Top Dry Weight Research Articles

Characterization of Vegetative Growth of a Supernodulating Soybean Genotype, Sakukei 4

ArticleThe supernodulating soybean cultivar Sakukei 4 was previously characterized by its superior ability to maintain a high leaf nitrogen (N) content and high photosynthetic rate. Despite these desirable traits, the growth performance of Sakukei 4 was inferior to that of its normally nodulating parental cultivar, Enrei. The physiological basis for the unique growth characteristics of Sakukei 4 remains unclear. The objective of the present study was to characterize in further detail thevegetative growth of Sakukei 4, particularly during the period before pod expansion. In the first experiment, the growth of Sakukei 4 was compared with that of its parental cultivar Enrei under various rates of N fertilizer. The dry weight of tops, roots and nodules of the plants grown at lower rates of N application was greater in Enrei than in Sakukei 4, but it was vice versa at higher rates of N application. The number and weight of nodules were far greater in Sakukei 4 than in Enrei at any rate of N application. These genotypic differences were significant on 39 days after sowing (DAS) and became greater at the flowering stage. In the second experiment, therefore, more detailed growth analysis was made during an earlier growth stage (DAS 31-46). During this period, relative growth rate (RGR), net assimilation rate (NAR) and leaf area ratio (LAR) were lower in Sakukei 4 than in Enrei and the related non-nodulating line En1282, whereas the leaf photosynthetic rate was higher in Sakukei 4 at all leaf positions. The dry-matter partitioning to each plant part excluding nodules was similar in all three genotypes. The rate of leaf expansion in Sakukei 4 during this period was significantly slower than that in the other genotypes. These results suggest that the inferior growth of Sakukei 4 prior to flowering is probably due to excessive dry-matter partitioning to nodules and depressed capability of leaf expansion and root growth, which might limit dry-matter production of the whole plant during pre-flowering stage.

Ecophysiological Traits of Field-Grown Crotalaria incana and C. pallida as Green Manure

To evaluate the growth capacity and some chemical characteristics of two Crotalaria species, C. incana and C. pallida, used as green manure, we conducted a field experiment at Osaka, Japan. Both Crotalaria species exhibited vigorous vegetative growth, and leaf area was expanded in C. pallida and branching was promoted in C. incan. Top dry weight and nitrogen content of C. pallida were twice as high as those of C. incana at 87 and 120 days after transplanting (DAT), and the lower values in C. incana were attributed to drastic defoliation of lower leaves due to earlier anthesis from mid-July. Several indicators for rapid decomposition of the plants used as green manure, such as C/N ratio, lignin (L) content and L/N ratio at 56, 87 and 120 DAT, were significantly higher in C. pallida than in C. incana. However, these values might not be critical for nitrogen mineralization after incorporation of the materials into soil. To evaluate the qualitative traits of the two species as green manures, the materials were mixed with soil at a rate of 20 g fresh weight per pot, and seeds of wheat were sown at 10 and 30 days after mixing the green manure (DAM). The growth and nitrogen uptake of wheat grown on the soil mixed with C. pallida were inferior to those of wheat grown on the soil mixed with C. incana on both sowing dates, and the difference between the effectiveness of the two species as green manure was larger in the wheat sown on 10 DAM than on 30 DAM. The possible increase in nitrogen supply and growth inhibition by incorporation of these materials to wheat plants were discussed.

作物の出芽，生育に及ぼす土塊の大きさの影響

Five crops with different seed size, corn (Zea mays), soybean (Glycine max), Japanese radish (Raphanus sativus), carrot (Daucus carota) and komatsuna (Brassica rapa), were used in the present examination. With the aim of clarifying the effectiveness of soil clod-size on emergence and early growth of these crops, emergence ratio, plant length and dry weight of top and root were measured using wagner pot (1/2000a) contained with 5 levels of soil clod-size, <4mm, 4-10mm, 10-20mm, 20-40mm and 40-50mm in diameter. Emergence ratio in any crops decreased as soil clad-size was large, especially in carrot. Emergence ratio was inhibited in the 20 mm-soil clod in corn and soybean that produce large seed, however, it was inhibited in 10mm soil clod in carrot that has small and flat seed. There is not a significant difference in plant length and top dry weight in all crops among the soil clad-size less than 40mm. On the other hand, root dry weight became small as soil clod-size was large, and soil clod-size affected the root growth more than top growth comparatively. From these result, it is necessary to prepare the soil clod less than 10mm in seeding ditch to obtain high emergence ratio and vigorous early growth for all crops in reduced tillage.

Effects of adding organic materials to an acid sulfate soil on the growth of cocoa ( Theobroma cacao L.) seedlings

Acid sulfate soils having a pH of less than 3.5 are widespread in Malaysia. Some of these soils are planted to cocoa, but the yield is reported to be low due to soil infertility related to Al toxicity. Cocoa growth is sensitive to the presence of Al in the soil. To a certain extent, Al toxicity in soils can be reduced by organic matter application and to a greater extent in iron-poor acid sulfate soil. A study was conducted to determine the efficacy of various types of organic materials easily available in the country to ameliorate acid sulfate soil infertility for growing cocoa seedlings. The treatments were control (nil), lime (3 t/ha), peat (10% w/w), peat plus green manure (10% w/w), peat plus rice straw (10% w/w), peat plus chicken dung (10% w/w) and peat plus POMS (Palm oil mill sludge) (10% w/w). The growth of cocoa seedlings was affected significantly by the presence of Al in the cocoa tissues. As the amount of Al in the leaves increased, the relative top dry weight of cocoa seedlings decreased. Likewise, the relative plant height was negatively correlated with Al in the leaves. Peat as well as peat in combination with green manure, rice straw, chicken dung or palm oil mill sludge was able to reduce Al toxicity in acid sulfate soil; the highest top dry weight of cocoa seedlings were obtained in the peat plus green manure treatment. The best cocoa seedlings root growth was found for the peat treatment alone. The relative top dry weight of cocoa seedlings was negatively correlated with Al 3+ as well as Al 3++Al(OH) 2++Al(OH) 2 + activity in the soil solution. The critical values for Al 3+ and the combination of Al 3++Al(OH) 2++Al(OH) 2 + activity in the soil solution were 10 μM and 15 μM, respectively.

Evaluation of Phosphorus Availability for Paddy Rice Using Eight Chemical Soil Tests Under Oxidized and Reduced Soil Conditions

Phosphorus (P) soil test methods have had limited success in prediction of lowland rice (Oryza Sativa L.) response to P fertilization. Therefore, the relative efficiency of Olsen, Colwell, Bray1, Soltanpour, Mehlich 3, Morgan, Sr-citrate, and Resin to predict P availability in waterlogged soils was evaluated by incubating 23 calcareous soils under oxidized and reduced soil conditions and P response of rice was assessed in a greenhouse experiment. Anion exchange resin extracted the highest amounts of P from both waterlogged and air-dried soils followed by Colwell, Morgan, Olsen, Sr-citrate, Mehlich 3, Soltanpour, and Bray 1. Reducing soil conditions increased the amount of P extracted by all soil test methods. The highest correlation coefficient was observed between Olsen and Colwell extractable P under both oxidized and reduced soil conditions. Olsen method gave the best correlation coefficients with rice growth parameters (dry matter yield and P uptake), followed by Colwell and Soltanpour under aerobic and Soltanpour under anaerobic conditions. Furthermore, the relationship between top dry weight and/or P uptake and P extracted by Olsen, Colwell, Soltanpour, Sr-citrate, and Resin were improved when organic matter (OM), pH, clay content (Clay), electrical conductivity (ECe), and calcium carbonate equivalent (CCE) were included in the multiple-regression equations. The results reported in the present study suggest that Olsen test method appears to be a more appropriate extractant for predicting P availability for rice under oxidized and reduced soil conditions. The relatively high variability in physical and chemical characteristics of the calcareous soils of southern Iran, due to variations in topography and geology justify more correlation and field calibration studies to improve P availability evaluation.

Evaluation of Chemical Extractants for Predicting Lowland Rice Response to Zinc in Highly Calcareous Soils

Zinc (Zn) deficiency has been observed in lowland rice (Oryza sativa L.) in Iran. Relatively high pH and abundant calcium carbonate of soils are responsible for Zn deficiency in the plant. However, the Zn status in paddy soils of Iran has not been reported. Therefore, available Zn in 20 highly calcareous soils with a wide range of chemical properties was evaluated with DTPA-CaCl2, EDTA-(NH4)2CO3, DTPA-NH4HCO3, EDTA, and Mehlich 3, using rice as a test crop. The results showed that extraction of Zn decreased in the order: Mehlich 3, EDTA, DTPA-NH4HCO3, EDTA-(NH4)2CO3, DTPA-CaCl2. A significant positive correlation was found between Zn extracted by all chemical extractants with the exception of EDTA. The highest correlation was observed between DTPA-CaCl2 and EDTA-(NH4)2CO3 extractable Zn. Application of Zn significantly increased mean top dry weight, Zn concentration, and Zn uptake by rice. Apparent Zn recovery of applied Zn was quite low in all soils, probably due to conversion of Zn to unavailable forms. The critical level of soil available Zn with DTPA-CaCl2, EDTA-(NH4)2CO3, DTPA-NH4HCO3, EDTA, and Mehlich 3 was 0.30, 0.70, 0.76, 2.2 and 2.5 mg kg−1, respectively. Plant dry matter and Zn uptake were significantly correlated with DTPA-CaCl2, EDTA-(NH4)2, DTPA-NH4HCO3 and Mehlich 3 extractable Zn. However, Zn extracted by EDTA-(NH4)2CO3 and DTPA-CaCl2 best explained the variation in plant dry matter, whereas DTPA-NH4HCO3 extractable Zn was more appropriate to predict the variation in Zn uptake by rice. Moreover, inclusion of pH and ECe in a multiple regression equation led to the best prediction of top dry weight and Zn uptake by the EDTA-(NH4)2CO3 soil test. It seems that EDTA-(NH4)2CO3 is the most suitable chemical extractant to differentiate the Zn responsive paddy soils from nonresponsive ones in view of its high statistical relationship with the rice growth parameters.

Laboratory and Greenhouse Evaluation of Five Chemical Extractants for Estimating Available Copper in Selected Calcareous Soils of Iran

Documented plant responses to copper (Cu) are rare and consequently Cu soil tests have not received much individual effort. However, soil extraction techniques to measure the status of available Cu for plants are important in the diagnosis of deficiency or toxicity. In the present study, DTPA-CaCl2, EDTA-NH4OAc, EDTA-(NH4)2CO3, DTPA-NH4HCO3, and EDTA were evaluated for their relative efficiency to extract Cu from 26 soil series with a wide range of chemical properties. Wheat (Triticum aestivum L.) was used as a test crop. The results showed that Cu extractability decreased in the order: EDTA-(NH4)2CO3, DTPA-NH4HCO3, EDTA, EDTA-NH4OAc, and DTPA-CaCl2. Significant positive correlations were found between extractable Cu among the five extractions. Stepwise multiple regression equations showed that organic matter (OM) and clay content followed by cation exchange capacity (CEC) and calcium carbonate equivalent (CCE) were the most influential soil characteristics affecting extractable Cu. Mean top dry weight, Cu concentration and Cu uptake were significantly higher in Cu-treated plants than those in untreated plants. Significant correlations were found between Cu extracted with DTPA-CaCl2 and EDTA-(NH4)2CO3 and Cu uptake by wheat. However, the two extractants were not adequately efficient to predict Cu uptake with each accounting for only about 30% of the variation. Among soil properties tested, clay, pH, OM, and CCE correlated negatively and CEC positively with wheat top dry weight, whereas, pH, CEC, and CCE related positively and clay, and OM negatively with Cu uptake. In conclusion, it appears that none of the five test procedures in view of their relatively low coefficient of determinations with plant response proved to be a promising extractant for the determination of available Cu in the soils tested.

Paper Mill Waste Mixed with Compost and Other Ingredients as Container Nursery Substrates

Growth performance of container-grown dogwood (Cornus alba L. ‘Sibirica’), forsythia (Forsythia x intermedia Zab ‘Lynwood’), ninebark (Physocarpus opulifolius L.), and weigela (Weigela florida (Bunge) A. DC. ‘Variegata Nana’) were evaluated in 20 waste-derived substrates classified into five groups. Each group had 0, 20, 40 or 60% (by volume) of paper mill biosolids in binary mixtures with bark (PB group), tertiary mixtures with topsoil and sand (PTS group), and quaternary mixtures with bark, topsoil and sand (PBTS group). There were also similar binary and quaternary mixtures with compost instead of bark (PC and PCTS groups, respectively). With few exceptions, top dry weights of all four species increased (linear or curvilinear responses) with increasing rate of biosolids, and were higher in the compost-amended PC and PCTS (forsythia, 72-99 g/plant, range over all rates of biosolids; ninebark, 97-116; dogwood, 45-60; and weigela, 18-25) than in bark-amended PB and PBTS (forsythia, 26-71; ninebark, 32-80; dogwood, 33-56; and weigela, 7.7-18) substrates. Top dry weights in a control nursery mix (80:15:5 by vol bark:peat:topsoil) used by nurseries were: forsythia, 70; ninebark, 110; dogwood, 51; and weigela, 48. While none of the weigela plants attained size comparable to that of the control, top dry weights of other species reached or exceeded their control counterparts in PC and PCTS substrates over most or all rates of biosolids (all species); in PB and PBTS with 40-60% of biosolids (forsythia and dogwood); and in PTS with the highest rate of biosolids(forsythia, 91; and ninebark, 140). Higher retention of nutrients in the substrates and/or more favorable bulk densities and air-filled porosities, primarily due to the biosolids, contributed to increased growth and/or foliar nutrient status of the plants.

Growth, Yield and Land Use Efficiency of Corn and Legumes Grown under Intercropping Systems

A field experiment was conducted at the experimental farm of Khon Kaen University in 2001. The objectives of this study were to investigate growth, yield and yield components of corn, peanut, soybean and mungbean under intercropping and single cropping, as well as to assess the land use efficiency. Yield and yield components of corn was unaffected by intercropping system. In legume crops; peanut, soybean and mungbean, intercropping systems reduced the leaf area and top dry weight per plant as compared with single cropping. Grain yield of peanut, soybean and mungbean was reduced by 28%, 39% and 51%, respectively, as compared with single cropping. The pod number per plant was the most affected by intercropping among the yield components. However, corn-legume intercropping increased land use efficiency by 48% to 66% depending on legume species. Corn-peanut intercropping gave the highest land use efficiency. The effects of light penetration and nutrient competition are discussed.

Tuber initiation and development in irrigated and non-irrigated potatoes

Tuber initiation and development are processes basic to potato production and are particularly critical in areas with short growing seasons. It is important to know how and to what extent management decisions affect these processes in order to maximize the yield of marketable tubers. A two-year field study, conducted in southcentral Alaska, examined top growth, tuber initiation, and tuber development in eight potato cultivars grown with and without irrigation. Plants of the cultivars Allagash Russet, Bake-King, Green Mountain, Kennebec, Lemhi Russet, Russet Burbank, Shepody, and Superior were harvested weekly throughout the growing season, and top dry weight, numbers of tubers, and individual tuber fresh weights were recorded. Top dry weight was reduced by moisture stress shortly after emergence in 1993, and about one month following emergence in 1994, when early-season soil moisture was greater. The weight of tubers was similarly affected within approximately 5 wk of emergence in 1993 and 6 weeks in 1994. Tuber weight at harvest was increased two-to three-fold by irrigation in all cultivars. The number of tubers each plant set was affected by irrigation in most, but not all, cultivars. Some varieties (Lemhi Russet in 1994, Allagash Russet both years) set more tubers than were maintained through the growing season. Tuber remnants found during sample collection indicated that tuber reabsorption had occurred. Irrigated Green Mountain had more than one tuber initiation period during the season, whereas other varieties such as Shepody maintained a relatively constant number of tubers following initial tuber set. Tuber size distribution at the end of the growing season showed that larger tubers were favored by irrigation.

Influence of FeEDDHA on Iron–Manganese Interaction in Soybean Genotypes in a Calcareous Soil

Iron (Fe) deficiency is common in calcareous soils. Application of FeEDDHA is effective in correction of Fe deficiency in such soils. However, it may decrease concentration and uptake of some micronutrients including manganese (Mn). The effect of Fe on Mn status of different soybean [Glycin max (L.) Merr.] genotypes was studied in a greenhouse experiment in a completely randomized design with three replicates. The treatments consisted of three Fe levels (0, 2.5, and 5 mg Fe kg−1 as FeEDDHA) and 12 soybean genotypes. Results showed that application of Fe increased top dry weight of Wells, Black hack, Elgin, and A3237, but decreased that of Steel and A3935 and had no effect on other genotypes. Addition of Fe increased concentration and uptake of Fe, but decreased that of Mn in all genotypes. The Fe:Mn ratio greater than 0.4 in plant tops when both Fe and Mn were in the nutrient sufficiency range were considered to be an indication of tolerance to Fe deficiency, as these genotypes did not respond to Fe fertilizer. Regression equations showed that the highest reduction of Mn concentration occurred at 2.5 mg Fe kg−1. Manganese concentration was reduced by 13, 17, and 19% due to the dilution effect only in Black hack, A3237, and Elgin, respectively. Iron application did not cause either Fe toxicity in soybean or suppression in root:shoot ratio. It seems that Fe addition reduced Mn concentration in some soybean genotypes probably either by reduction of Mn concentration and/or translocation of Mn from root to shoot. The fact that soybeans are highly sensitive to Fe and Mn deficiencies and use of expensive FeEDDHA might accentuate Mn deficiency or imbalance in soybeans demonstrates a need to screen out and select soybean genotypes resistant to Fe stress.

Effect of population densities of Heterodera glycines race 3 on leaf area, photosynthesis and yield of soybean

The effect of Heterodera glycines on photosynthesis, leaf area and yield of soybean (Glycine max) was studied in two experiments carried out under greenhouse condition. Soybean seeds were sown in 1.5 l (Experiment 1) or 5.0 l (Experiment 2) clay pots filled with a mixture of field soil + sand (1:1) sterilized with methyl bromide. Eight days after sowing, seedlings were thinned to one per pot, and one day later inoculated with 0; 1.200; 3.600; 10.800; 32.400 or 97.200 J2 juveniles of H. glycines. Experiment 1 was carried out during the first 45 days of the inoculation while Experiment 2 was conducted during the whole cycle of the crop. Measurements of photosynthetic rate, stomatic conductance, chlorophyll fluorescence, leaf color, leaf area, and chlorophyll leaf content were taken at ten-day intervals throughout the experiments. Data on fresh root weight, top dry weight, grain yield, number of eggs/gram of roots, and nematode reproduction factor were obtained at the end of the trials. Each treatment was replicated ten times. There was a marked reduction in both photosynthetic rate and chlorophyll content, as well as an evident yellowing of the leaves of the infected plants. Even at the lowest Pi, the effects of H. glycines on the top dry weight or grain yield were quite severe. Despite the parasitism, soybean yield was highly correlated with the integrated leaf area and, accordingly, the use of this parameter was suggested for the design of potential damage prediction models that include physiological aspects of nematode-diseased plants.

Heat Stability of Resistance to Southern Root-knot Nematode in Bell Pepper Genotypes Homozygous and Heterozygous for the N Gene

Expression of the N gene, which confers resistance to southern root-knot nematode (Meloidogyne incognita Kofoid and White) in bell pepper [(Capsicum annuum L. var. annuum (Grossum Group)], is modified at high temperatures (28 °C and 32 °C), but its expression in the heterozygous condition (Nn) has not been documented at moderate or high temperatures. Responses of the near-isogenic bell pepper cultivars, Charleston Belle and Keystone Resistant Giant (differing at the N locus), and the F1 and reciprocal F1 crosses between these cultivars to M. incognita race 3 were determined at 24, 28, and 32 °C in growth chamber experiments. `Keystone Resistant Giant' (nn) was susceptible at 24, 28, and 32 °C. `Charleston Belle' (NN) exhibited high resistance at 24 °C and resistance was partially lost at 28 and 32 °C. However, at 32 °C root gall and egg mass severity indices for `Charleston Belle' were still in the resistant range, and the number of M. incognita eggs per gram fresh root and reproductive index were 97% and 90% less, respectively, than for `Keystone Resistant Giant'. Responses of the F1 and F1 reciprocal hybrid populations to M. incognita were similar to the response of the resistant parent at all temperatures. Root fresh weights and top dry weights indicated that both hybrid populations tolerated M. incognita infections at least as well as `Charleston Belle'. These findings indicate that i) only one of the parental inbred lines needs to be converted to the NN genotype to produce F1 hybrid cultivars with fully functional N-type resistance to M. incognita; and ii) cytoplasmic factors are not involved in expression of N-type resistance and the resistant parental inbred can used to equal advantage as either the paternal or the maternal parent.

Studies on the Low-Temperature Damage in Rice Seedlings.

インド型品種(浙 9248,湘 24号)と日本型品種(胆振早稲,はやゆき)を供試し,低温下における苗の生長に及ぼす土壌水分の影響を検討した.水分条件として湿潤(最大容水量の70%)および湛水の二処理区を設け,苗の第3葉展開期から12日間,低温処理(11℃)を行った後,常温(20℃)に戻しさらに14日間生育させた.低温時においては地上部乾物増加量はいずれの品種も湿潤区の方が大きく,品種間差がほとんど見られなかった.根の諸形質についてみると,根の乾物重,根数,種子根長および種子根における側根の増加量はいずれも湿潤区で多く,インド型品種に比べ日本型品種で大きかった.一方,出液速度は日本型品種よりインド型品種で著しく抑制されたが,いずれの品種においても湛水区より湿潤区で高く維持され,このことから根の生理活性の維持能力の差は湿潤区と湛水区における根の生長量の差と密接な関係を有するものと考えられた.常温回復後の反応についてみると,地上部乾物重,根乾物重,根数の増加量および出液速度の回復程度はいずれも湛水区より湿潤区で大きかった.また,常温回復後の根活着能力も湿潤区で勝っていた.このことと前述した低温時における根の生長および出液速度との関係から,湿潤処理によって低温時における根の生長および根の生理活性がともに高く維持されたことが常温回復後の生長回復の優勢につながったと考えられた.以上のことより,湿潤土壌条件下での育苗はインド型品種水稲二期作の第一作目の苗代期における低温障害を軽減し,苗質を維持する上で有効であると考えられた.

Confirmation of the Productivity of the Stored Seeds of Wheat and Two-Rowed Barley

SummaryTo confirm the excellence in productivity of the stored seeds of wheat and two-rowed barley, we examined the growth characters and productivity of the plants developed from the seeds stored at 5°C and 40% relative humidity for various periods but showed a 80% or higher germination percentage, in comparison with those of newly harvested seeds (new seeds). The cultivars of stored seeds were identified by the random amplified polymorphic DNA (RAPD) method. There were no differences in the morphological characters of the seedlings 3 months after emergence between the new seeds and the old seeds (stored for 2 years and 5 months) or the very old seeds (stored for 10 years and 5 months or 16 years and 5 months). On the other hand, there was a positive correlation between the top dry weight at 3 months after emergence and 1,000-grain weight of the seed. In the plants from the old seeds, no significant differences from those from new seeds were observed either in the mean heading date, maturing date, culm lengths, ear length, yield components, grain yield or inspection-grade. On the other hand, in the plants from the very old seeds, the mean heading date, maturing date, culm lengths, yield components and grain yield were significantly different from those in the new seeds in some cultivars. The results of RAPD analysis showed that the band pattern of the very old seeds was the same as that of the new seed in each cultivar. We concluded that the seeds of wheat and two-rowed barley stored for 2 years and 5 months with a germination percentage of higher than 80% are practically useful, showing normal growth characters and productivity. However, it should be noted that some cultivars had inferior grain yield after the seed storage for over 10 years.

Competitiveness of Four Rice Cultivars against Barnyardgrass, Echinochloa oryzicola Vasing, with Reference to Root and Shoot Competition

Four cultivars of rice (Oryza sativa L.) different in plant stature were grown on a paddy field, fairly fertile without nitrogen application, with or without barnyard grass, Echinochloa oryzicola Vasing, in the middle of the rice rows. The reduction of the growth variables of the four cultivars by competition with E. oryzicola was examined. The effect of a veneer board inserted in the soil between the rice and barnyardgrass rows was also examined to evaluate the growth reduction by shoot competition (WCS) and root competition (WCr) separately. On the average, the reduction of top dry weight (DWtop) by competition with weed (full competition, WCf) and by WCr increased with the time during the early growth period. Thereafter, the reduction of DWtop by WCr decreased steeply and instead the reduction by WCS increased and became a primary factor of the reduction by WCf in the late growth period. Nitrogen accumulation in the top (Ntop) tended to be reduced at a higher rate than DWtop by WCr. The cultivar difference in the rate of DWt0P reduction by WCf was largest at maturity ranging from 0.22 in Ch86 (very tall indica) to 0.45 in Taichung65d47 (short japonica), and was intermediate in Taichung65 (moderately tall japonica) and Takanari (moderately short indica). The reduction of DWtop and Ntop by WCS in all cultivars almost fully accounted for that by WCf at maturity and closely correlated with the height of rice plant. Although the rate of DWt0P reduction by WCr before heading significantly differed among cultivars (0.13 - 0.28), it did not contribute to the rate of DWtop reduction by WCf at maturity (0.01 - 0.06). These results indicated that shoot competition was a more important factor to cause cultivar difference in the reduction of final biomass by competition with E. oryzicola. Considering its great contribution to WCf during the early growth period especially for Ntop, WCr might be an important factor in the competition with weed of rice cultivars under crucially nitrogen-limited conditions.

Temperature after flower initiation affects morphology and flowering of cyclamen

Cyclamen persicum Mill. ‘Miracle Salmon’ (MS) and ‘Miracle White’ (MW) were grown at 8, 12, 16, 20 or 24°C for 8 weeks following visible bud (2 mm flower bud, 101 days from seeding). Prior to and following the 8 weeks, the temperature was 16°C. The light integral was 10 mol m −2 per day. Days (MS)=174.4+11.307(°C)−1.196(°C) 2+0.0299(°C) 3 and days (MW)=181.0+11.280(°C)−1.268(°C) 2+0.0339(°C) 3 best described time to flower from seeding. Fastest flowering is predicted after 161 days at 20.5°C for MS and after 170 days at 19.2°C for MW. The number of leaves at flowering increased from 48 at 8°C to 64 at 24°C in MS and averaged 42 at all temperatures in MW. Total plant leaf area was largest in the warmest conditions with markedly increased individual leaf size at 24°C. Estimated leaf canopy volume increased from 2264 cm 3 at 8°C to 7371 cm 3 at 24°C for MS and from 3586 to 8388 cm 3 for MW. At first open flower, MS had 47 flower buds at 16, 20 or 24°C and MW had 44 at 20°C and 41 at 24°C. Flower petal length decreased with 0.2 cm in MS and 0.4 cm in MW at 24°C compared to other temperatures. Top dry weight increased between 8 and 24°C with 4 g in MS and 4.5 g in MW. The two cultivars had similar sized enlarged hypocotyls. Heavier enlarged hypocotyls (2.4 g) developed at 8 or 12°C and the smallest (0.8 g) at 16°C.

Influence of nitrogen and potassium application on growth, yield and nutrient uptake by onion (Allium cepa)

A field experiment was conducted during spring season of 1996 and 1997 to study the influence of nitrogen and potassium on the onion (Allium cepa L.) cultivar Pusa Madhavi , at Indian Agricultural Research Insitute, New Delhi. The enhancement in dry weight of tops and bulbs was recorded up to 120 kg Nlha. Similarly, yield attributes like bulb diamefer and 100 bulb weight also improved up to 120 kg Nlha. The average increase in bulb yield over the control was 18.3 and 29.6% with the application of 60 and 120 kg Nlha respectively. The onion bulb yield significantly responded to nitrogen application up to 120 kglha. There was significant increase in nitrogen uptake up to 120 kg Nlha and in potassium uptake upJto 60 kg Nlha. Potassium application significantly increased the dry weight of tops and bulbs, bulb diameter, 100 bulb weight and bulb yield up to 40 kg K,O/ha. The potassium uptake enhanced up to 80 kg K,O/ha application during both the years and nitrogen uptake was affected significantly only in the second year.

Effect of population densities of Pratylenchus brachyurus on the growth of cotton plants

The effect of different population densities of Pratylenchus brachyurus on the growth of cotton (Gossypium hirsutum) plants was studied in three greenhouse experiments, using cultivars IAC 20 and IAC 22. Both cultivars proved to be good hosts to the nematode, which however did not affect plant height and affected only slightly fresh root weight and dry top weight of both cultivars, even at the highest population density (over 9,000 nematodes/plant).

Studies on the Low-temperature Damage in Rice Seedlings. Effect of a low temperature on several characteristics of rice seedlings.

The effects of low temperature at the seedling stage on the growth of some indica and japonica varieties were examined. Five varieties, three indica and two japonica, were used. Seedlings were kept at normal temperature (20°C) until the third leaf blade was fully emerged. Then they were exposed to 8, 10, 12 or 14°C for 3, 6, 9 or 12 days. The increase on leaf area, top dry weight and number of roots during the treatment period was suppressed with the decrease of temperature and the increase of treatment period, in both indica and japonica varieties. The content of chlorophyll also decreased with the decrease of temperature and the increase of treatment period, and this tendency was remarkable in indica. After transplanted to the paddy field, the top dry weight, leaf age, the number of stem and the number of roots increased. The leaf age increased more rapidly, the severer the low-temperature treatment, and finally recovered to the control level in both indica and japonica varieties. On the other hand, the top dry weight, the number of roots and the number of stem increased more slowly, the severer the low-temperature treatment, and this tendency was remarkable in indica. The number of productive culms also showed a similer response to a low-temperature treatment. It was considered that the difference in the recovery of growing after transplanting to the paddy field between indica and japonica varieties was caused by the difference in the recovery of the root activity and photosynthetic activity after the low-temperature treatment.