Effect of heterogeneous distribution of nutrients on root growth, ABA content and drought resistance of wheat plants

Heterogeneous distribution of nutrients influenced morphology of wheat roots; they were shorter and had more laterals at the site of high nutrient content. The roots outside the nutrient-rich patch were longer and penetrated deeper in the soil than those of the plants supplied with the same quantity of nutrients but having them homogeneously distributed. The ABA content of roots sampled from the site of high nutrient content was greater than in those elsewhere. It is suggested that this might be important for inhibition of their extension growth and stimulation of laterals in the nutrient rich patch. Heterogeneously distributed nutrients beneficially influenced accumulation of ¹⁵N and assimilation of CO₂ by the plants, enabling an increased supply of nutrients to the parts of the root system beyond the nutrient rich patch and sustained their rapid extension. Enhanced penetration of roots into the deeper soil layers could contribute to the observed increase in drought resistance of plants grown with localised placement of fertilisers under field conditions.     

Effects of preliminary heat-shock treatment on accumulation of osmolytes and drought resistance in cotton plants during water deficiency

To elucidate how plants adapt to overheating followed by water deficiency, experiments with two cotton ( Gossypium hirsutum L.) cultivars (Ok-oltin and INEBR-85) were performed. Preliminary heat-shock (HS) treatment (45°C for 1.5 h) increased resistance of both cultivars to subsequent progressive soil drought [40 days without watering, with soil moisture gradually decreasing from 70 to 20% of field moisture capacity (FMC)]. HS induced accumulation of amino acids and amides and increased their contribution to the osmotic pressure (OP) of the leaf cell sap. HS also enhanced resistance to water deficiency and to overheating of the leaves, especially in cv. INEBR-85, the more drought resistant of the two cultivars. The results suggest the existence of common resistance systems to both stress factors, in particular, accumulation of amino acids and amides (mainly arginine, proline and asparagine) – their concentration in the cell sap increased up to 240-, 160- and 150-fold, respectively.     

Effect of cadmium on growth and respiration of barley plants grown under two temperature regimes

We studied cadmium effect on the respiratory pathways ratio in the organs of barley (Hordeum distichum L., cv. Novichok) plants grown in water culture at two temperature regimes. Mineral nutrients were supplied daily in exponentially increasing amounts in order to provide for steady-state growth. CdSO₄ (30, 60, or 100 μmol/l) was added to nutrient solution at a single time in the beginning of the exponential growth period (19 days after germination). In further 6 days, the relative growth rate and biomass accumulation declined stronger with the increase in the cadmium concentration in plants grown at 13/8°C (day/night) than at 21/17°C (day/night). Cadmium suppressed root respiration (down to 60% of control) stronger than leaf respiration, and the roots manifested a higher sensitivity to the inhibitor of alternative oxidase, salicylhydroxamic acid. The respiratory pathways ratio in the roots occurred against the background of activated lipid peroxidation (POL). The highest POL activity and the highest proportion of alternative respiration pathway (AP) (up to 46% of total respiration) were observed in the roots in the presence of the highest cadmium concentration (100 μM) under lower temperature (13/8°C). Thus, high cadmium concentrations affected strongly the total rate of respiration and respiratory pathways ratio. Growth temperature modulated Cd effects on respiration. AP activation is one of the mechanisms for maintenance of root cell homeostasis under cadmium-induced stress.     

不同覆盖物对烤烟根温及生长和生理特性的影响

分别以大棚膜、稻草+大棚膜、普通膜、稻草、稻草+遮阳网和遮阳网为覆盖材料,研究覆盖物对烤烟根温以及生长和生理特性的影响.结果表明,各覆盖处理22 d对5和15 cm土壤总积温的影响明显不同,5 cm土壤总积温最高为大棚膜处理（424.75 ℃）,最低为稻草+遮阳网处理（378.75 ℃）,22 d 的15 cm土壤总积温最高为大棚膜处理（396.75 ℃）,最低为遮阳网处理（368.31 ℃）.随着土壤总积温的升高,烟株地上部和地下部干重都呈增长趋势,光合作用增强,根系活力提高;揭膜后第10天烟株根系干重有所增加,普通地膜处理的根系生物量增加最多,稻草+遮阳网处理最少.     

木本植物水力结构与抗旱性

着重介绍了水力结构及其种种上参数（即导水率Ｋｈ、比导率Ｋｓ、叶比导率ＬＳＣ、胡伯尔值Ｈｖ以及水溶量Ｃ）的生理意义,树木和其它木本植物的水力结构格局以及树木水力结构研究的发展趋势,并试图从机理上阐述树木力结构和抗旱性之间的关系。     

Optimal temperature drop for the growth and development of young cucumber plants

The thermomorphological responses of young cucumber plants to a temperature drop lasting 2, 4 and 6 hours applied at the beginning, in the middle and at the end of the night were examined. Plant height, leaf petiole length and plant dry weight were measured and, based on the experimental data, the regression dependences of growth variables on the temperature drop were fitted. A method to determine the optimal temperature drop (the duration and time of exposure) which results in shortened plant height and leaf petiole length without a decrease in plant dry weight is proposed.     

温度对火鹤花生长发育的影响

本文就温度对火鹤花生长发育的影响进行研究,结果表明,全年中日均温15℃的时段,火鹤花产量和品质最差,并造成寒害;日均温29.5℃的时段,有轻微高温伤害;日均温26℃时段最适于火鹤花生长,此时切花品质最好.     

Influence of temperature and water potential on root growth of white oak

Root growth of white oak ( Quercus alba L.) was observed under field conditions using a rhizotron. The effects of temperature, soil water potential, and leaf water potential were evaluated on three measures of root growth and development: root elongation rate, number of growing roots, and root growth intensity (sum of projected root area compared to the total root viewing area). Root elongation rate was linearly related to changes in soil temperature and soil water potential. At soil temperatures less than 17deg;C, temperature was the dominant factor affecting rate of growth, bat at temperatures greater than 17°C soil water potential became the important factor. Unlike root elongation rate, the number of growing roots and root growth intensity increased at cold soil temperatures (8°C) and at soil water potentials of-0.3 to -0.8 MPa. At high soil water potentials (-0.1 MPa) root elongation rate reached a maximum while the number of growing roots and root growth intensity were low. These differences showed that root growth and development were not exclusively affected by the soil environment. In addition, the relationship between root growth and predawn leaf water potential suggested that root growth was a contributing factor to the drought resistance of white oak.     

Interactive effects of elevated carbon dioxide and growth temperature on photosynthesis in cotton leaves

Cotton (Gossypium hirsutum L., cv DPL 5415) plants were grown in naturally lit environment chambers at day/night temperature regimes of 26/18 (T-26/18), 31/23 (T-31/23) and 36/28 °C (T-36/28) and CO2 concentrations of 350 (C-350), 450 (C-450) and 700 L L-1 (C-700). Net photosynthesis rates, stomatal conductance, transpiration, RuBP carboxylase activity and the foliar contents of starch and sucrose were measured during different growth stages. Net CO2 assimilation rates increased with increasing CO2 and temperature regimes. The enhancement of photosynthesis was from 24 mol CO2 m-2 s-1 (with C-350 and T-26/18) to 41 mol m-2 s-1 (with C-700 and T-36/28). Stomatal conductance decreased with increasing CO2 while it increased up to T-31/23 and then declined. The interactive effects of CO2 and temperature resulted in a 30% decrease in transpiration. Although the leaves grown in elevated CO2 had high starch and sucrose concentrations, their content decreased with increasing temperature. Increasing temperature from T-26/18 to 36/28 increased RuBP carboxylase activity in the order of 121, 172 and 190 mol mg-1 chl h-1 at C-350, C-450 and C-700 respectively. Our data suggest that leaf photosynthesis in cotton benefited more from CO_2 enrichment at warm temperatures than at low growth temperature regimes.     

Effect of far-red light on malate and potassium contents in cotton leaves: Relation to drought resistance

Long- or short-term far-red light given before a dark treatment modified the water status and the potassium and malate contents in cotton ( Gossypium hirsutum L. cv. Bou) leaves. Upon a long-term treatment, the leaf water content and the leaf water and osmotic potentials were lower whereas stomatal resistance was greater with a decrease in daily transpiration. There was a parallel increase in potassium and malate, but the calcium content was not significantly changed. This resulted in better water economy with an increase in drought resistance. Upon a short-term treatment, the accumulation of potassium and malate was reversible and the drought resistance was modified accordingly. There was a positive correlation between the ability of a plant to resist water stress and the content of potassium and malate.     

秸秆覆盖量对红壤旱地棉花生长及土壤温度的影响

为探索红壤旱地较适宜的秸秆覆盖量,采取随机区组大田试验,设置4个秸秆覆盖水平:S1为0 kg/hm~2、S2为4375 kg/hm~2,S3为8750 kg/hm~2和S4为13125 kg/hm~2,研究秸秆覆盖量对红壤旱地棉花产量、出苗率、株高、叶绿素含量和土壤温度的影响。结果表明:秸秆覆盖处理(S2—S4)较不覆盖处理(S1),一是提高棉花出苗率,差异极显著(P0.01);二是影响棉花生育后期的主茎生长速度,以S4效果最好;三是可明显促进棉花叶绿素含量的增加,且以S3和S4的效果较好;四是调节土壤温度,在8:00和20:00提高土壤温度,在14:00降低土壤温度,且日均地温变化幅度小,但随着土层的加深,调温作用逐渐减弱,整个覆盖期内日均温的差值与土壤深度具有高度的相关性;五是显著增加棉花产量,S2、S3和S4分别比S1高11.4%、35.9%和37.7%,差异极显著(P0.01),且随着覆盖量的增加,增产效果逐渐提高。综合来看,秸秆覆盖在改善红壤旱地棉花产量、出苗率、株高、叶绿素含量、调节土壤温度方面发挥着重要作用,且以8750—13125 kg/hm~2效果显著,是红壤旱地值得推广的栽培模式。     

The effect of root temperature on growth of curled parsley

Summary Curled parsley was grown at root-zone temperature (RZT) of 18, 21, 24, 27 and 36°C at air temperature (AT) of 18 and 21°C. Maximum growth was obtained at 18°C AT and 24°C RZT, but there were no significant differences between 18 and 27°C RZT. Shoot and root growth were severely inhibited at 36°C constant RZT. The growth was also retarded when RZT rose to 36°C for 30 minutes per day, even when compared to a RZT of constant 27°C. This indicates that a short exposure to RZT above 30°C retards growth. A relatively low daily average RZT did not compensate for the damage caused by a short daily high temperature exposure. Optimum temperature for curled parsley seems to be about 21°C. Report No. 316.     

不同温度和寄主植物对扶桑绵粉蚧生长发育的影响

为明确温度和寄主对扶桑绵粉蚧Phenacoccus solenopsis生长发育的影响,本文在室内研究了不同温度和不同寄主上该虫的发育历期、发育起点温度、有效积温、成虫性比和存活率,结果表明:18℃-30℃范围内,随着温度升高,扶桑绵粉蚧发育历期逐渐缩短,34℃与30℃下无明显差异。该虫不同虫期发育起点温度均较高,其中2龄雄若虫和雌若虫最高,分别为19.11℃、16.14℃,蛹最低,为12.22℃。有效积温蛹最大,为87.40日·度,1龄若虫次之(77.12日·度),2龄雄若虫最小(26.32日·度)。18℃-30℃时各虫期死亡率随着温度升高而降低,34℃时又有升高。取食4种寄主时扶桑绵粉蚧发育历期有所变化,1龄若虫番茄上显著长于马铃薯;2龄雌雄若虫番茄上显著长于扶桑和马铃薯;3龄雌若虫以烟草和番茄上较长,扶桑和马铃薯上较短;雄蛹、雄成虫历期均无差异;烟草上雌成虫存活时间最长;雌虫整个虫期存活时间最长,为53.77 d,番茄次之(48.65 d),扶桑、马铃薯较短,分别为43.39 d、39.79 d。雄虫整个虫期存活时间烟草明显长于扶桑。不同寄主上扶桑绵粉蚧雌雄虫比率差异较大,以马铃薯上雄虫率最高(37.78%),其次为扶桑(26.67%),烟草上最低(8.01%)。     

Further studies of drought resistance in woody plants

This publication is an extension of the 1956 review of drought resistance in woody plants. The more important recently used terms are listed and defined. Summaries of reports of drought effects on forest trees are presented in tabular form. Frost-drought is discussed as an important factor in the limitation of woody plants’ geographical ranges. The role that droughts play in the initiation of tree diseases is considered, especially in the light of new evidence from studies of diebacks-declines of forest trees. Interactions between soil moisture and transpiration are discussed as well as ways to control transpiration in large stands. Also considered are drought experiments with tree seedlings and symptomatology of drought injury. The means by which woody plants survive drought (excluding ephemerals) are discussed.     

短时间高温处理对棉蚜存活的影响

为探索棉蚜Aphis gossypii Glover种群动态与高温的关系,研究了不同温度(30、34、38、42、46℃)、不同处理时间(1、2、5、8h)对棉蚜存活的影响。结果表明:在同一处理时间条件下,棉蚜的存活率随着温度的升高而降低;在同一处理温度下,棉蚜的存活率随处理时间的延长而降低。30～38℃温度范围内,棉蚜存活率降低缓慢,从42℃开始棉蚜的存活率迅速降低。棉蚜半数致死温度随着处理时间的延长而降低;相同处理时间条件下,若蚜半数致死温度高于成蚜,若蚜较成蚜更耐高温。     

Effect of temperature on growth parameters of psychrophilic bacteria and yeasts

Three bacterial (Pedobacter heparinus, Pedobacter piscium, Pedobacter cryoconitis) and three yeast strains (Saccharomyces cerevisiae, Leucosporidiella creatinivora, Rhodotorula glacialis) of different thermal classes (mesophiles and psychrophiles) were tested for the effect of temperature on a range of growth parameters, including optical density, viable cell numbers, and cell dry mass, in order to determine the temperature conditions under which maximum biomass formation is obtained. Maximum values of growth parameters obtained at the stationary growth phase of the strains were used for statistical calculation. Temperature had a significant (P ≤ 0.05) effect on all growth parameters for each strain; correlations between the growth parameters were significant (P ≤ 0.05–0.01). The maximum growth temperature or the temperature at which microbial growth was fastest was in no case the temperature at which the investigated strains produced the highest amount of biomass. All tested psychrophilic bacteria and yeast strains produced highest amounts of cells (as calculated per mg cell dry mass or per OD₆₀₀ unit) at 1°C, while cell numbers of mesophiles were highest at 20°C. Thus, cultivation temperatures close to the maximum growth temperature are not appropriate for studying psychrophiles.     

Effect of temperature on the progamic phase in high-mountain plants

Progamic processes are particularly temperature-sensitive and, in lowland plants, are usually drastically reduced below 10 °C and above 30 °C. Little is known about how effectively sexual processes of mountain plants function under the large temperature fluctuations at higher altitudes. The present study examines duration and thermal thresholds for progamic processes in six common plant species (Cerastium uniflorum, Gentianella germanica, Ranunculus alpestris, R. glacialis, Saxifraga bryoides, S. caesia) from different altitudinal zones in the European Alps. Whole plants were collected from natural sites shortly before anthesis and kept in a climate chamber until further processing. Flowers with receptive stigmas were hand-pollinated with allopollen and exposed to controlled temperatures between -2 and 40 °C. Pollen performance (adhesion to the stigma, germination, tube growth, fertilisation) was quantitatively analysed, using the aniline blue fluorescence method. Pollen adhesion was possible from -2 to 40 °C. Pollen germination and tube growth occurred from around 0 to 35 °C in most species. Fertilisation was observed from 5 to 30-32 °C (0-35 °C in G. germanica). The progamic phase was shortest in G. germanica (2 h at 30 °C, 12 h at 5 °C, 24 h at 0 °C), followed by R. glacialis (first fertilisation after 2 h at 30 °C, 18 h at 5 °C). In the remaining species, first fertilisation usually occurred after 4-6 h at 30 °C and after 24-30 h at 5 °C. Thus, mountain plants show remarkably flexible pollen performance over a wide temperature range and a short progamic phase, which may be essential for successful reproduction in the stochastic high-mountain climate.     

Effect of temperature on growth and chemotactic behaviour of Campylobacter jejuni

AIM: To determine the effect of two physiologically important temperatures on growth and chemotaxis in Campylobacter jejuni. METHODS AND RESULTS: Growth curves of Camp. jejuni were compared at 37 degrees C and 42 degrees C. Chemotaxis was compared at 37 degrees C and 42 degrees C by the disc and capillary assays. Student's t-test was applied to the results of the capillary assay to assess the significance in the difference between chemotaxis at the two temperatures. Both, the growth rate and chemotactic ability of the isolate, were found to be greater at 37 degrees C. CONCLUSIONS: Quorum sensing (related to population density), a regulation mechanism of virulence in micro-organisms, has been reported in Campylobacter. Chemotaxis is also a known virulence factor of Campylobacter. Both, growth (in terms of population density) and chemotaxis, being greater at 37 degrees C than at 42 degrees C, suggests that the physiological temperature of humans (37 degrees C) might be more favourable for the expression of virulence in Campylobacter than that of birds (42 degrees C). SIGNIFICANCE AND IMPACT OF THE STUDY: It is as yet not known why Campylobacter causes disease in humans but is avirulent in birds. This study suggests that the human body temperature is optimum for growth and chemotaxis in Campylobacter. There is scope for the study of temperature regulation of other virulence determinants of Campylobacter.