水稻茎秆抗倒伏的综合评价

利用力学理论和方法,综合分析了水稻茎秆各性状对抗倒伏的影响．突破以往的单性状分析方法,得到水稻茎秆抗倒伏的综合评价指标λ(茎秆柔度),它综合反映了秆长、截面尺寸和形状等茎秆性状．λ是一个无量纲的量,λ值越小,抗倒伏能力越强．     

玉米茎秆抗倒伏的力学机制研究

建立了玉米茎秆的力学模型,给出了玉米茎秆抗倒伏的各种性质参数的关系式,为玉米抗倒品种的选育提供了理论基础。     

基于主成分分析水稻植株CH4排放估算模型

估算稻田甲烷（CH4）排放量是开展稻田甲烷排放研究的重要内容之一．通过观测南方红黄壤稻田不同水稻品种甲烷排放通量,测定了16个早稻、20个晚稻品种的植株节间组织的数量特征．选取株高、茎秆长度、茎秆维管束面积／茎壁横切面积、茎壁横切面积／节间横切面积、叶鞘横切面积／节间横切面积、气腔面积／茎壁横切面积、维管束总面积／茎壁横切面积等相关因子进行了主成分分析,建立基于水稻植株的CHa排放估算模型,早、晚稻估算模型相关系数分别为0．827、0．853．同时构造了综合评价函数,得出了水稻品种CH4排放综合分值,与实测结果相比较,吻合度较高．利用估算模型进行模拟,比较模拟值与实测值,相对误差较小,证明模型具有有效性和可行性,为估算水稻CH4排放提供参考依据,为评价水稻品种CH4排放高低提供经验参考．     

不同养分和水分管理模式对水稻抗倒伏能力的影响

大田试验下,通过对水稻茎秆基部物理性状、形态特征和硅、钾含量的测定和比较,系统研究了不同养分和水分管理模式对水稻茎秆抗倒伏能力的影响．结果表明,有机无机肥配施,特别是秸秆与化肥配施(CS)养分模式可明显提高水稻植侏茎秆粗度、茎壁厚度和茎重,从而有效提高了基部茎秆的抗折力(RS)和明显降低了水稻的倒伏指数(LI),秸秆与化肥配施(CS)养分模式对水稻抗倒伏能力的效果在干湿交替(AWD)和控水模式(DRA)下表现更为明显。有机无机肥配施,特别是秸秆与化肥配施(CS)的养分模式在干湿交替(AWD)和控水模式(DRA)下更有助于提高水稻茎秆的硅、钾含量、相关分析表明,水稻基部茎秆茎壁厚度、茎重和抗折力与茎秆硅、钾含量存在显著(P<0．05)或极显著正相关(P<0．01)。     

水稻茎秆形态结构特征和化学成分与抗倒伏关系综述

水稻茎秆形态结构特征和化学成分与其抗倒伏性能相关。本文对水稻茎秆高度、茎秆基部第1、2节间长度、茎秆粗细、茎壁厚度、厚壁组织(机械组织)数量和强度、维管束数量、细胞壁纤维素和木质素含量、细胞中碳水化合物积累的数量、硅与钾的含量以及茎秆抗倒伏相关的QTL等与水稻的抗倒伏性的相互关系进行了综述,为水稻抗倒伏优良品种性状的选育提供参考。     

水稻不同生育期茎秆生化成分的变化及其与抗倒伏能力的关系

以抗倒伏品种‘南粳44’、‘武运粳7号’与不抗倒伏品系‘宁7412’为试验材料,通过对水稻不同生育期茎秆硅、钾、钙、镁含量及可溶性糖含量的测定,结合氮钾肥配比试验,研究了水稻不同生育期茎秆硅、钾、钙、镁含量及可溶性糖含量的变化及其与茎秆抗倒伏能力的关系。结果表明：水稻茎秆的硅、钙、镁含量及可溶性糖含量随生育进程呈上升趋势,而茎秆的钾含量呈现先降后升的趋势。在不同施肥水平条件下,水稻茎秆的硅、钾、钙、镁含量及可溶性糖含量存在一定的差异。抗倒伏品种‘南粳44’和‘武运粳7号’茎秆基部抗折力较强,施肥对水稻茎秆基部抗折力有一定的影响。水稻生殖生育期茎秆的硅含量、可溶性糖含量与茎秆基部抗折力呈极显著正相关（P〈0.01）,与水稻抗倒伏能力的强弱有一定的关系。     

大田增强UV-B辐射对元阳梯田地方水稻茎秆性状和倒伏指数的影响

大田原位种植元阳梯田2个地方水稻品种——白脚老粳和月亮谷,研究2年不同强度(0、2.5、5.0和7.5 kJ·m^-2)UV-B辐射对水稻穗下第1至第4节的茎秆性状(节间长、茎秆粗和茎壁厚)和倒伏指数的影响.结果表明: 增强UV-B辐射对水稻茎秆的节间长和茎秆粗没有显著影响,但导致茎壁厚度显著减小,其中,7.5 kJ·m^-2 UV-B辐射对水稻穗下第4节茎秆茎壁厚度的影响较大,降幅为11.6%～19.6%;增强UV-B辐射导致水稻茎秆的倒伏指数增加,增大水稻倒伏的风险,水稻穗下第4节茎秆倒伏指数最大,并大于倒伏临界值(200);水稻穗下第4节、第3节和第2节茎秆的倒伏指数与茎壁厚度呈显著负相关.表明增强UV-B辐射显著减小元阳梯田水稻茎秆的茎壁厚是增加其倒伏风险的主要原因.
     

未来CO2浓度增加和相应增温对水稻产量影响的模拟——以浙江省为例

采用水稻生育生理生态综合模型ORYZA1,模拟分析了未来15种可能气候变化对浙江省水稻产量的影响结果表明,CO2浓度的增加将使水稻增产,温度增加将导致水稻减产虽然CO2增加和相应增温对各季水稻产量在各地区的影响表现不同,但在不考虑温室效应将同时导致旱涝和病虫害变化条件下．GFDL、GISS和UKMO模型预测的气候变化将使浙江省全年水稻产量分别平均增产9．53％、8．92％和0．04％．     

稻鸭共作下水稻植株的壮秆效应及生理特性

通过田间小区对比试验,分析了稻鸭共作下水稻植株的壮秆效应及其相关生理特性.结果表明：由于鸭子在稻田的活动使水稻植株形态发生了明显变化,植株碳水化合物含量、植株碳氮比、茎秆干物质输出率都明显增加,茎秆基部节间长度比对照缩短2.88%,茎粗增加64.90%,茎秆强度和抗倒伏指数也分别提高了11.78%和10.95%;稻鸭共作提高了水稻深层根系比例和根系活力,黑根比例降低了16.63%.因此,稻鸭共作对水稻植株有壮秆效应,提高了植株的抗逆性,有利于水稻稳产高产.     

土壤水分亏缺对水稻茎秆贮藏碳水化合物向籽粒运转的调节

以两个茎秆贮藏物质利用效率不同的水稻(Oryza sativa)杂交组合(‘汕优63’和‘Pc311/早献党’)为材料,进行土壤水分亏缺处理(Water-deficit),以水层灌溉为对照(Well-watered),研究水分亏缺对水稻茎贮藏性碳水化合物运转及其关键酶活性的调节作用。结果表明,水分亏缺促进了水稻茎秆贮藏物质的运转和对籽粒产量的贡献,开花前茎秆贮藏的碳水化合物对产量贡献率分别提高了1.9~3.0倍(与水层灌溉相比)。土壤水分亏缺诱导了水稻茎节间α-淀粉酶、β-淀粉酶、α-葡萄糖苷酶、D-酶活性上升,但淀粉磷酸化酶受到了抑制,说明土壤水分亏缺加强水稻茎秆贮藏淀粉水解途径,而不是磷酸解途径。就蔗糖代谢而言,土壤水分亏缺提高了蔗糖磷酸合成酶的活性和活化状态,抑制蔗糖转化酶活性,促进蔗糖合成,加速贮藏物质快速降解和转移,从而调节稻株贮藏碳水化合物向籽粒的分配。     

Dynamic behaviour of inflorescence-bearing Triticale and Triticum stems

The mechanical response of cereal plant shoots to loads caused by wind and gravity in the field is swaying in flexure around the vertical or near vertical transient equilibrium position determined by the stationary component of the wind pressure. The aim of this work was to characterise the kinematic and dynamic attributes and their interrelations in freely swaying inflorescence-bearing stems of wheat (Triticum aestivum L.) and Triticale. The fundamental natural frequency of the stems appeared to be considerably lower than predicted from the theory of vibration using the model of a cantilever beam oscillator and assuming the spring constant to be equal to the force-deflection ratio. Because of the rate of deformation and visco-elastic behaviour of the plant material, a discrepancy of about 10% was found between the dynamic and static stem bending resistance. The presence of the tip inflorescence caused vibrating vertical stems to behave as compressed columns in which the effective spring constant was strongly biased by the apical load due to the weight of the inflorescence. At the late milk stage, in the freely swaying stems of wheat and Triticale, the resistance to dynamic lateral loads was reduced by about 30% as a result of compression exerted by the inflorescence. So the prominent effect of the tip inflorescence on the dynamic behaviour (the effective spring constant and the natural frequency) of the stem is attributed to the non-negligible magnitude of the inflorescence weight relative to the critical load producing elastic buckling in slender vertical structures. Stem softening as a consequence of increasing inflorescence weight is assumed to be one of the essential factors reducing the lodging resistance in cereal crops at the late milk stage. The feasibility of the compressed-column approach for predicting the dynamic bending performance of slender vertical plant organs is discussed. Received: 4 March 1998 / Accepted: 20 July 1998     

Antixenosis and Antibiosis Resistance in Rice Cultivars against <Emphasis Type="Italic">Chilo suppressalis</Emphasis> (Walker) (Lepidoptera: Crambidae)

The striped stem borer, Chilo suppressalis (Walker) (Lepidoptera: Crambidae), is an important pest afflicting rice in most rice-growing countries in the world. Deliniating the categories of resistance in rice genotypes under field conditions could be helpful in managment of this pest. Two categories of resistance, antixenosis and antibiosis, were examined in ten popular and diverse rice genotypes of different origin that had been selected for their resistance to the striped stem borer in a previous study. Significant differences were found between genotypes for the number of egg masses, number of eggs, preference index, larval and pupal weight, larval development time, larval survival rate, larval mine length, and leaf trichome density. It was found that the rice genotypes Novator, A7801, and Nemat had the more pronounced antixenosis-type resistance, whereas AB1 and Shirodi had better antiobiosis-type resistance. Interestingly, the rice genotype AN-74 for which Nemat is the parental line showed both types of resistance and could be effectively used in an integrated pest management of the rice striped stem borer.     

Damped oscillations of the giant reed Arundo donax (Poaceae)

The slender upright culms of the giant reed (Arundo donax L.) are often exposed to dynamic wind loads causing significant swaying. The giant reed has slightly tapered hollow stems (4-6 m high) with flat leaves and an extensive underground rhizomatous system with solid branches bearing adventitious roots. Quantitative analyses of videorecordings prove that A. donax responds to dynamic deflections of the stem with damped harmonic bending oscillations. The logarithmic decrement can be used to calculate the relative damping, as a measure of the plant's capacity to dissipate vibrational energy. Plants with leaves have a significantly higher damping compared to plants without leaves. A comparison of the relative damping of plants with and without leaves shows that this finding is only partly due to aerodynamic resistance of the leaves. Structural damping also contributes considerably to the overall damping of the foliate A. donax stem. By stepwise removal of the underground plant organs the influence of rhizome, roots, and soil on the vibrational behavior was determined. The data indicate that underground plant organs as well as leaf sheaths covering the nodes have no significant influence on damping.     

Crown structure and wood properties: Influence on tree sway and response to high winds

Wind can alter plant growth and cause extensive, irreversible damage in forested areas. To better understand how to mitigate the effects of wind action, we investigated the sensitivity of tree aerodynamic behavior to the material and geometrical factors characterizing the aerial system. The mechanical response of a 35-yr-old maritime pine (Pinus pinaster, Pinaceae) submitted to static and dynamic wind loads is simulated with a finite element model. The branching structure is represented in three dimensions. Factor effects are evaluated using a fractional experimental design. Results show that material properties play only a limited role in tree dynamics. In contrast, small morphological variations can produce extreme behaviors such as either very little or nearly critical dissipation of stem oscillations. Slender trees are shown to be relatively more vulnerable to stem breakage than uprooting. Dynamic loading leads to deflections and forces up to 20% higher near the base of the tree than those calculated for a static loading of similar magnitude. Effects of branch geometry on dynamic amplification are substantial yet not linear. The flexibility of the aerial system is found to be critical to reducing the resistance to the airflow and thus to minimizing the risk of failure.     

The effects of air flow and stem flexure on the mechanical and hydraulic properties of the stems of sunflowers Helianthus annuus L

Many studies have shown that wind affects plant development, causing them to develop shorter and usually stronger stems. Many of these effects have been shown to be due to a response to mechanical flexing of the stem which is known as thigmomorphogenesis. However, it is not known how wind affects the hydraulic properties of stems, nor have the effects of air flow past leaves been examined in isolation from mechanical flexing. This study, therefore, used a factorial experiment to distinguish between the effects of stem flexing and air flow, and examined the morphology, hydraulics and mechanics of developing sunflowers Helianthus annuus. It was found that flexure and air flow had opposite effects on several aspects of development; air flow increased plant height and length-specific stem hydraulic conductivity, k(h), and reduced stem rigidity and strength, while flexing did the reverse. There was also a clear trade-off between hydraulic and mechanical capability: as one increased the other decreased. A plant's response to wind must, therefore, be a complex response to at least two different stimuli and this might help explain why it varies with species and environment.     

Improvement of lodging resistance with QTLs for stem diameter in rice (Oryza sativa L.)

Varietal differences among ten rice cultivars showed that stem diameter is a key factor in lodging resistance (measured in terms of pushing resistance). Two near-isogenic lines (NILs) were selected from a series of chromosome segment substitution lines developed between cultivars Nipponbar and Kasalath, one containing a single stem diameter QTL (sdm8; NIL114), and another with four stem diameter QTLs (sdm1, sdm7, sdm8, sdm12; NIL28). Compared with the Nipponbare control, stem diameters were larger in NIL114 and NIL28 by about 7 and 39%, respectively. Pushing resistance in NIL28 was significantly greater than in Nipponbare, but NIL114 was similar to Nipponbare. The two NILs had greater weight of lower stem and culm wall thickness than Nipponbare. NIL28 had higher plant height, which is a negative effect on lodging resistance, than Nipponbare. The non-structural carbohydrate contents of NIL stems were higher than that of Nipponbare, whereas the silicon contents were lower in the NILs, and cellulose contents were lower only in NIL28. The basal internodes of the two NILs were significantly stiffer than those of Nipponbare. These results suggest that increasing stem diameter in rice breeding programs would improve lodging resistance, although the combination of multiple QTLs would be necessary to produce thicker stems with higher pushing resistance, whereas the higher plant height could also result from the combination of multiple QTLs.     

Rice (<i>Oryza sativa</i> L.) Breeding among Hassawi Landrace and Egyptian Genotypes for Stem Borer (<i>Chilo agamemnon</i> Bles.) Resistance and Related Quantitative Traits

Rice stem borer (Chilo agamemnon Bles.) is a primary insect pest of rice and is a major limiting factor to rice production. Breeding for insect-resistant crop varieties has been an economic way of integrated pest management (IPM) as it offers a viable and ecologically acceptable approach. This study was aimed to evaluate rice genotypes for their resistance against rice stem borer. Seven parental genotypes with twenty one F1 crosses were evaluated for genotypic variation in field experiments. Analysis of variance revealed significant differences for the studied traits in almost all crosses and parents. In addition, the mean squares of parents versus their crosses were signifi- cant for stem borer resistance and other associated traits. Moreover, both general combining ability (GCA) and specific combining ability (SCA) variances were highly significant for all characters studied in the F1 generation. Based on GCA, 4 genotypes (Sakha101, Gz6903-3-4-2-1, Gz9577-4-1-1 and Hassawi) exhibited highly significant negative values for stem borer resistance (–0.53, –1.06, –0.18 and –0.49, respectively) indicating they are the best combiners for stem borer resistance. Based on SCA analysis, nine cross combinations showed highly significant negative effects for stem borer resistance. Similarly, the cross Giza178 Hassawi was the best combination with significantly highest value for early maturity. In addition, seven crosses showed highly significant negative SCA for plant height trait. On the other hand, for panicle length, number of primary branches/panicle, panicle weight and 1000-grain weight, seven, four, eight and six crosses showed highly significant positive SCA, respectively. The result further revealed that the non-additive dominance genetic variance was higher than the additive variance for all evaluated traits indicating that non-additive genetic variances have a role in their inheritance. The broad-sense heritability estimates were high for all the studied traits. The stem borer resistance was significantly correlated with panicle weight and 1000-grain weight, which also showed a highly significant correlation with grain yield/plant. Thus these traits can be effectively employed in a breeding program to confer resistance against stem borer infestation in rice. It was further supported by biplot analysis, which clustered these potentially important traits into two quadrants showing their importance in any future breeding program to control stem borer infestation. This study has contributed valuable information for evaluation of genetic diversity in the local rice germplasm and its utilization in futuristic rice genetic improvement programs.