Effect of Phenological Stages on Plant Dry Matter Partitioning and Seed Production in Berseem (Trifolium alexandrinum L.)

Berseem clover ( Trifolium alexandrinum L.) is an annual forage crop widely grown in Mediterranean environments. Dry matter partitioning in the leaf, stem and root and seed production of three populations of Egyptian as well as Italian origin were evaluated under four cutting regimes. The cutting treatments were applied to the plants at different stages of plant development: at the fourth (A) and eighth nodes elongation (B), at early flowering (C) and physiological maturity of seeds (D), After herbage, harvest plants were utilized for seed yield and evaluation of its seed yield components. Higher dry matter and seed yield was obtained in treatments D and B, respectively. In the other treatments, dry matter content was lower than in treatment D and related to the phenological development of the plant. Dry matter content in the root was higher when the cut was applied at early flowering. Cutting regimes influenced plant mortality, with the number of dead plants increasing from the cut applied in early (A) to that in the final treatment (D). Cuts applied at early stage of development depleted root reserves causing plant death. This peculiarity could be a tool for selecting populations with higher persistence and with a more tolerant physiological response to stress imposed by cuts. The populations of Egyptian origin, in comparison with the Italian ones, were more productive in dry matter in the early stage of growth and in all treatments were higher in seed weight.     

Dry Matter Partitioning in Linseed (Linum usitatissimum L.)

A pot experiment was conducted at University of Wales Aberystwyth, UK, Frongach field station to evaluate the effects of sowing dates on the dry matter partitioning of linseed. Root, stem and capsule (boll) weight increased progressively as sowing was delayed up to third sowing (19 April) but showed a gradual decrease when sowing was further delayed. The contribution of each of the three parts to total weight did not respond to sowing date in any consistent manner. The total dry matter per plant followed a similar pattern to the dry matter of plant parts, which increased with sowing up to third sowing (19 April) and then decreased when sowing was further delayed. Dry matter accumulation per day degree > 4 °C also increased as sowing was delayed with a peak at third sowing (19 April). Dry matter accumulation per day degree is concluded to be directly related to the total day degrees received during the growth period.     

三个超高产夏玉米品种的物质生产及光合特性

探明不同株高、穗位高具有超高产潜力(>15 000 kg hm^-2)夏玉米品种的物质生产及光合特性,有利于密植增产。本研究在多年高产试验基础上(连续3年达15 000 kg hm^-2以上),选用了登海661 (DH661,低秆低穗位)、登海701(DH701,中秆中穗位)和先玉335 (XY335,高秆高穗位) 3个具有超高产潜力的品种进行试验。在一般高产条件下,这3个品种间产量无显著差异,但干物质生产特性的模型解析表明,DH661的产量潜力高于DH701和XY335,其活跃生长期比XY335长近3周。开花后光合特征参数显示,DH661光合作用与光能利用效率明显较高,尤其是当XY335进入生理功能速衰期时(开花后28 d),DH661仍处于缓慢下降阶段,且具有较高的光合速率和光能利用效率,DH661的这一特性表明其具有更高的产量潜力。     

Alternate Row Spacing and Plant Density Effects on Forage and Dry Matter Yield of Corn Hybrids (Zea mays L.)

Irrigated field experiments were conducted in the Marmara region of Turkey in 2002 and 2003 to compare alternate 40 : 25 cm row spacings and conventional 65 cm with four different plant densities (65 000, 85 000, 105 000 and 125 000 plants ha⁻¹) of three corn hybrids (DK-585, ADA 95–10 and C-955) in some morphological traits and forage and dry matter yield. Morphological traits such as plant height, leaf per plant, stem diameter, ear per plant and ear percentage were measured, forage and dry matter yield was also determined in this study. Hybrids, row spacings and plant densities significantly affected some morphological traits, forage and dry matter yield at 0.01 level. Later maturing hybrids tended to produce taller and thicker stemmed plants. Row spacings and plant densities did not affect plant height. Average stem diameter increased significantly with population density. Row spacings did not influence leaf number, whereas leaf number increased slightly with plant density. On average, all corn plants had slightly more than 1.0 ear per plant in our experiment. Row spacings and plant densities did not affect significantly number of ear per plant. Early maturing DK-585 had the highest ear percentage whilst late maturing C-955 lowest. Yields usually increased with hybrid maturity. When averaged across years, row spacings and plant densities, late maturing C-955 performed significantly better in forage and dry matter yield in all experimental years and combined years. The studies showed favourable advantage for alternate 40 : 25 cm rows over conventional 65 cm row spacings at all plant densities. Average forage and dry matter yields were greater for alternate 40 : 25 cm row spacings than for 65 cm row spacings. However, strong hybrid × row spacing interactions for both forage and dry matter yield were detected.     

Allometric Relationships of Growth Components in Maize (Zen mays L.) Cultivars

Allometric relationship (W₁=αW₂^β, where α and β are the parameters) was fitted among growth components in two maize cultivars viz., Decani hybrid and Deccan 101 in order to obtain estimates of other components of the plant system which are time consuming measurements. The results of the agronomic field trial conducted at the University of Agricultural Sciences, Bangalore were used. This model's predictability was compared with linear regression model. In both the cultivars, allometric model using leaf area (LA - W₂.) and leaf dry matter (LDM - W₂) simulated total dry matter production (DMP - W₂) by 79 to 98 % of actual values. Further allometric model fitted well to predict stem dry matter by 91 to 93 % using LDM and LA 89 to 92 % using LDW. Whereas linear regression model estimated total DMP by 95 to 96 % using cob dry matter. In case of LDM - LA association, linear regression model was found to be the best than other model. The leaf area decreased after silking in both the cultivars and the ratio of growth rates of DMP – LA ( β ₂) was negative. Between cultivars, cv. Deccan 101 had higher R² values in most of the relationships than cv. Deccan hybrid indicating the varietal difference.     

Productivity of Maize (Zea mays L.) in Relation to Morphological and Physiological Characteristics under Varying Amounts of Nitrogen Supply

In a field trial located in a northern region of Germany, characterized by a Podzol soil and increasing N fertilization resulted in an enhanced N uptake of the maize (Zea mays L.) variety “Felix” with increasing N fertilization ranging from 0 kg N ha^-1 (N1) to 60 kg N ha^-1 (N2) and to 160 kg N ha^-1 (N3). The growth conditions reached only nearly optimal temperature for biomass allocation in a short period of July and August 1990. The plant productivity was stimulated due to higher N uptake and N utilization to values of nearly 1600 g ha^-1. The N efficiency decreased with increasing N fertilization. A greenhouse experiment was conducted to study the effects of varied nitrogen nutrition on the development of maize plants under standardized growth conditions, comparable to the sub optimal growth conditions of the field experiment. Physiological and anatomical parameters were measured. Within a range of 0.2—1.0 mg N cm^-2 of leaf nitrogen, the chlorophyll concentration and the CO₂ exchange rate showed a linear relationship with the reduced N in the leaf. Above 1.0 mg N cm^-2 no further increases in chlorophyll levels or photosynthesis were observed. Nitrate reductase activity was stimulated throughout the N range supplied. The activities of photosynthetic enzymes (PEP carboxylase, Nadp malic enzyme, RubP carboxylase) was increased from the low (0.19 g N kg^-1 soil) to the middle N level (0.37 g N kg^-1 soil). Under conditions of a high N supply (0.75 g N kg^-1 soil) the activity decreased, except Nadp malic enzyme. This effect was accompanied by alterations of the internal structure of the leaf. Leaf thickness and size of the mesophyll parenchyma were less at the medium nitrate supply. Other anatomical parameters were influenced in proportion to leaf nitrogen status. Stomatal index was not affected by N supply, but lengths and widths of epidermal and stomatal cells as well as the distance between stomata and vascular bundles were increased by high N supply. It is proposed that above an optimal range of leaf nitrogen, maize plants cannot use the potential advantage of the C₄ mechanism and the N utilization shows maximum efficiency in the intermediate N level under the sub optimal growth conditions used in the greenhouse experiment.     

Effects of Thiourea, Thiamine and Ascorbic Acid on Growth and Yield of Maize (Zea mays L.)

Three chemicals, viz., thiourea, thiamine and ascorbic acid capable of potentiating-SH turnover, were tested with the objective to improve growth and productivity of maize. Thiourea was tested as seed-soaking and foliar-applied treatments as also in combination. Thiamine and ascorbic acid were tested as foliar sprays alone. Foliar treatments were applied at vegetative stage (30 and 45 days after sowing).
The results of the field experiment showed that seed soaking with thiourea (500 ppm) tended to improve grain yield (13.4 per cent over control), but improvement in biological yield was significant. However, seed soaking plus foliar treatment of thiourea significantly increased both biological and grain yields, besides causing significant improvement in leaf area index and number of green leaves plant^-1. The increase in grain yield ha^-1 was of the order of 34.6 per cent over control.
It was further noted that foliar sprays of thiourea (1000 ppm), thiamine (100 ppm) and ascorbic acid (100 ppm) significantly increased leaf area index, number of green leaves plant^-1 and biological yield ha^-1. These treatments also significantly increased grain yield ha^-1 by 40.6, 20.2 and 26.3 per cent, respectively over control. Improvement in maize yield with thiourea, thiamine and ascorbic acid treatments appeared to have resulted from increased photosynthetic efficiency and canopy photosynthesis on account of the biological activity of -SH group. It was also apparent that leaf senescence was delayed under the influence of these chemicals. It is therefore suggested that thiourea, thiamine and ascorbic acid are the potential bioregulators for improving photosynthetic efficiency and grain yield of maize and possibly other cereals, and that thiourea, a sulphydryl compound, holds considerable promise in this context.     

Functional Crop and Cob Growth Models of Maize (Zea mays L.) Cultivars

Various mathematical models were fitted to describe total dry matter production (DMP) and cob weight in two maize cultivars viz., Deccan hybrid and Deccan 101 . The data on periodical crop growth from an agronomic trial conducted at the University of Agricultural Sciences, Bangalore, were used to predict crop and cob growth empirically. In cv. Deccan hybrid , Gompertz followed by Richards models predicted DMP by 99 % nearer to the actual values. Whereas in cv. Deccan 101 , Richards-cum-logistic for vegetative-cum-reproductive stage simulated DMP with R² of 92 to 99 %. Further, cob growth was estimated realistically with high R² of 97 to 98 % using empirical models of logistic followed by Richards in cv. Deccan 101 and Richards followed by Gompertz in cv. Deccan hybrid . Comparing the empirical models in describing DMP and cob growth, the models showing higher predictions in DMP also estimated cob growth meaningfully in both the cultivars, indicating similarity in growth functions.     

Physiological Responses and Dry Matter Partitioning of Summer Mungbean (Vigna radiata L.) Genotypes Subjected to Drought Conditions

Drought is the most important limitation to summer mungbean production in the tropics and subtropics dependent on usually insufficient summer rainfall. As increased irrigation is not a viable answer to the problem, an economically and environmentally desirable solution is new varieties with drought tolerance. However, there is little genotypic information on drought tolerance in summer mungbean. The objectives of this study were to assess the genotypic differences in physiological traits and dry matter partitioning in mungbean and to measure the association of these traits with crop performance under drought conditions. Six mungbean genotypes were tested in drought micro plots at CCS Haryana Agricultural University, Hisar, India. A split plot design was used; two irrigation treatments (watered and droughted) in the main plots and six mungbean genotypes in the subplots with three replicate micro plots. Drought decreased leaf water status, rates of photosynthesis (P_n) and altered dry matter partitioning in different plant parts. Our results showed that P_n did not limit yield, but it was partitioning of dry matter governed by leaf water content (RWC) which influenced the final yield. RWC was positively correlated to the number of pods per plant and seed yield, genotypes maintaining high RWC produced higher seed yield. Therefore, the drought tolerance of summer mungbean was related to the maintenance of high RWC, which can be used as a physiological marker to identify and develop superior genotypes suited to drought-prone environments.     

不同地力水平下控释尿素对玉米物质生产及光合特性的影响

氮肥是玉米生产中最重要的增产要素之一。为探明不同地力水平下控释尿素对玉米物质生产及光合特性的影响, 采用盆栽试验研究了释放期不同的2种控释尿素(CRU₃₀, 释放期为30 d; CRU₆₀, 释放期为60 d)的作用效果, 以普通尿素为对照(U)。结果表明, 控释尿素处理显著增加玉米干物质积累量, 但释放期不同的控释尿素在不同地力水平下增产效果不同, 低地力水平下增产效果为CRU₃₀>CRU₆₀>U (P<0.05), CRU₃₀处理比施用普通尿素增产18.9%; 高地力水平下增产效果为CRU₆₀>CRU₃₀>U(P<0.05), CRU₆₀处理比U增产18.2%。与对照相比, 控释尿素使干物质向开花后分配比例增加, 氮肥偏生产力(PFPN)显著提高, 低地力时CRU₃₀最高, 而高地力时CRU₆₀最高。控释尿素处理的单株干物质积累量、穗粒数及千粒重显著增加, 主要因为生育中后期叶面积、光合速率、叶绿素及叶片氮含量维持较高水平。所以, 在等氮量做基肥一次性施入时, 低地力水平下施用释放期较短的控释尿素为宜, 而高地力水平下应施用释放期较长的控释尿素。     

环境条件和栽培管理对夏玉米干物质积累、分配及转移的试验研究

作物生产的最主要的过程就是光合产物的积累、分配、转移及最终经济产量的形成. 为研究环境条件和栽培管理对这一过程的动态影响, 1998至1999年2年共进行了19个处理的田间试验, 系统地测定了不同播期、不同密度、不同施肥、灌溉水平以及不同含盐量的灌溉水质下, 包括地下部分的夏玉米各器官干物质动态. 本文以有效积温表示的     

Genotypic Variation for Cold Tolerance among Twelve Maize (Zea mays L.) Populations

The objectives of this study were (1) to ascertain the genetic differences for cold-tolerance traits in a series of diallel crosses among 12 maize populations grown in field experiments, and (2) to compare, in controlled environment rooms, the modification of various metabolic parameters of two sets of four F1 variety crosses which, according to the field experiments, differed largely in seedling early vigour (cold-tolerant [Ct] vs cold-sensitive [Cs] Fl sets). Under field conditions, cold-tolerance adaptability, as monitored by shoot dry matter accumulation, appeared genetically controlled; moreover, considerable differences existed among genotypes. Field data suggested that shoot dry weight was a good indicator of plant adaptability to periods of unfavorable cool conditions. The growth-chamber experiments showed that shoot dry weights of the two sets of hybrids (Ct vs Cs), were more uniform at the highest temperature regimes than under suboptimal temperatures. Moreover, the laboratory study indicated that the interval of time of attain a specific stage of development provided a meaningful and useful criterion for differentiating the capacity of maize plants to grow at low temperatures. Although a clear association between a particular metabolite and the capacity of plants to grow at low temperatures was not observed, it was of interest to note that the total N concentration in the shoot was significantly higher in the Ct plants compared to the Cs ones.     

玉米群体根系活力与物质积累及产量的关系

以玉米中熟种苏玉9号为材料,通过施氮量和种植密度处理,研究群体根系伤流强度动态和节根组成与物质积累、产量构成的关系。结果表明：玉米群体气生根数与节根量、灌浆结实期根系伤流强度、总粒数、抽丝后干物质积累量及产量呈正相关。生育过程中抽丝期的群体根系伤流量强度与抽丝后干物质积累量、总干物质积累量及籽粒产量     

苗期水分胁迫对玉米根系生长杂种优势的影响

以玉米杂交种高油115及其亲本(母本220、父本1145) 为材料, 研究了玉米苗期根系生长的杂种优势及水分胁迫的影响。试验设水分充足、轻度干旱和严重干旱3个处理, 田间持水量分别为75%、55%和35%。结果表明, 在水分充足条件下, 根长(RL)、根表面积(SA)和根干重(RDW)均表现出不同程度的中亲优势和超亲优势, 轻度干旱显著降低了各指标的杂种优势, 而严重干旱则完全抑制了根系生长的杂种优势。根系各性状中, RL的杂种优势最强。在水分充足条件下, 与中等根(根直径0.25~0.45 mm)和粗根(根直径>0.45 mm)相比, 细根(根直径0.05~0.20 mm)的RL、SA及其占总根系比例的杂种优势最高。轻度干旱胁迫虽然降低了根系的杂种优势, 但RL、SA仍表现出显著的超亲优势和中亲优势(粗根的超亲优势除外)。此外, 只有细根RL和SA占总根系的比例在轻度干旱胁迫下具有显著的中亲优势, 说明杂交种可以通过生成较亲本更高比例的细根来抵抗轻度干旱胁迫。     

玉米花期性状的全基因组关联分析

花期性状是玉米的重要性状,与熟期、散粉结实率和产量关系密切,对玉米品种选育至关重要。为探究玉米花期性状的遗传基础,本研究以248份遗传多样性丰富的玉米自交系作为关联群体,通过2017年和2018年在河北保定和辛集的田间试验调查抽雄期、散粉期、吐丝期和散粉吐丝间隔期4个花期相关性状,利用分布于全基因组的83057个SNP标记进行关联分析。结果表明,4个花期相关性状的基因型、年份、地点、基因型与地点的互作、基因型与年份的互作均达到极显著水平;抽雄期、散粉期、吐丝期的遗传率分别为71.77%、71.27%、73.93%,并且两两性状间呈极显著正相关,散粉吐丝间隔期遗传率为62.50%,仅与吐丝期呈极显著正相关;4个花期性状共检测到18个SNPs-性状关联(共涉及16个SNP位点),单个位点的表型贡献率范围为5.46%~28.36%,仅1个位点在不同性状中检测到;筛选到81个候选基因,其中36个在GO分析中具有功能注释。潜在候选基因GRMZM5G877647编码early flowering 4蛋白,参与光周期的调节;GRMZM2G173630编码类赤霉素受体蛋白参与植物激素信号转导;GRMZM2G001139、GRMZM2G375707编码与花器官建成的MADS转录因子。这些潜在候选基因为解析玉米花期性状遗传基础和分子辅助选择育种提供参考。     

不同氮肥管理对春玉米干物质生产、分配及转运的影响

为探索华北地区春玉米高产可持续栽培技术,研究了不同氮素管理(不施氮、推荐施氮、经验施氮)对春玉米的干物质积累、分配及转运的影响。结果表明,在高肥力土壤条件下,第一年推荐和经验施氮同不施氮相比在干物质积累、叶面积指数、籽粒产量、穗位叶光合速率等方面都没有起到明显的促进作用,但在第二年不施氮处理产量比推荐施氮和经验施氮分别下降了12.0%和11.6%。推荐施氮的优势不仅体现在减少氮肥投入的前提下保持产量的稳定,同时也明显促进了生育后期植株营养体干物质向籽粒的转运,各器官干物质转运总量占籽粒总干质量的22.1%,比经验施氮高6.1%。     

四川地方玉米种质的SSR聚类分析

利用SSR分子标记方法研究28个玉米自交系的遗传变异。分析四川地方玉米种质的遗传基础,并进行SSR聚类分析,探讨四川地方玉米种质与国内主要杂种优势群的关系。结果表明：大部分四川地方玉米种质均可被划分到常见的几大杂种优势群中去,少数地方玉米自交系可形成单独的类群,四川地方玉米种质具有广泛的遗传基础;SSRs能较真     

Polynomial Functional Models to Simulate Crop Growth in Maize (Zea mays L.) Cultivars

Polynomial and polynomial exponential models of order one to four were tried to describe crop growth in two maize cultivars viz., Deccan hybrid and Deccan 101 of an agronomic trial conducted at the University of Agricultural Sciences, Bangalore, on alfisols. Relative growth rate (RGR) of classical and functional methods was compared. Models performance was assessed based on r², χ² residuals sum of squares (RSS), root mean standard deviation (RMSD) and presence or absence of heteroscedasticity in models' predictions. In the cultivars, polynomials of order three and four in Deccan hybrid and cubic polynomial in Deccan 101 simulated dry matter production (DMP) by 99.5 % and showed good distribution of error variance over the observed DMP. The RGR from the third and fourth degree polynomials in both the cultivars was comparable to the classical method and explained better during post-silking period. Polynomial exponentials predicted very low RGR. Between cultivars, Deccan 101 showed higher RGR during 45–80 days after sowing and contributed significantly more to final DMP.     

高温对玉米籽粒淀粉合成及产量的影响

以农大108和山农3号为试材，采用田间生长箱增温的方法，研究了不同生育时期高温对玉米淀粉合成及产量的影响。结果表明，第1期（出苗后0~28 d）高温处理对玉米的产量没有显著影响，第2期（出苗后29~57 d）和第3期（出苗后58~86 d）高温处理显著降低玉米产量，以第2期对产量的影响最大；同时高温降低1,6-二磷酸酯酶（FBPase）、磷酸蔗糖合成酶（SPS）、蔗糖合成酶（SS）和腺苷二磷酸葡萄糖焦磷酸化酶（ADPGPPase）的活性，且以第2期降低的幅度最大；籽粒淀粉含量，以第1期高温处理高于对照，其他2个处理显著低于对照。     

渍涝胁迫对玉米生理生化的影响研究进展

渍涝胁迫是玉米生产中重要的非生物逆境之一,对玉米的生长发育造成危害,严重制约了玉米产量的提升。因此回顾了人们针对渍涝胁迫对玉米生理生化的影响及其适应机制的研究,介绍了人们从栽培耕作和遗传育种两个角度提高玉米抗渍涝能力的研究现状,并展望了未来玉米抗渍涝胁迫的重点研究方向。