Polycarpic Perennials Research Articles

Population demography of rare sedges (Eriophorum gracile and Carex livida) north of the Arctic Circle in Murmansk Region and climate change impacts

Species of Cyperaceae are little studied on the population level globally. Also in Murmansk Region, species from this family were not included in long-term population studies of rare plant species whereas other representatives from 21 families were put in [Blinova, 2009]. Experimental works with sedges is often neglected because of taxonomic difficulties and a lack of methods for study populations of this group [Kitamura et al., 2016; Sosnovska, Danylyk, 2017]. Such difficulties became obvious while the IUCN-red data book testing. Of rare sedges studied in this paper Eriophorum gracile is included in the regional Red data book [Kozhin, 2014] and Carex livida is in the Appendix of this book in the group Need of monitoring. 
 
 The Murmansk Region (6670 N), located in the north-eastern corner of Russian Fennoscandia, is a part of the Atlantic-Arctic zone of temperate belt with a rather mild climate. The region is very heterogeneous. Two latitudinal vegetation zones can be distinguished: tundra and taiga. So, many boreal plant species reach here their northern limit of distribution. Our field work has been conducted in the center part of the region in a recently found rich fen [Blinova, Petrovskij, 2014]. Both study species (Eriophorum gracile и Carex livida) have circumpolar distribution in wetlands of northern hemisphere [Hulten, Fries, 1986], and they are at the northern range in Murmansk Region [Kuzeneva, 1954; Chernov, 1954]. They are polycarpic perennials. An annual shoot has been selected as a counting unit (Fig. 1). In E. gracile only the number of generative shoots has been counted in the field. For non-destructive purposes, from herbarium data, the ratio between generative and vegetative shoots was defined as 1:1. The total population size for this species has been estimated from this ratio. In population of C. livida, the direct counting in the field has been done on 3-5 small plots (0.25*0.25 м2). Lately this value has been recalculated according to the area of population subset. Clusters and subsets have been distinguished in population structure according to suggested aggregation patterns of spatial structure in local plant populations [Blinova, 2018]. Marked population subsets have been monitored several times in the growing period in 2014-2016 years. In the field the boundaries and areas of rich fen and populations (including subsets) have been estimated with the help of GPS navigation device Garmin Dakota 20, in the lab all data are further processed using Garmin Software BaseCamp 4.2.5. Nomenclature for vascular plants is given according to S. K. Czerepanov [1995], for mosses after M. S. Ignatov O. M. Afonina [1992]. 
 
 Our results show that extremely low (0.2% for Eriophorum gracile) and relatively low (3.1% для Carex livida) population cover is characteristic for a large long-term monitored fen. Spatial aggregation of E. gracile population is structured on very small area (40 м2) whereas C. livida is established on relatively representative area (633 м2). E. gracile develops small population subsets (8 m2 on average) at a distance to next about 70 m in different parts of rich fen. Each such subset contains 9-10 mature individuals on average. C. livida has larger subsets (211 m2 on average) at 30 m away from the neighbor. The size of each subset makes c. 2500 generative shoots. The spatial population pattern of E. gracile shows isolated subsets with single clusters, whereas of C. livida represents isolated subsets with merged clusters. High fluctuations of population size and its subsets are revealed in E. gracile from year to year. The number of generative shoots and air temperature in the growing season (June-September) of the current year establish negative relationship.
 
 This study in one of the northernmost populations of Eriophorum gracile confirms other data from different parts of its distribution area that populations of this species are very fragmented and show high fluctuations in the number of generative shoots [Barr 1996; Ksermann, Moser, 1999; Dickenmann, Keel, 2004; Decker et al., 2006; Chatters, Sanderson, 2014]. An analysis of spatial structure of populations has been pointed out that anemochory of E. gracile could be a bottleneck for the population fitness in rich fens conditions, whereas baro- and hydrochory of C. livida promotes further seed germination and survival. Additionally, current climate-changed impacts could cause an extirpation of E. gracile from floristic composition of rich fens, whereas such a threat is minimal for C. livida. Both species need regional protection of their populations. An introduction into culture is essential for further ontogenetic studies and trigger examination of clonal division of labor.

Width of the temperature range for seed germination of herbaceous plant species in temperate eastern North America: life cycles, seasons and temperature variation and implication for climate warming

AbstractTo persist (without immigration) in habitats with unpredictable environmental conditions, annuals must produce seeds each year or have a seed bank. Thus, we predicted that compared to perennials, annuals have a wider germination temperature range (GTR, the difference in temperature between the week with the highest and the week with the lowest germination during the natural germination season). We determined the GTR via germination phenology data for 350 herbaceous species in 59 families from the eastern USA: summer annuals (SA), 63; winter annuals (WA), 83; monocarpic perennials (MP), 28; and polycarpic perennials (PP), 176. There was no significant phylogenetic signal for the GTR. The width of the GTR during the first spring germination season was 9.6, 8.7 and 8.8°C for MP, PP and SA, respectively, and during the first autumn germination season 12.8, 11.8 and 12.4°C for MP, PP and WA, respectively. Annuals did not have a wider GTR than perennials in either the spring or the autumn germination season. Our data suggest that selection for early germination in either spring or autumn has resulted in only small differences in the GTR. We predict that global warming will have little or no effect on reshaping the germination phenology of herbaceous species of temperate eastern North America.

The Regulation of Plant Vegetative Phase Transition and Rejuvenation: miRNAs, a Key Regulator.

In contrast to animals, adult organs in plants are not formed during embryogenesis but generated from meristematic cells as plants advance through development. Plant development involves a succession of different phenotypic stages and the transition between these stages is termed phase transition. Phase transitions need to be tightly regulated and coordinated to ensure they occur under optimal seasonal, environmental conditions. Polycarpic perennials transition through vegetative stages and the mature, reproductive stage many times during their lifecycles and, in both perennial and annual species, environmental factors and culturing methods can reverse the otherwise unidirectional vector of plant development. Epigenetic factors regulating gene expression in response to internal cues and external (environmental) stimuli influencing the plant’s phenotype and development have been shown to control phase transitions. How developmental and environmental cues interact to epigenetically alter gene expression and influence these transitions is not well understood, and understanding this interaction is important considering the current climate change scenarios, since epigenetic maladaptation could have catastrophic consequences for perennial plants in natural and agricultural ecosystems. Here, we review studies focusing on the epigenetic regulators of the vegetative phase change and highlight how these mechanisms might act in exogenously induced plant rejuvenation and regrowth following stress.

Beyond flowering time: diverse roles of an APETALA2-like transcription factor in shoot architecture and perennial traits.

Polycarpic perennials maintain vegetative growth after flowering. PERPETUAL FLOWERING 1 (PEP1), the orthologue of FLOWERING LOCUS C (FLC) in Arabis alpina regulates flowering and contributes to polycarpy in a vernalisation-dependent pathway. pep1 mutants do not require vernalisation to flower and have reduced return to vegetative growth as all of their axillary branches become reproductive. To identify additional genes that regulate flowering and contribute to perennial traits we performed an enhancer screen of pep1. Using mapping-by-sequencing, we cloned a mutant (enhancer of pep1-055, eop055), performed transcriptome analysis and physiologically characterised the role it plays on perennial traits in an introgression line carrying the eop055 mutation and a functional PEP1 wild-type allele. eop055 flowers earlier than pep1 and carries a lesion in the A.alpina orthologue of the APETALA2 (AP2)-like gene, TARGET OF EAT2 (AaTOE2). AaTOE2 is a floral repressor and acts upstream of SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE 5 (AaSPL5). In the wild-type background, which requires cold treatment to flower, AaTOE2 regulates the age-dependent response to vernalisation. In addition, AaTOE2 ensures the maintenance of vegetative growth by delaying axillary meristem initiation and repressing flowering of axillary buds before and during cold exposure. We conclude that AaTOE2 is instrumental in fine tuning different developmental traits in the perennial life cycle of A.alpina.

Modest Pollen Limitation of Lifetime Seed Production Is in Good Agreement with Modest Uncertainty in Whole-Plant Pollen Receipt.

We recently introduced a model that predicts the degree to which a plant's lifetime seed production may be constrained by unpredictable shortfalls of pollen receipt ("pollen limitation"). Burd's comment in this issue criticized our analysis, first by arguing that the empirical literature documents much higher levels of pollen limitation than our model predicts and then suggesting that the apparent discrepancy stemmed from our (1) underestimating the costs of securing a fertilized ovule and (2) assuming too little unpredictability in whole-plant pollen receipt. We reply as follows. First, the empirical literature must be consulted carefully. Burd relies on pollen supplementation experiments performed on parts of plants or on whole plants but during only one reproductive season for polycarpic perennials; in both cases, resource reallocation often leads to gross overestimates of pollen limitation. We comprehensively review pollen limitation estimates that are free of these estimation problems and find strong agreement with our model predictions. Second, although cost estimates for different components of seed production are imprecise, errors are likely to be small relative to the >1,000-fold differences observed across plant species, the primary focus of our article. Finally, contrary to Burd's argument, pollen receipt by entire plants is much more predictable than that by individual flowers because the flower-to-flower variation "averages out" when summed across many flowers. Our model uses parameter values that are in broad agreement with the empirical record of modest plant-to-plant variation in pollen receipt and thus predicts the generally modest pollen limitation that is observed in nature.

To resprout or not to resprout? Modeling population dynamics of a root-sprouting monocarpic plant under various disturbance regimes

Monocarpic plants are favored in conditions of high mortality of reproductive individuals, whereas situations with low juvenile survival give an advantage to polycarpic perennials. However, certain plant species combine both strategies, showing high plasticity and life-history variation in recurrently disturbed habitats. Life-history variation caused by resprouting from roots after injury has been reported in many weedy and invasive species, but the long-term effects of resprouting on population dynamics are not known. In this study, we asked how different disturbance scenarios affect long-term fitness of plants with varied capacities for root-sprouting. We used projection matrix analysis to simulate growth of populations of the annual herb Rorippa palustris having factorial combinations of root-sprouting intensities, disturbance timings (intra-annual), and frequencies (inter-annual). The contributions of these factors to population growth variation were enumerated using variance decomposition. Population growth was affected by all examined parameters. Disturbance frequency negatively affected population growth rate, but its effect was modulated by disturbance timing. Summer disturbance decreased population growth rate dramatically, whereas winter disturbance had no effect. Resprouting from roots was important for plant overwintering. In pre-reproductive plants, disturbance frequency and root-sprouting intensity strongly interacted in the spring, such that the negative effect of frequent disturbance was overcome by resprouting. Our results imply that, in this species, conditions of unpredictable, severe disturbance, would select for high phenotypic plasticity in life histories, whereas only regular spring disturbance would favor resprouting.

Optimal allocation patterns and optimal seed mass of a perennial plant

We present a novel optimal allocation model for perennial plants, in which assimilates are not allocated directly to vegetative or reproductive parts but instead go first to a storage compartment from where they are then optimally redistributed. We do not restrict considerations purely to periods favourable for photosynthesis, as it was done in published models of perennial species, but analyse the whole life period of a perennial plant. As a result, we obtain the general scheme of perennial plant development, for which annual and monocarpic strategies are special cases.We not only re-derive predictions from several previous optimal allocation models, but also obtain more information about plants׳ strategies during transitions between favourable and unfavourable seasons. One of the model׳s predictions is that a plant can begin to re-establish vegetative tissues from storage some time before the beginning of favourable conditions, which in turn allows for better production potential when conditions become better. By means of numerical examples we show that annual plants with single or multiple reproduction periods, monocarps, evergreen perennials and polycarpic perennials can be studied successfully with the help of our unified model.Finally, we build a bridge between optimal allocation models and models describing trade-offs between size and the number of seeds: a modelled plant can control the distribution of not only allocated carbohydrates but also seed size. We provide sufficient conditions for the optimality of producing the smallest and largest seeds possible.

Interactions Between Temperature and Sugars in the Regulation of Leaf Senescence in the Perennial Herb Arabis alpina L.F

Annual plants usually flower and set seed once before senescence results in the death of the whole plant (monocarpic senescence). Leaf senescence also occurs in polycarpic perennials; even in "evergreen" species individual leaves senesce. In the annual model Arabidopsis thaliana sugars accumulate in the senescent leaves and senescence is accelerated by high sugar availability. Similar to A. thaliana, sugar contents increased with leaf age in the perennial Arabis alpina grown under warm conditions (22 °C day/18 night). At 5 °C, sugar contents in non-senescent leaves were higher than at a warm temperature, but dependent on the accession, either sugars did not accumulate or their contents decreased in old leaves. In A. alpina plants grown in their natural habitat in the Alps, sugar contents declined with leaf age. Growth at a cold temperature slightly delayed senescence in A. alpina. In both warm and cold conditions, an external glucose supply accelerated senescence, but natural variation was found in this response. In conclusion, sugar accumulation under warm conditions could accelerate leaf senescence in A. alpina plants, but genotype-specific responses and interactions with growth temperature are likely to influence senescence under natural conditions.

Life-history variation in the short-lived herb Rorippa palustris: effect of germination date and injury timing

Life-history variation in annuals is known to be caused by size requirements for photoinduction of flowering, but the importance of germination date and injury was overlooked so far even though they may play an important role in disturbed habitats. To test the effect of germina- tion date and timing of injury on life-history variation of an annual plant, we performed a 2-year pot experiment with the root-sprouting herb Rorippa palustris. Plants belonging to six different cohorts, and sown at monthly intervals from April to September, were injured (all stem parts removed) in three ontogenetic stages: vegetative rosettes, flow- ering plants and fruiting plants. Plants from the April, and partly from the May, cohort behaved as summer annuals: they started to bolt at the same time, resprouted and overwintered poorly. Plants from the June cohort flowered in the first season as well, but they entered the bolting stage a month later than the preceding cohorts, produced the least fruits, but overwintered successfully and flowered again the second year (polycarpic perennials). Cohorts germinating after the summer solstice did not flower during the first year and, with the exception of the September cohort, overwintered successfully and flowered the second year (winter annuals). After injury, the pattern of life-histories was the same as in control plants, although gener- ative reproduction was interrupted by injury in the first year of the experiment. About one quarter of plants injured in the vegetative stage regener- ated after injury irrespective of cohort, however, regeneration was enhanced in larger plants. Regeneration of plants in the flowering and fruiting stages depended on date of injury in relation to day length, being the most successful after the summer solstice. Life-history variation, together with the ability to resprout after severe injury in the pioneer wetland herb Rorippa palustris is caused by its ability to germinate throughout the season. Even the second tested factor, the effect of injury, is modified by germination time. The experiment points to a complex nature of factors affecting life- history variation as well as resprouting after severe injury in short lived plants.

Population dynamics of Agrimonia eupatoria and Geum rivale, two perennial grassland species

The population dynamics of two polycarpic perennials,Agrimonia eupatoria and Geum rivale, characteristic ofsemi-natural grasslands in Scandinavia, were examined in south-eastern Sweden.The perennial forbs were studied for several years in two populations each,located in habitats characteristic for the species in the study area.Demographic transition probabilities varied significantly between populationsand among years for the species. Transition matrix modelling yieldedλ-values (population growth rates) that ranged from 0.89 to 1.14 forA. eupatoria and from 0.94 to 1.04 for G.rivale. The elasticity analysis showed that stasis in the adultstageclasses contributed most to λ. The life-table response experimentanalysis produced similar results as the elasticity analysis, where stasistogether with progression in the adult stage classes made a large contributionto the observed spatial variation in λ. Simulations of expected time toextinction were in the order of centuries for the study populations. Seedlingrecruitment was enhanced by seed addition and small scale disturbance inpopulations. For the intermediately abundant and more patchily distributedA. eupatoria, a regional survey of local populations wasconducted in the study area which revealed that most populations wererelativelysmall (< 100 individuals) and restricted to grassland fragments in roadverges. Furthermore, an attempt was made to estimate fruit dispersal from localpopulations.

Age of maturity and life span in herbaceous, polycarpic perennials

A review of age of maturity in herbaceous, polycarpic perennials found that the most common year of earliest maturity for wild and cultivated conditions was the second year of life, followed by the first year and then the third year. A comparison of age of maturity in wild and cultivated conditions for individual taxa confirmed the assumption that perennials generally do not mature sooner in the wild than in cultivation. This validated use of the pattern for maturity in cultivation (second year or later) against which to judge that for maturity in the wild. For plants of the same age of maturity, those with clonal growth had longer life spans than did those with little or no clonal growth. This difference in life span was more pronounced for plants of first- and second-year maturity than it was for those of later maturity. Herbaceous, polycarpic perennials in the wild generally were either short-lived with first-year maturity or long-lived with later maturity. These results were also true for nonclonal taxa only. For application to the real world, theoretical plant-population models must take these results into account.

An analysis of life history evolution in terms of the density-dependent Lefkovitch matrix model

The evolution of demographic characteristics is considered in terms of the density-dependent Lefkovitch matrix model, which describes a species' population dynamics with a stage-specific pattern of reproduction and mortality. We obtain the invadability condition of a mutant-type into the wild-type population at the equilibrium state. The condition depends on the left and right eigenvectors at the equilibrium state and the difference, between wild-type and mutant-type populations, of the values of elements in the Lefkovitch matrix at the equilibrium state. It is also shown that if elements of the density-dependent Lefkovitch matrix are decreasing functions of population density, then the equilibrium population density increases in the process of natural selection; that is, K-selection acts even on the stage-structured population. The evolution of life history in perennial plants is discussed through two models as an application of the above results. The evolution of perennial plants with no vegetative reproduction is analyzed in the first example. It is shown that whether monocarpic perennials (which reproduce once and die) or polycarpic perennial plants (which reproduce more than once) are favored depends on the cost of a produced seed. The second example concerns perennial plants that reproduce vegetatively. It is shown that whether monocarpic or polycarpic perennial plants are favored depends on the cost of a seed and that where vegetative reproduction is common, polycarpic perennials with no seed reproduction are favored.

Life history and plant architecture: size-dependent reproductive allocation in annual and biennialCentauriumspecies

SUMMARY The frequency of annuals, monocarpic perennials and polycarpic perennials among the dicotyledonous, herbaceous representatives of the European plant families are compared and related to various characteristics of plant architecture. It is suggested that the evolution of life-history may be governed by plant architecture. A comparison between annual and biennial Centaurium species suggests that the selective advantage of bienniality could relate to the production of a large stem within a short period. The typical architecture of a monocarpic perennial does not automatically imply an allometric relation between seed production and plant size. Size-dependent seed allocation, when present, is due to disproportionality between the plant's size and the amount of resources available for reproductive allocation, and not to the size constraints imposed by the plant's architecture. The evolution of monocarpic perenniality is therefore not a simple allometric step. Interpopulation differences in seed allocation may arise from differences in the nature or the availability of that particular resource that limits the reproductive allocation of biomass, and do not necessarily reflect differences in partitioning strategies.

Germination Ecophysiology of Herbaceous Plant Species in a Temperate Region

Germination phenology data have been collected from 75 winter annuals, 49 summer annuals, 28 monocarpic perennials, and 122 polycarpic perennials, and experimental investigations of dormancy breaking and germination requirements have been conducted on 56 winter annuals, 32 summer annuals, 18 monocarpic perennials, and 73 polycarpic perennials. The purpose of these studies was to determine if there are correlations between the dormancy breaking and germination requirements of seeds and the germination phenology, life cycle type, habitat requirements, range of geographical distribution, and phylogenetic relationships of the species. Germination phenology is highly correlated with the responses of seeds to the yearly temperature cycle. Species with winter and summer annual life cycles have predictable germination characteristics, but monocarpic and polycarpic perennials do not. Several dormancy types may be found in a given habitat, and narrowly endemic and widely-distributed species in the same genus may have similar germination characteristics. Within some families there is a tendency for a particular type of seed-temperature response to be very important, but frequently this is related to the predominance of a given life cycle type in the family.

GERMINATION ECOPHYSIOLOGY OF HERBACEOUS PLANT SPECIES IN A TEMPERATE REGION

Germination phenology data have been collected from 75 winter annuals, 49 summer annuals, 28 monocarpic perennials, and 122 polycarpic perennials, and experimental investigations of dormancy breaking and germination requirements have been conducted on 56 winter annuals, 32 summer annuals, 18 monocarpic perennials, and 73 polycarpic perennials. The purpose of these studies was to determine if there are correlations between the dormancy breaking and germination requirements of seeds and the germination phenology, life cycle type, habitat requirements, range of geographical distribution, and phylogenetic relationships of the species. Germination phenology is highly correlated with the responses of seeds to the yearly temperature cycle. Species with winter and summer annual life cycles have predictable germination characteristics, but monocarpic and polycarpic perennials do not. Several dormancy types may be found in a given habitat, and narrowly endemic and widely‐distributed species in the same genus may have similar germination characteristics. Within some families there is a tendency for a particular type of seed‐temperature response to be very important, but frequently this is related to the predominance of a given life cycle type in the family.