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1.
Abstract

Blackbeans (Phaseolus vulgaris (L.) var ‘Black Turtle') were grown on a Lakeland soil in a factorial growth chamber experiment with 0 and 8 ppm added Zn; 0, 20, 40, 80, and 160 ppm added P; and under two temperature regimes ‐ a 28°C/23°C (day/night) temperature and a 20°C/15°C (day/night) temperature. Blackbeans were also grown at two field sites in Southern Manitoba which were selected for their low supply of available zinc. Zinc, at 0 and 15 kg/ha, and phosphorus, at 0, 100, 200, 400, and 800 kg P205/ha vere disced into the soil in a factorial experiment.

Blackbean zinc uptake was much greater at the higher temperature, while phosphorus uptake was not similarly affected by temperature. Blackbean phosphorus uptake was regulated by the plant when sufficient Zn was present but was not regulated at low plant Zn levels. At low blackbean Zn levels, plant uptake of phosphorus further decreased blackbean Zn uptake. Blackbean Zn uptake was not affected by phosphorus concentration as long as Zn levels remained sufficiently high.  相似文献   

2.
Abstract

The effects of night temperature on biomass accumulation and plant morphology were examined in rice (Oryza sativa L.) during vegetative growth. Plants were grown under three different night temperatures (17, 22 and 27°C) for 63 days. The day temperature was maintained at 27°C in all treatments. The final biomass of the plants was greatest in the plants grown at the highest night temperature. Total leaf area and tiller number were also the greatest in this treatment. Growth analysis indicated that the relative growth rate in the 27°C night-temperature treatment was maximal between days 21–42 and this was caused by increases in leaf area ratio, leaf weight ratio and specific leaf area. Plant total nitrogen contents did not differ among treatments. However, nitrogen allocation to the leaf blades was highest and the accumulation of sucrose and starch in the leaf blades and sheaths was the lowest in the 27°C night-temperature treatment by day 42. Despite this, dark respiration was also highest, and both the gross and net rates of CO2 uptake at the level of the whole plant at day 63 were the highest in the 27°C night-temperature treatment. Thus, high night temperature strongly stimulated the growth of leaf blades during the early stage of rice plant growth, leading to increased biomass during the vegetative stage of the rice plants. As the CO2 uptake rate per total leaf area was higher, photosynthesis at the level of the whole plant was also stimulated by a high night temperature.  相似文献   

3.
Abstract

The hilly terrain of the Appalachian region creates an environment in which large differences in soil temperature occur over a very short distance on the landscape. The ability of a grass to display adequate growth over a range of temperatures would greatly enhance its adaptability and use as a forage or for soil conservation. A growth chamber experiment was conducted to evaluate the influence of temperature on the growth of six bermudagrass [Cynodon dactylon (L.) Pers.] selections from the Appalachian region. Midland, a cold tolerant bermudagrass, was included in the study for comparison purposes. The grasses were grown under a 14 hour day length with three day/night temperature regimes: 18°C/13°C, 27°C/21°C, and 35OC/29°C. Two of the selections had significantly higher dry matter production than Midland over the range of temperatures.

This effect was especially pronounced at 35°C where the top growth of Quicksand common and Selection 13 exceeded that of Midland by 206% and 158%, respectively. The higher yielding selections were comparable to the other bermudagrasses when mineral concentrations, neutral detergent fiber, acid detergent fiber and acid detergent lignin levels were considered. Both Quicksand common and Selection 13 seem to have the potential to be particularily useful on south facing slopes where elevated soil temperatures are encountered.  相似文献   

4.
Abstract

Recommendations for the use of preplant N in alfalfa establishment are controversial. Growth chamber experiments were conducted to examine the effect of preplant N and soil temperature on yield and N accumulation of alfalfa (Medicago sativa L.). Alfalfa was grown in river sand at three day/night soil temperatures (18/12°C, 24/16°C, and 27/21°C), and at five levels of preplant N (0, 10, 20, 40, 80 kg ha?1). At 18/12°C, 40 kg ha?1 preplant N resulted in a 69% increase in shoot dry matter yield. Dry matter and N accumulation rates were greatest at 40 and 80 kg ha?1. Preplant N effects on dry matter and N accumulation at 18/12°C were expressed primarily between the early bud and early flowering stages. Assessment of soil temperature and soil N availability is necessary to determine the potential for a yield response of alfalfa to preplant N.  相似文献   

5.
Abstract

One‐year‐old slash pine seedlings (Pinus elliottii Engelm.) accumulated more radioactive phosphorus in needles at a 15–10°C day‐night temperature and 2500 foot candles than at higher temperatures and reduced light. Rate of phosphorus uptake was related to concentrations of ethanol‐soluble carbohydrates but not to those of starch or all carbohydrates. Results suggest that temperature and light can be important for optimum phosphorus nutrition of slash pine.  相似文献   

6.
The effects of different temperature treatments during the seedling stage on growth and nutrient absorbance of Gerbera jamesonii cv ‘Sunshine Coast’ growing in the organic substrate were investigated. The temperature treatments were conducted in growth chamber where the day/night temperature were set to 15/10, 20/15, 25/20, and 30/25°C individually. The results showed that the fresh and dry weight of aboveground part and that of roots, average number of leaves and lateral roots were greater at 30/25°C than other treatments. The highest level of macro elements nitrogen (N), phosphorus (P), and potassium (K) in the leaf samples were also detected at 25/20°C and 30/25°C. However, there was no significant influence of different temperatures on zinc (Zn) levels in leaves. In general, the day temperature 25～30°C and night temperature 20～25°C are thought to be the better temperature condition for gerbera growth as well as the nutrient uptake and accumulation in the plants during the seedling stage.  相似文献   

7.
The growth of sesame (Sesamum indicum L.) was studied at three root temperature regimes (25/25, 20/10 and 15/15°C day/night) factorially combined with three NO3 ‐: NH4 + ratios (mM ratios, 10:0, 8:2, or 6:4), as a source of nitrogen (N), in the irrigation solution. The air temperature was kept constant at 30°C. Transpiration, nutrient composition, and level of root‐born cytokinins and gibberellins in the xylem exudate were monitored. The two low root temperature regimes, 15/15 and 20/10°C, restricted the growth of sesame, reduced transpiration and increased the accumulation of soluble carbohydrates in the shoot and in the roots compared to the 25/25°C regime. The NO3:NH4 + ratios had no effect on growth. Nutrient contents in the shoot at low root temperatures, particularly K+, NO3 ‐, and H2PO4 ‐ were decreased markedly, but Na+ increased relative to it's content in the 25/25°C regime. Increasing NH4 + proportion in the irrigation solution raised total N concentration in the plant tissues at all root temperatures. The amounts of cytokinins and gibberellins in the xylem exudate decreased at the low root temperature regimes relative to the 25/25°C regime. Low root temperature reduced xylem transport of nutrients and root born‐phytohormones, most probably because of reduced water flow through the plant relative to the 25/25°C regime.  相似文献   

8.
Abstract

The effects of different night temperatures on grain yield were examined in rice (Oryza sativa L. Akita-63) during the ripening period. Plants were grown under two different night temperatures (22 and 27°C) from anthesis to harvesting. The day temperature was maintained at 27°C in both treatments. Although the final biomass at harvest did not differ between the treatments, the dry weight of the panicles was significantly greater in the cool night temperature treatment. This increase in panicle weight was associated with increases in the 1000-kernel weight and the ratio of filled spikelets. Although panicle respiration in the high night temperature treatment decreased to almost zero just after the cessation of grain filling, the net CO2 fixation rate per day in the whole plant in this treatment tended to be higher, and this was associated with a higher level of starch accumulation. After grain filling, the starch content decreased and the final dry weight of other plant parts, including dead organs and new tillers, was greater in the high night temperature treatment. Thus, the noted decline in yield at the high night temperature led to changes in carbon allocation to new sinks for vegetative reproduction at the whole plant level. From these results, we considered the possibility that a cool night temperature tends to favor carbon allocation to panicles, resulting in higher yield.  相似文献   

9.
The effects of air temperature and light on the grain filling of an indica (IR20) and ajaponica rice (Fujisaka 5) was studied in artificially lighted cabinets. Within the daily mean temperature range of 16° to 28°C, the higher the temperature, the faster the grains filled and matured. At 28°C, the upper grains of IR20 rice took 13 days to reach the maximum weight, whereas those of Fujisaka 5 took 18 days. The optimum daily mean temperature range to achieve maximum weight per grain was 19° to 25°C for IR20 and 16° to 22°C for Fujisaka 5.

Apparently, IR20 rice is better adapted to higher temperatures during the ripening period than is Fujisaka 5 rice. More chalky grains occurred when the temperature was above or below the optimum range. Both day and night temperatures affected grain weight and grain quality.

The daily mean temperature was found to be the most meaningful expression for describing the effect of temperature on grain filling. Low light intensity appeared to cause a slight delay in the grain filling of the whole panicle and a reduction in the percentage of filled grains on the lower branches. A combination of high light intensity and low temperature gave the best ripening grade (grain weight × percent filled grains).  相似文献   

10.
ABSTRACT

The present study was conducted at the Composting Unit, Universiti Putra Malaysia to determine the physico-chemical changes, microbial dynamics, and enzyme activities during microbial composting of rice straw at different pH conditions. Different treatments comprising of composting substrates (A), substrates with microbial consortium (B), substrates, microbial consortium, and acetic acid (C), substrates, microbial consortium, and sodium hydroxide (D) were used to enhance the composting process of rice straw. In inoculated treatments, the temperature increased rapidly to higher than 50°C by day 5 and remained above 40°C up to day 17, while in the control the temperature increased slowly and peaked (46°C) at day 9 and remained above 40°C until day 23. The results showed that biodegradation was at its maximum in microbial-infused treatments within 14–21 days as indicated by profiles of pH, reduction of C/N ratio, lignocellulolytic (lignin peroxidase, endoglucanase, and exoglucanase) enzyme activities, and lignocellulose bioconversion. After day 21, the C/N ratio of microbial-infused treatment without any pH adjustment (B) was reduced to 17.5 from an initial value of 29.2 suggesting that there were no additive effects of pH adjustment during the microbial composting of rice straw.  相似文献   

11.
Abstract

Phosphorus sorption isotherms were constructed for two Idaho soils with widely different chemical properties. The soils were equilibrated with various amounts of Ca(H2PO4)2 in 0.01 M CaCl2 for 1, 3, 7, and 11 days at temperatures of 5°C and 20°C. The two soils which had been equilibrated previously for 11 days at 20°C with various amounts of Ca(H2PO4)2 in 0.01 M CaCl2 were desorbed at 5°C and 20°C.

The rates of sorption and desorption were decreased as the equilibration temperatures were lowered. The effect of temperature on these processes was detected during the first day of equilibration. Less P was found in the equilibrating solution at the lower temperature. The two soils varied widely in sorption and desorption properties.  相似文献   

12.
Three rice cultivars, IR712, M1–48 and E425 were grown in solution culture for 10 weeks in temperature controlled glasshouses at IRRI, Los Baños, Philippines. Treatments consisted of two Mn levels, 0.5 and 50 μg.cm‐3 and two temperature regimes, 35/27 and 20/20 (day/night) in °C. Dry matter and Mn concentrations were determined at 2‐week intervals. In a second experiment, the M1–48 cultivar was grown in solutions containing 0.5, 1, 40 and 80 μg.cm‐3 Mn at 35/27, 29/21 and 20/20 °C (day/night) temperatures.

It was concluded that rice is more sensitive to excess Mn under cool conditions and that the concentration of Mn in the tissue at which toxicity symptoms appear or growth is decreased depends on the age of the tissues and the environmental conditions under which the plant is growing. Growth of two‐day old seedlings exposed to excess Mn was decreased to a greater degree than was that of 2‐week old seedlings. It is suggested that in screening rice cultivars for tolerance to excess Mn the environmental conditions should be rather rigidly controlled.  相似文献   


13.
Abstract

Oilseed rape (Brassica napus) is sensitive to low boron (B) supply, and its growth response to B may be influenced by soil temperature. To test the relationship between B and temperature, oilseed rape (cv. Hyola 42) seedlings were grown at 10°C (low) root zone temperature (RZT) with B supply from deficient to adequate B levels until growth of low B plants just began to slow down. Half of the pots were then transferred to 20°C (warm) RZT for 11 days before they were moved back to 10°C RZT for the final 4 days. Both plant dry mass and B uptake increased after plants were exposed to warm RZT. However, plant B deficiency was exacerbated by warm RZT in low B plants because of increased relative growth rate and shoot–root ratio without a commensurate increase in B uptake rate. It is concluded that RZT above the critical threshold for chilling injury in oilseed rape can nevertheless affect the incidence of B deficiency by altering shoot–root ratio and hence the balance between shoot B demand and B uptake.  相似文献   

14.
Abstract

Two contrasting soils were extracted with 0.05 M EDTA in 1 M CH3 COONH4 at pH 6, before and after incubation for 4 weeks at constant (10, 20 or 30°C) or fluctuating (10/30, mean 20°C) temperatures. Less copper was extracted from soils which were incubated at fluctuating temperature than from those maintained at a constant 20 C. Where incubation temperature was constant, extractable copper increased or decreased with increasing temperature depending on the soil and how it was treated. Recovery of added copper was low initially but increased during the incubation. Maximum recovery was associated with low incubation temperature in one soil, but high temperature in the other. The amounts of copper extracted were slightly increased by γ‐irradiation of the soils. Extractable copper was also increased by increasing the temperature at which the extraction was performed.  相似文献   

15.
Temperature is a limiting factor on legume-Bradyrhizobium symbiosis of subtropical plants in the temperate region. Twelve strains of Bradyrhizobium spp. that nodulate pigeonpea [Cajanus cajan (L.) Millsp], and cowpea [Vigna unguiculata (L.) Walp], were evaluated for tolerance to three temperature regimes (20°C/10°C, 30°C/20°C, and 38°C/25°C day/night temperature) by determining their growth following exposure to the regimes. The five most temperature-tolerant strains were further evaluated for symbiotic effectiveness with pigeonpea and cowpea under controlled temperatures. These strains were USDA 3278, USDA 3362, USDA 3364, USDA 3458, and USDA 3472. Plant heights of both crops were generally independent of Bradyrhizobium strains and were dependent mainly on temperature regimes. Plant heights were the shortest at the lowest temperature. At the lowest temperature regime, biological nitrogen (N) fixation by pigeonpea was almost completely inhibited. Cowpea genotype IT82E-16 inoculated with USDA 3458 formed the most effective symbiosis. The 30°C/20°C temperature regime was optimum for effective symbiotic association in both crops, and also for Bradyrhizobium survival.  相似文献   

16.
Oilseed rape (Brassica napus L.) response to root temperature regimes (20/20, 16/8 and 12/12°C day/night) at constant 20°C air temperature was studied. At each regime, three NO3 ‐:NH4 + ratios (10:0, 8:2, or 6:4), at constant 10 mM N, in the irrigation solution were tested. Plant growth, transpiration, ionic composition and level of cytokinins and gibberellins in the xylem exudate were monitored. The two low root temperature regimes, 12/12 and 16/8°C, reduced rape shoot growth by 28 and 22%, and increased the accumulation of soluble carbohydrates by 42 and 26% in the roots, respectively, as compared to the 20/20°C regime. Low root temperatures reduced plants transpiration. The NO3 ‐:NH4 + ratios had no effect on rape growth. At low root temperatures NO3 ‐contents increased in the shoot and decreased in the roots. The sum of cations and that of anions at 12/12 and 16/8°C root temperatures decreased significantly as compared to 20/20°C. The presence of NH4 + in the irrigation solution decreased the concentrations of Ca2+ and Mg2+ in the shoots and roots and increased that of Cl‐ in the shoots and of H2PO4 ‐ in the roots at all root temperatures. Cytokinins and gibberellins contents in the xylem exúdate decreased at the low root temperature regimes. Low root temperature reduced total upward transport of the mineral nutrients and phytohormones, most probably because of reduced water flow through the plant.  相似文献   

17.
Abstract

Milk thistle [Silybum marianum (L.) Gaertn] is an annual plant belonging to the Asteraceae family whose ripe seeds contain flavonoid substances, which are important in the modern pharmaceutical industry. Seed germination is a major factor limiting the establishment of plants under saline conditions. The effect of salinity and temperatures on germination and seedling establishment was studied in two genotypes of milk thistle, an Iranian wild type and German (Royston) type in the laboratory and in the field. Experiments were done with seven salt concentrations [0.1 (control), 1, 3, 6, 9, 12, and 15 dS/m] and three temperatures (15, 25, and 35°C). There were three replications for each treatment, and the experiment was run three times. The results showed that the percentage of germination and the number of normal seedlings at different salt treatment at 15°C were higher than at 25 or 35°C. The mean time to 50% germination was least at this temperature for both genotypes. Results suggested all germination indices and seedling emergence (50%) were achieved at levels up to 9 dS/m salinity at 15°C. Also, seeds at a salinity of 9–15 dS/m will germinate and up to 25% of the control nonstress treatment could emerge at the low temperature of 15°C.  相似文献   

18.
Abstract

Seed dormancy and slow germination often cause poor establishment of Poa pratensis L. in lawns and pastures. This study was conducted to determine whether persistent dormancy occurs and the influence of light and temperature on germination of Poa pratensis L. strains from Northern Norway. Seed from 23 different genotypes and seed lots was germinated in various phytotron chambers during the winters of 1986 and 1990. At 21°C constant temperature, dormancy was evident even after seven years of storage in a dry room at 0–10°C. By contrast, alternating temperatures (21/12°C) elicited 80–100% germination of viable seed of nearly all genotypes and seed lots. Light treatment had no impact on germination after 28 days at 21/12°C, but continuous darkness and continuous fluorescent light were both inferior to 8 h light/16 h dark illumination cycles at 21°C constant temperature. Seed of the commercial cultivar Lavang produced in Southern Norway developed the same long-term, temperature-dependent dormancy as seed produced in Northern Norway. One lot of the cultivar Holt showed a higher ability to germinate at low temperatures than any of the other genotypes.  相似文献   

19.
The effects of high growth temperature on sorghum starch structures were examined from the grains of three inbred lines (BTx623, IS8525, and Karper669), and the possible mechanism by which the growth of amylopectin molecules is terminated was discussed. Sorghum plants were grown at high temperature (38/21°C day/night) and control temperature (32/22°C day/night) from sowing to maturity. The grains sampled from plants grown at high temperature had significantly lower starch weights per grain (except BTx623) and smaller starch granule sizes than those grown at control temperature. Nevertheless, the amylose contents were similar. BTx623 and IS8525 samples grown at high temperature also had higher ratios of long to short amylopectin branches and lower degree of branching than their control counterparts. These results suggested that the activities of starch biosynthetic enzymes were evidently affected by elevated growth temperature. However, the weight‐average molecular weight and the z‐average radius of gyration of sorghum starch molecules were not significantly affected by the growth temperatures, suggesting that the effects of growth temperature on starch yield, starch granule size, and the branching structure of amylopectin molecules did not influence the events that stopped the overall growth of amylopectin molecules. This observation was consistent with the cessation of whole‐molecule growth being through increasing hindrance to enzyme access as the size of the starch molecule increases, controlled largely by the molecular density of the outermost part of an amylopectin molecule.  相似文献   

20.
Tomato (Lycopersicon esculuntum Mill.) grown in open fields in dry land areas or in non‐controlled greenhouses are subjected to substantial daily changes in root temperature. In the field, root‐zone temperatures fluctuate both diurnally and during the growing season. The purpose of this study was to monitor root‐zone temperature effects on tomato initial growth, transpiration, sap flow rate, leaf and air temperatures differences, nitrate accumulation, total nitrogen, and soluble carbohydrates in the shoot and roots as well as levels of endogenous cytokinins and gibberellins in xylem exudate. Tomato seedlings were grown in three growth cabinets with variable control of root temperatures. Three day/night root temperature regimes (12/12, 16/8 and 20/20°C) were employed. Low day root temperatures of 12 and 16°C reduced shoot dry weight by 47 and 26%, root dry weight by 36 and 14%, shoot nitrate by 79 and 50%, root nitrate by 49 and 16%, levels of cytokinins in root xylem exudate by 27 and 13% and gibberellins by 65 and 23%, in relation to the respective values of 20°C day root temperature. Soluble carbohydrates in the shoot and roots were increased significantly (18 and 111%) by 12°C root temperature. The main effects of low root temperatures on shoot growth stem from slow upward transport of plant hormones and nitrate rather than reduction in their rate of biosynthesis or entry to the root, respectively.  相似文献   

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