Flowering and true seed production in potato (Solanum tuberosum L.). 1. Effects of inflorescence position,nitrogen treatment,and harvest date of berries

Summary Flowering and true seed production from different order inflorescences in potato (Solanum tuberosum L.) were evaluated in two experiments. The number of flowers per inflorescence, berry set, berry weight, number of seeds per berry and seed weight generally decreased from primary inflorescences to tertiary inflorescences and inflorescences on lateral stems. The possible relation with carbohydrate distribution is discussed. Quality of the seeds produced from the different orders of inflorescences was a function of seed size; larger seeds showed better germination, emergence and seedling growth. Late harvest of berries increased berry weight and number of seeds per berry from primary inflorescences. Application of additional nitrogen during the flowering period did not affect flowering or differences between inflorescence positions in seed production, but it significantly decreased the number of seeds per berry. The practical implications of these results for true seed production are discussed.     

Evaluation of seed production potential in white clover (Trifolium repens L. varietal improvement programmes

The components of actual and potential seed yield were examined in field experiments on a wide range of varieties of white clover (Trifolium repens L.). The factors affecting seed yield under conditions typical of management regimes used in the production of commercial seed crops were assessed in two experiments. In the first, carried out on spaced plants, considerable diferences are shown between six varieties across the range of leaf sizes in the distribution and profuseness of inflorescence production through the flowering season. In the second, carried out in plots, typical on-farm criteria were used to choose a single harvest date. Significant variation was found between varieties, including representatives of different leaf size categories, for seed yield components that include number of inflorescences m^?2, number of florets per inflorescence and harvestable seed weight. Large-leaved varieties tended to produce more seeds per floret and higher seed weights per inflorescence, whereas small-leaved varieties gave the highest number of inflorescences ^?2. However, the small-leaved variety AderDale, selected for strong peduncles, was exceptional, giving high values for all seed yield components. The impact of weather conditions on many seed yield components (e.g. total number of inflorescences) was demonstrated by the differences between the 2 years of the experiment. However, other characterstics, e.g. number of florets per inflorescence and number of seeds per floret, did not vary between years. Deviations from potential seed yield were assessed fromthe perspective of commerical seed production. The implications of these results for the production of white clover varieties with increased seed yields under UK conditions are discussed.     

Effect of plant density on stolon growth and development of contrasting white clover (Trifolium repens) varieties and its influence on the components of seed yield

Plants of two contrasting white clover varieties (cv. Aberystwyth S184 and Olwen) were planted in the field in spring in each of 2 years at four densities (9, 25, 49 and 100 plants m⁻²) in 1-m² plots. The effect of plant density on stolon growth and development and the components of seed yield was subsequently measured.
Stolon growth and development was influenced by plant density, variety and year. At low plant densities both white clover varieties produced longer primary stolons than at higher densities. Plant density, however, had no significant effect on the number of inflorescences at harvest. At the high stolon densities there were significantly fewer reproductive nodes per primary stolon than at the lower plant densities. Plant density did not significantly affect any other seed yield components, but the number of inflorescences at harvest, florets per inflorescence, seed set per floret and 1000-seed weight were all significantly influenced by both variety and year.
The relationship between the vegetative and reproductive growth of white clover is discussed in relation to plant density, variety and climate and the possible role of defoliation managements on inflorescence development.     

Variability and regulation of the number of ovules, seeds and pods according to assimilate availability in winter oilseed rape (Brassica napus L.)

The number of pods per plant and the number of seeds per pod are the most variable yield components in winter oilseed rape (WOSR). Both the number of ovules per pod and the potential for the ovule to develop into a mature seed may depend on pod position in the plant architecture and time of appearance. The complex developmental pattern of WOSR makes it difficult to analyse. The objectives of this study were to investigate the variability of the following yield components (a) ovules/pod, (b) seeds/pod, and (c) pods/axis in relation to two explanatory variables. These two variables include (1) flower and inflorescence position and (2) time of pod appearance, linked to the effect of assimilate availability.Field experiments were conducted with the variety Mendel. Different trophic states were created by clipping the main stem or ramifications. The number and position of flowers that bloomed within the inflorescence were recorded based on observations every two to three days throughout the flowering season.On the control plants, for the main stem we observed that the number of ovules per pod decreased for a few ranks and then tended to increase and again to decrease at the end. On ramification R1 and R4, the number of ovules increased at first, and then remained constant with the pod rank. Furthermore, the number of ovules per pod remained constant along the inflorescence on the other ramifications and increased with ramifications from top to bottom. The number of seeds per pod did not vary with the pod rank at the basal positions on inflorescences and decreased afterwards along the inflorescence. The clipping of the main stem or ramifications increased the number of ovules per pod, seeds per pod and pods per axis. The number of ovules and seeds per pod did not vary with the time of pod appearance for the pods located at normalised rank 0.01-0.1. However, the number of ovules and seeds per pod can be impacted by the time of pod appearance on the plant scale. Thus, our results indicate that the amount of available assimilates was the primary determinant of pod and seed production during the flowering period. The distribution of resources was significantly affected by both the positions of pods within an inflorescence and the position of inflorescences within a plant.     

去枝、疏花对甘蓝型杂交油菜苏优3号千粒重及产量的影响

以杂交油菜苏优3号为材料，研究去枝、疏花处理对千粒重及单株产量的影响，结果表明，去枝，蔬花后，主轴，一次分枝和二次分枝的千粒重显著增加，角果宽度和长度亦增加，去枝后单株千粒重增加16．61％，疏花后单株千粒重增加14．05％，均达极显著水平，去枝后单株产量下降，下降幅度最高为9．77％，达极显著水平，每个花序疏花5朵，单株产量增加0．38％，增产不显著，疏花10朵以上则单株产量逐渐下降。     

Post-flowering tillering in contrasting light environments of two New Zealand perennial ryegrass cultivars with different perennation strategies

Post-flowering tillering responses of 'Ellett' and 'Grasslands Ruanui' perennial ryegrass ( Lolium perenne L.) cultivars after inflorescence production were studied at INRA, Lusignan in France, at near ambient light (absence of light competition, control treatment) and under shading (low-light intensity and low red–far red ratio). A dense sward containing inflorescence bearing plants of both perennial ryegrass cultivars at ambient light was cut to a height of 50 mm above ground level after which the light treatments were imposed. Forty-five days later, data were collected on the number of tillers per plant, the number of new tillers per original tiller and the dry weight of vegetative and reproductive tillers. Regardless of light treatment, cv. 'Ellett' had fewer tillers per plant, higher weight per tiller and a higher proportion of reproductive tillers than did cv. 'Grasslands Ruanui'. Number of tillers per plant and number of new tillers per tiller were consistently reduced under shade compared with the control treatment for both cultivars. When shaded, weight of reproductive tillers of cvs 'Ellett' and 'Grasslands Ruanui' were 40% and 43%, respectively, less than the control, whereas vegetative tiller weight did not change. In addition, differences between cultivars in the tillering strategy after flowering seem to be unaffected by the light environment. Thus, field observations regarding tillering of cvs 'Ellett' and 'Grasslands Ruanui' were consistent with current results suggesting different grazing managements are needed after flowering to optimize the replacement of tillers for both cultivars.     

白菜型春油菜不同密度的产量及其构成因素分布特性

白菜型春油菜（ＢｒａｓｓｉｃａＣａｍｐｅｓｔｒｉｓ）两个品种８种栽培密度的产量及其构成因素分布特性分析结果表明，单位面积产量与各枝序粒重和角果数占单株粒重和角果数的比率有密切关系。角粒重较高，较稳定下，单位面积产量随一次分枝粒重比率和角果数比率的下降，或主序粒重比率和角果数比率的上升而提高；角粒重低，且随一次分枝粒重比率和角果数比率的下降，或主序粒重比率和角果数比率的上升而降低．一次分枝粒重比率和角果数比率为５０％－５５％，或主序粒重比率和角果数比率为２５％－３０％，同时每角粒重较高，可获得最高单位的面积产量。     

Sulphur nutrition of sunflower (Helianthus annuus) as affected by nitrogen supply: Effects on vegetative growth,the development of yield components,and seed yield and quality

The effects of sulphur and nitrogen nutrition on the growth and yield components of a hybrid confectionery sunflower (cv. Kernel) were investigated in a glasshouse experiment using controlled S and N supplies that ranged from deficient to more than adequate, and in which the S supplies of some plants were changed at defined stages of growth. S deficiency delayed floret initiation and anthesis but not seed maturity; N deficiency delayed all developmental phases including seed maturity. S and N deficiencies reduced plant height and leaf area. N deficiency caused a reduction in leaf number, but S deficiency did not. Both S and N deficiencies reduced yield by reducing the number of seeds per plant and by decreasing single seed weight. Oil concentration in seeds was the same for all levels of S supplied, but it was reduced by increased N supply. Changing the S supply at the end of floret initiation and at anthesis indicated that floret number and therefore seed number per plant were mainly established by the S suplly before the end of floret initiation. Single seed weight responded positively to increased S supply after floret initiation but only if the N supply was adequate; there was no response to increased S supply after anthesis.Concentrations of S and N in plant organs increased with increasing S and Nsupplies, but seeds were much less responsive than vegetative organs. Plants grown on high N but low S had the highest concentrations of N in their tissues, but the highest S concentrations did not occur in high S low N plants. Cysteine and methionine decreased by 30% in seeds of S-deficient but N-sufficient plants, whereas arginine increased by 34% compared with nutrient-adequate plants.We suggest that an adequate supply of S to young sunflower plants is required, particularly up to floret initiation, to obtain large floret numbers and maximum leaf area. An adequate supply of S is also required between the end of floret initiation and anthesis to prevent floret abortion and allow development of large seeds. Sulphur stress in sunflower during seed filling results in kernels with low levels of essential S-containing amino acids.     

Seed production in grassland species: Morpho‐biological determinants in a species‐rich semi‐natural grassland

Studying the seed production of herbaceous species can help to conserve grassland habitats and re‐create new high‐value grassland surfaces. Studies on grassland seed production have focused mainly on individual species and traits, without characterizing their relative importance at the plant community level. The aim of this study was to investigate the entire seed production process of the main species in a temperate grassland. Fertile shoots (FS) of twenty‐nine grasses and forbs were collected over 4 years and analysed for sixteen traits that determine inflorescence size, seed production and seed quality. The per cent viability played a predominant role in determining the total production of viable seeds. Forbs showed a range of reproductive strategies, including variable distribution of flowers among growth periods, number of inflorescences per FS and relationship between seed size and FS density in the grassland. The flower production for grasses was concentrated in the first growth period, but this limitation was mitigated by a higher seed dormancy. The number of viable seeds per FS and seed size were important components of the reproductive strategy of forbs, with heavy‐seeded species being characterised by high individual densities in the community, but producing few seeds per FS. Light‐seeded species showed an opposite pattern. The results suggest that when using seeds from semi‐natural grasslands for ecological restoration, special attention should be paid to the seed amount, germinability and viability of forbs, as they seem to depend more on seed reproduction and have a lower ovule to seed transformation efficiency.     

The effect of photoperiod on flowering and TPS production in the warm tropics

Summary Three similar field experiments with five cultivars were carried out to evaluate the effect of a 5-hour extension of the natural daylength and a 3-hour night break on flowering and TPS production in the warm tropics. Shoot length, number of inflorescence positions per plant and number of flowers per inflorescence varied considerably between the experiments. In each experiment, the supplementary photoperiods delayed cessation of shoot growth and thereby increased the orders of branching and the number of inflorescence positions per plant. The photoperiod treatments significantly increased the number of flowers at the last produced inflorescence positions, but not at other ones. Pollen production and quality, berry set, seed set and 100-seed weight were not affected by the photoperiod treatments. TPS production was characterized by variability in flowering and low and variable seed production per flower.     

基于结构方程模型的油菜性状和产量关系研究

为量化描述和分析甘蓝型油菜(Brassica napus L.)种植结构的调整以及相关性状变化对产量的影响,本研究利用结构方程模型对连续10年品种选育所得的168组产量和相关性状等数据进行分析,并对不同密度下相关性状和产量数据进行显著性分析。结果显示,在本实验密度范围内随着种植密度的增加,单株产量显著降低,且主要通过单株有效角果数影响单株产量,但总产量呈上升的趋势。研究所选各个性状对单株产量的总效应为:单株有效角果数>分枝数>千粒重>主花序有效角数>主花序有效长>每果粒数。因此,在培育更具有耐密性和对环境适用性的品种的同时,要选育拥有更多单株有效角果数和分枝数的品种以稳定单株产量,综合提高油菜总产量。     

Flowering and true seed production in potato (Solanum tuberosum L.). 2. Effects of stem density and pruning of lateral stems

Summary Field experiments were carried out to evaluate the effect of stem density and pruning of lateral stems on flowering and true seed production in potato (Solanum tuberosum L.). Increasing stem density reduced flowering, berry and seed production from every inflorescence in all cultivars. Increasing density increased the proportion of primary flowers in the total number of flowers per plant and reduced the proportion of flowers on lateral stems, but its effect on the quality of the seed production was small. Differences in total seed production were principally determined by differences in flowering. There was an interaction between stem density and cultivars for the number of flowers produced and on the yield of true seed per m². Pruning lateral stems enhanced flowering of the main stem and decreased the total number of flowers per plant, but it did not affect berry and seed production from main-stem inflorescences.     

江苏淮北地区夏大豆品种更替中产量及有关性状的改良与展望

本文通过对江苏淮北地区50～80年代先后推广的16个夏大豆代表品种的产量及有关性状变化的研究,看出本区大豆品种更替过程中,品种产量潜力的提高主要变化因素为:百粒重与每荚粒重的增加、收获指数的大幅度提高和生物量的稳步增长;植株矮化、节数和分枝数减少;全生育期缩短,而以鼓粒期为主的生殖生长期有所延长。本区今后大豆高产育种应在现有百粒重的基础上,协调好粒重、粒数和荚数三者关系,适当提高株荚数和每荚粒数,同时注意增加生物量,提高收获指数;生育期不宜再缩短,注意长鼓粒期的选择;进而提高育成品种的增产潜力和适应性。     

Effects of physical agitation on yield of greenhouse-grown soybean

Agronomic and horticultural crop species experience reductions in growth and harvestable yield after exposure to physical agitation (also known as mechanical stress), as by wind or rain. A greenhouse study was conducted to test the influence of mechanical stress on soybean yield and to determine if exposure to mechanical stress during discrete growth periods has differential effects on seed yield. A modified rotatory shaker was used to apply seismic (i.e., shaking) stress. Brief, periodic episodes of seismic stress reduced stem length, total seed dry weight, and seed number of soybean [Glycine max (L.) Merr.]. Lodging resistance was greater for plants stressed during vegetative growth or throughout vegetative and reproductive growth than during reproductive growth only. Seed dry weight yield was reduced regardless of the timing or duration of stress application, but was lowest when applied during reproductive development. Seismic stress applied during reproductive growth stages R1 to R2 (Days 3 to 4) was as detrimental to seed dry weight accumulation as was stress applied during growth stages R1 to R6 (Days 39 to 42). Seed dry weight per plant was highly correlated with seed number per plant, and seed number was correlated with the seed number of two- and three-seeded pods. Dry weight per 100 seeds was unaffected by seismic-stress treatment. Growth and yield reductions resulting from treatments applied only during the vegetative stage imply that long-term mechanical effects were induced, from which the plants did not fully recover. It is unclear which yield-controlling physiological processes were affected by mechanical stress. Both transient and long-term effects on yield-controlling processes remain to be elucidated.     

新麦草种子产量与繁殖性状的关联性分析

为了解新麦草的种子产量及繁殖性状间的关系,对27份新麦草种质资源的单株种子产量与7个产量性状的关联性进行了分析。结果表明,新麦草的单株生殖枝数、穗轴节数、单穗小花数和千粒重与单株种子产量关联最密切,其相关性表现为单株生殖枝数＞千粒重＞穗轴节数＞单穗小花数。经通径分析,单株生殖枝数（X₁）对单株种子产量（Y）直接效应最大,其余依次是单穗小花数（X₄）、单穗小穗数（X₃）、千粒重（X₇）、穗轴节数（X₂）和单穗结实种子数（X₅）,其中单穗结实种子数和结实率对种子产量均表现为负效应,且未达到显著水平。经逐步回归分析得到回归方程Y= -9.880 2+0.27X₁+0.012X₄+2.011 1X₇（R=0.805 8,P<0.001）,说明提高单株生殖枝数、千粒重、单穗小花数对新麦草增产的贡献最大,增加结实率也可间接提高新麦草的单株种子产量。     

硼钼锌对双低油菜华双4号籽粒发育进程中干物质累积的影响

通过水泥池小区试验，研究了B、Mo、Zn三种微量元素对甘蓝型油菜双低品种华双4号角果发育进程中干物质累积过程的影响。结果表明：硼、锌缺乏阻碍了主茎和第一次分枝角果皮干物质向籽粒的转运，进而影响籽粒干重的增加；三种微肥以及硼、锌配施利于角果皮干物质向籽粒的转移，促进籽粒增重。华双4号主茎角果皮干重在开花后43d达最大值，第一次分枝角果皮干重在开花后38d达最大值，主茎籽粒干重在开花后53d达最大值，第一次分枝籽粒干重在开花后49d达最大值。各处理主茎籽粒干重和粒壳比在花后38d出现明显差异，而第一次分枝的籽粒干重和粒壳比在花后33d开始出现明显差异。硼钼锌配合施用有利于油菜籽增产，对产量影响顺序为，完全处理（NPKBMoZn）>-Zn（NPKBMo配合）>-B（NPKZnMo配合）>-Mo（NPKBZn配合）>CK（NPK）。     

Post-flowering photoperiodic effect on reproductive efficiency and seed growth in soybean

Photoperiod not only controls soybean (Glycine max (L.) Merr.) flower induction, but also affects later stages of reproductive growth. Its effect on different yield-determining processes, however, is not well understood. The objective of this work was to determine the post-flowering photoperiodic effect on yield components, reproductive efficiency, and assimilate partitioning to developing seeds in the soybean cultivar Hood 75. Plants were induced to flower in short days. After flowering, three photoperiodic treatments were applied: (1) short days (SD); (2) short days with interrupted night (NI); and (3) a sequential combination of both (NI-SD). Flower differentation, pod lenthening, and seed-filling periods were shortest in SD, intermediate in NI-SD, and longest in NI. The number of differentiated flowers, pods, and seeds were doubled by NI as compared to SD, but the percentages of setting and retained pods were not changed. The percentage of seeds that completed development was, however, increased by SD. More assimilates were partitioned into the seeds in SD, while NI increased the proportion partitioned into shoots. The nitrogen content of seeds was similar in NI and SD, while NI-SD seeds showed a slight increment in their N content. The N content of carpels, however, was high in NI, medium in NI-SD, and low in SD. Compared to NI, duration of the seed-filling period was decreased but the seed-growth rate and final seed size were increased by SD. Final yield was similar for plants in NI or SD, because seed number and seed growth rate compensated each other. Plants in NI-SD has a significantly higher yield, however, as a result of sequential increase in seed number caused by NI, followed by an increase in the rate of seed-filling caused by SD. The results support the existence of two sequential photoperiodic effects on soybean reproductive development: (1), the number of growing seeds is enhanced by NI and decreased by SD; and (2), the assimilate partitioning to seeds is enhanced by SD and decreased by NI. A non-destructive method for seed growth-rate calculation is also described.     

Factors that modify early and late reproductive phases in oilseed rape (Brassica napus L.): Its impact on seed yield and oil content

Oilseed rape yield potential could be improved lengthening the duration of the late reproductive phase by increasing the number of grains per unit area. Photoperiod sensitivity could be used as a tool to manipulate the reproductive phase and thereby the number of grains. The aim of this study was to assess (i) the effects of different combinations of photoperiod on the duration of different phases and (ii) analyze how the changes in that duration affect yield (and its components) as well as oil seed content in oilseed rape. Field experiments were conducted in a factorial combination of three cultivars and three photoperiod regimes: natural photoperiod (NP) which represents the control and extended photoperiod of 6 h over NP (NP + 6) during emergence (E)-flower buds visible (FBV) and FBV-maturity (M) arranged in a randomized complete block design with three replicates, during two years representing three environments. Results showed that oilseed rape evidenced photoperiod responses during vegetative and early reproductive phases. Due to the lack of correlation between the duration of the vegetative and reproductive phases, it is possible to speculate the vegetative period may be altered independently of the modification of the rest of the phases. The positive relationship between grain number per m² and the duration of the late reproductive phase suggests that yield could be increased by lengthening the duration of that phase. Thus, regardless of the effect on the previous phase, the photoperiod sensitivity found in the early reproductive phase opens the possibility to manipulate the relative durations of vegetative and reproductive phases. Therefore, the length of the reproductive phase will be increased at the expense of a reduction in the duration of the vegetative phase, but without changing the whole duration of the crop cycle. This strategy could increase yield in oilseed rape in the future. Variations in yield were mostly explained by changes in the grain number per unit area without significant correlation with grain weight. However, a negative relationship between grain weight and grain number was found, showing a slight counterbalance in yield, by decreasing the grain weight. Since oil concentration appeared to be a more conservative attribute, increases in crop yield through a higher grain number per unit area would be a suitable strategy for improving oil yield as no reductions in oil concentration can be expected.     

离体穗培养条件下C、N供给对小麦穗粒数、粒重及蛋白质含量的影响

为探究C、N供给时期和供给水平对小麦籽粒建成及蛋白质含量的影响,以冬小麦品种济麦22为材料,采用离体穗培养的方法,设置了三个蔗糖浓度(C1:20 g·L-1;C2:40 g·L-1;C3:80 g·L-1)和四个硝酸铵水平(N1:0.57g·L-1;N2:1.14g·L-1;N3:2.28 g·L-1;N4:4.56g...     

Association of growth dynamics, yield components and seed quality in long-term trials covering rapeseed cultivation history at high latitudes

Brassica oilseed yield trend has declined in Finland by over 20% during the last 15 years. Improved genetic yield potential of turnip rape (B. rapa L.) and oilseed rape (B. napus L.) can be better realised with increased understanding of yield determining processes under northernmost growing conditions. This study aimed at (1) determining the genetic improvements in seed yield, yield components, quality traits and duration of the main growth phases and (2) comparing all these traits in turnip rape and oilseed rape. This work is based on the dataset from long-term Official Variety Trials (1976–2006), covering the entire historically relevant period of rapeseed cultivation in Finland. The results indicated that number of seeds per square metre dominated production of high yields, while single seed weight was not correlated with yield. Over the years, seed yields were produced with very different combinations of seed numbers and weights, differing markedly between the two crops. While high seed numbers were required for production of superior seed yields, single seed weights were not particularly high. Environmental variation markedly affected seed yield, seed number per square metre and duration of flowering compared with its effect on single seed weight. Duration of flowering was, however, negatively associated with seed number. Even though seed weight was largely determined by genotype, no marked plant breeding improvements were identified, contrary to those in number of seeds per square metre, seed yield, oil content and oil yield. For oilseed rape the increase in seed yield (41%) was far higher than for turnip rape (19%) without being associated with a longer seed-filling phase and later ripening, but rather the contrary.