Effect of Azolla Application and Plant Spacing on Rice Yield

Azolla is a small aquatic fern, that can be used as a green manure for irrigated rice before the transplanting of rice and under the rice crop. In a field experiment the interaction between Azolla application and rice spacing and its effect on the yield of rice in Azolla-rice dual culture were studied. The rice was planted in double-narrow-rows ([53 + 13] × 12cm) and in the regular 20 × 20cm spacing. Azolla was grown together with rice twice and also incorporated into the soil twice. Double-narrow-row planting slightly increased the Azolla growth, but reduced the grain yield due to the reduction of tillering by stronger competition between the rice plants. The Azolla application had no effect with double-narrow-rows. With 20 × 20cm spacing two Azolla crops had an effect equivalent to 15kg NH₄-N/ha. An appreciable amount of Azolla-N seemed to be available to the rice plants already 25 days after incorporation.     

Effect of Soil Temperature on the Carbohydrate Status in the Potato Plant (S. tuberosum L.)

Seed tubers of the variety Ostara were raised in growth chambers of 16°C air temperature continuously. The vessels were placed in a water bath of automatic temperature regulation so that soil temperatures of 16°C and 28°C could be maintained. Four weeks after emergence the plants were treated with ¹⁴CO₂ and 24 hours later the plants were harvested. Three more treatments and time harvests followed in two weeks intervals. C-14 activity was determined in soluble carbohydrates, in insoluble carbohydrates, and in non extractable residues respectively of the various plant parts in order to obtain information about the translocation of assimilates in the plant.
While the plants at 28°C soil temperature reduced the soluble sugar levels to 50% up to 70 days after emergence, the plants at 16° brought it down to 33% much faster. — The C-14 activity in insoluble carbohydrates amounted to only 50 % in the plants at 28°C while at 16°C it was more than 2/3 (Tables 1 and 2). — The C-14 activity in non extractable residues is much less at 28°C than at 16°C (Tables 3 and 4). — The starch weight reaches only 30% of the value obtained at lower temperature 70 days after emergence (Table 5). — At the higher temperature starch is also increasingly transferred to the tubers but to a much lesser extent and not from the stems and stolons (Table 6).
Possible causes, particularly the role of phytohormones, and consequences are discussed.     

Effects of Temperature on the Alkaloid Content of Seeds of Lupinus angustifolius Cultivars

Three experiments were conducted to investigate the effects of high temperatures during seed filling on the alkaloid content of narrow-leaf lupin cultivars. Six cultivars of Lupinus angustifolius were grown in field experiments under different weather conditions in four subsequent years. A high content of alkaloids was found in the seeds harvested in 2006, in which the growing season was characterized by high ambient temperatures during seed filling. A second experiment was performed in the green house at different temperatures (10, 20 and 30 °C) using one cultivar in 2006. This experiment confirmed the results of the field experiments as higher temperatures resulted in a higher alkaloid content of the seeds. In a third temperature stress experiment, three cultivars were grown under long day conditions at day/night temperatures of 30 °C/16 °C and 20 °C/16 °C in growth chambers in comparison with an outdoor control at mean temperatures of 15.5 °C. Like in the other experiments, the seed alkaloid content increased with rising temperature. From these results, it may be concluded that the seed alkaloid content is strongly influenced by the temperature during initiation of flowering up to pod ripening. This has to be taken into account e.g. in trials for cultivar release in which the alkaloid content is a knock-out criterion.     

Effect of Low Temperature of Irrigation Water on Rice Growth and Nutrient Uptake

The study was designed to investigate the effect of cold irrigation water on rice growth and on uptake of N, P, K and Zn applied ca. 50, 20, 35 and 5 mg kg⁻¹ soil, respectively. Cold temperature of irrigation water reduced rice shoot and root dry weight and plant height, significantly compared to hot temperature treatment. Under low temperature stress N was a major rice growth determinant. Increased shoot concentrations of both P and Zn allevated the low temperature stress. The uptake of N, P, K and Zn reduced significantly at low temperature (16.5–20 °C soil and 20–24 °C flood water) compared to high temperature (24.5–27 °C soil and 26.5–29.0 °C), with the strongest effect being noticed for N, followed by P, K and Zn. Application of N, P, K and Zn increased their uptake in rice shoots. Nitrogen and K had synergistic effect on their uptake. Responses to N and K application and their uptake behavior were well marked at higher than at low temperature whereas reverse was true for P and Zn.     

Micrometeorological Influences at High Crop Density on Different Genotypes of Silage Maize

In the year 1979, 1981 and 1982 two-factorial experiments with the factors genotypes and crop densities were conducted, connected with the following agrometeorological analyses:
a) outside the canopies: determination of air temperature, air humidity, wind velocity, precipitation, global radiation and photosynthetically active radiation (PAR)
b) in the interior of the canopies: measurements of air temperature at cobheight, of precipitation components, of the penetration of PAR and of the leaf area index.
The following results were obtained:
a) Influence of high crop densities
1. In high crop densities the greatest part of radiation was absorbed, so that at 30 plants/m² 57% and at 70 plants/m² only 28% of the PAR reached cob height.
2. As a consequence of temperature and decrease of radiation the contents in the leaves of biological energy, of water soluble K.H. and rough protein were reduced.
b) Influence of the leaf posture
3. For genotypes with erected leaf posture the leaf temperatures increased by 0.3°C, on the ground even by 1.2°C above the values of the stand with horizontal leaf posture.
4. Higher air temperatures were measured in the stands with erected leaf posture than in those with a horizontal one.
5. In the cool year 1981 on days with temperatures above 27°C outside the stands, those temperatures were exceeded during 7 hours in canopies with erected leaf posture at a higher plant density (30 plants/m²) and only during 2 hours in canopies with a horizontal leaf posture.     

Nitrogen Uptake by Rice (Oryza sativa L.) Exposed to Low Water Temperatures at Different Growth Stages

The responses of nitrogen (N) uptake by rice (Oryza sativa L.) to low water temperatures at different growth stages were examined during a 3‐year field trial in northern Japan. Cool irrigation water was applied at two to three temperature levels (16–25 °C) for 20–34 days during the vegetative stage and then during reproductive growth. We measured the N uptake rate, N content and canopy radiation interception during both growth stages. Exposure to low water temperature during either the vegetative or the reproductive growth stage slowed N uptake, and the magnitude of the decrease differed between the growth stages; the decrease was greater during vegetative growth than during reproductive growth. Consequently, total N uptake at maturity was most strongly reduced by low water temperature during vegetative growth and was not affected by low water temperature during reproductive growth, even though N distribution to the panicle was greatly reduced. The variations in N uptake during the growing season among growth stages and years were explained better by the amount of canopy radiation capture than by the number of degree‐days based on water temperature. This strong dependency on canopy radiation capture improves our understanding of the factors responsible for variations in N uptake under different levels of water temperature, and this knowledge will provide an opportunity to simplify the modelling of N uptake.     

Predicting temperature induced sterility of rice spikelets requires simulation of crop-generated microclimate

Extreme temperatures cause spikelet sterility in rice and thus yield losses. Predicting sterility is difficult because organ temperature may differ from air temperature. Four rice genotypes were planted under irrigated flooded conditions in a similar replicated design in four environments: the relatively humid dry season in the Philippines, the summer season in southern France and the cold-dry and hot-dry seasons in northern Senegal. Panicle temperature was measured by IR photography on ca. 4000 images, complemented with simultaneous monitoring of micro-climatic variables on the floodwater-canopy-air continuum. Spikelet sterility was observed at the population scale at grain maturity, and canopy morphology was also characterized (plant height, leaf area index, panicle position within the canopy and panicle exertion). The period and time of day of anthesis (TOA) was estimated using a model developed on the same experiments as described in a previous paper. Panicle temperature varied between 9.5 °C below and 2 °C above air temperature at 2 m. During TOA it was on average slightly warmer than the air in the Philippines and significantly colder in Senegal. Spikelet sterility was disaggregated into three components caused by chilling at microspore stage, incomplete panicle exertion at anthesis and high panicle temperature at anthesis. Chilling caused up to 100% and heat up to 40% sterility, the former mainly in the Senegal cool-dry season and the latter in the Philippines. All genotypes avoided heat sterility in the hot-dry season in Senegal despite air temperatures up to 40 °C, by a combination of escape (early TOA) and avoidance (transpiration cooling). Only one genotype had no chilling induced sterility due to physiological tolerance. It is concluded that heat stress causing sterility is more likely to occur in warm-humid than hot-arid environments due to humidity effects on transpiration cooling. Models predicting global warming effects on sterility losses need to consider microclimate and organ temperature, and research is now needed on the genetic control of panicle transpiration cooling     

Seedling Development of Maize Genotypes at Constant and at Fluctuating Temperatures

Four maize genotypes from North West Europe, tropical highlands and tropical lowlands were grown at constant temperatures (14°C; 24°C), diurnal temperature variations (18°/10°C; 28°/20°C) and at temperatures alternating every three days (18°+ 10°C; 28°+ 20°C) until the three leaves stage. Fluctuating temperatures were generally favourable for growth with most marked effects at an average of 14°C when 18°/10°C were applied. Temperature situation had pronounced effects on morphological and biochemical traits like area of second leaves and activity of phosphofructokinase but between these traits and growth rates no close relationship existed. For all traits genotype specific reaction patterns to temperature situation existed. One tropical highland variety excelled by fast growth, especially at low fluctuating temperatures. A specific chilling susceptibility of the tropical lowland variety was only marked for growth at constant 14°C.     

Effect of an Azolla Cover on the Conditions in Floodwater

Azolla, a free floating waterfern which is used as green manure for rice, forms mats that cover the water surface. Light intensity, oxygen concentration and pH in the water under the Azolla cover were determined in the laboratory and in the field. The relative light intensity under a full cover of Azolla was about 10 percent. Azolla reduced the maximum oxygene concentration in water by 3–8 ppm. The pH was lowered by 1.4 points. The relationship between these characters and possible effects on the utrient conditions in floodwater and soil are discussed.     

Influence of Warm Intervals on the Effects of Vernalization and the Composition of Phospholipid Fatty Acids in Seedlings of Winter Wheat

Excised embryos of winter wheat were submitted to a different number of vernalization (2 °C) and devernalization (20 °C) cycles of different lengths. In all treatments sum of cold and warm intervals was 50 and 10 days, respectively. The influence of different temperature conditions of seedling growth on the effectiveness of vernalization and correlations between effectiveness of vernalization and final content of phospholipid fatty acids were analyzed.
All indexes of generative development of plants (length of vegetative phase, % of generative plants, number of side shoots) showed the most effective was uninterrupted vernalization beginning immediately after excision of embryos. Increasing the number of 2 ° C/20 °C cycles rapidly depressed effectiveness of vernalization, which reached the minimum with the 8.3 days at 2 °C and 2 days at 20 °C cycle and then improved again as cycles became shorter and more numerous.
Correlations between indexes of generative plant growth and indexes describing composition of fatty acids in seedlings showed that from 50 % to 60 % of variability in the composition of phospholipid can be associated with changes in the degree of generative induction. A higher degree of generative induction was associated with a higher share of < 16, 16: 0 and 18:2 acids and a lower share of 18: 3 acid and also with a lower value of the 16: 0/< 16 ratio of phospholipids.
The relation between the generative induction of plants and the composition of phospholipid fatty acids may however be blurred when induction proceeds under conditions of alternate short spells of vernalization and devernalization temperatures.     

Effect of Low Night Temperatures on Photosynthetic Activity of the Maize Seedlings (Zea mays L.)

Night chilling (5 °C) subsequently lowered photosynthetic intensity in the leaves of maize seedlings at 20 °C through an increase in leaf diffusive resistance brought on by lower tissue water content in morning hours. A more significant increase in leaf diffusion resistance was observed when soil temperature was lowered than in the case of lower air temperature.
The unfavorable effect of soil and air cooling temperature on photosynthesis was limited by air saturated with water vapour. However, as a result of lowering the night temperature from 5 °C to 1 °C, the efficiency of the protective influence of higher atmospheric humidity was decreased. This demonstrates that the participation of factors unrelated to plant water status in inhibiting photosynthesis increases with lower night temperatures.
An additional reason for inhibited photosynthesis following cool nights was a decrease in chlorophyll accumulation, below 50 μg per 1 cm² of leaf area.     

Hydrogen peroxide reduces heat‐induced yield losses in cotton (Gossypium hirsutum L.) by protecting cellular membrane damage

We investigated the effect of various growth substances such as hydrogen peroxide, salicylic acid (SA), moringa leaf‐extract (MLE) and ascorbic acid (ASA) on leaf physiology and seed cotton yield (SCY) of heat‐stressed cotton. Cotton plants were exposed to elevated temperatures at three reproductive stages, either by staggering planting time in the field or by increasing growth cabinet temperatures (38/24°C and 45/30°C) in glasshouse. Elevated temperature at any reproductive phase significantly damaged cellular membrane and reduced SCY. Plants exposed to 38/24°C and 45/30°C in glasshouse produced 63% and 22% lower SCY, respectively, compared with plants under optimal temperature ((32/20°C). In response to high temperature, cotton plants up‐regulated activities of anti‐oxidative enzymes e.g. peroxidase and ascorbic acid. However, this defensive system could not protect cellular membrane of stressed plants from extreme temperature (38 and 45°C). In contrast, growth substances such as H2O2, ASA and MLE significantly increased anti‐oxidative enzymes activity to an extent, which reduced heat‐induced damage to cellular membrane. No significant effect of any regulator was observed on SCY under optimum temperatures; although H2O2, MLE and ASA significantly increased SCY of heat‐stressed cotton. Hydrogen peroxide increased SCY of April and May thermal regimes crops by 16% (averaged across both sowing dates) under field, while it caused 14% and 20% increase in SCY of plants exposed to sub (38/24°C) and supra optimal (45/30°C) thermal regimes under glasshouse. We concluded that growth regulators, specifically, H2O2 can protect cotton crops from heat‐induced cellular membrane damage by up‐regulating antioxidant defense system.     

北方白菜型冬油菜的膜脂脂肪酸组分和ATPase活性对温度的响应

为了解北方白菜型冬油菜膜脂脂肪酸和ATPase活性与抗寒性的关系,以抗寒性强的冬油菜品种陇油7号和抗寒性弱的品种天油2号为材料,研究了不同温度处理(25°C、10°C、2°C、–5°C)后叶片和根系膜脂脂肪酸组分和ATPase酶活性的变化。结果表明,低温胁迫下2个冬油菜品种叶片和根系膜脂脂肪酸组分相同,叶片中不饱和脂肪酸以亚麻酸为主,根系不饱和脂肪酸以亚油酸为主。随处理温度的降低,2个冬油菜品种叶片不饱和脂肪酸含量呈先降低(10°C,2°C)后增加(–5°C)的趋势;陇油7号根中不饱和脂肪酸含量逐步增加,天油2号则逐步降低;在低温条件下(2°C,–5°C),陇油7号膜脂U/S比值、IUFA值高于天油2号;ATPase活性表现为陇油7号逐渐高于天油2号。说明2个冬油菜品种的膜脂在低温响应上存在一定差异,低温下不饱和脂肪酸含量和ATPase活性的提高是强抗寒冬油菜品种在北方旱寒区严酷环境条件下能安全越冬的重要原因。     

Osmotically Primed Seed and Seedling Reactions to Variations in Day/Night Temperature

The effects of alternating day/night temperatures, varying in maxima and minima but all averaging 30 °C, on germination and seedling characteristics of Sorghum bicolor L. (Moench) were investigated. Seeds of sorghum CSV 15 were soaked in 2, 4 or 6 g NaCl l⁻¹ solutions for 2 days at 25 °C, soaked in water for 1 day at 25 °C, or untreated. After treatment, drying and storage, seeds were germinated at 30/30 (day/night), 35/25, 40/20 or 41/19 °C temperature regimes under a polyethylene glycol-induced drought level of −3 bar. Results revealed no advancement of germination percentage but a partial increase in germination speed by osmotic seed treatments. All three osmotic treatments also reduced the plumule/radicle ratio owing to a speculated increase in root over shoot growth. Temperature regimes significantly influenced both germination and seedling characteristics with the optimum temperature appearing to be 35/25 °C. Increasing the temperature amplitude from 30/30 to 35/25 °C increased germination speed, which was reduced by incremental increases in temperature amplitude to 40/20 or 41/19 °C.     

Carbon and Nitrogen Transport during Grain Filling in Rice Under High-temperature Conditions

Rice ( Oryza sativa cv. Koshihikari) seedlings were grown in a sandy dune soil in pots with a basal dressing of N (0.5 g N), P and K. Two N treatments were applied, a +N treatment in which a top dressing of ¹⁵N-labeled 0.5 g N was supplied on July 20 and a −N treatment in which no additional fertilizer was supplied. During the grain-filling stage from August 6 to 13, plants were subjected to one of three temperature treatments; controlled low temperature, LT (day/night 28/23 °C), controlled high temperature, HT (35/30 °C) and uncontrolled glasshouse temperature, UT (day/night averages, 38/26 °C). All plants were then exposed to ¹³CO₂ for 1 h on August 11 in a growth chamber at 25 °C. On August 13, all plants were harvested and the ¹³C and ¹⁵N abundances and starch and sugar concentrations in the ears, shoots and roots were determined. The ¹³C content of the ear was lower in UT than in LT irrespective of the +N or −N treatment. The translocation of ¹⁵N to the ears was also slightly depressed in UT compared with LT. Under high-temperature conditions (HT and UT), the starch content per plant was reduced for −N, but for +N, it was not significantly different among the temperature treatments. A high accumulation of sucrose was observed in all plant parts under UT conditions. It is suggested that extreme high day temperatures during the grain-filling period may reduce starch synthesis in the grains and, especially so under N-deficient conditions. High temperatures also induce an accumulation of sucrose and a decrease in carbon and nitrogen transport from the shoots to the ears via the phloem.     

不同行距配置方式对夏玉米冠层结构和群体抗性的影响

为探究行距配置方式对冠层微气象因子及群体抗逆性的影响,明确夏玉米适宜的行距配置方式,在方城和辉县设置大田试验,以3个不同株高类型的玉米杂交种为材料(中秆品种郑单958、高秆品种先玉335和矮秆品种512-4),设置2个种植密度(60 000株 hm^-2和75 000株 hm^-2),研究了5种行距配置方式(50 cm、60 cm、70 cm、80 cm等行距和80 cm+40 cm宽窄行)下冠层结构和群体抗逆性的变化。结果表明,不同株高类型杂交种在相同密度下,随行距扩大,株型变得松散,穗部叶片叶向值减小,并偏离种植行,向种植行垂直方向发展,冠层温湿度降低,群体抗逆性增强,但冠层光照截获率降低,产量也随之减少。对比发现,不同品种和密度下,60 cm等行距能够较好地协调冠层微气象因子与玉米产量的关系,叶片分布适宜,冠层温湿度和光能分布合理,显著提高了中下部的光能截获率,病虫害和倒伏的发生率较低,获得最高产量的频率最高,且适宜机械化田间作业,建议作为适宜黄淮海地区推广的种植方式。     

Climatic determinants of lowland rice development

Accurate modelling of plant development is the basis for any assessment of climate change impact on crop yields. Most rice models simulate development (phenology) based on temperature and photoperiod, but often the reliability of these models is reduced beyond the environment they were calibrated for. In our study, we tested the effects of relative air humidity and solar radiation on leaf appearance rate in greenhouse experiments and analysed data sets from field studies conducted in two extremely different rice-growing environments in Nepal and Senegal. We also analysed environmental effects on duration to flowering of one popular IRRI material (IR64) for eight different sites covering the entire temperature range where rice is widely cultivated. Both low relative air humidity and low solar radiation significantly decreased leaf appearance rate. Mean air temperature explained 81% of the variation in duration to flowering across sites, which was furthermore significantly influenced by relative air humidity. Across all sites, a simple linear regression approach including mean air temperature and mean relative humidity in the calculation of duration to flowering led to a root mean square error (RMSE) of 10 days, which was slightly lower than the RMSE of 11 days achieved with an automated calibration tool for parameter optimization of cardinal temperatures and photoperiod sensitivity. Parameter optimization for individual sites led to a much smaller prediction error, but also to large differences in cardinal temperatures between sites, mainly lower optimum temperatures for the cooler sites. To increase the predictive power of phenological models outside their calibration range and especially in climate change scenarios, a more mechanistic modelling approach is needed. A starting point could be including relative air humidity and radiation in the simulation procedure of crop development, and presumably, a closer link between growth and development procedures could help to increase the robustness of phenological models.     

Electrolyte Leakage, ATP Content in Leaves and Intensity of Net Photosynthesis in Maize Seedlings at Permanent or Different Daily Exposure to Low Temperatures

Changes were determined in electrolyte leakage (EL), ATP content in leaves and intensity of net photosynthesis (FJ in maize seedlings as a result of continued exposure to low temperatures for several days or, after a cold night (5 °C, 9 h), alternating application of 5 °C and 20 °C temperatures during the lit phase of the day (h of chilling during day/night: 0/9, 5/9, 10/9, 15/9).
At continuous exposure to low temperatures, permanent reduction of ATP content occurred between days 7 and 10, while EL increased significantly between days 4 to 7 (depending on experimental conditions). Of three leaves differing in age, most injuries were found in the oldest leaf. An increased intensity of irradiation from 150 to 500 μE. m⁻².s⁻¹ caused an earlier decrease in the ATP content and a further increase in electrolyte leakage. ATP content showed a 24 h rhythm, it increased at the end of the night and decreased at the end of the day. The rhythm was particularly noticeable in the control plants (20 °C), as well as, however to a lesser extent, in plants exposed to daily fluctuating chilling temperatures. It has also been observed that higher temperatures occurring in day time may diminish electrolyte leakage induced by previous low temperatures
The intensity of F_n determined at 20 °C, 4 h after withdrawal of chilling, decreased with the prolongation of the chilling period during the day.
Thus, it may be assumed that the EL and F_n values as indicators of the plants' sensitivity are in better agreement with the induced chill doses than the ATP content in leaves, which to a greater extent depends on the interaction between chilling and other experimental factors, such as irradiation intensity or the sequence of light and darkness.     

早稻全生育期气温、水温、泥温特征及避灾应用

采用农田小气候与实景观测系统,辅以人工观测,以获取早稻各发育期气温、水温、泥温特点,探讨水分干预避灾措施的效果。试验表明：全生育期以水温积温最高,气温积温最低。营养生长期日平均气温落后于水温、泥温,生殖生长期气温、水温、泥温日均值均比营养生长期提高4℃左右并非常接近。叶面积指数较小或衰减时,受太阳辐射影响,午间水温常常超过气温值。水温维持较高的时间约9~ 10 h,是理想的调温目标介质。高温逼熟时采用活水灌溉3天,可拉低水稻冠层上方最高气温2.5℃、日均气温低1.0℃。且稻米粗脂肪含量、直链淀粉含量较高,垩白度较低;结实率提高,千粒重比高温逼熟对照要高6.65%。结果认为：叶面积指数与水温呈反相关特点,高温逼熟时、叶面积衰减时对应高水温、泥温。水分干预调温对产量和品质要素有确定改善,并以活水灌溉2~3天以上的控温效果较佳。     

Physiological Effects of Winter Rape (Brassica napus var. oleifera) Prehardening to Frost. I. Frost Resistance and Photosynthesis during Cold Acclimation

The objective of the research was to define the changes in photosynthetic activity induced by prehardening and to determine their involvement in frost tolerance of winter rape.
Prehardening of winter rape, consisting of keeping the plants at + 12°C during the light periods from sprouting until the beginning of the 1st stage of cold hardening, contributed to increasing its effectiveness. After 42 days of hardening at + 2°C the resistance of the prehardened plants equalled that attained by winter rape in the most favourable seasons of vegetation in the field. Prehardening stimulated the efficiency of photosynthesis at chill temperatures (+ 2–5°C). Differences in photosynthetic efficiency, like those in frost resistance, increase with successive weeks of hardening. They also concern the leaves already developed at the hardening temperature. A prehardened photosynthetic apparatus is less susceptible to the progress of photoinactivation taking place when the seedlings are kept at + 2°C. It also demonstrated greater activity even during the first hour of hardening or in the newly expanding leaves, and also at higher temperatures, most probably because of the more efficient progress of the dark, processes. The described changes in the functioning of the photosynthetic apparatus induced by prehardening were thus qualitatively very similar to those observed during long-term growth at + 5°C. already described in the literature.