Risk Of Lodging Research Articles

Manipulation of lignin metabolism by plant densities and its relationship with lodging resistance in wheat

Increasing plant density is one of the most efficient ways of increasing wheat (Triticum aestivum L.) grain production. However, overly dense plant populations have an increased risk of lodging. We examined lignin deposition during wheat stem development and the regulatory effects of plant density using the wheat cultivars shannong23 and weimai8. Plants were cultivated at densities of 75, 225 and 375 plants per m2 during two growing seasons. Our results showed that decreasing plant density enhanced culm quality, as revealed by increased culm diameter, wall thickness and dry weight per unit length, and improved the structure of sclerenchyma and vascular bundles by increasing lignification. In addition, more lignins were deposited in the secondary cell walls, resulting in strong lodging resistance. The guaiacyl unit was the major component of lignin and there was a higher content of the syringyl unit than that of the hydroxybenzyl unit. Furthermore, we hypothesised that the syringyl unit may correlate with stem stiffness. We describe here, to the best of our knowledge, the systematic study of the mechanism involved in the regulation of stem breaking strength by plant density, particularly the effect of plant density on lignin biosynthesis and its relationship with lodging resistance in wheat.

Management of poppy (Papaver somniferum L.) stand height using growth regulators

The possibility of reduce the length of poppy plants and their risk of lodging by applying selected plant growth regulators and effects on the plant and yield were studied in field experiments during 2010–2012. Statistically significant reduction was achieved only with ethephon (576 g a.i./ha) in all experimental years. In 2010 reduction for metconazole (60 g a.i./ha) was recorded. In 2012, ethephon at rates of 576 and 288 g a.i./ha prevented significantly poppy lodging. The 576 g a.i./ha rate was phytotoxic and decreased yield. The commonly used 576 g a.i./ha rate diminished heights by 16–20 cm in all experimental years and significantly reduced lodging in 2012, but decreased yields in two of the 3 years.

Effects of mepiquat chloride applications on non-oilseed sunflower

Non-oilseed sunflower plants can be exposed to lodging in some production regions due to higher plant height and larger heads, which is further exacerbated by heavily rainfall and strong winds. In this context, plant growth regulators such as mepiquat chloride (MC) can be considered as an alternative approach in reducing plant height and lodging. This study was conducted to determine the effect of MC application on the growth, yield, and yield components of non-oilseed sunflowers at different growth stages (V4, R1, R2, and R3) and rates (0, 30, 60, and 90 g a.i. ha-1) in Erzurum Province, eastern Anatolia, Turkey, in the 2012 and 2013 growing seasons. In general, the MC applications had significant effects on the plant parameters investigated. In comparison with the control treatment, the MC application of 60 g a.i. ha-1 decreased plant height by 5.38% and increased stem diameter, head diameter, seed filling percentage, ratio of dehulled/hulled seed weight, 1000-achene weight, and seed yield by 14.01%, 3.78%, 1.61%, 4.20%, 5.94%, and 5.26%, respectively. Similarly, the applications of MC at different growth stages also significantly affected seed yield and other characteristics such as plant height, stem diameter, and head diameter. The application of MC at the early growth stage (V4) was more effective compared to the later growth stages (R1, R2, and R3). The results of this study suggest that the mepiquat application rate of 60 g a.i. ha-1 in the early growth stage (V4) was more effective on the plant characteristics and that MC application could be effectively used as a means of reducing plant height and the risk of lodging in non-oilseed sunflower production.

Stem lodging parameters of the basal three internodes associated with plant population densities and developmental stages in foxtail millet (Setaria italica) cultivars differing in resistance to lodging

Foxtail millet (Setaria italica (L.) Beauv.) is a soft-stemmed summer cereal crop that is grown at a high crop density; however, stem lodging is recognised as a serious yield-limiting factor. The stem-breaking strength of the third to fifth basal internodes has previously been identified as the most important factor in determining the lodging resistance of foxtail millet. We measured variation in stem-breaking strength, length and weight of these internodes at different developmental stages and in response to different crop densities by using foxtail millet cultivars that differed in lodging resistance. The stem-breaking strength of the third internode was greater than of the fourth and fifth internodes, which had comparable stem-breaking strengths; this result was independent of genotype and developmental stage. The stem-breaking strengths of the three internodes were significantly correlated with each other and linearly related across different developmental stages and crop densities. The stem-breaking strength of the three internodes at hard dough stage (Zadoks growth stage Z87, at 30 days after flowering) was less than at other developmental stages in the lodging-resistant genotypes. Stem-breaking strength for the three internodes was correlated with fresh weight (FW) and dry weight (DW) per cm. The variation of FW and DW per cm of the internodes in response to crop density was attributed to the change of FW and DW of the corresponding internodes, rather than to variation in their length. Results from this study showed that the fourth or fifth basal internode was more prone to lodging than the third basal internode because of their lesser stem-breaking strength. Crop density linearly influenced the stem-breaking strength of the three basal internodes. Reducing crop density enhanced stem-breaking strength of third to fifth internodes, which may reduce the risk of stem lodging in this crop. Based on the findings, the stem-breaking strength of the fourth or fifth basal internode measured at the late grain-filling stage from Z77 (late milk) to Z87 (hard dough) differentiated stem-breaking strength, the most important stem lodging associated parameter, in the foxtail millet genotypes.

Lodging stress in cereal-effects and management: an overview.

Uncertainty in climatic and weather conditions may result in lodging. Lodging is a most chronic constraint, which is causing tremendous yield reduction in crop plants; therefore, better understanding to control lodging-induced adversities or to enhance lodging resistance in cereals is imperative. In this review, we presented a contemporary synthesis of the existing data regarding the effects of lodging on growth and yield of cereals. Moreover, we highlighted key factors which trigger the detrimental effects of lodging in cereals. Numerous morphological, anatomical, and biochemical traits in plants that can influence lodging risk have also been discussed. These traits showed significant correlation with lodging resistance in cereals. At end, we tried to link our hypothetical concepts with previous evidences and provided a comprehensive summary of all the possible management approaches that can be used to further control lodging effects on cereals. The selection of a management option though is based on cereal type and genotype; nonetheless, different agronomic approaches including seeding rate, sowing time, tillage system, crop rotation, and fertilizer application help in reducing lodging risk in cereals.

The effect of nitrogen application and planting density on the radiation use efficiency and the stem lignin metabolism in rapeseed (Brassica napus L.)

Using the rapeseed Huayouza 62 as experimental material, yield and lodging related traits were evaluated under various nitrogen applications [120,240 and 360kgha−1 (N1–N3, respectively)] and planting densities [15×104, 30×104 and 45×104 plants ha−1 (D1–D3, respectively)]. Results showed: (1) the increase of nitrogen fertilizer elevated the leaf (and silique) area index (LAI) and light interception rate (LIR), significantly affecting the bud stage. In addition, the radiation use efficiency (RUE) for different growth stages and biomass accumulation were increased, which improved yield by facilitating formation of siliques in both single plants and populations. The increase of planting density significantly elevated the population LAI and LIR in seedlings, and the RUE in various growth stages, increased population biomass accumulation, which may have also improved yield by promoting the formation of siliques in the population. The correlation between LIR/LAI and yield was the highest at the bud stage, while the strongest correlation between RUE and yield was at silique development. (2) More nitrogen increased the lodging angle, base lodging index (LIL) and the upper lodging index (LIU), resulting in elevated whole plant lodging risk. With increases in nitrogen fertilizer, expression of phenylalanine ammonia-lyase (PAL) of lignin biosynthesis decreased in the upper stem, leading to lower lignin content and lodging resistance. However, higher plant density reduced the lodging angle and LIU, but increased LIL. The increase in planting density induced the expression of PAL, cinnamoyl-CoA reductase 1 (CCR1), 4-coumarate: CoA ligase (4CL) in the stem, which showed their highest expression in the N2D3 treatment, leading to higher lignin content and lodging resistance. (3) In this study, N2D3 achieved relative high yield and the lowest lodging index, which will meet the requirements for mechanized harvest.

A new method for assessing plant lodging and the impact of management options on lodging in canola crop production.

Lodging, defined as the permanent displacement of aboveground parts, is a common problem to cause yield loss, deterioration in seed quality and difficult to harvest in canola (Brassica napus L.) crop production. This study aimed to develop a method for assessing crop lodging, to examine how agronomic practices affected the relationships between root lodging and electrical capacitance traits. Canola plants were more susceptible to root lodging than stem lodging. The electrical measurements were more closely related with anchorage strength (Sp) than stem bending strength (Ss). Among the three electrical measurements, the root capacitance (C) displayed the most consistent and significant relationships with Sp in all three field experiments (R2 = 0.88–0.56; P ≤ 0.01). This study indicates that the risk of lodging can be reduced by using appropriate management practices and variety selection. Enhancing root Sp was advocated as a priority over enhancing stem Ss in cultivar improvement. Electrical measurements, especially of root C, can be considered as a non–invasive technique that could partially replace the intrusive methods used for the in situ assessment of lodging resistance among various agronomic practices or can be applied in breeding programs for selecting genotypes with high yield potentials and strong Sp values.

Contribution of Reserves to Kernel Weight and Grain Yield Determination in Maize: Phenotypic and Genotypic Variation

Maize (Zea mays L.) kernel weight (KW) and grain yield depend on plant growth during active grain filling and reserves use. The objective of our study was to analyze the phenotypic and genotypic variation in these traits in a family of recombinant inbred lines (RIL). In two field experiments we measured plant grain yield (PGY) and its components (KW and kernel number per plant, KNP), biomass production per plant and per kernel during active grain filling, and apparent reserves use (ARU) per plant (ARUP, difference between PGY and plant biomass production during active grain filling) and per kernel (ARUK, difference between KW and plant biomass production per kernel during active grain filling). Heritability (h2) and phenotypic plasticity were computed for all traits. Large differences were always evident among genotypes, but phenotypic plasticity was (i) low for KW and plant biomass at R2 and physiological maturity; (ii) intermediate for KNP and PGY; and (iii) high for plant growth, plant growth per kernel after R2, and ARUs. Traits with highest h2 were KW (0.70), KNP (0.61), and ARUP (0.59). Final KW was related to plant growth per kernel (r2 = 0.64; P < 0.001) but not to ARUK, and ARUP was driven (r2 ≥ 0.49; P < 0.001) by KNP. Because of its positive relationship with KNP (main determinant of PGY), high h2 and high phenotypic plasticity, breeding must consider the increase in ARUP for improving grain yield, an objective that needs to be coupled with large reserves accumulation before silking to avoid the risk of lodging.

Vegetative nitrogen stress decreases lodging risk and increases yield of irrigated spring wheat in the subtropics

In-crop nitrogen (N) application is used widely in rainfed winter wheat production to reduce lodging risk; however, uncertainty exists as to its ability to reduce lodging risk in subtropical irrigated wheat production without simultaneously reducing yield potential. The objective of this study was therefore to determine whether in-crop N application reduces lodging risk without reducing yield of irrigated spring wheat in a subtropical environment. Irrigated small-plot experiments were conducted to compare the effect of alternative N timing on lodging and yield in two cultivars. Variable N regimes were imposed during the vegetative growth phase, after which additional N was applied to ensure that total season N application was uniform across N-timing treatments. Treatments with low N at sowing had significantly less lodging and were the highest yielding, exhibiting yield increases of up to 0.8 t ha–1 compared to treatments with high N at sowing. Increased leaf area index, biomass and tiller count at the end of the vegetative growth phase were correlated with increased lodging in both cultivars, although the strength of the correlation varied with cultivar and season. We conclude that canopy-management techniques can be used to simultaneously increase yield and decrease lodging in irrigated spring wheat in the subtropics, but require different implementation from techniques used in temperate regions of Australia.

Effects of Seed Dressing with Uniconazole Powder on Lodging Resistance of Culm in Common Buckwheat

Lodging is one of the important factors affecting the yield and quality of common buckwheat(Fagopyrum esculentum M.) worldwide. Ningqiao 1, a cultivar of common buckwheat with moderate lodging resistance was used in this study to investigate the dynamic changes of lodging behavior, yield, culm snapping resistance, lodging index, culm morphological characteristics and culm anatomical structure seed dressing with uniconazole powder(0, 100, 200, and 300 mg kg–1). The results indicated that seed dressing with uniconazole powder had significantly effects on the lodging resistance of culm in common buckwheat. With the increase of uniconazole powder concentration, the yield, culm snapping resistance, diameter of the 2nd internode, dry weight of the 2nd internode, filling degree, mechanical tissue layer number, mechanical tissue thickness, culm wall thickness, vascular bundle number, and vascular bundle area showed an increased-decreased trend, whereas, the lodging percentage, lodging index, plant height, culm gravity height, culm fresh weight, and length of the 2nd internode showed an decreased-increased trend. In this case, the treatment of seed dressing with 200 mg kg–1 uniconazole powder could optimize the culm structure, improve the culm quality, reduce the lodging risk, and enhance the yield of common buckwheat.

Growth and Yield Responses of Soybean to Planting Density in Late Planting

Soybean is one of the important food crop around the world. Especially in East Asia, it is the main ingredient for traditional food like soy sauce and soy paste. The double cropping system including soybean following onion, Chinese cabbage, and potato is widely adopted in Southern region of Korea. In this system, sowing date of second crop (soybean) can be delayed depending on first crops' growth period and weather condition. When planting date is delayed it is known that soybean yield is declined because of shorter vegetative growth period and earlier flowering induced by warm temperature and changes in photoperiod. The objective of this study was to determine soybean growth and yield responses as plant populations at late planting date. Field experiment was conducted at Department of Functional Crop, National Institute of Crop Science, RDA located in Miryang, Gyeongsangnam-Do for two years ('13-'14) in upland field with mid-late maturity cultivar Daewon. A split-plot block design was used with three replications. Main plots were three sowing dates from June 20 to July 20 with 15 days intervals, and subplots were 4 levels of planting densities. Data of maturity (R8) was recorded, yield components and yield were examined after harvesting. Experimental data were analyzed by using PROC GLM, and DMRT were used for mean comparison. Optimum planting population for maximizing soybean yield in late planting which compared with standard population. In mid-June planting, higher planting density causes increased plant height and decreased diameter which lead to higher risk of lodging, however, reduced growth period due to late planting alleviated this problem. Therefore higher seeding rates can provide protection against low seedling emergence caused by late planting in this region.

Ethephon improved stalk strength associated with summer maize adaptations to environments differing in nitrogen availability in the North China Plain

SUMMARYNitrogen (N) supply is essential for achieving high grain yield in maize production, but excessive N application can lead to lodging risks and potential yield loss. The main objective of the present study was to investigate the effect of ethephon application under different N fertilizer rates in reducing maize lodging. Field experiments were conducted to determine the interactive effects of ethephon (0 and 180 g/ha) and N rate (0, 75, 150 and 225 kg N/ha) on the morphological and chemical characteristics of basal internode and yield across two summer maize-growing seasons (2011/12) in Wuqiao of the North China Plain. Findings showed that ethephon significantly increased the maximum diameter of the 7th to 14th internodes, and decreased the internode lengths, which led to a decrease in plant and ear heights under different N rates. Significant ethephon × N interaction effects were observed on the diameter and length of internode, dry weight per unit internode length and breaking resistance. Ethephon significantly increased N, cellulose and hemicellulose contents of the basal internode, but cellulose and hemicellulose contents decreased as the rate of N application increased. Internode diameter, dry weight per unit internode length, and N content of the basal internode were significantly positively correlated with breaking resistance. Ethephon significantly increased grain yield and harvest index in 2011, but not in 2012. Grain yield and above-ground biomass were increased with increasing N application in both growing seasons, showing linear and quadratic responses. These results suggested that ethephon could increase stalk strength by improving the morphological and chemical characteristics of the basal internode, and maintain high yield and biomass under high N rates.

Effects of Nitrogen Fertilizer and Planting Density onthe Lignin Synthesis in the Culm in Relation to Lodging Resistance of Buckwheat

Lodging is an important constraint limiting buckwheat yield and quality by bending or breaking culm on buckwheat production worldwide. This study was conducted with Ningqiao 01, a moderate lodging resistance cultivar of buckwheat, to determine whether lignin synthesis and lodging resistance of buckwheat are affected by nitrogen fertilizer and planting density. The results showed that the lignin content at the bottom of the 2nd internode was significantly and negatively correlated with lodging index and lodging percentage, but significantly and positively correlated with snapping resistance. The snapping resistance rose and then fell with the increase of nitrogen fertilizer. The snapping resistance decreased with the increase of planting density. The lodging index increased with the increase of nitrogen fertilizer and planting density. The lignin content and its related enzymes activities decreased with the increase of nitrogen fertilizer and planting density. These results suggested that the lignin content is closely related to the lodging resistance of buckwheat, and a higher lignin content could strengthen the lodging resistance of buckwheat. The increase of nitrogen fertilizer and planting density significantly increased the risk of lodging by decreasing the lignin content and its related enzymes activities at the bottom of the 2nd internode.

QTLs for Shoot Length and Chlorophyll Content of Rice Seedlings Grown under Low-Temperature Conditions, using a Cross between Indica and Japonica Cultivars

Quantitative trait loci (QTLs) affecting the shoot length and chlorophyll content of seedlings grown at a low temperature (16ºC) for 4 weeks were analyzed using inbred lines derived from a cross between an indica rice cultivar, Habataki, and a japonica rice cultivar, Arroz da Terra. Culm length of the inbred lines, measured at the harvesting stage, was also analyzed. The QTLs linked to increased shoot length (qSL1 ) and culm length (qCL1 ) on the Arroz da Terra allele were detected in the same region of chromosome 1, where the gibberellin 20 oxidase-2 gene (identical to Semi Dwarf1 : SD1 ) located. Other QTLs ( qSL and qSL8 ) that were linked to increased shoot length on Arroz da Terra and Habataki alleles, but had no effects on the culm length, were detected on chromosomes 3 and 8, respectively. The alleles of qSL3 and qSL8 might improve early shoot growth without increasing the risk of lodging caused by a long culm length. A novel QTL (qCC1 ) linked to increased chlorophyll content of seedlings grown at low temperatures through the effect of an Arroz da Terra allele was detected on chromosome 1, but it differed in position from the QTLs for shoot length.

Historical analysis of the effects of breeding on the height of winter wheat (Triticum aestivum) and consequences for lodging

The relationship between crop height and yield is complex with genes and genetic markers for greater height associated with both increases and decreases in yield. As a result of this the optimum height for maximum potential yield is not well understood and has been estimated at between 70 and 100 cm. This study investigated the effect of plant breeding on the height of UK winter wheat varieties by analysing data on straw shortness scores and absolute height collected from UK national variety testing trials between 1977 and 2013. The analysis showed that varietal introductions between the early 1970s and 1980 shortened plant height by approximately 15 cm (110–95 cm) followed by a gradual reduction to about 88 cm by the 1990s. There was no significant trend in height between 1990 and 2013. It was estimated that the reduction in plant height between 1970 and 2000 would have been sufficient to counteract the increase in lodging risk caused by the increase in yield potential of new varieties over this period of approximately 3 t/ha. It is predicted that the lodging risk of varieties introduced since 2000 are likely to have increased due to further increases in yield potential and the absence of further shortening. Possible reasons why UK plant breeders have not continued to shorten wheat are considered.

A generalised model of crop lodging

The lodging of cereal crops due to high wind and rain is of considerable significance in many parts of the world, leading to major economic losses and yield reductions. In earlier papers the authors have developed a model of the lodging of winter wheat that identified the major parameters of the problem and enabled the relationship between root and stem lodging to be examined. It has formed the basis of a methodology used in the UK for guidance to farmers and agronomists on ways of reducing lodging risk. However the authors would be the first to acknowledge that there are limitations to the model that make it difficult to apply for a wide range of crops – particularly in the specification of the wind field and the root/soil interaction, and in allowing for stem lodging elsewhere than at the base of the stem. This paper thus describes the development of a generalised model that overcomes these shortcomings. After a discussion of the lodging phenomenon in general and a description of the earlier work, the basis of the new model is set out, based upon a mechanical model of the wind/plant/soil interactions that capture most of the important physical processes. The manner in which this model can be applied to clarify the nature of the lodging process and calculate lodging risk through a simple graphical formulation is discussed. In particular simple formulae are defined for lodging risk that are functions of a small number of dimensionless variables with identified physical meanings. The model is then applied to the lodging of wheat, oat and oilseed rape crops and considers the sensitivity of the risk calculations to uncertainties in the model parameters. In general it is suggested that the risk of lodging can be determined from very simple functions of dimensionless stem and root lodging velocities.

GIS-based evaluation of maize cultivar lodging resistance performance in target growing environments.

Lodging in maize is one of the major problems in maize production worldwide, which causes serious yield and economic losses annually. By evaluating cultivar lodging resistance performance in target growing environments before cultivar extension and application, the risks and losses can be significantly reduced. In this study, a GIS-based quantitative method for evaluating maize cultivar lodging resistance performance in target growing environments was established based on full cognition of environment stress, cultivar resistance, and the interaction between them. At first, comprehensive environment lodging stress is measured by three factors: 1) extreme wind event in maize vegetative stage which is the direct factor, 2) soil potassium content in target growing environment which is an indirect factor affecting corn stem sturdiness, and 3) planting density which is a human influence factor. Quantification methods of extreme probability analysis, spatial interpolation, normalization, and so on were used. Then, maize cultivar lodging resistance was determined using cumulative frequency distribution analysis of tested lodging data. At last, an evaluation matrix was established combining environment lodging stress and cultivar lodging resistance together, which was very simple and easy to understand method and the result is promising providing good direct support in practical cultivar application. The method used in this study, at county-level, cultivar-level and stress-level with GIS, can facilitate the identification of better-adapted growing environments for a specific maize cultivar, and provide direct support for maize cultivar recommendation and extension, so as to reduce the risk and loss of lodging in maize. It is more easy-operational and feasible than traditional surveying approach, especially for large-scale spatial trend analysis. So it is of both academic significance in accelerating precision agriculture development and practical significance in improving maize cultivar application. Keywords: lodging in maize, environment lodging stress, cultivar lodging resistance, GIS, maize production, growing environment DOI: 10.3965/j.ijabe.20140703.007 Citation: Mi C Q, Liu Z, Zhang X D, Peng X N, Huang B. GIS-based evaluation of maize cultivar lodging resistance performance in target growing environments. Int J Agric & Biol Eng, 2014; 7(3): 51－58.

SUNFLOWER MORPHOLOGY AND YIELD AS AFFECTED BY FOLIAR APPLICATIONS OF PLANT GROWTH REGULATORS

Plant height of sunflower is a major agronomic trait affecting crop performance in the field and its adaptation to mechanical harvest. Field experiments were conducted to study the effect of foliar application of paclobutrazol (PBZ) at 12.5 g ai/ha, mepiquat chloride (MPC) at 25.0 g ai/ha and chlormequat chloride (CCC) at 1,500 g ai/ha in single or double applications on sunflower plant morphology, growth and achene yield and oil content. Single applications of PBZ or MPC reduced sunflower plant height at maturity by 11.1% and 11.7%, respectively. Single applications of PBZ, MPC or CCC did not reduce the above ground dry weight of the plants, provided similar achene yield per plant and 100-achenes weight compared with those of the non-treated control, whereas increased the total number of achenes as well as the number of filled achenes per capitulum. Double applications of PBZ, MPC or CCC reduced plant height by 13.9%, 15.6% and 13.4%, respectively, but proved in certain cases to have a phytotoxic effect on achene and oil production. Double application of PBZ resulted in lower achene and oil yield than the non-treated control, whereas double application of MPC resulted in lower above ground dry weight at maturity, achene yield and 100-achenes weight. Double application of CCC resulted in reduced 100-achenes weight. Overall, PBZ and MPC under the single dose scheme applied can reduce plant height in sunflower without adverse effects on achene and oil yields, thus providing a basis for reducing the risk of plant lodging.

Lodging resistance of winter wheat (Triticum aestivum L.): Lignin accumulation and its related enzymes activities due to the application of paclobutrazol or gibberellin acid

Lodging is an important constraint limiting wheat yields and quality by bending or breaking stems on wheat (Triticum aestivum L.) production worldwide. This study was conducted to determine whether lignin accumulation and lodging resistance of winter wheat could be affected by application of paclobutrazol (PP333) or gibberellin acid (GA3) at stem elongation stage (DC 3.0). Two winter wheat cultivars, Jimai22 (lodging-tolerant cultivar; JM22) and Shannong16 (lodging-susceptible cultivar; SN16), were used to investigate the effect of exogenous hormones on wheat lodging behavior, lignin accumulation in culms and its relation to lodging resistance. Results showed that application of PP333 significantly reduced plant height and the length of basal second internode, while GA3 had the opposite effect. Lignin accumulation was positively and significantly correlated with the breaking strength of internode and culm lodging resistance index (CLRI). PP333 significantly increased lignin accumulation and its related enzymes activities in the basal second internode, and also increased the diameter, wall thickness, filling degree of the internode, thus the breaking strength and lodging resistance of wheat increased. Whereas, GA3 caused opposite effect on those characteristics. These results suggested that the exogenous PP333 or GA3 application significantly changed the risk of lodging occurred not only by altering the plant height but also by altering the physical strength of the basal part of the culm internode, especially, altering the lignin accumulation and its related enzymes activities in basal internode.

Effect of Panicle Nitrogen Fertilizer Management on Yield and Population Quality in Mechanical Transplanted Super Rice Ningjing 1 with Different Seedling Ages

Adopting super high yield rice Ningjing 1 as material,the effect of panicle nitrogen fertilizer application time on yield and population quality of transplanted seedlings with different ages was studied.The results showed that,with the same panicle nitrogen fertilizer application time,rice yield,growth rate of rice population,dynamics of culm and tillers number,leaf area index and photosynthetic potential of right age seedlings were all better than those of overage seedlings in mechanical transplanted rice production.With the right age seedlings,when the panicle nitrogen fertilizer applied equally at the fourth leaf age from top and at the third leaf age from top(D4-3),rice yield,growth rate of population,percentage of productive tiller,leaf area index and photosynthetic potential after heading,leaf area of productive tillers at heading and its ratio,leaf area from flag leaf to the 3rd leaf from top of productive tillers at heading and its ratio,the drop angle of top three leaves were all higher than those when the panicle nitrogen fertilizer applied equally at the fifth leaf age from top and at the third leaf age from top(D5-3) or applied equally at the fifth leaf age from top and at the fourth leaf age from top(D5-4).With the overage seedlings,when the panicle fertilizer applied at D5-4,rice yield,growth rate of population from heading to maturing,dynamics of culm and tillers number and leaf area index after elongating,photosynthetic potential after the critical stage of productive tillers,leaf area of productive tillers and leaf area from flag leaf to 3rd leaf from top of productive tillers at heading,the length of basal three internodes of stem and its ratio to the whole stem were all higher than those when the panicle nitrogen fertilizer applied equally at the fifth leaf age from top and at the third leaf age from top D5-3 or applied at D4-3.The results indicated that seedling age is important for high yield of mechanical transplanted rice.Using right age seedlings is helpful for forming the high quality rice population and obtaining high yield when the panicle nitrogen fertilizer applied at D4-3.Instead,with the overage seedlings,the early applying of panicle nitrogen fertilizer,such as applying at D5-4,would promote some shaky tillers to be transformed into effective tillers and consequently form the ears,which provides a compensation for some insufficient growth due to transplanting with overage rice seedlings.However,the early applying of panicle nitrogen fertilizer would elongate the basal internodes of stem excessively and increase the risk of lodging.