野生大豆种子雨的研究

对野生大豆种子雨的时空动态及其与外界天气情况关系的初步研究表明,在野生大豆整个种子雨的历程中,出现3个较为明显的炸荚和种子散落的高峰,并且峰的出现与天气晴朗(相对湿度)相关,而与气温相关性不大.野生大豆种子雨的空间分布格局主要是野生大豆种子炸荚的自身习性(炸荚弹力)和荚本身在植株上的空间分布有关,而与风向(风力≤7级)关系不大.     

大豆炸荚发生规律及分子遗传基础

炸荚是野生大豆繁衍后代的一种原始自然属性,同时也是栽培大豆减产的主要原因之一,因此对其发生规律和分子遗传基础的研究具有重要的理论意义和潜在的育种应用价值。文章在剖析抗炸荚大豆荚部细胞学微观组织结构特征的基础上,总结了大豆炸荚的发生规律和大豆炸荚表型性状的鉴定指标与方法,介绍了抗炸荚种质鉴定与抗炸荚品种选育概况,同时详细阐述了大豆抗炸荚性状的分子遗传基础研究进展,最后对大豆抗炸荚性的研究与应用进行了展望。     

小兴安岭阔叶红松(Pinus koraiensis)林种子雨的时空动态

研究种子散布的时空动态对于揭示群落更新机制和植被斑块分布格局具有重要意义。于2005～2007年在凉水自然保护区的9hm^2阔叶红松林永久样地的中心地带（150m×150m）,设置287～319个种子接收器（面积为0.5m^2,网口位于离地面1m处）,定期收集并鉴定其中的种子。结果表明：（1）乔木树种的种子雨强度在不同的年份间存在差异,由2005年到2007年逐年递减（分别为（864.2±1084.3）粒·m^-2、（300.9±349.4）粒·m^-2和（144.8±195.5）粒·m^-2）。11个树种均表现出了年际间的差异,一些树种如水曲柳、糠椴、白桦、红皮云杉、冷杉在某一年份结实量很小或几乎不结实,而红松受人为干扰较大。（2）种子散布存在明显的季节变化,从5月份到11月份均收集到了各树种的种子,且种子雨在10月达到高峰,11月中旬基本结束,但不同的树种的时间变化形式不同。高峰期,种子雨以完整种子为主;而在这之前的种子雨主要以未成熟种子为主。（3）种子雨的构成在各年份间保持稳定。（4）变异函数分析表明,在不同的年份种子雨空间异质性不同,而空间异质性与种子雨强度呈正相关。     

辽东山区长白落叶松(Larix olgensis)种子雨和种子库

长白落叶松是东北地区主要的用材树种,其种子雨和种子库研究鲜见报道。在辽东山区用收集器收集的种子分析了长白落叶松种子雨组成、质量和扩散距离,每隔2个月调查1次种子库数量,并结合靛蓝染色法测定每次种子的活力来分析土壤种子库动态。结果表明,辽东山区的长白落叶松种子雨从8月中旬开始,9月末到10月初达到高峰期,11月初结束。在起始期,种子雨以干瘪的不完整种子为主,而从高峰期开始,种子雨以完整种子为主。整个长白落叶松种子雨中不完整种子约占种子雨总量的45％,这些不完整种子由被动物取食、空粒和病虫害危害种子组成。完整种子的平均生活力为56．4％,即有活力的种子仅占整个种子雨的30％。种子雨集中在母树周围,在林缘1次扩散距离一般不超过1．5倍树高。种子雨到达地面之后,主要分布在枯枝落叶层,土壤0—5em层有少量分布,土壤5em以下没有种子分布;土壤种子库的种子主要在翌年雪融化后开始萌发、被取食、搬运以及腐烂,其中腐烂种子数占45．4％,动物取食为30．0％。种子库的种子数量和活力在冬季没有明显变化,而在翌年,种子数量和活力明显减少,4、6月和8月份种子数量分别为（506．3±35．56）粒m^-2,（267．1±17．47）粒m^-2和（143．6±9．83）粒m^-2,对应的活力分别为47．8％±4．68％,19．4％±3．39％和0％,这表明长白落叶松种子不能在地面形成连续的种子库。     

北京东灵山落叶阔叶林中辽东栎种子雨

在北京东灵山地区的一个落叶阔叶林中调查了辽东栎（Ｑｕｅｒｃｕｓ ｌｉａｏｔｕｎｇｅｎｓｉｓ Ｋｏｉｄｚ．）的种子雨。对于选定的４棵辽东栎中的３棵,树冠下的种子雨分布格局符合二次分布,具有很高的决定系数。由设置在树冠下的种子捕捉器收集的坚果数量来估计整棵树的种子雨。４棵树的种子雨中有活力的种子很少,变化范围从２６到２５９个。每棵树的树冠下的种子雨密度变化范围从０．７６到７．２６个／ｍ＾２。林中平均种     

山地常绿落叶阔叶混交林种子雨的地形格局

种子雨是森林群落更新繁殖体的主要来源。而地形对植被空间格局异质性的影响机制之一 ,就是作用于种子雨的空间分布。为了在亚热带山地常绿落叶阔叶混交林群落中检验这一假设 ,在湖北宜昌市大老岭国家森林公园内、海拔 130 0～ 14 95 m之间的一片天然次生林内进行野外比较观测实验。选择 10个不同的地形部位 ,在每一点设置重复 (5个 )的种子雨收集器 ,在种子雨期间定期收集并记录种子雨的种类及数量。 2 0 0 1、2 0 0 2年的观测数据分析表明 :(1)种子雨密度和物种丰富度在不同地形坡位、坡形上差异显著 ,都沿山脊 -山坡 -山谷梯度和凸坡 -平坡 -凹坡梯度而减小 ;(2 )种子雨的密度和物种丰富度受坡向和坡度的影响不显著 ;(3)种子雨和乔木层物种构成的相似性与坡位和坡形呈显著的正相关 ;与坡度呈不显著的负相关 ,与坡向值间存在非线性关系 ;(4 )地形影响种子雨扩散的可能机制包括 ,影响不同种类母树的分布及其密度格局 ,影响不同坡位或坡形上分布的母树种子生产的强度和节律 ,影响风力的方向和大小的分布 ,从而形成水平方向种子流的源 -汇分化。     

大兴安岭中部天然次生林种子雨动态

本研究于2018—2019年对大兴安岭中部白桦林、针叶林和针阔混交林3种林型的种子雨落种量进行了动态监测,并对3种林型主要树种的种子雨季节动态、落叶动态、种子雨千粒重、种子雨年际变化和种子雨空间格局进行了分析。结果表明: 各林型中兴安落叶松种子雨和白桦种子雨呈现明显的单峰型分布。针阔树种(落叶松、樟子松、云杉、白桦、山杨)的落叶量呈现出明显的季节动态,各林型落叶量大多在9月中上旬达到高峰。在针阔混交林和针叶林中,处于高峰期的兴安落叶松种子雨千粒重明显大于初始期和末尾期的兴安落叶松种子雨千粒重,3种林型下白桦千粒重在季节上未表现出明显的差异。兴安落叶松和白桦的种子雨均呈现出明显的年际变化,2018年为种子散种量的丰年,2019年为歉年。两年时间内,所有种子雨的空间格局在总体上均表现为聚集分布,种子雨和幼苗幼树在空间分布格局上存在一致性。     

种子雨研究进展

种子雨是指在特定的时间和特定的空间从母株上散落的种子量。种子雨的组成和大小具有时空异质性。种子雨的空间异质性表现在种子雨的组成和大小因群落而异,种群间的种子雨因种群而异,种群内部的种子雨因个体而异;种子雨的时间异质性表现在不管是群落、种群还是种群内部的个体,其种子雨既具有季节动态,又具有年际变化。种子雨、种子库、幼苗库和地上植被相互联系、相互作用。种子雨的研究对更好地了解种群和群落动态等具有重要意义。应用现代的分子遗传标记技术、同位素标记法和荧光染料法等研究种子雨的散布过程和种子命运将是未来种子雨研究的热点,种子雨和种子库的结合研究及其与动植物关系的研究尚需加强。     

东灵山地区辽东栎种子库统计

东灵山地区辽东栎成熟林内辽东栎（Ｑｕｅｒｃｕｓ ｌｉａｏｔｕｎｇｅｎｓｉｓ）种群更新记要依赖于萌蘖,而实生苗极少。为探索其原因,我们应用随机样方法进行了辽东栎种子库统计。结果表明：１）种子雨持续时间短、强度大,种子散落总密度为１２３个．ｍ＾－２。２）种子大小在种子雨的不同时期差异很大,大的种子在种子雨高峰中后期所占比例较高。３）土壤种子库存在时间约１００ｄ左右,种子密度最高时为４２．７个．ｍ＾－２     

中国野生大豆遗传资源搜集基本策略与方法

遗传资源搜集原则是通过种子采集追求样本具有最高程度的遗传多样性。为了合理而有效地搜集野生大豆资源,近年来通过野生大豆居群考察和遗传多样性分析,初步明确了野生大豆资源居群的遗传多样性分布动态:遗传多样性地理的和生态的区域性、生态系统内居群的遗传相关性及各种生境下居群遗传多样性差异,从理论上奠定了野生大豆资源合理有效搜集的依据。根据居群遗传多样性的分布规律,初步建立了居群野生大豆资源的搜集策略和方法。     

Effect of N source during soybean pod filling on nitrogen and sulfur assimilation and remobilization

During pod filling, a grain legume remobilizes vegetative nitrogen and sulfur to its developing fruit. This study was conducted to determine whether different nitrogen sources affected N and S assimilation and remobilization during pod filling. Well-nodulated plants fed 1.0 mM KNO₃, 0.5 mM urea, or 2.5 mM urea assimilated 0%, 37%, or 114% more N, respectively, and 25%, 46%, or 56% more S, respectively, than did the average non-nodulated control plant fed 5.0 mM KNO₃. Thus, N source during pod filling greatly affected both N and S assimilation. Depending upon N source, plant N concentration during pod filling decreased from 2.96% to between 1.36% and 1.82%. Non-nodulated control plants fed 5.0 mM KNO₃ had the highest residual N at harvest. During the same treatments, plant S concentration decreased from 0.246% to a relatively uniform 0.215%. Thus, during pod filling, vegetative N was seemingly remobilized more efficiently (38–54%) than was S (13%). N source also affected seed yield and seed quality. Non-nodulated control plants fed 5.0 mM KNO₃ produced the lowest yield (21.1 g seeds plant^-1), whereas well nodulated plants fed 1.0 mM KNO₃, 0.5 mM urea, or 2.5 mM urea produced yields of 26.2 g, 31.8 g, and 36.7 g seeds plant^-1, respectively. Non-nodulated plants fed 2.5 mM urea yielded 28.6 g of seeds plant^-1. Seed N concentrations of non-nodulated plants and nodulated plants fed 2.5 mM urea were high, 6.30% and 6.11% N, respectively, whereas their seed S concentrations were low, 0.348% and 0.330% S, respectively. N sources that produced both a relatively high seed yield and seed N concentration (i.e., a relatively high total seed N plant^-1) produced a proportionately smaller increase in total seed sulfur. Consequently, seed quality, as judged solely by seed S concentration, was lowered.     

Ineffective utilization of nitrate by soybean during pod fill

The relative effectiveness of nitrate, allantoin, or nitrate plus allantoin as sources of nitrogen for the indeterminate soybean plant [ Glycine max (L.) Merr cv. Harper] was studied throughout vegetative and reproductive growth. All plants were provided with 3.0 m M nitrogen and were grown hydroponically in growth chambers. During vegetative and early reproductive growth, plants given nitrate or nitrate plus allantoin grew faster than plants provided allantoin only. However, during pod fill, plants provided with allantoin or allantoin plus nitrate gained weight more rapidly than plants receiving just nitrate. More importantly, at maturity plants that had been provided with allantoin or allantoin plus nitrate during pod fill were 30% heavier in total dry weight, 50% higher in nitrogen content, and 50% higher in seed yield than plants that had received just nitrate. At full bloom, all plants were inoculated with the same culture of Bradyrhizobium japonicum , and twice each week throughout pod fill each plant was assayed for nitrogen fixation (acetylene reduction). Correlation coefficients obtained by linear regression analysis show a strong positive correlation between the measured rate of nitrogen fixation and maximum plant fresh weight (r = 0.83), total plant nitrogen (r = 0.81), or seed yield (r = 0.76). The fact that nitrogen fixation during pod fill stimulates plant growth and seed yield, coupled with the facts that nitrate blocks nodulation and is not used efficiently during pod fill by the soybean plant, may explain why seed yield of field-grown soybeans usually does not respond to added fertilizer nitrogen. Thus, it is suggested that enhanced nitrogen fixation may be the key factor in improving soybean seed yield.     

Allantoinase and asparaginase activities in maturing fruits of nodulated and non -nodulated soybeans

Immature fruits of soybean ( Glycine max L. Merr. cv. Santa Rosa) were found to contain high ureide/amino acid ratios for plants dependent on atmospheric nitrogen (nodulated), but low ratios for plants cultivated on NO⁻₃ (non-nodulated). The pod tissue was responsible for almost all this difference, which reflects the N metabolism of these plants (nodulated:urcide-based; NO⁻₃ dependent: asparagine based). The capacity of fruit tissues to utilize ureides and asparagine via allantoinase (EC 3.5.2.5) and asparaginase (EC 3.5.1.1) was investigated during fruit development. Both enzymes were present in crude desalted extracts of all parts of the fruit analysed (pod, cotyledon and seed coat). Asparaginase was detected in pod tissue only at early stages and with very low activities, whereas high activities of allantoinase (up to 20 [imol pod⁻¹ h⁻¹) were present after this organ reached full expansion. The cotyledons contained most of the allantoinase and asparaginase activities of the seed, the highest activities being recorded during the period of rapid protein accumulation. There was little difference in the activity patterns for nodulated and NO⁻₃-grown plants, despite the large difference in nitrogen nutrition of the fruits.     

Maternal control of seed weight in rapeseed (Brassica napus L.): the causal link between the size of pod (mother,source) and seed (offspring,sink)

Seed size/weight is one of the key traits related to plant domestication and crop improvement. In rapeseed (Brassica napus L.) germplasm, seed weight shows extensive variation, but its regulatory mechanism is poorly understood. To identify the key mechanism of seed weight regulation, a systematic comparative study was performed. Genetic, morphological and cytological evidence showed that seed weight was controlled by maternal genotype, through the regulation of seed size mainly via cell number. The physiological evidence indicated that differences in the pod length might result in differences in pod wall photosynthetic area, carbohydrates and the final seed weight. We also identified two pleiotropic major quantitative trait loci that acted indirectly on seed weight via their effects on pod length. RNA‐seq results showed that genes related to pod development and hormones were significantly differentially expressed in the pod wall; genes related to development, cell division, nutrient reservoir and ribosomal proteins were all up‐regulated in the seeds of the large‐seed pool. Finally, we proposed a potential seed weight regulatory mechanism that is specific to rapeseed and novel in plants. The results demonstrate a causal link between the size of the pod (mother, source) and the seed (offspring, sink) in rapeseed, which provides novel insight into the maternal control of seed weight and will open a new research field in plants.     

Pathway and regulation of phosphate translocation to the pods of soybean explants

We investigated the degree to which developing fruit compete directly with leaves for mineral nutrients, e.g. phosphate coming up from the roots. When soybean ( Glycine max (L.) Merrill cv. Anoka) explants cut at mid-late podfill were given a 15-min pulse of ³²Pi via the cut stem and then transferred to distilled water, 75% of the ³²P accumulated in the leaves and 21% in stem and petiole during the first hour. The amount of ³²P entering the seeds was low (1%) initially, but thereafter increased to 30% in 48 h. An accumulation of ³²P in the seed coats preceded its entry into the embryos. Disruption (with hot steam) of the phloem between the leaf and the pods after pulse labelling indicated that more than 80% of the ³²Pi pulse moved to the leaf before redistribution to the pods. Increasing "sink" size by adjusting the pod load from 1 to 2–3 did not increase the ³²P accumulated by the pods proportionally. Conversely, excision of the seeds after pulse labelling did not prevent translocation of ³²P out of the leaves. These results suggest that the rate of transport of phosphate to the pods at mid-late podfill is controlled primarily by factors in the leaves. The results are consistent with the observation that the relative size of the sink (pod load) does not regulate leaf senescence.     

Morphological development of normal and phyllody expressing Rosa hybrida cv. Motrea flowers

A large number of soybean (Glycine max L. Merr.)flowers and young pods abscise rather than develop into mature pods. Flower andpod drop or abortion accounts for the majority of total reproductive abscissionand influences potential soybean yield. The objectives of this study were todetermine the patterns of flower, pod and seed development under treatmentswiththe growth regulators, 2-(2,4-dichlorophenoxy) propanoic acid (2,4-DP) and6-benzylaminopurine (BAP), applied at the early reproductive stages, and toexamine the association of reproductive abscission with growth characteristicsand agronomic traits, including seed yield and seed weight. Small seeded [cvPungsan (11.1±0.4 g100-seed^–1)] and large seeded [cv Manlee(21.0±0.5 g 100-seed^–1)]genotypes were separately planted in the greenhouse and field, and treated witheither 2,4-DP or BAP. 2,4-DP (a synthetic auxin) and BAP (a syntheticcytokinin)were each applied at three concentrations (i.e. high, intermediate or low):0.12mM, 0.08 mM, 0.04 mM, and 1.5mM, 1 mM, 0.5 mM respectively. High andlow concentrations were employed for greenhouse experiments to examine thenumber of flowers per plant in pots. With the exception of low BAP (0.5mM) treatment in Pungsan, all treatments increased total podnumberwith various numbers of seeds per pod. Low 2,4-DP (0.04 mM) inbothgenotypes or BAP (0.5 mM) in Manlee significantly reduced flowerabortion and delayed abscission of pods in both genotypes, resulting inincreased pod setting rates. Under field conditions using intermediateconcentrations, 1 mM BAP significantly increased 100-seed weightto22.3 g at R1 in Manlee and 11.9 g at R3 in Pungsan.BAP (1 mM) at R3 in Pungsan significantly improved seed yield(40.1g plant^–1). Maturity was not significantlyaffected by either application in Manlee, but was significantly affected by BAPin Pungsan. In Pungsan, 2,4-DP increased pod number, plant height and nodenumber, but decreased 100-seed weight in Pungsan treated at R1, causing nosignificant change of seed yield. This study suggested that exogenousregulatorssignificantly influenced reproductive and growth characteristics, andconsequently seed yield, but increase of pod number was not always beneficialfor seed yield.     

Spectral quality during pod development modulates soybean seed fatty acid desaturation

High-density cropping of soybeans results in considerable mutual shading. Consequently, pods mature under a range of light conditions, with those lower in the canopy exposed to drastically altered spectral quality as well as lower irradiance. The influence of spectral quality on reproductive development and seed quality was investigated in soybeans raised to physiological maturity under either broad spectrum or blue-deficient light sources. The absence of blue light had a large influence on vegetative morphology, but the timing of reproductive events was not affected. Total seed yield per plant, dry matter per seed, per cent protein and per cent oil were similar for all treatments. However, seeds harvested from plants matured under broad spectrum illumination contained high levels of oleic acid (18:1) and low linoleic acid (18:2) compared to seeds from plants grown under blue-deficient conditions. In addition to the spectral quality effect, there was a smaller effect of pod position. Seeds from pods lower in the canopy contained less 18:1 and more 18:2 than seeds that matured closer to the top of the canopy. Considering both spectral quality and pod position, the ratio of 18:1 to 18:2 varied four-fold between 0·35 and 1·43, indicative of a possible photoregulatory step in fatty acid desaturation. The spectral effects are consistent with the participation of a photomorphogenetic photoreceptor in the control of fatty acid metabolism during seed maturation and triglyceride accumulation.     

Heterocarpy diversifies diaspore propagation of the desert shrub Ammopiptanthus mongolicus

In the desert, plant diaspore spreading usually relies on both external vectors, such as wind, and internal factors, such as diaspore shape. Ammopiptanthus mongolicus is a heterocarpous shrub species in the cold desert in northwest China. Mature pods may have dehisced or not yet dehisced when abscising, and the dehiscent pods may be twisted or flattened. The propagation distances of diaspores might vary due to differences in their buoyancies in upward air and ground friction according to pod shape. The wind tunnel experiments were conducted to measure the horizontal displacement upon fruit dropping (D1) and the wind-blown distance traveled by a fallen pod (D2) of A. mongolicus. A generalized linear mixed model and generalized linear model were used to test the effects of pod shape, release height, wind speed and ground substrate type on the spread distance of pods. D1 is jointly determined by the effects of release height and pod shape. Wind speed, pod shape and ground substrate type together affect D2. A twisted pod has higher dispersibility than a flat pod, and dehiscent pods spread further than indehiscent ones. The positive correlation of D1 and D2 indicates that the difference in pod shape additively broadens the range of seed-spreading distance. Differential seed-spreading properties could be adaptively advantageous to disperse the risks associated with diasporic dissemination compared with the maintenance of a single optimal dissemination characteristic. Thus, heterodiaspory is an advantageous adaptive characteristic for seed spreading in the windy, arid and harsh desert environment.     

Internal recycling of respiratory CO2 in pods of chickpea (Cicer arietinum L.): the role of pod wall, seed coat, and embryo

It has previously been proposed that respiratory CO2 released from the embryo in grain legume pods is refixed by a layer of cells on the inner pod wall. In chickpea this refixation process is thought to be of significance to the seed carbon budget, particularly under drought. In this study it is reported that the excised embryo, seed coat, and pod wall in chickpea are all photosynthetically competent, but the pod wall alone is capable of net O2 evolution over and above respiration. The predominant role of the pod wall in refixation is supported by measurements of fixation of isotopically labelled CO2, which show that more than 80% of CO2 is fixed by this tissue when provided to the pod interior. Chlorophyll concentrations are of the same order for embryo, seed coat, and pod wall tissues in younger pods on both an area and a fresh weight basis, but decline differentially with development from 12-30 d after podding. Imaging of chlorophyll distribution in the pod wall suggests that less than 15% of chloroplasts are located in the inner layer of cells thought to refix CO2 in legumes; this would be sufficient to refix less than 40% of respired CO2. It is concluded that while all tissues of the pod are capable of refixing respiratory carbon, the entire pod wall is responsible for the majority of this process, rather than a specialized layer of cells on the inner epidermis. The role of this fixed carbon in the pod for reallocation to the seed is discussed