Responses of Caragana korshinskii to different aboveground shoot removal: combining defence and tolerance strategies

BACKGROUND AND AIMS: It is generally assumed that plants respond to natural enemies by either allocating resources to resistance traits or compensating for damage. This study evaluated how different methods of artificial shoot removal influence two alternative strategies (i.e. tolerance and defence) of Caragana korshinskii in the semi-arid area of China. METHODS: Zero per cent (control), 30% (30%) and 60% (60%) of the main shoot length and 25% (25%), 50% (50%) and 100% (100%) of the numbers of main shoots were removed from shrubs. KEY RESULTS: Moderate clipping treatments [30% removal of partial shoot length (RSL), 25% removal of shoot number (RSN) and 50% RSN] improved seed production, whereas the most intensive clipping treatments (60% RSL and 100% RSN) with most or total removal of potential flower buds reduced current reproduction fitness compared with controls. All treatments produced a similar leaf phenolic content, with the exception of 100% RSN which resulted in a low leaf phenolic content. In spite of a substantial investment in regrowth, clipped plants increased biomass allocation to physical defence. Control plants almost did not grow, had lower levels of physical defence and a lower photosynthetic rate, mobilized fewer carbohydrates from roots and produced more flowers. However, their current fitness was lower than that of plants undergoing clipping treatments (30% RSL, 25% RSN and 50% RSN) because of the high level of abortion of flowers and fruits. CONCLUSIONS: Caragana korshinskii responded to aboveground shoot removal through combining defence and tolerance strategies.     

Activities of starch hydrolytic enzymes and starch mobilization in roots of <Emphasis Type="Italic">Caragana korshinskii</Emphasis> following above-ground partial shoot removal

In many resprouting plants, carbohydrates are stored as starch in roots and will be mobilized to support above-ground tissue regrowth after shoot damage. Our objective was to determine how activities of starch hydrolytic enzymes change damage-induced starch mobilization in Caragana korshinskii roots after above-ground tissue loss. Zero percent (control), 30% (30% RSL), 60% (60% RSL) of main shoot length, and 25% (25% RSN), 50% (50% RSN), and 100% (100% RSN) of main shoot number were removed. Compared with control plants, clipping accelerated the reduction of starch in the roots, increased sucrose flux per flower per hour and nectar production per flower per day in 30% RSL, 60% RSL, 25% RSN, and 50% RSN treatments, and improved vegetative growth in 100% RSN treatment. All treatments had similar total nonstructural carbohydrate (TNC) concentrations in leaves, shoots, and stems with the exception of 100% RSN with higher TNC concentration in shoots. Both α-, and β-amylase activities were enhanced by clipping, the former being more strongly correlated with starch degradation in the roots than the latter. The other two possible starch-breaking enzymes, α-glucosidase, and starch phosphorylase showed no significant differences in the activities between treatments. The results suggest that starch degradation in the roots of C. korshinskii was regulated by α-amylase activity and more mobilized starch was used to support vegetative growth in 100% RSN treatment and support sexual reproduction followed by other clipping treatments.     

扰动环境中不同刈割方式柠条营养生长补偿的影响

 柠条（Caragana korshinskii）在地上组织破坏后进行补偿性生长,这是重复利用柠条资源的基础,但对 柠条不同刈割方式下营养生长补偿的模式有待探讨。该文通过5种刈割方式：去除主枝长的30%（30%RSL） 、去除主枝长的60%（60%RSL）、去除分枝数的25%（25%RSN）、去除分枝数的50%（50%RSN）和去除分枝 数的100%（100%RSN）来研究柠条的营养生长补偿。结果表明：刈割处理的柠条生物量当年发生了超补偿 ,当年生枝数/枝、当年生枝长、当年生枝生物量/枝、当年生枝生物量/株比对照高。对照、30%RSL和 60%RSL 处理未长出基梢。 100%RSN处理的基梢数/刈割枝、基梢长、单个基梢平均生物量显著高于25%RSN 和50%RSN处理,基梢生物量/株随刈割去除生物量的增加而增加。100%RSN 处理未结果,其它处理果实产量 表现出超补偿或精确补偿。对照处理营养生长和生殖生长均低,其它处理当年生枝生物量与果实产量成显 著负相关。从整个生长季节来看,营养生长主要集中在果实成熟之前。我们认为,100%RSN处理是柠条地上 组织破坏后尽快恢复的合理方式,其当年生生物量远高于其它处理。顶端优势的破坏促使休眠芽的萌发, 根冠比的改变使地上组织获得较多养分和水分,根系储存的碳水化合物的供应是促使刈割柠条营养生长超 补偿的的可能机制,而减少生殖生长对资源的消耗,是100%RSN处理地上生物量尽快恢复的另一重要因素 。     

Competition and the compensatory regulation of fruit and seed set in the perennial herb Epilobium dodonaei (Onagraceae)

I studied the effects of competition and soil fertilization on variation of seed yield components of the outcrossing perennial Epilobium dodonaei Vill. using a randomized complete block design. Fertilization as a main effect was not significant. Competition, however, reduced the number of flower buds per shoot (-29%), the number of ovules per fruit (-12%), and the number of ripe fruits per shoot (-51%). In addition, competition caused an increase in abortion of flower buds. Consequently the fruit/flower bud ratio decreased from 0.71 to 0.47. Average seed mass was not reduced significantly by competition. Some of the negative effects of competition on fruit production were mitigated by fertilization. However, competition considerably reduced the proportion of late-aborted seeds, which resulted in an increase of the seed/ovule ratio from 0.31 to 0.49 (+58%). As a consequence of this compensation, the reduction in the number of seeds per shoot due to competition was not significant. At the level of the genet, competition had a strong effect on seed yield due to decreases in the number of shoots produced. I discuss patterns of regulation at consecutive levels of reproduction. Shoots of plants suffering from competition initially invested less in reproductive structures than the control and showed a higher abortion rate of less costly structures early in reproductive development, but also had a lower abortion rate later in their development. The observed compensatory pattern in yield components illustrates the fine-tuning regulation capacity at different levels of reproductive development in plants.     

Relationships between Respiration Rate and Adenylate and Carbohydrate Pools of the Soybean Fruit

Relationships between respiration rate and adenylate and carbohydrate pools of the soybean (Glycine max L. Merrill) fruit during rapid seed growth were evaluated. Plants at mid pod-fill were subjected to different concentrations of CO(2) to alter the amount of photosynthate produced and, thus, available to the fruit. Respiration rate of the intact fruits was measured, along with glucose, sucrose, and starch concentrations, adenylate energy charge (AEC), and total adenylate pool (SigmaAdN) in the pod wall, seed coat, and cotyledons. The concentration of sucrose remained relatively constant in the pod wall (1.0 milligram per 100 milligrams dry weight), seed coat (6.5 milligrams per 100 milligrams dry weight), and cotyledons (4.5 milligrams per 100 milligrams dry weight) at moderate and high respiration rates. Furthermore, AEC remained relatively constant in the pod wall (0.55), seed coat (0.24), and cotyledons (0.44) during changes in respiration rate. This suggests that the amount of assimilate transported to the fruit, and its flux through the sucrose pools of the fruit parts, were important in the regulation of the respiration rate of the fruit. The average SigmaAdN in the seed coat (1300 picomoles per milligram dry weight) was significantly greater than in the cotyledons (750 picomoles per milligram dry weight) and pod wall (300 picomoles per milligram dry weight). In addition, the SigmaAdN in the seed coat and cotyledons increased with increasing respiration rate of the fruit. The high SigmaAdN in the seed coat and its increase with increases in respiration rate of the fruit suggest that an energy-requiring process is involved in the movement of sucrose through the seed coat.     

Nectar dynamics and reproductive success in Saponaria officinalis (Caryophyllaceae) in southern Germany

Nectar production and flower visitors of the night-flowering Saponaria officinalis L. (Caryophyllaceae) were studied in relation to the reproductive success. Nectar production was worthwhile for nocturnal flower visitors. Nectar standing crop was about 267 μg sugar per flower, and comparison of nectar offering of covered and freely exposed flowers revealed that main nectar secretion time is mainly during the night up to the morning hours. In both covered and freely exposed flowers nectar volumes decreased over the day. In covered flowers, nectar volume, sugar concentration, and sugar amount per flower increased up to the third day; in older flowers sugar secretion ceased. In 1996 Autographa gamma (Noctuidae) was the exclusive nocturnal flower visitor, but pollen transfer experiments proved that A. gamma (Noctuidae) is a very ineffective pollinator of S. officinalis. In 1999 up to 50% of the observed visitors were Sphingidae, which resulted in a significantly higher seed set. Fruit set was constantly high independent of pollinator availability. In the nectar manipulation experiments seed set was highest in non-emasculated flowers filled with unnaturally high concentrated sucrose solutions. Differences to seed set on stalks treated with a sucrose solution mimicking naturally concentrated nectar were significant. Lowest fruit and seed set were found on inflorescences with emasculated flowers filled with a sucrose solution mimicking naturally concentrated nectar.     

Determinants of seed production in Geranium maculatum

Summary We experimentally examined factors limiting seed production in two populations of the perennial woodland herb Geranium maculatum in central Illinois, USA. To test the pollinator-limitation hypothesis, we compared the seed production of plants whose flowers were supplementarily pollinated with outcross pollen to that of control plants receiving natural pollination only. To test if fruit production by early flowers suppresses fruit and seed formation by late flowers, a third group of plants was prevented from producing seed from the first 50% of the flowers to open (stigmas were excised at flower opening). Finally, to test if seed maturation and flower initiation are correlated with photosynthetic capacity, we performed a defoliation experiment in which either the stem leaves within the inflorescence, the stem leaves below the inflorescence, or the rosette leaves were removed during late flowering. Plants that reccived supplemental pollination produced 1.5–1.6 times more seeds than control plants. We found no difference between hand-pollinated plants and controls in mortality, flowering frequency or number of flowers produced in the year following the experiment. In both control and hand-pollinated plants, the fruit set and total seed production of early flowers were more than twice as high as those of late flowers. In one of the two populations, plants whose early flowers were prevented from setting seed produced significantly more seeds from their late flowers than did control plants. Seed predation was low and did not differ between early and late flowers. Leaf removal did not affect seed number or size in the year of defoliation, nor did it reduce survival or flower production in the subsequent year. This suggests that the plants were able to compensate for a partial defoliation by using stored resources or by increasing photosynthetic rates in the remaining leaves. Taken together, the results demonstrate that both pollinator activity and resource levels influence patterns of seed production in G. maculatum. While seed production was pollinatorlimited in both populations, a seasonal decline in resource availability was apparently responsible for the low seed production by late flowers.     

Regulation of reproduction in wild and cultivatedLycopersicon esculentum Mill. by vesicular-arbuscular mycorrhizal infection

Summary We examined how mycorrhizal infection byGlomus etunicatum Becker and Gerd. affected flowering phenology and components of reproduction in eight wild accessions and two cultivars ofLycopersicon esculentum Mill. We did this by performing a detailed demographic study of flower, fruit and seed production. Mycorrhizal infection had variable effects on the ten accessions. Infection significantly decreased the time taken to initiate flowering in some accessions. In addition, infection increased flowering duration in some accessions. In many accessions, infection significantly increased seed production, primarily by increasing the number of inflorescences and infructescences. In some accessions, mycorrhizal infection also increased the proportion of flowers that produced mature fruits or the number of seeds per fruit. Among accessions, shoot phosphorus content was correlated with seed productivity for both mycorrhizal and non-mycorrhizal plants. However, non-mycorrhizal plants produced more seed biomass per mg of shoot phosphorus than mycorrhizal plants.     

Patterns of fruit and seed production inBauhinia ungulata (Leguminosae)

Patterns of seed and fruit production ofBauhinia ungulata, a small tree legume indigenous in tropical America, were studied in Costa Rica. Only about 8% of flowers produced fruits. The average pod had 19 ovules and about two thirds of these began seed development, with mature pods containing an average of 9.7 mature undamaged seeds. About half of the mature pods were damaged by herbivores and within these, 27% of ovules or seeds had been eaten. Among trees there was no significant variation in pod production, but the number of ovules per pod and seed production per pod varied significantly. Within infructescences most pods were retained at middle positions. Within pods, the probability of an ovule developing into a seed increased toward the distal end. The pattern of seed and fruit production in this species agrees well in general with that reported for other neotropical legumes. The abortion of seeds and fruits can be regarded as a way of controlling maternal investment, and as a response to herbivory.     

Interactive effect of cytokinin and potassium on sink-source relationships in Lupinus angustifolius

This study examined whether increased K supply in conjunction with BAPcould increase lupin seed yield and harvest index by enlarging sink volume (podnumber), increasing assimilate and improving assimilate partitioning to filltheadditional pods induced by BAP treatment. Narrow-leafed lupin(Lupinusangustifolius, cv. Danja abs^– mutant) was grown inaglasshouse, in pots containing sandy soil with four K treatments (0, 15, 60 and120 mg K/kg soil). BAP (2 mM) was applied daily toallmain stem flowers throughout the life of each flower from opening to senesced.BAP application did not affect assimilate production (as measured by totalabove-ground biomass), but changed assimilate partitioning. On BAP-treatedplants, there were greater proportions of seed to pod wall dry weight on themain stem but smaller proportions on the branches, and an increased weightratioof seed to pod wall overall which meant more assimilate was used for seedgrowthrather than pod wall growth. BAP increased the number of pods per plant by35% and this more than compensated for the decreases in seeds per podandseed weight. Therefore, there was an increased harvest index (+11%)and seed yield per plant (+13%) in BAP-treated plants. BAP alsoincreased the number of pods with filled seeds (146%) on the main stemand main stem seed K⁺ concentration (from 0.81% to0.87%). Added K increased biomass but only slightly affected assimilatepartitioning. As applied K increased, relatively more assimilate was used forpod wall growth rather than seed growth. Added K increased seed yield per plantby about 14% due to increases in seed weight and the number of pods onthe main stem. Moreover, K⁺ concentration in seeds and shootsincreased with increasing level of applied K. Seed yield was enhanced more byBAP when K was supplied at high levels. Increasing K supply interactedpositively with added BAP by increasing narrow-leaf lupin seed yield andharvestindex through increases in assimilate supply and its partitioning into seeds.     

Timing of canopy closure influences carbon translocation and seed production of an understorey herb, Trillium apetalon (Trilliaceae)

BACKGROUND AND AIMS: The light availability on a temperate, deciduous-forest floor varies greatly, reflecting the seasonal leaf dynamics of the canopy trees. The growth and/or reproductive activity of understorey plants should be influenced by the length of the high-irradiance period from snowmelt to canopy closure. The aim of the present study was to clarify how spring-blooming species regulate the translocation of photosynthetic products to current reproduction and storage organs during a growing season in accordance with the changing light conditions. METHODS: Growth pattern, net photosynthetic rate, seed production, and shoot and flower production in the next year of Trillium apetalon were compared between natural and experimentally shaded conditions. Furthermore, translocation of current photosynthetic products within plants was assessed by a labelled carbon-chase experiment. KEY RESULTS: During the high-irradiance period, plants showed high photosynthetic ability, in which current products were initially used for shoot growth, then reserved in the rhizome. Carbon translocation to developing fruit occurred after canopy closure, but this was very small due to low photosynthetic rates under the darker conditions. The shading treatment in the early season advanced the time of carbon translocation to fruit, but reduced seed production in the current year and flower production of the next year. CONCLUSIONS: Carbon translocation to the storage organ had priority over seed production under high-irradiance conditions. A shortened bright period due to early canopy closure effectively restricts carbon assimilation, which greatly reduces subsequent reproductive output owing to low photosynthetic products for fruit development and small carbon storage for future reproduction. As populations of this species are maintained by seedling recruitment, acceleration of canopy closure timing may influence the maintenance and dynamics of populations.     

星油藤蒴果及种子的性状变异研究

为进行星油藤(Plukenetia volubilis L.)良种选育,对其蒴果和种子的性状变异进行了研究。结果表明,星油藤蒴果中4、5、6裂片果分别为49.71%、37.69%和12.60%,以4和5裂片为主;种子性状变异系数比果实的小,种子性状比果实更稳定。按果裂片类型统计,以4裂片的性状变异系数最小,性状也较为稳定,性状分化变异率有54.19%~95.63%来自蒴果间,而果实和种子性状分化变异率分别有79.81%~95.76%和67.66%~93.0%来源于裂片类型,性状分化变异受裂片数影响大,而相同裂片数不同蒴果间的变异程度低。不同裂片类型的果实与种子大多数性状间均存在显著或极显著差异,果裂数是造成性状差异的主要原因。种子萌发率以6裂片果5裂片果4裂片果,平均萌发率超过91%;种子萌发率与单果重、单果重与果形态指标、种子重与种子形态性状间均存在极显著正相关关系,其中单果重对果厚、种子重对种子宽的影响大于其它性状。综合分析星油藤以4裂片果的生物产量最高,平均果重和种子重均好于其他类型。     

Effects of mixtalol and paclobutrazol on photosynthesis and yield of rape (Brassica napus)

Photosynthetic and yield effects of paclobutrazol and mixtalol sprayed, respectively, on rape at the three-leaf stage and shoot or anthesis stages were examined. They significantly increased chlorophyll content and photosynthetic rates, prolonged leaf longevity, and increased green pod area. Paclobutrazol-treated plants were shorter, more branched, and produced more seeds. Foliar sprays of mixtalol increased podding percentage, pods per plant, and seeds per pod. A high seed yield of 1809.0 kg/ha was obtained with mixtalol sprayed at anthesis, while significant yields were also achieved with treatments of mixtalol at the shoot stage and paclobutrazol at the three-leaf stage. The photosynthetic and yield effects of mixtalol or paclobutrazol were reduced when both growth regulators were applied together, and this led to yield reductions. No adverse effects from mixtalol or paclobutrazol were observed on seed oil content, erucic acid, and glucosinolate content. The total rape oil production with mixtalol sprayed at anthesis and shoot stages and paclobutrazol at the three-leaf stage increased significantly by 20.9%, 14.4%, and 13.4%, respectively, over the controls.     

Factors affecting fruit and seed production of Paeonia ostii “Feng Dan”, an economically important oil tree

Many factors may affect reproduction of animal-pollinated species. In this study, the effects of pollen limitation, attractive traits (flower number, plant height and flower width) and flowering phenological traits (flowering onset, duration and synchrony) on female reproduction, as well as the patterns of variation in fruit and seed production within plants, were investigated in Paeonia ostii “Feng Dan” over two flowering seasons (2018 and 2019). Fruit set was very high (90%), and pollen supplementation did not increase fruit and seed production in either year, indicating no pollen limitation. Fruit set, ovule number per fruit and mean individual seed weight per fruit were not affected by any of the six attractive and phenological traits in either year, whereas seed number per fruit was related to the three attractive traits in one or both years. Seed number per plant was positively affected by the three attractive traits and best explained by flower number in both years, but the effect of each of the three phenological traits on seed number per plant differed between years. Within plants, the fruit set, ovule number, seed set and seed number per fruit declined from early- to late-opening flowers, presumably because of resource preemption, but the mean individual seed weight did not vary across the flowering sequence. Our study shows that attractive traits of Paeonia ostii “Feng Dan” are more important than flowering phenological traits in the prediction of total seed production per plant.     

荒漠植物准噶尔无叶豆结实、结籽格局及其生态适应意义

连续2a采用野外记录的方式对荒漠植物准噶尔无叶豆的结实、结籽格局进行了比较研究。结果表明:植株内花序生成格局表现为不同大小的花序在总花序中的比重与其结实率存在显著正相关,其中含有中等花数目的花序所占的比重及其结实率均最高,此种分布格局能够最大程度的保证繁殖成功;果序内果实生成格局表现为单花着生位置(从近柄端算起)与其结实量占总结实量的比例成线性负相关,花序基部的结实比例最高,顶部结实比例近为0;荚果内种子生成格局表现为:中间位置的胚珠败育率最低。另外,年际间荚果内仅有(1.08±0.03)粒和(1.07±0.03)粒种子能够完全成熟,此种结籽格局是准噶尔无叶豆保证后代质量的最佳策略。     

云南草寇花序内不同部位的性分配

两性花植物花序内的性分配常存在差异,资源竞争、结构效应、交配环境(雌雄异熟、传粉者定向访花行为等)或授粉不均匀等几种假说可以解释这种现象。为验证上述假说,该研究以云南草寇两种表型(雄先熟型和雌先熟型)为材料,分析了其花序内不同部位(基部、中部和顶部)的每花花粉数、胚珠数、花粉/胚珠比、结实率和结籽率,花序内传粉者的定向访花行为,以及人工辅助授粉和去花处理对结实率和结籽率的影响。结果表明:两种表型花序内每花花粉数不随部位而变化,每花胚珠数、结实率和结籽率由基部到顶部依次降低,每花花粉/胚珠比由基部到顶部依次增加,表明顶部花存在偏雄的性分配。人工辅助授粉后,结实率、结籽率仍由基部到顶部依次降低,表明授粉不均匀假说不能解释云南草寇花序内不同部位结实率、结籽率的差异。去除基部和中部花后,顶部花人工辅助授粉条件下的结实率、结籽率与基部花人工辅助授粉条件下的结实率、结籽率无差异,表明云南草寇花序内不同部位结实率、结籽率的差异主要由资源竞争引起。雌先熟表型每花花粉数、花粉/胚珠比高于雄先熟表型,表明两种表型存在性分配差异。传粉者主要先访问云南草寇基部的花,然后向顶部移动。云南草寇花序内顶部偏雄的性分配可能是由资源竞争和传粉者定向访花造成的。     

Developing embryos of Sesbania sesban have unique potential to photosynthesize under high osmotic environment

This study has been carried out to investigate the photosynthetic activities in developing embryos of Sesbania sesban under a highly osmotic environment. In S. sesban, the embryo turns green/chlorophyllous at the early heart shape stage. Interestingly, despite being deeply embedded within the supporting tissues (several layers of pod wall, seed coat and endosperm) and developing in a highly osmotic environment, the growing embryo of the developing seed showed the presence of various components of photosynthetic machinery besides being chlorophyllous. The shade-adaptive nature of the photosynthetic machinery of the embryo is evident from (a) low chlorophyll a/b ratio, (b) photosystem (PS) II attaining maximal activity at low photon flux density and (c) lesser plastoquinone pool. The photosynthetic potential of the growing embryo seems to contribute towards seed filling as it has the potential not only to harvest light energy but also to fix CO2 as efficiently as other photosynthetic parts of S. sesban. In fact, ribulose-1,5 bisphosphate carboxylase purified from embryos manifested subunit composition similar to that of leaves. The PS II activity in leaves, cotyledonary leaves and pod wall declined sharply with increase in the level of NaCl and sucrose above 150 and 300 mmol, respectively. Amazingly, PS II activity in developing embryos was maximal in the presence of 250 mmol NaCl or 500 mmol sucrose and remained high even when NaCl and sucrose levels were increased to 500 and 1000 mmol, respectively. We hypothesize that the developing embryos have some factor(s) which protect(s) the photosynthetic machinery in an environment of high osmotic strength.     

Comparison of two cacao (Theobroma cacao L.) clones for the effect of pollination intensity on fruit set and seed content

We compared the influence of pollination intensity (PI) on fruit set and seed number per pod in two cacao (Theobroma cacao L.) clones, IFC5 (Forastero Lower-Amazon Amelonado), which is self-compatible and known to produce a high number of seeds per pod under open pollination, and SCA6 (Forastero Upper-Amazon), which is self-incompatible and known to produce a low number of seeds per pod under open pollination. With both clones, PI had a positive effect on fruit set, with the maximum rate requiring more than 150 pollen grains per pod. One-half of the maximum rate of fruit set was reached with 39 pollen grains per pod for SCA6, and 78 for IFC5. With SCA6, a significant positive effect of PI on seed number per pod was also observed, with maximum seed number requiring more than 200 pollen grains per pod. In contrast, seed numbers with IFC5 were approximately equal over the PI range 100–800 pollen grains per pod. Patterns of seed number per pod were compared after: (1) open insect pollination, (2) low-intensity hand pollination and (3) high-intensity hand pollination. The patterns obtained with IFC5 under open pollination showed a peak of 40–50 seeds per pod, whereas the distribution patterns were more even with SCA6. The pattern of seed number under open pollination was similar to that obtained with high-intensity hand pollination for IFC5, and with low-intensity hand pollination for SCA6. We concluded that the high number of seeds per pod observed with IFC5 under natural insect pollination may be explained by a high number of compatible self-pollen grains on the stigma and by a severe drop of low-pollinated flowers eliminating potential lowfilled fruits. With SCA6, however, the number of compatible pollen grains deposited on the stigma was probably low under open pollination, and the flowers required lower pollen quantities to set fruit, which resulted in a high frequency of low seed numbers per fruit. This difference in the capacity to set low-seeded fruits might be considered as an adaptive trait related to the mode of reproduction.     

Reproductive trade-offs in genetically distinct clones ofVaccinium macrocarpon,the American cranberry

Patterns of resource allocation to growth, current reproduction, and potential future reproduction were quantified in six genetically distinct cultivars ofVaccinium macrocarpon. For all cultivars (genotypes), vegetative size is positively correlated with some measures of current reproduction (fruit and flower number) but negatively correlated with others (seed number per fruit, seed weight per fruit). Vegetative growth in the current year is significantly related to the production of reproductive terminal buds, a measure of the potential for reproduction in the following year. Stems with low levels of current reproduction — lower flower number, fruit number, and seed weight — were more likely to form reproductive terminal buds than stems with higher levels of current reproduction. Individual genotypes differed significantly for vegetative size, fruit number, fruit weight, seed number, and seed weight, as well as for the frequency of fruiting stems and reproductive terminal buds produced. Genotypes were segregated in principal component space, indicating overall differences between them in allocation to the suite of variables measured. These results indicate the possibility of fitness differences among cultivars due to genetically determined allocation strategy, which has implications for fitness differences among genotypes within natural populations.     

Pollination thoroughness and maternal yield regulation in wild radish,Raphanus raphanistrum (Brassicaceae)

Summary Under conditions where resources are limited, there are often negative correlations between components of maternal yield, or between fruit and flower production. Pollination, in turn, may vary among individuals and influence total maternal expenditure. We examined the impact of variation in pollination thoroughness upon yield components and overall plant growth in wild radish (R. raphanistrum) plants grown in the greenhouse. Plants received different pollination treatments in which 0% to 100% of all flowers produced were hand-pollinated. Fruit set was increased by hand-pollination, but rarely exceeded 30%, even when more than 50% of the flowers were pollinated. Plants receiving more thorough pollination or having greater proportion fruit set produced significantly smaller seeds. Seed number per fruit was not influenced by pollination treatment. Mean values of yield components and interactions between components often varied among plants from different maternal families. Increasing pollination thoroughness also resulted in dramatic decreases in flower production. If male fitness is related to flower number, there may be a tradeoff between maternal fecundity and successful pollen export operating at the whole-plant level in this species.