Mechanical Harvesting Effects on Seed Yield Loss,Quality Traits and Profitability of Winter Oilseed Rape (Brassica napus L.)

China is one of the most important rapeseed producing countries in the world. Effective mechanical harvesting time for decreasing harvesting loss of winter oilseed rape has been becoming a critical factor. An elite cultivar Zhongshuang 11 （Brassica napus L.） was employed in two rounds of field experiments from 2009 to 2011. Seeds were sown with machine, three combine harvesting times namely combine harvesting A, B, and C （CHA, CHB, and CHC） were designed and manual harvesting （MH） as control was performed at maturity. The harvesting treatments were determined according to color of pod and seed in the field. Seed yield loss and quality in different treatments were evaluated. Results showed that both seed yields and harvesting losses in 2009-2010 were higher than that in 2010-2011, whereas seed oil contents in 2010-2011 were higher than that in 2009-2010. The highest yield appeared in CHB, which was significantly higher than that in MH. Furthermore, harvesting loss in CHB were 50% that in MH. Seed oil content and chlorophyll exhibited no obvious difference between CHB and MH. Economic profit analysis demonstrated that mechanical sowing/combine harvesting （MS/CH） showed an input/output ratio of 1：1.6, and it was 1：1.2 in mechanical sowing/manual harvesting （MS/MH）. Labor-cost accounted for more than 70% of the total cost in MS/MH, which led to low profitability to a great extent. Our results suggested that CHB was the optimum harvesting time for winter oilseed rape along the Yangtze River.

Studies on rice seed quality through analysis of a large- scale T-DNA insertion population

A rice （Oryza sativa） T-DNA insertion population, which included more than 63 000 independent transgenic lines and 8 840 identified flanking sequence tags （FSTs） that were mapped onto the rice genome, was developed to systemi- cally study the rice seed quality control. Genome-wide analysis of the FST distribution showed that T-DNA insertions were positively correlated with expressed genes, but negatively with transposable elements and small RNAs. In addition, the recovered T-DNAs were preferentially located at the untranslated region of the expressed genes. More than 11 000 putative homozygous lines were obtained through multi-generations of planting and resistance screening, and measurement of seed quality of around half of them, including the contents of starch, amylose, protein and fat, with a nondestructive near-infrared spectroscopy method, identified 551 mutants with unique or multiple altered param- eters of seed quality. Analysis of the corresponding FSTs showed that genes participating in diverse functions, including metabolic processes and transcriptional regulation, were involved, indicating that seed quality is regulated by a complex network.

Controls of seed quantity and quality on seedling recruitment of smith fir along altitudinal gradient in southeastern Tibetan Plateau

Alpine treeline ecotones are harsh environment for tree establishment due to low temperature. Tree establishment at treelines requires favorable climate, suitable microsites, and viable seeds. But most researches have been addressed treeline microclimate and its effects on tree regeneration, the knowledge of seed quantity and quality and its controls on seedling recruitment were limited. We measured seed rain, soil seed bank, seed germination rate and seedling recruitment in natural forests in combination with seed transplanting manipulation to evaluate the controls of seed quantity and quality on seedling recruitment of Abies georgei var. smithii （smith fir） along altitudinal gradient, with focus on treeline ecotone in the Sygera Mountains, southeastern Tibetan Plateau. Both seed quantity and seed quality of smith fir decreased with increasing altitude and was thereby associated with decline in seed germination rate. Seed quantity and seedling recruitment were better in north-facing slope than in south slope. The treeline ecotone above 42oo m appeared as the threshold altitude to sharply decrease seed quality and seedling recruitment. The emergence and overwintering rates of transplanting seeds from 3600-38oo m also went down remarkably above 4200 m at north-facing slope. It also underpins the fact that treeline ecotone is the bottleneck of seedling recruitment. Our results suggest that seed quantity and quality are the principal limitation of treeline upward advance. This study also provides evidence to support stable treeline position in southeastern Tibetan Plateau.

Application of oxygen-sensing technology to measure seed quality of Ginkgo biloba

Germination tests are currently the most widely used method to evaluate seed quality of Ginkgo biloba L., but they are time-consuming and labor intensive. Oxygen-sensing technology, based on the principle of fluorescence quenching to detect oxygen and assess seed quality was used to rapidly evaluate seed quality of two varieties (Shandong Tancheng 202 and Zhejiang Dafoshou) of G. biloba from five mother plants. Fifteen samples of three vigor levels were produced by accelerated aging treatments. This process was applied in duplicate. A portable oxygen-sensing detector was employed to measure oxygen content during seed germination in a closed system at 25 A degrees C each day until day 14. Four oxygen metabolism indices were calculated: oxygen consumption index, oxygen consumption rate, critical oxygen concentration, and theoretical germination time (T (GT)). Additionally, we tested laboratory germination and field emergence. The results of a one-way analysis of variance and correlation analysis showed that T (GT) was the candidate index to evaluate seed quality of G. biloba. Therefore, the T (GT) value was used to validate the reliability of oxygen-sensing evaluation for Zhejiang Dafoshou seeds kept under four storage conditions. The trend in the change in oxygen metabolism agreed completely agreement with that of seed germination under all storage conditions. The oxygen-sensing test reliably and rapidly assessed seed quality of G. biloba. The germination rate of Zhejiang Dafoshou was accurately predicted by T (GT).

Field mold stress induced catabolism of storage reserves in soybean seed and the resulting deterioration of seed quality in the field

Excessive rainfall provides a favorable condition for field mold infection of plants, which triggers field mold(FM) stress. If FM stress occurs during the late maturation stage of soybean seed, it negatively affects seed yield and quality. To investigate the responses of soybean seed against FM stress and identify the underlying biochemical pathways involved, a greenhouse was equipped with an artificial rain producing system to allow the induction of mold growth on soybean seed. The induced quality changes and stress responses were revealed on the levels of both transcriptome and metabolome. The results showed that soybean seeds produced under FM stress conditions had an abnormal and inferior appearance, and also contained less storage reserves, such as protein and polysaccharide. Transcriptional analysis demonstrated that genes involved in amino acid metabolism, glycolysis, tricarboxylic acid, β-oxidation of fatty acids, and isoflavone biosynthesis were induced by FM stress. These results were supported by a multiple metabolic analysis which exhibited increases in the concentrations of a variety of amino acids, sugars, organic acids, and isoflavones, as well as reductions of several fatty acids. Reprogramming of these metabolic pathways mobilized and consumed stored protein, sugar and fatty acid reserves in the soybean seed in order to meet the energy and substrate demand on the defense system, but led to deterioration of seed quality. In general, FM stress induced catabolism of storage reserves and diminished the quality of soybean seed in the field. This study provides a more profound insight into seed deterioration caused by FM stress.

Egg quality, fatty acid composition and immunoglobulin Y content in eggs from laying hens fed full fat camelina or flax seed

Background： The current study was conducted to evaluate egg quality and egg yolk fatty acids and immunoglobulin（Ig Y） content from laying hens fed full fat camelina or flax seed.Methods： A total of 75, 48-week-old Lohman brown hens were randomly allocated to 3 treatments, with 5replicates containing 5 laying hens each replicate. The hens were fed corn-soybean basal diet（Control）, or Control diet with 10 % of full fat camelina（Camelina） or flax seed（Flax） for a period of 16 wk. Hen production performance egg quality, egg yolk lipids, fatty acids and Ig Y were determined every 28 d during the experimental period.Results： Egg production was higher in hens fed Camelina and Flax than in Control hens（P 〈 0.05）. Egg weight and albumen weight was lowest in eggs from hens fed Camelina（P 〈 0.05）. Shell weight relative to egg weight（shell weight %）, and shell thickness was lowest in eggs from hens fed Flax（P 〈 0.05）. No difference was noted in Haugh unit, yolk：albumen ratio, and yolk weight. Significant increase in α-linolenic（18：3 n-3）, docosapentaenoic（22：5 n-3）and docoshexaenoic（22：6 n-3） acids were observed in egg yolk from hens fed Camelina and Flax. Total n-3 fatty acids constituted 1.19 % in Control eggs compared to 3.12 and 3.09 % in Camelina and Flax eggs, respectively（P 〈 0.05）. Eggs from hens fed Camelina and Flax had the higher Ig Y concentration than those hens fed Control diet when expressed on a mg/g of yolk basis（P 〈 0.05）. Although the egg weight was significantly lower in Camelina-fed hens, the total egg content of Ig Y was highest in eggs from hens fed Camelina（P 〈 0.05）.Conclusions： The egg n-3 fatty acid and Ig Y enhancing effect of dietary camelina seed warrants further attention into the potential of using camelina as a functional feed ingredient in poultry feeding.

Influence of Water Content on the Quality of Pigeonpea Seeds

The species Cajanus cajan L. where pigeonpea is from presents a harvest potential in tropical regions for it is used as human and animal feed, besides being used as green fertilizer. However, the harvest area of this Fabaceae is still insignificant, due to especially the lack of quality seeds. In this context, it is possible to affirm that drying and store are portrayed as important steps for obtaining superior quality seeds. The aim of this study is to evaluate the physiologic quality of dwarf pigeonpea seeds, with different water content during storage. A factorial scheme 3 × 6 was adopted in the delimitation completely randomized, with four replications. Treatments were constituted by the combination of lots of seeds containing three different water contents (11%, 14% and 16%), submitted to a 10-month storage period, with evaluations every two months (0, 2, 4, 6, 8 and 10). Seeds were stocked in a bag type kraft under normal lab conditions, that is, no control. Physiologic quality of the seeds was evaluated through the following tests: Germination Pattern Test—GPT, first count of germination, accelerated aging and electric conductivity. It can be concluded that pigeonpea with hard seeds containing water content at 11% existing superior physiologic quality throughout the 10-month storage, under no controlled condition, certainly promoted by the less intense breathing from the reserves cumulated in the seed lot. Pigeonpea seeds storage with water content superior to 14% promotes a sharp decrease of physiologic quality, due to an increase in metabolic activity.

Ultraviolet-B Radiation Alters Soybean Growth and Seed Quality

Research on the effects of ultraviolet-B (UV-B) radiation on soybean seed quality is limited. The objective of this study was to quantify UV-B doses, 0, 5, 10 & 15 kJ•m–2•d–1, on soybean growth and seed quality. The experiment was conducted in the Soil-Plant-Atmosphere-Research (SPAR) facility. Chambers located at the R.R. Foil Plant Science Research Facility of Mississippi State University, Mississippi, USA, were used. Each SPAR chamber consists of a steel soil bin to accommodate the root system, a Plexiglas chamber to accommodate plant canopy and a heating, and cooling system connected to air ducts that pass conditioned air to cause leaf flutter through the plant canopy. The SPAR units, supported by an environmental monitoring and control systems, are networked to provide automatic acquisition and storage of the data, monitored every 10 seconds throughout the day and night. Soybean cultivar Pioneer 93Y92 (maturity group IV, Roundup Ready) was used in the study. The desired UV-B radiation was supplied by square-wave UV-B supplementation systems under near ambient PAR and delivered to plants for eight hours, each day, from 08:00 to 16:00 h by eight fluorescent UV-313 lamps. The results showed that increased UV-B did not influence many of the growth parameters because the treatments were imposed at mid-fruiting period. Seed quality parameters that are important for seed industry and human and animal nutrition were all affected by UV-B. Protein and palmitic and oleic acids declined linearly, while oil and linoleic and linolenic acid contents increased with increased UV-B. Sucrose, stachyose, and stearic acid contents showed quadratic trends, increased to about 4 - 5 kJ of UV-B and declined at higher doses. Thus, both current and projected UV-B radiation levels can modify soybean growth and seed quality. The functional algorithms developed in this study could be useful to develop UV-B- specific sub-models for soybean farm management and in policy decision areas.

Influence of Crop Nutrition on Grain Yield,Seed Quality and Water Productivity under Two Rice Cultivation Systems

The system of rice intensification （SRI） is reported to have advantages like lower seed requirement,less pest attack,shorter crop duration,higher water use efficiency and the ability to withstand higher degree of moisture stress than traditional method of rice cultivation.With this background,SRI was compared with traditional transplanting technique at Indian Agricultural Research Institute,New Delhi,India during two wet seasons （2009-2011）.In the experiment laid out in a factorial randomized block design,two methods of rice cultivation [conventional transplanting （CT） and SRI] and two rice varieties （Pusa Basmati 1 and Pusa 44） were used under seven crop nutrition treatments,viz.T 1,120 kg/hm2 N,26.2 kg/hm2 P and 33 kg/hm2 K;T 2,20 t/hm2 farmyard manure （FYM）;T 3,10 t/hm2 FYM＋ 60 kg/hm2 N;T 4,5 t/hm2 FYM＋ 90 kg/hm2 N;T 5,5 t/hm2 FYM＋ 60 kg/hm2 N＋ 1.5 kg/hm2 blue green algae （BGA）;T 6,5 t/hm2 FYM＋ 60 kg/hm2 N＋ 1.0 t/hm2 Azolla,and T 7,N 0 P 0 K 0 （control,no NPK application） to study the effect on seed quality,yield and water use.In SRI,soil was kept at saturated moisture condition throughout vegetative phase and thin layer of water （2-3 cm） was maintained during the reproductive phase of rice,however,in CT,standing water was maintained in crop growing season.Results revealed that CT and SRI gave statistically at par grain yield but straw yield was significantly higher in CT as compared to SRI.Seed quality was superior in SRI as compared to CT.Integrated nutrient management （INM） resulted in higher plant height with longer leaves than chemical fertilizer alone in both the rice varieties.Grain yield attributes such as number of effective tillers per hill,panicle length and panicle weight of rice in both the varieties were significantly higher in INM as compared to chemical fertilizer alone.Grain yields of both the varieties were the highest in INM followed by the recommended doses of chemical fertilizer.The grain yield and its attributes of Pusa 44 were significantly higher than those of Pusa Basmati 1.The seed quality parameters like germination rate and vigor index as well as N uptake and soil organic carbon content were higher in INM than those in chemical fertilizer alone.CT rice used higher amount of water than SRI,with water saving of 37.6% to 34.5% in SRI.Significantly higher water productivity was recorded in SRI as compared to CT rice.

Effects of Seeding Rate and Light on the Seed Yield and Bioactive Ingredient Contents of Vernonia anthelmintica

[Objectives]This study was conducted to investigate the effects of seeding rate and light on the seed yield and active ingredients of Vernonia anthelmintica.[Methods]With V.anthelmintica L.Willd as the research object,the seed yield was determined by staged harvesting combined with the actual cutting and measuring method;and the caffeoylquinic acids(CQA)were used as the characterization indexes,and high performance liquid chromatography was used to determine the contents of 3,4-CQA,3,5-CQA and 4,5-CQA of V.anthelmintica seeds under different seeding rate+light treatments,so as to compare the changes in seed yield and chemical composition of V.anthelmintica under different seeding rates and light factors.[Results]In Moyu County,Hetian and similar areas,the suitable planting rate of V.anthelmintica was in the range of 13.5-15.0 kg/hm^(2).For different harvesting purposes,the optimal seeding rate and light conditions of V.Anthelmintica were different.[Conclusions]The seeding rate and light conditions can be used to interfere with the seed yield and quality of V.anthelmintica.

Analysis of seed and maternal genetic effects on cooking quality characters in indica hybrid rice

We analysed seed and maternal genetic effects on characters of cooking quality in indica hybrid rice by using the model for quantitative characters of seeds of cereal crops. Incomplete diallel crosses were made by using six male sterile lines (Zhenshan 97A, Erjiuqing A, Erjiunan 1A, V20A, Zhe’nan 1A and Zhe’nan 3A)as females and three restorer lines(Cezao 2-2, T49 and 26715)as males. Sampled seeds were used to measure the cooking quality characters, including amylose content(%), gelatinization temperature(alkali spreading score)and gel consistency(mm). Results indicated that some rice cooking quality characters were controlled by both seed genes and maternal genes (see table). Gel consistency was mainly controlled by maternal effects, but also

Machine Vision Analysis of Characteristics and Image Information Base Construction for Hybrid Rice Seed

Incompletely closed glumes, germination on panicle and disease are three important factors causing poor seed quality of hybrid rice. To determine how many and which categories should be classified to meet the demand for seed in rice production, the effects of various degrees of incompletely closed glumes, germination on panicle and disease on germination percentage at the harvest and after storage for six months were studied by standard germination percentage test. Six categories of seeds with germ (germinated seeds), severe disease, incompletely closed glumes, spot disease, fine fissure and normal seeds were inspected and then treated separately. Images of the five hybrid rice seed (Jinyou 402, Shanyou 10, Zhongyou 27, Jiayou 99 and Ⅱ you 3207) were acquired with a self-developed machine vision system. Each image could be processed to get the feature values of seed region such as length, width, ratio of length to width, area, solidity and hue. Then all the images of normal seeds were calculated to draw the feature value ranges of each hybrid rice variety. Finally, an image information base that stores typical images and related feature values of each variety was established. This image information base can help us to identify the classification limit of characteristics, and provide the reference of the threshold selection. The management of large numbers of pictures and the addition of new varieties have been supported. The research laid a foundation for extracting image features of hybrid rice seed, which is a key approach to future quality inspection with machine vision.

Variability and divergence in horsegram (Dolichos uniflorus)

Horsegram is an important and unexploited tropic and sub-tropic legume crop grown mostly in dry land agriculture. The study involving 23 cultivars of horsegram （Dolichos uniflorus） was conducted at the Seed Research ＆ Technology Centre in Rajendranagar, Hyderabad, India during the early spring seasons of 2008 and 2009 to assess the nature and magnitude of variability in the existing species and also to identify diverse parents for use in further breeding programmes. The results indicated significant differences among the 23 cultivars for all characters studied, indicating the presence of sufficient genetic variation. High variability and heritability coupled with high genetic advance were reported for seed yield per plant and pod hulm per plant, indicating additive gene action and a possible scope for the improvement of these characters. Mahalanobis D2 statistics grouped all the 23 cultivars of horsegram into six ,clusters. The maximum inter cluster distance （62.39） was noticed between cluster IV （HG 50） and cluster V （HG 11）. The maximum Jntra cluster distance ranged from 0 （clusters III, IV, V and VI） to 15.17 （cluster I）, indicating that the genotypes in these clusters were relatively more diverse than the genotypes within other clusters. Seed yield per plant contributed the maximum （33.20%） to the genetic divergence.

Physiological and Phytosanitary Potentials of Coriander and Radish Seeds

Information on seed vigor of the vegetable crops is always important and necessary due to the increasing demand of high quality seeds for sowing and high-value commercial. The cultivation of these species, conducted intensively, should be established with seed high potential physiological and health for the development of a more productive and sustainable agriculture. The present study was conducted to evaluate the potential physiological of seed lots of radish and coriander. The experiment was conducted at the laboratory of seed analysis and greenhouse of the plant science department of the Federal University of Pelotas in South Brazil. Four radish seed lots, cultivar ＂Saxa＂, and four coriander seed lots, cultivar ＂Verdito＂ were used. Germination seed test, first count of germination, accelerated aging test, electrical conductivity and seedling emergence were used to evaluate the physiological quality of the lots. The experimental design was completely randomized design with five replications. Means were compared by Tukey test. The accelerated aging test was the most efficient test in assessing the physiological quality for both lots of radish seeds and coriander and this test provide coherent results with seedlings emergence.

Effectiveness of Hermetic Storage Using PICS Bags and Plastic Jars for Post-Harvest Preservation of <i>Acacia macrostachya</i>Seeds

In Burkina Faso, the availability of Acacia macrostachya “Zamnè” seeds throughout the year is threatened by the attacks of pests. So, the effectiveness of airtight (hermetic) storage for the preservation of these seeds was evaluated using 20-litre plastic jars and 50 kg PICS bags as hermetic containers with 50 kg polypropylene bags as controls. Seeds of Acacia macrostachya (17.5 kg) were stored in each of these storage devices for six months under ambient conditions in the laboratory. The number of storage pest Bruchidius silaceus increased significantly in polypropylene bags from 235 to 715 individuals on average/500 g of seeds. But in PICS bags and plastic drums, the number of this pest did not vary significantly (191 and 239 individuals on average/500 g of seeds for plastic jars and PICS bags respectively). In both hermetic devices, we found few individuals of another major storage pest Caryedon furcatus. However, polypropylene bags, haboured more pests’ in addition high numbers of C. furcatus and Oryzaephilus mercator which were not found in the hermetic devices. Seeds damage and weight loss increased significantly in polypropylene bags from 7.40% to 20.23% and 0.50% to 3% respectively compared to PICS bags and plastic jars. The germination rate of A. macrostachya seeds decreased significantly in PICS bags, plastic jars and polypropylene bags with average percentages of 14%;11% and 15% respectively compared to the initial average of 27%. PICS bags and plastic jars are therefore effective in preserving the quality of A. macrostachya seeds, but the effects of these hermetic devices on seed viability need to be explored further.

Sustainable Potato Production in the Mountain Area of Ecuador, an Approach to Increase Productivity with Small Scale Farmers

Ecuador potato crop is family based production system. Potato production has two roles in their economy, the first is providing food for their families and the second is a source of income for the household. However small scale farmers have limited access to local markets and most of the sales are through intermediates’ who purchase directly in the field at the lowest price possible. Potato production challenges for the small-scale farmers are among others availability of quality potato seed, direct sales, purchase of agrochemical inputs to maintain their crops and lack of education. In 2021, only 4% of potato farmers used certified seed. Potato yield is still low around 16.1 t·ha-1, in the last 10 years the total potato cultivated area was reduced by at least 50%. The farmers produce “Bokashi” and other organic fertilizer and these are effective to improve soil fertility and plant health. Homemade bio-pesticides reduce agrochemical pesticides. The Decision Support System (DSS) is a handheld device to control late blight, minimizes fungicide applications and improve fungicide rotation. In 2018 Candidatus Liberibacter solanacearum (Lso), the causal agent of zebra chip, and its vector, the potato psyllid Bactericera cockerelli, together created havoc for farmers and researchers. Promotion of early potato varieties INIAP—Libertad is an alternative to lower the impact of this newest pest.

A Transaction Cost Analysis on the Acquisition of Rice Seed by Small-Scale Farmers in ECA Region： Generating Empirical Evidence in Tanzania

The present study is an attempt to develop empirical evidence of transaction costs that rice farmers incur in production and other factors that affect farmers＇ demand for seed and estimating the proportion of costs accounted for by transaction costs due to quality seed in the formal and informal sectors, and analyze how these costs affect sourcing decision. An agricultural household model was developed from the study area. To test the model, information was collected in a survey of 387 households. There is now empirical evidence that transaction cost in rice seed acquisition in Tanzanian agriculture is an added cost to the farmer in the process of purchasing seed. Descriptive analysis shows that about 18% of the total seed cost is accounted for transaction cost, which is 2% of the total variable cost in farmers＇ rice farming. Econometric model was fitted to the household data to determine the factors hindering farmers to use purchased quality seed. Factors that were significant in influencing transaction cost include information search, seed source, farmers＇ seed arrangements, trust, and distance from farmers＇ homestead to the seed source, location and age of the farmer. We recommend that, policy amendments inclined towards reduction of the transaction costs can improve the profitability of the rice enterprise by increasing the demand for inputs.

Design and test of a double compression seeder for pre-sowing and seed furrow of wheat in wide-seedling belts

To solve the problem of poor sowing quality due to loose soil in wheat seedbed after land preparation in the Huang-Huaihai region of China,a double compression seeder for pre-sowing and seed furrow of wheat in wide-seedling belts was designed.The machine sowing operation was divided into two processes:pre-sowing compression and seed ditch compression,pre-sowing compression was carried out homogenization of the pre-sowing seed bed that the tractor wheel has crushed,and the seed ditch compression compresses the seeds and soil in the seed ditch,so that the seeds were embedded in the seed ditch soil.By analyzing the kinematics of the pre-planting compression device and the spiral blade in the process of soil levelling and compression,the structure of the equal-difference variable-diameter equal-pitch spiral conveying winch was designed,and the key parameters of the drum spiral blade were determined,and then the height of the spiral blades,the rutting distance and the speed of the compression roller were taken as the test factors,and the soil flatness was used as the index to carry out the discrete element simulation test.The simulation results show that when the spiral blade was 4.85 cm,the rut distance was 37.4 cm,and the rotation speed was 327.16 r/min,the optimal land flatness was 0.18.Finally,field experiments were carried out on the seeder,and the results showed that:the soil bulk density after operation was 22.7%greater than that before sowing(p<0.01),and the soil flatness was 1.9 cm,which was consistent with the simulated results.The use of pre-sowing compression and seed furrow compression methods improved the soil environment of the seed bed,increased the uniformity of the seeding depth,and promoted the root growth of wheat.This study provides equipment support and technical reference for agricultural production in wheat-corn rotation areas in the Huang-Huaihai region of China.

High seed losses in mountain birch(Betula pubescens ssp.tortuosa)and developmental,ecological,and environmental correlates

Plants typically experience great losses from their reproductive potential represented by ovule production to the post-dispersal crop of viable seed.We examined seed density and viability in a founder population of mountain birch(Betula pubescens ssp.tortuosa),aiming to quantify losses at different stages and examine potential selection forces on the reproduction success of the founder generation of an isolated population.At the time of the study(2017-2020),the population had recently reached reproductive maturity,following its colonization around 1990 through long-distance dispersal onto an early successional outwash plain in southeast Iceland.Seed densities were high,but 89% of apparently intact seeds did not contain an embryo,despite being visually indistinguishable from filled seeds.Externally evident losses amounted to about 45% of the total seed crop and were mostly due to predation by the gall midge Semudobia betulae.When all losses were accounted for,2.7% of the seed crop remained viable and germinated.Pollen limitation may partially explain the high incidence of empty seeds.Excessive flower production is compatible with the predator satiation hypothesis but cannot explain pre-dispersal losses.Another adaptation to predation,masting,appears poorly developed in Iceland.Our results suggest the presence of constraints on the reproduction potential of the new island population,that are more limiting than in neighbouring populations,and we discuss their developmental,ecological,and environmental correlates.

Flowering and seeding patterns in pure and mixed Nothofagus forests in Southern Patagonia

Introduction:Variation in reproductive phenology among species is an important mechanism for maintaining species coexistence.In mixed forests,the impact of limiting(biotic and abiotic)factors on tree reproductive success regulates the maintenance of species in balanced proportions or the conversion towards monospecific forests.This study offer a significant first approach to the reproductive phenology of mixed forests,assessing flowering,seeding and loss factors on reproductive success in three forest types(pure deciduous Nothofagus pumilio(Np),evergreen Nothofagus betuloides(Nb)and mixed(M)forests),comparing also between two geographical locations(coast and mountain),during one growing season.Results:Flowering falling started early in Np.Seed fall occurred first and more concentrated in Np,while in Nb,it was progressive during autumn.Phenology in M combined both patterns,but with better reproductive performance of both species.Seed production was greater in Nb(42,900,000 ha^(−1))than in Np(710,000 ha^(−1)),while M presented intermediate values(31,900,000 ha^(−1)).Abortion was greatest in Np(19% of female flowers and 10% of immature fruits),while fruit predation was low(7-9%)in all forest types.Empty seed was the main loss factor,but with low net values for each species in M.Regarding geographical location,sea proximity generated a quick starting of the growing season in coast compared to mountain sites.However,we detected forest types×location interactions in flowering and seeding patterns(e.g.in male flower production and in empty and viable seeds),with differences in species response according to location.Conclusions:Both deciduous and evergreen species have reproductive advantages in mixed compared to pure forests.However,mixed were more similar to pure evergreen forests in their reproductive traits and the incidence of the limiting factors.The study of only one growing season does not allow us to conclude whether mixed forests are stable communities,but we contribute to understand the roles of reproductive phenology in mixed forest dynamics.