(GR)活性(P<0.05),并使其脯氨酸含量显著增加(P<0.05),而对其超氧化物歧化酶(SOD)的活性没有显著影响。可见,He-Ne激光可通过提高根系活力、抗氧化酶活性和脯氨酸含量来显著增强小麦幼苗的抗旱性。     

Leaf Response to Water Deficits in Soybeans

Soybeans [Glycine max (L.) Merrill cv. Wayne] plants were subjected to an extended drying cycle in the field to investigate the leaf sensitivity to water deficits. Soybeans in irrigated plots were superior to those in non-irrigated plots in the average size and number of leaflets per plant. Apparent differences in the leaf area distributions in the canopy seemed to be mediated by moisture stress effects associated with leaf senescence and light penetration in the lower depths of the canopy. A major decrease in leaf enlargement occurred near a leaf-water potential of -8 bars, and at - 12 bars, the growth was completely halted. Similar decreases were observed at a stomatal conductance of 0.4 cm/s and at 0.2 cm/s no enlargement was observed.     

Oculomotor Deficits after Chemotherapy in Childhood

Advances in the diagnosis and treatment of pediatric malignancies have substantially increased the number of childhood cancer survivors. However, reports suggest that some of the chemotherapy agents used for treatment can cross the blood brain barrier which may lead to a host of neurological symptoms including oculomotor dysfunction. Whether chemotherapy at young age causes oculomotor dysfunction later in life is unknown. Oculomotor performance was assessed with traditional and novel methods in 23 adults (mean age 25.3 years, treatment age 10.2 years) treated with chemotherapy for a solid malignant tumor not affecting the central nervous system. Their results were compared to those from 25 healthy, age-matched controls (mean age 25.1 years). Correlation analysis was performed between the subjective symptoms reported by the chemotherapy treated subjects (CTS) and oculomotor performance. In CTS, the temporal control of the smooth pursuit velocity (velocity accuracy) was markedly poorer (p<0.001) and the saccades had disproportionally shorter amplitude than normal for the associated saccade peak velocity (main sequence) (p = 0.004), whereas smooth pursuit and saccade onset times were shorter (p = 0.004) in CTS compared with controls. The CTS treated before 12 years of age manifested more severe oculomotor deficits. CTS frequently reported subjective symptoms of visual disturbances (70%), unsteadiness, light-headedness and that things around them were spinning or moving (87%). Several subjective symptoms were significantly related to deficits in oculomotor performance. To conclude, chemotherapy in childhood or adolescence can result in severe oculomotor dysfunctions in adulthood. The revealed oculomotor dysfunctions were significantly related to the subjects’ self-perception of visual disturbances, dizziness, light-headedness and sensing unsteadiness. Assessments of oculomotor function may, thus, offer an objective method to track and rate the level of neurological complications following chemotherapy.     

Carotenoid Synthesis in Leaves of Etiolated Wheat Seedlings after Varying Light and Dark Treatments

A short impulse of red light has a varying effect on carotenoid synthesis in dark-grown wheat seedlings. Except for β-carotene, which remains unchanged in the dark (it increases in continuous light), the carotenoid synthesis shows the same tendency as during constant irradiation. Thus, lutein and neoxanthin slowly increases, while violaxanthin decreases. During a period of constant light following various periods of darkness after the short impulse of light, the pigment changes correspond to those occurring in the dark, but are much more pronounced. The changes are discussed on the basis of phytochrome action.     

Response of Indoor-Grown Cassava to Water Deficits and Recovery of Leaf Water Potential and Stomatal Activity after Water Stress

Wilting of the leaves occurred in acropetal succession at leafwater potentials between –0.9 and –1.1 MPa. Onlysevere water stress caused the discoloration and abscissionof the basal leaves. Leaf resistance was independent of leafwater potential above –0.5 MPa but increased as the potentialdropped below this value. When the stressed plants were rewatered,leaf water potentials recovered rapidly within the first h.Subsequently, the rate of recovery declined gradually. The maximumvalue of leaf water potential after rewatering was dependenton the severity of the water stress.     

Amantadine Ameliorates Dopamine-Releasing Deficits and Behavioral Deficits in Rats after Fluid Percussion Injury

Aims

To investigate the role of dopamine in cognitive and motor learning skill deficits after a traumatic brain injury (TBI), we investigated dopamine release and behavioral changes at a series of time points after fluid percussion injury, and explored the potential of amantadine hydrochloride as a chronic treatment to provide behavioral recovery.

Materials and Methods

In this study, we sequentially investigated dopamine release at the striatum and behavioral changes at 1, 2, 4, 6, and 8 weeks after fluid percussion injury. Rats subjected to 6-Pa cerebral cortical fluid percussion injury were treated by using subcutaneous infusion pumps filled with either saline (sham group) or amantadine hydrochloride, with a releasing rate of 3.6mg/kg/hour for 8 weeks. The dopamine-releasing conditions and metabolism were analyzed sequentially by fast scan cyclic voltammetry (FSCV) and high-pressure liquid chromatography (HPLC). Novel object recognition (NOR) and fixed-speed rotarod (FSRR) behavioral tests were used to determine treatment effects on cognitive and motor deficits after injury.

Results

Sequential dopamine-release deficits were revealed in 6-Pa-fluid-percussion cerebral cortical injured animals. The reuptake rate (tau value) of dopamine in injured animals was prolonged, but the tau value became close to the value for the control group after amantadine therapy. Cognitive and motor learning impairments were shown evidenced by the NOR and FSRR behavioral tests after injury. Chronic amantadine therapy reversed dopamine-release deficits, and behavioral impairment after fluid percussion injuries were ameliorated in the rats treated by using amantadine-pumping infusion.

Conclusion

Chronic treatment with amantadine hydrochloride can ameliorate dopamine-release deficits as well as cognitive and motor deficits caused by cerebral fluid-percussion injury.     

Nitrite Uptake by Nitrogen-Depleted Wheat Seedlings

Intact, 14-day-old nitrogen-depleted wheat (Triticum vulgare cv. Blueboy) seedlings were exposed to solutions of 0.5 mM KNO₂, 0.05 mM CaSO₄ and 1 mM sodium 2-[N-morpholino]-ethanesulfonate, pH 6.1. Nitrite uptake was determined from depletion of the ambient solution or from incorporation of ¹⁵N in the tissue. An initial nitrite uptake shoulder was followed by a relatively slow uptake rate which subsequently increased to a substantially greater rate. This accelerated phase was maintained through 24 h. Nitrite accumulated to a slight extent in the root tissues during the first few hours but declined to low values when the accelerated rate was fully developed, indicating an increase in nitrite reductase activity paralleling the increase in nitrite uptake capacity. About 50% of the nitrogen absorbed as nitrite was translocated to the shoots by 9–12 h. Development of the accelerated nitrite uptake rate was restricted in excised roots, in intact plants kept in darkness, by 400 μg puromycin ml^?1 and by 1 mM L-ethionine. When puromycin and L-ethionine were added after the accelerated phase had been initiated, their effects were not as detrimental as when they were added at first exposure to KNO₂. The two inhibitors restricted translocation more than uptake. The data indicate an involvement of protein synthesis and a requirement for movement of a substance from shoots to roots for maximal development of the accelerated nitrite uptake phase. A requirement for protein synthesis in the transport of soluble organic nitrogen from roots to shoots is also suggested.     

小麦幼苗根系镉螯合素

从经Cd~(2+)处理的小麦幼苗根系中分离得到一种镉结合复合物(Cd-BC)。通过SephadexG75,DEAE-52柱层析纯化,鉴定了此复合物性质:(1)紫外吸收光谱在255～265 tim间有一个“肩”,A_(250)/A_(280)>1;(2)在Sephadex G75柱层析上的表观分子量约为10kD,但在SDS-聚丙烯酰胺凝胶电泳上呈现的条带紧接着前沿,分子量非常小;(3)氨基酸组分分析,约90％的氨基酸残基为Glu/Gln,Cys和Gly,三者比例约为4:4:1。结果说明小麦幼苗根系Cd-BC是寡聚肽,是植物镉螯合素(Cd-PCs)的聚合体。     

Apoptosis in Wheat Seedlings Grown under Normal Daylight

Apoptosis was observed in the coleoptile and initial leaf in 5-8-day-old wheat seedlings grown under normal daylight. Apoptosis is an obligatory event in early wheat plant ontogenesis, and it is characterized by cytoplasmic structural reorganization and fragmentation, in particular, with the appearance in vacuoles of specific vesicles containing intact organelles, chromatin condensation and margination in the nucleus, and internucleosomal fragmentation of nuclear DNA. The earliest signs of programmed cell death (PCD) were observed in the cytoplasm, but the elements of apoptotic degradation in the nucleus appeared later. Nuclear DNA fragmentation was detected after chromatin condensation and the appearance in vacuoles of specific vesicles containing mitochondria. Two PCD varieties were observed in the initial leaf of 5-day-old seedlings grown under normal daylight: a proper apoptosis and vacuolar collapse. On the contrary, PCD in coleoptiles under various growing (light) conditions and in the initial leaf of etiolated seedlings is only a classical plant apoptosis. Therefore, various tissue-specific and light-dependent PCD forms do exist in plants. Amounts of O2*- and H2O2 evolved by seedlings grown under normal daylight are less than that evolved by etiolated seedlings. The amount of H2O2 formed in the presence of sodium salicylate or azide by seedlings grown under normal daylight was increased. Contrary to etiolated seedlings, the antioxidant BHT (ionol) did not inhibit O2*- formation and apoptosis and it had no influence on ontogenesis in the seedlings grown under normal daylight. Thus, in plants grown under the normal light regime the powerful system controlling the balance between formation and inactivation of reactive oxygen species (ROS) does exist and it effectively functions. This system is responsible for maintenance of cell homeostasis, and it regulates the crucial ROS level controlling plant growth and development. In etiolated plants, this system seems to be absent, or it is much less effective.     

Aspects of the Effect of ABA on the Water Status of Barley and Wheat Seedlings

The effect of abscisic acid on plant growth and survival during water deprivation was studied in barley and wheat seedlings. Under conditions of both limited and ample water supply, treatment with abscisic acid greatly reduced transpiration and, in addition, suppressed root growth. In water-deprived seedlings, abscisic acid increased the total dry matter, reflecting improved efficiency in water-use. In addition, the growth period and survival of water-deprived seedlings were markedly prolonged. In field trials, however, abscisic acid had no significant effect on waterdeprived seedlings. Possible reasons for this lack of response are discussed.     

强光诱导小麦叶片花青素积累的研究

以'小偃54'、'京411'等67份小麦品种(系)为试材,对强光诱导小麦叶片花青素积累的现象及品种间变异进行分析,以探讨花青素在小麦响应强光过程中的生理与分子机制.结果显示,'小偃54'和'京411'分别经25℃强光处理24 h和48 h叶片花青素含量大幅增加,而15℃和30℃强光处理增幅较小;强光处理48 h后,'京411'的花青素含量高达7.2 μg·g-1FW,约为'小偃54'的10倍.对'京411'而言,花青素含量随叶位自下而上递减,并且按叶鞘、叶基部、叶中部和叶尖的部位依次递减.强光处理24 h和48 h后能诱导'小偃54'和'京411'的PAL活性增强.强光处理48 h后,紫色胚芽鞘类品种的花青素含量高于绿色胚芽鞘类品种,不同品种强光下的花青素吸收峰均在520 nm处.研究表明,强光下叶片花青素含量升高可能是紫色胚芽鞘类小麦品种抗强光的一种机制.