Reproductive Shoots Research Articles

Cultivation Strategies to Modify Biomass Partitioning and Improve Yield in Controlled-environment Production of High-cannabidiol Cannabis (Cannabis sativa L.)

Two common challenges reported by cannabis growers are low yields and small profit margins. Although recent research of cannabis yield has focused on lighting and nutrition, little research has examined how changes in other cultivation practices may be beneficial. The objective of this study was to evaluate the following two techniques to potentially improve yield: fertilizer restriction (FR) to reduce plant size and, thus, increase plant density and shoot number manipulation (SNM) to reduce shoot length and improve biomass partitioning. The FR technique involves leaching the substrate and providing only tap water for 0, 1, or 2 weeks at the start of flower initiation, whereas SNM involves pinching shoot tips 2, 3, or 4 times to produce 4, 8, or 16 shoots/plant, respectively. This study used a full factorial treatment design for a total of nine treatments (three FR × three SNM). Plants were flowered under 12-hour photoperiods for 8 weeks and then destructively harvested for data collection. The results demonstrated that both techniques improve plant productivity in different ways. The FR technique reduced all mass measurements (g/plant) and decreased plant area (m2/plant); therefore, the yield metrics (kg·m−2) increased with the increasing FR treatments. The SNM technique did not affect plant area, but more pinching events resulted in a decrease in reproductive shoot length (cm/shoot) and an increase in inflorescence to trim the dry mass ratio (inflorescence:trim). Shorter shoot lengths are desirable for eliminating trellis support netting, which helps growers reduce material costs and improve labor efficiency during harvest. Increasing the inflorescence:trim may also reduce labor costs related to trimming, which comprise the largest cost of production by many growers. Although both techniques offer advantages, there are trade-offs that must be considered in the context of overall profitability.

Cytokinin and reproductive shoot architecture: bigger and better?

Cytokinin (CK) is a key plant hormone, but one whose effects are often misunderstood, partly due to reliance on older data from before the molecular genetic age of plant science. In this mini-review, we examine the role of CK in controlling the reproductive shoot architecture of flowering plants. We begin with a long overdue re-examination of the role of CK in shoot branching, and discuss the relatively paucity of genetic evidence that CK does play a major role in this process. We then examine the role of CK in determining the number of inflorescences, flowers, fruit and seed that plants initiate during reproductive development, and how these are arranged in space and time. The genetic evidence for a major role of CK in controlling these processes is much clearer, and CK has profound effects in boosting the size and number of most reproductive structures. Conversely, the attenuation of CK levels during the reproductive phase likely contributes to reduced organ size seen later in flowering, and the ultimate arrest of inflorescence meristems during end-of-flowering. We finish by discussing how this information can potentially be used to improve crop yields.

Elimination of Exogenous Pollution Influence on the Microelement Composition of Medicinal Plants

INTRODUCTION. The compendial analytical procedure for determining the content of heavy metals and arsenic impurities in herbal drugs does not differentiate between endogenous and exogenous elemental impurities. Higher-precision data on the microelement composition of plants, particularly data on endogenous and exogenous impurities, could be instrumental in chemosystematics and in the identification of raw materials.AIM. This study aimed to modify the analytical procedure for quantifying macro- and microelements in herbal drugs with the intention to eliminate the influence of exogenous pollutants on test results.MATERIALS AND METHODS. The study focused on herbal drugs from the Boraginaceae family, including reproductive shoots of lungwort (Pulmonaria mollis Wulf. ex Hornem) and leaves of common borage (Borago officinalis L.). A portion was spiked with elemental pollutants. All herbal drugs were ground and fractionated by sieving. Quantitative determination was performed by inductively coupled plasma mass spectrometry. Statistical analysis of the results used Microsoft Excel and Statistica 8 software.RESULTS. A total of 30 elements were quantified in 9 fractions of herbal drugs with different particle sizes. Cluster analysis showed that unfractionated herbal drugs and the fraction comprising particles smaller than 0.2 mm formed sepa rate clusters, indicating significant differences in elemental compositions. Grubbs’ test confirmed that these two samples were significantly different from the others. The fraction of particles smaller than 0.2 mm had the maximum content of the spiked elements; more than 90% of the spiked amounts were recovered from this fraction. The high content of elements observed in unfractionated herbal drugs was due to the plant parts that would have passed the 0.2 mm sieve had they been ground and fractionated.CONCLUSIONS. The use of unfractionated herbal drugs leads to a systematic error in the results of elemental content determination, which significantly hinders the applicability of such results for the identification of herbal drugs. To ensure reliable results in the determination of the microelement status of plants, the authors suggest performing additional fractionation of herbal drugs and discarding the fraction under 0.2 mm.

Genome-Wide Identification, Characterization and Expression Profile of F-Box Protein Family Genes Shed Light on Lateral Branch Development in Cultivated Peanut (Arachis hypogaea L.)

F-box proteins are a large gene family in plants, and play crucial roles in plant growth, development, and stress response. To date, a comprehensive investigation of F-box family genes in peanuts, and their expression pattern in lateral branch development has not been performed. In this study, a total of 95 F-box protein family members on 18 chromosomes, named AhFBX1-AhFBX95, were identified in cultivated peanut (Arachis hypogaea L.), which were classified into four groups (Group I–IV). The gene structures and protein motifs of these peanut FBX genes were highly conserved among most FBXs. We found that significant segmental duplication events occurred between wild diploid species and the allotetraploid of peanut FBXs, and observed that AhFBXs underwent strong purifying selection throughout evolution. Cis-acting elements related to development, hormones, and stresses were identified in the promoters of AhFBX genes. In silico analysis of AhFBX genes revealed expression patterns across 22 different tissues. A total of 32 genes were predominantly expressed in leaves, pistils, and the aerial gynophore tip. Additionally, 37 genes displayed tissue-specific expression specifically at the apex of both vegetative and reproductive shoots. During our analysis of transcriptome data for lateral branch development in spreading and erect varieties, namely M130 and JH5, we identified nine deferentially expressed genes (DEGs). Quantitative real-time PCR (qRT-PCR) results further confirmed the expression patterns of these DEGs. These DEGs exhibited significant differences in their expression levels at different stages between M130 and JH5, suggesting their potential involvement in the regulation of lateral branch development. This systematic research offers valuable insights into the functional dissection of AhFBX genes in regulating plant growth habit in peanut.

A hidden herbivory effect on Sphagnum reproduction.

Defence theories provide predictions about trade-offs in the allocation of resources to defence and growth. However, very little is known about how pressure from herbivores influences the allocation of resources during reproduction. Two common peatland bryophyte species, Sphagnum angustifolium and S. capillifolium, were chosen as study species. Vegetative and reproductive shoots of both Sphagnum species were subjected to treatments with and without herbivores in a lab experiment. After 4 weeks of exposure to herbivores in a growth chamber, we measured biomass production, net photosynthesis rate, defence traits (phenolics in leachate and phenolics in extract), nonstructural carbohydrates (soluble sugar and starch), and reproductive traits (capsule number, weight and diameter, and spore germination) of both Sphagnum species. Reproductive shoots had higher constitutive defence than vegetative shoots in S. angustifolium, and a similar pattern was observed in S. capillifolium. With herbivory, reproductive shoots showed stronger induced defence (released more phenolics) than vegetative shoots in S. capillifolium, but not in S. angustifolium. Herbivory had no effect on capsule number, weight, or diameter, but reduced spore germination percentage by more than half in both species. Our study highlights the hidden effects of herbivory on reproduction of Sphagnum and indicates the presence of maternal effects in bryophytes. Ecologists will benefit from examining both quality- and quantity-based traits when attempting to estimate the herbivory effect on plant fitness.

Population dynamics and seed productivity of Dactylorhiza maculata (Orchidaceae) population in the Komi Republic (European Russia) as a response to the effects of weather factors

Conservation of biodiversity is the most important problem at present time. One of its important tasks is a preserving of selected species and groups of plants. The Orchidaceae family, despite its high species diversity, is one of the most threatened groups of flowering plants in the world, which is caused by peculiarities of their biology and ornamental properties. One of the priorities in the study and conservation of Orchidaceae is long-term monitoring studies. This paper presents results of a nine-year study of the population of a rare orchid, Dactylorhiza maculata, in the Komi Republic (north-east of European Russia). The morphological features of plants and seeds, the number and structure of population and the reproductive success have been studied. It was revealed that the height of the Dactylorhiza maculata shoots is influenced by the weather conditions of the current growing season, while the number of leaves and flowers is influenced by the conditions of the previous year. The number of reproductive shoots in the Dactylorhiza maculata population is positively correlated with the temperature in July of the previous growing season. The fruit set varied between 26.0% and 73.7% during various study years. A significant positive correlation was found between the seed size and the precipitation amount at the mid-July of the current growing season. The average seed number was 3865 per fruit (by changing between 2557 and 4808 seeds in various study years). The real seed productivity was 32 761 seeds (with changes from 17 830 seeds to 41 548 seeds). A positive correlation was observed between the size of flowers and the number of seeds per fruit; these parameters positively correlate with the precipitation amount at the beginning of the growing season. The presence of juvenile individuals (from 10.8% to 24.2%) in all study years indicates the successful seed reproduction in the studied Dactylorhiza maculata population.

Reproductive Responses to Increased Shoot Density and Global Change Drivers in a Widespread Clonal Wetland Species, Schoenoplectus americanus

The expansion of many wetland species is a function of both clonal propagation and sexual reproduction. The production of ramets through clonal propagation enables plants to move and occupy space near parent ramets, while seeds produced by sexual reproduction enable species to disperse and colonize open or disturbed sites both near and far from parents. The balance between clonal propagation and sexual reproduction is known to vary with plant density but few studies have focused on reproductive allocation with density changes in response to global climate change. Schoenoplectus americanus is a widespread clonal wetland species in North America and a dominant species in Chesapeake Bay brackish tidal wetlands. Long-term experiments on responses of S. americanus to global change provided the opportunity to compare the two modes of propagation under different treatments. Seed production increased with increasing shoot density, supporting the hypothesis that factors causing increased clonal reproduction (e.g., higher shoot density) stimulate sexual reproduction and dispersal of genets. The increase in allocation to sexual reproduction was mainly the result of an increase in the number of ramets that flowered and not an increase in the number of seeds per reproductive shoot, or the ratio between the number of flowers produced per inflorescence and the number of flowers that developed into seeds. Seed production increased in response to increasing temperatures and decreased or did not change in response to increased CO2 or nitrogen. Results from this comparative study demonstrate that plant responses to global change treatments affect resource allocation and can alter the ability of species to produce seeds.

Genome-wide characterization of AP2/ERF genes and their potential roles in bulb and bolt development in Allium sativum

Garlic is an essential flavoring and health vegetable. Its bulb and bolt, as important edible tissues, are targets to be improved in garlic breeding. AP2/ERF transcription factor plays crucial regulatory roles in multiple biological processes. Nevertheless, identification and characterization of AP2/ERFs are poorly elucidated in garlic. Here, 163 AsAP2/ERFs were identified in garlic genome and categorized into four subfamilies including AP2 (23), ERF (131), RAV (7), and Soloist (2). Gene structural analysis showed that most AsERFs and all AsRAVs were intron-less, while majority of AsAP2s were intron-rich. Thirty-one pairs of gene duplications were classified as 14 tandem duplications and 17 segmental duplications that were underwent purification selection. Abundant cis-acting elements associated with development, hormone signaling and stress responses were detected in promoter regions. AsAP2/ERFs exhibited different tissue-specific expression profiles. Diverse expression patterns of AsAP2/ERFs at different stages during bulb expansion and bolting processes suggested that these genes played different and well-coordinated roles in bulb and bolt development. The co-expression network analysis showed that 11 AsAP2/ERFs had high connectivity values and might play roles in garlic bolting process along with their co-expression genes which were enriched in ‘reproductive shoot system development’, ‘reproductive process’, and ‘flower development’. These results provide valuable foundation for investigating the function of AsAP2/ERFs for genetic improvement of garlic.

Pseudanthia in angiosperms: a review.

Pseudanthia or 'false flowers' are multiflowered units that resemble solitary flowers in form and function. Over the last century the term 'pseudanthium' has been applied to a wide array of morphologically divergent blossoms, ranging from those with easily noticeable florets to derived, reduced units in which individual flowers become almost indistinguishable. And although initially admired mostly by botanists, the diversity and widespread distribution of pseudanthia across angiosperms has already made them a fascinating topic for evolutionary and developmental comparative studies. This review synthesizes historical and current concepts on the biology of pseudanthia. Our first aim is to establish a clear, operational definition of pseudanthium and disentangle common terminological misconceptions surrounding that term. Our second aim is to summarize the knowledge of morphological and developmental diversity of pseudanthia and embed it within a modern phylogenetic framework. Lastly, we want to provide a comprehensive overview on the evolution and ecological importance of pseudanthia and outline perspectives for future studies. The understanding of pseudanthia changed multiple times and reflects three different interpretations of their 'flower-like' qualities: developmental (similarity in structure), figural (similarity in form and function), and phylogenetic (homology between angiosperm flowers and monoecious reproductive shoots in gymnosperms). Here, we propose to narrow the term pseudanthium to multiflowered blossoms resembling zoophilous flowers in form, i.e., in being structurally subdivided in a showy periphery and a reproductive center. According to this definition, pseudanthia sensu stricto. evolved independently in at least 40 angiosperm families. The recurrent acquisition of pseudanthia sensu stricto in all major lineages of flowering plants indicates repeated interactions between developmental constraints (smallness of flowers, meristematic conditions) and selective pressures, such as demands of pollinators and/or environmental conditions.

A New Gnetalean Macrofossil from the Mid-Jurassic Daohugou Formation.

Macrofossil evidence has demonstrated a first radiation of gnetophytes in the Early Cretaceous. However, the origin of the diversity of gnetophytes remains ambiguous because gnetalean macrofossils have rarely been reported from pre-Cretaceous strata. Here, we report a new putative gnetalean macrofossil reproductive shoot which possesses opposite phyllotaxy, long linear leaves more or less decurrent and having a prominent midvein and pedicled ovoid-ellipsoid and longitudinally striated chlamydosperms. Our new fossil is different from other known gnetalean macrofossils in the linear-lanceolate leaves with a midvein and pedicled chlamydosperms. As a result, we describe this new macrofossil reproductive shoot as new to science, i.e., Daohugoucladus sinensis gen. et sp. nov. Our new macrofossil displays additional morphological characters distinct from other known Mesozoic and modern gnetalean species and provides additional evidence of the origin and early evolution of female reproductive organs of gnetophytes.

When sunlight goes out, avoidance mechanisms are defective for protecting flowers from freezing damage

In high mountain species, flowers are considered the most frost-sensitive organs of plants. Such frost sensibility relates to the fact that most flowers do not tolerate ice formation in their tissues, suggesting that freezing avoidance mechanisms would be highly selected to protecting these vital organs from freezing damage. Despite this, the function and regulation of avoidance mechanisms in flowers have been poorly studied. This study assessed the importance of freezing avoidance mechanisms in alpine species from the central Chilean Andes. Reproductive shoots of 14 herbaceous species from the subalpine and low alpine belts in the central Chilean Andes were collected during peak flowering in the field and transported to the lab to study ice formation and propagation. The frequency and effectiveness of structural ice barriers (SIB) and the effect of inflorescence morphology on thermal decoupling were quantified by infrared thermography. SIBs were detected in 9 out of the 14 studied species but were effective only in three. Moreover, no thermal decoupling was detected in any studied species, independent of their inflorescence type. We conclude that SIBs and inflorescence morphology are insufficient to protect flowers from damage caused by night freezing events.

Seed Provision Efficacy of Detached Reproductive Shoots in Restoration Projects for Degraded Eelgrass (Zostera marina L.) Meadows

Eelgrass (Zostera marina L.) is a dominant seagrass species in the temperate waters of the northern hemisphere and is experiencing global declines. The use of eelgrass seeds is increasingly being recognized as a viable option for large-scale restoration projects. Eelgrass reproductive shoots are often collected to obtain seeds or to broadcast seeds in restoration projects. Here, a new method to accurately evaluate the seed provision efficacy of detached eelgrass reproductive is proposed. Viable seeds of detached eelgrass reproductive shoots were collected using in situ net cages at Swan Lake, China. The seed yield and quality of detached eelgrass reproductive shoots under five different treatments (with or without rhizomes and roots, vegetative shoots, and sediment) were compared to select the optimal treatment for this method. The results showed that each detached eelgrass reproductive shoot produced approximately 50 viable seeds on average and the potential seed yield overestimated the actual seed yields by around four times. Seed quality evaluated by size and weight was consistent with that of the natural eelgrass meadow in Swan Lake. Comparing the five different treatments, the simplest treatment (a single reproductive shoot) was convenient and robust for this method. The results indicate that this method is worth further extending to other populations to improve the efficiency of seed use and for effectiveness evaluation in restoration projects.

Habitats and population structure of rare orchids from the genus Cypripedium in Siberia

Cypripedium calceolus L., C. macranthos Sw. and C. ventricosum Sw. are rare Eurasian orchid species, whose habitats are poorly studied in Siberia. In this paper, we describe 55 sympatric and 10 separated populations of the three species, located in Russia within Republic of Buryatia, Irkutsk Region, Krasnoyarsk Territory, and Republic of Altai. Cypripedium macranthos plants dominated the most of the sympatric populations. Vegetation surveys were performed in all localities, and the collected data were analyzed using the IBIS software. We applied the phytoindication scales elaborated by Tsatsenkin and his colleagues for ecological indicator value analysis. The Cypripedium populations were characterized by high floristic diversity of their habitats; however, all of them were found in areas where both canopy density and ground cover were low. In the most of the separated populations, ontogenetic spectra of Cypripedium species corresponded to the base spectrum with a predominance of the adult vegetative and reproductive shoots.

Nomenclature and typification of Cathayaargyrophylla (Pinaceae).

In 1958, Chun and Kuang described Cathaya Chun & Kuang as a new genus of Pinaceae. They included one fossil species, C.loehri (Engelh. & Kink.) Chun & Kuang and two extant species, C.argyrophylla Chun & Kuang and C.nanchuanensis Chun & Kuang. Under Art. 40.1 of the Shenzhen Code, they did not validly publish Cathaya because they did not designate a type species for the generic name. Four years later (Chun and Kuang 1962), they again published on Cathaya (in Chinese) where they cited the 1958 publication and included one species C.argyrophylla (with C.nanchuanensis in synonymy) under Cathaya. According to Art. 40.3, they validated both the generic name Cathaya and C.argyrophylla in 1962. Further examination of the type collection and botanical history of the discovery of C.argyrophylla revealed that the type collection Guang-Fu-Lin-Qu Exped. 00198 consists of 11 duplicates in the South China Institute of Botany (IBSC) and 9 duplicates in other herbaria (GAC, IBK, PE, SZ) and that the intended type specimen (IBSC0000004) consists of two gatherings: the bark, reproductive shoot and seed cones collected in 1955, whereas pollen-bearing cones were collected in 1956. We thus lectotypify the name C.argyrophylla with the specimen Guang-Fu-Lin-Qu Exped. 00198 (IBSC0000004 excl. pollen-bearing cones).

Impacts of huanglongbing on fruit yield and quality and on flushing dynamics of Sicilian lemon trees.

The severe Asian form of huanglongbing (HLB), a vascular disease associated with the phloem-limited bacterium 'Candidatus Liberibacter asiaticus', is transmitted by the Asian citrus psyllid (ACP) Diaphorina citri. Disease impacts are known for sweet oranges and acid limes but not lemons. In a five-year study (2017-2021) we compared yield and fruit quality between naturally-infected and healthy 5-yr-old trees of Sicilian lemon 'Femminello', and shoot phenology on both lemon and 'Valencia' orange, both grafted onto 'Swingle' citrumelo, grown in southeastern São Paulo State, Brazil. HLB severity (percentage of tree canopy area with HLB symptoms) was assessed every 3-4 months, fruit yield and quality in May (2017 to 2019) or June/July (2020-2021), and vegetative and reproductive shoots fortnightly on 50-cm-long branches. The development of ACP on one-year-old seedlings of five lemon varieties, 'Tahiti' acid lime, 'Valencia' orange, and orange jasmine was evaluated. Symptoms increased from 11% in 2017 to 64% in 2021, and a monomolecular model estimated 10 years for symptoms to occupy >90% of the tree canopy. On average, production of trees with symptom on 20%, 50% or 80% of the canopy respectively dropped by 18%, 38%, and 53% compared to healthy trees. Fruits of symptomatic branches of lemons were 4.22% lighter and the number of dropped fruits did not correlate with symptom severity. Flushing on symptomatic branches started earlier by 15 to 55 days as compared to the healthy branches of lemon and orange. On diseased trees, vegetative and reproductive shoots respectively increased by 24.5% and 17.5% on lemon and by 67.2% and 70.6% on sweet orange, but fruit set was reduced by 12.9% and 19.7% on lemon and orange trees, respectively. ACP reproduced similarly on all tested plants. The fast symptom progress, significant yield reduction, and earlier flushing on diseased trees, providing conditions highly favorable for the pathogen to spread, reinforce the need of prompt diseased tree removal and frequent ACP preventive control to manage HLB in lemons as in any other citrus crop.

Obtaining new records of critically endangered Potamogeton praelongus (Potamogetonaceae) depending on groundwater springs in northern coastal areas of Hokkaido, Japan

Potamogeton praelongus Wulfen is an aquatic macrophyte that is critically endangered in Japan. Although it is widely distributed throughout the boreal climatic zone, several European countries also recognize it as an endangered species. In Japan, it was once widely distributed throughout Hokkaido but has disappeared or reduced in abundance at its known locations. During 2020–2021, we discovered five new locations of this species in Wakkanai-shi and Sarufutsu-mura, Northern Hokkaido. Growing conditions must be suitable for this species in three of the five locations as it is present with several reproductive shoots or is widely distributed in source pond or lake. However, conditions were poor in the other two locations because few shoots were found or plants were observed only in 2020. Environmental conditions in the new locations were similar to those reported in Europe and North America. In three of the four locations at Wakkanai-shi, P. praelongus was distributed mainly along the eastern shore facing sand dunes, suggesting that the distribution of this species depends on groundwater springs flowing from sand dunes. Further populations may be discovered in the future by intensively surveying areas near springs since many sand dune lakes and similar environments are present in Hokkaido.

Post-veraison increase in source-sink ratio via manipulation of sink availability gradually reduces leaf functionality in grapevine (cv. Pinot noir)

The vegetative-reproductive balance is critical in determining grapevine quality and productivity. Many agricultural practices (bunch thinning, defoliation, green pruning) can modify the source-sink relationships leading to altered vineyard efficiency and berry quality. Field experiments aimed at understanding how a decrease in sink availability influences leaf physiology of the reproductive shoot. In Pinot noir trained to guyot, control shoots were compared to shoots subjected to basal girdling (G), bunch removal (BR) or a combination of both treatments (G + BR). Morpho-physiological traits including leaf water status, gas-exchange, leaf temperature, chlorophyll fluorescence, leaf starch and soluble sugars, petiole and leaf dry weight were collected at different time of the day and over several days to evaluate the dynamics of leaf functionality following treatments application. The gradual reduction in sink availability induced significant reductions in leaf gas-exchange and PSII efficiency from the second day after the treatments’ application. Nonetheless, while reductions in photosynthetic capacity and increases in leaf temperature associated with a compromised stomatal physiology were present in the G + BR shoots, no differences were observed between bunch removal and control treatments. Girdling and G + BR showed a significant reduction in leaf chlorophyll a and b as well as carotenoids content when compared to control shoots. The increase in the source-sink ratio subsequently produced a marked increase in leaf starch, hexoses and sucrose accompanied by a reduction in the specific leaf area while the girdling did not affect the weight and brix degree of the bunches. This work shows how the progressive reduction in sink availability compromises leaf physiological functionality putatively owing to a reduction in assimilates translocation capacity from the leaf and hence starch storage and accumulation. However, limited effects were observed for shoots in which only the bunch was removed suggesting that assimilates allocation to other vegetative and/or reproductive sinks can maintain leaf functionality even in days characterized by unfavourable environmental conditions. • Sink availability greatly influences source dynamics • Reducing sink availability in grapevine resulted in higher diurnal susceptibility of the leaf to environmental stresses such as high VPD and air temperature • Source-sink relationships can indirectly govern water status via stomatal regulation of transpiration • Source-sink dynamics should be considered as a potential mechanism to exploit for reducing the impact of climate change in grapevine.

Chemical compositions of raspberry leaves influenced by growth season, cultivars and leaf position

Raspberry leaves with high polyphenols have high utilization value, but the accumulation trend of phenolics in raspberry leaves in different growing seasons, cultivars, and leaf positions, is not clear. The utilization of leaves and raspberry comprehensive income are limited due to the uncertain factors. Therefore, the content changes of chlorophyll a, chlorophyll b, carotenoids, total phenolic content (TPC), total flavonoids content (TFC), saponins, hydrolyzed tannins and condensed tannins of raspberry leaves from May to October, in annual-fruiting (AF) raspberry (cv. Heritage) and biennial-fruiting (BF) raspberry (cv. Reveille, cv. Tulameen and cv. Australian Red), and three leaf positions were investigated. Eighteen phenolic compounds were identified in which quercetin-3-glucuronide, kaempferol-3-rutinoside, ellagic acid, chlorogenic acid, epicatechin and procyanidin B1 were quantitatively analyzed by HPLC-MS. The results showed that chlorophyll a, chlorophyll b, carotenoids showed a parabolic trend of rising first and then falling, while TPC, TFC, hydrolyzed tannins, condensed tannins and saponins showed a gradual increase trend from May to October. The total accumulation of secondary metabolites was the Heritage, Australian Red, Tulameen and the Reveille from high to low. The apical leaves accumulated TPC, TFC and quercetin-3-glucuronide, kaempferol-3-rutinoside, ellagic acid, while the basal leaves accumulated condensed tannins and saponins. Overall, growth season was the main factor affecting the accumulation of secondary metabolites, followed by cultivar and leaf positions. Therefore, according the properties of cultivars, it can be recommended that AF and BF cultivar leaves can be harvested twice in early summer and late autumn after reproductive shoot preservation, while the leaves of BF cultivar without fruiting shoots can be extensively harvested once in late autumn.

Massive loss and microbial decomposition in reproductive biomass of Zosteramarina

The biomass of Zostera marina in the temperate coastal zone has seasonal variations in their dry weight, with a peak during the spring season when a large section of the shoots develops reproductive organs. However, the period of high biomass is only short-term, after which large numbers of reproductive shoots drastically disappeared. Dislodgement is an important fate of the reproductive biomass. The fraction of biomass that reaches the deep sea contributes to carbon sequestration, however the processes of dislodgement and transportation of reproductive shoots of Z. marina has been rarely studied. Here, based on a monitoring survey of two Z. marina meadows, we estimated the net loss of biomass, including their reproductive one. In addition, microbial decomposition was assessed by dark incubation to evaluate the fate of the dislodged biomass. The apparent loss of biomass from the Z. marina meadows in the “Declining Period”, defined with the most rapid decrease in biomass, accounted for 82–100% of the biomass at the initial time-point of this period. By subtracting the biomass production from the apparent loss, we calculated the net loss of biomass in the Declining Period, accounting for 14–81% of the annual production. Approximately half of the biomass loss in the Declining Period was attributed to reproductive biomass, suggesting that dislodgement of reproductive shoots is an important fate of photosynthetic products of Z. marina. The carbon to nitrogen (CN) ratio of the reproductive shoots was found to be significantly higher than that of vegetative shoots. Since nitrogenous materials are relatively labile, we expected a lower bioavailability of reproductive shoots. However, microbial decomposition did not reflect the CN ratio, probably due to the heterogeneity of nitrogenous materials and/or due to the contribution of carbohydrates consisting mostly of non-nitrogenous compounds.

Increased Coastal Nutrient Loading Enhances Reproductive Intensity of Zostera marina: Implications for Seagrass Meadow Resilience

Because sexual reproduction is essential for the establishment and persistence of seagrass meadows, flowering intensity is an important trait that influences the resilience and stability of seagrass populations. Although the effects of excessive coastal nutrient loading on seagrass vegetative growth have been extensively documented, the effects on seagrass reproductive phenology and intensity remain unclear. To examine the reproductive responses of seagrass populations to increased coastal nutrient loading, the flowering phenology and intensity of Zostera marina were compared between sites with high-nutrient, low-light conditions (Deukryang Bay and Dongdae Bay) and low-nutrient, high-light conditions (Koje Bay) on the southern coast of Korea. Nutrient contents of the above- and below-ground tissues of Z. marina reflected in situ nutrient and light availability at the study sites. Reproductive shoot density and biomass, as well as flowering frequency and reproductive effort, were much higher (1.5–4.6-fold) at the high-nutrient, low-light study sites of Deukryang Bay and Dongdae Bay than at the low-nutrient, high-light site of Koje Bay. Consequently, potential seed production was higher in Deukryang Bay and Dongdae Bay than in Koje Bay. Chronic high-nutrient and low-light conditions significantly increased the reproductive intensity of Z. marina, supporting the persistence and resilience of Z. marina populations. The results of this study could provide insights into the conservation and management of seagrass meadows under increased coastal nutrient loading.