Dormant Plants Research Articles

Understory growth of Paris polyphylla accumulates a reservoir of secondary metabolites of plants.

Paris polyphylla is an important traditional medicinal plant of the Himalayan region. It is extensively used for the production of natural steroidal saponins and flavonoids. Although seed dormancy of wild plants can be broken to be artificially maintained and regenerated through micropropagation in the laboratory, the success of secondary metabolite production in higher quantities and the synthesis of superior plant metabolites have been very limited. In this study, we present differential metabolic profiling of P. polyphylla plants maintained for 8 years in natural and greenhouse conditions. Untargeted profiling of the metabolites through ultra-performance liquid chromatography-mass spectrometry/mass spectrometry (UPLC-MS/MS), followed by statistical analysis, identified secondary metabolites that were enriched in the naturally occurring plant roots compared with the greenhouse plant roots. A multivariate statistical analysis revealed the differential distribution of the compounds between the two groups. Overall, we identified 1,182 secondary metabolites, with 116 metabolites being differentially upregulated and 256 metabolites being downregulated. Moreover, 810 metabolites showed no significant variation under both growing conditions. The Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that the naturally forest-grown P. polyphylla plants were significantly enriched in steroidal saponins, lipids, vitamins, flavonoids, and flavonols. An analysis of the top 10 differentially upregulated secondary metabolites indicated a significantly enriched quantity of spirost-5-en-3,12-diol and kaempferol synthesis pathways, which are known to reduce the effect of free radicals scavengers inside the cell. In addition, veratramine alkaloids were also enriched under natural conditions. Our findings indicated that naturally maintained P. polyphylla plants are suitable for the extraction of medicinally important compounds. Our study established a causal relationship between the metabolic composition of the roots and their natural growth condition. This study highlighted the importance of environmental conditions in the biosynthesis of secondary metabolites of plants.

Chemical Solutions for Seed Dormancy: A Comprehensive Review on Strategy to Combat Pre-harvest Sprouting in Mung Bean

The mung bean, or Vigna radiata (L.) Wilczek, is a significant grain legume with enormous global economic value. Kharif is the most significant of the three seasons and during this time pre-harvest sprouting (PHS) is a major issue that results in significant production losses. Due to PHS, yield losses in green gram have been estimated to be between 60 and 70 per cent. Chemical treatments that induce seed dormancy may prevent premature germination and enable a timely harvest. This study covers the effectiveness of inducing dormancy in mung bean plants with various chemicals at critical developmental stages before harvest. Treatment with various chemicals like maleic hydrazide, sodium azide and plant growth regulators (abscisic acid, ethylene, gibberellins) following chemical administration at pre-arranged intervals, physiological parameters such as seed moisture content, germination rates and antioxidant enzyme activities can be considered to prevent PHS. Mitigating pre-harvest sprouting losses and increasing mung bean output can be achieved by optimising dormancy induction by prudent chemical use. To increase mung bean output, PHS-tolerant cultivars must be developed due to the significant losses incurred by PHS. This review discusses various aspects, including how different traits affect pre-harvest sprouting.

Recent advances and prospects of constructed wetlands in cold climates: a review from 2013 to 2023.

Constructed wetland (CW), a promising, environmentally responsible, and effective green ecological treatment technology, is actively involved in the treatment of various forms of wastewater. Low temperatures will, however, lead to issues including plant dormancy, decreased microbial activity, and ice formation in CWs, which will influence how well CWs process wastewater. Applying CWs successfully and continuously in cold areas is extremely difficult. Therefore, it is crucial to find solutions for the pressing issue of increasing the CWs' ability to process wastewater at low temperatures. This review focuses on the effect of cold climate on CWs (plants, substrates, microorganisms, removal effect of pollutants). It meticulously outlines current strategies to enhance CWs' performance under low-temperature conditions, including modifications for the improvement and optimization of the internal components (i.e., plant and substrate selection, bio-augmentation) and enhancement of the external operation conditions of CWs (such as process combination, effluent recirculation, aeration, heat preservation, and operation parameter optimization). Finally, future perspectives on potential research directions and technological innovations that could strengthen CWs' performance in cold climates are prospected. This review aims to contribute valuable insights into the operation strategies, widespread implementation, and subsequent study of CWs in colder climate regions.

Seed dormancy types and germination response of 15 plant species in temperate montane peatlands.

Despite their crucial role in determining the fate of seeds, the type and breaking mode of seed dormancy in peatland plants in temperate Asia with a continental monsoon climate are rarely known. Fifteen common peatland plant species were used to test their seed germination response to various dormancy-breaking treatments, including dry storage (D), gibberellin acid soaking (GA), cold stratification (CS), warm followed cold stratification (WCS), GA soaking + cold stratification (GA + CS) and GA soaking + warm followed cold stratification (GA + WCS). Germination experiment, viability and imbibition test, and morphological observation of embryos were conducted. Of the 15 species, nine showed physiological dormancy (PD), with non-deep PD being the dominant type. Four species, Angelica pubescens, Cicuta virosa, Iris laevigata, and Iris setosa exhibited morphophysiological dormancy. Two species, Lycopus uniflorus and Spiraea salicifolia, demonstrated nondormancy. Overall, the effect hierarchy of dormancy-breaking is: CS > GA > WCS > GA + CS > D > GA + WCS. Principal component analysis demonstrated that seed traits, including embryo length: seed length ratio, seed size, and monocot/eudicot divergence, are more likely to influence seed dormancy than environmental factors. Our study suggests that nearly 90% of the tested peatland plant species in the Changbai Mountains demonstrated seed dormancy, and seed traits (e.g. embryo-to-seed ratio and seed size) and abiotic environmental factors (e.g. pH and temperature seasonality) are related to germination behavior, suggesting seed dormancy being a common adaptation strategy for the peatland plants in the temperate montane environment.

Функциональные характеристики почек возобновления Нeracleum sosnowskyi Manden. в период подготовки к перезимовке

Based on the study of the physiological and biochemical characteristics of Heracleum sosnowskyi buds we identified functional adaptations during the preparation of plants for overwintering. The freezing point of water in the buds tissues was –12 оC in October, while maintaining high water content (more than 80%). Buds has a relatively high efficiency of respiration at low positive temperatures (2–5 оC), which favors morphogenesis processes in the shoot vegetative cone in autumn. During the preparation for overwintering the buds accumulated osmoregulators – soluble sugars, free amino acids, including proline. A relatively high level of cytokinin growth hormones was found in the buds tissues. This contributes to morphogenesis processes and increases plant cold tolerance. We found that in December the abscisic acid (a growth inhibitor and resting hormone) content increases and the level of cytokinins decrease. Heracleum sosnowskyi formed buds differing in the photosynthetic pigments content. Buds with green scale leaves accumulated the greatest amount of chlorophylls and carotenoids, while those with red-brown and yellow ones accumulated the least. The carotenoids accumulation in the green buds tissues protects the formed photosynthetic apparatus at low positive temperatures in autumn. The results on the functional state of H. sosnowskyi terminal buds in natural populations indicate the absence of deep dormancy in plants, and morphogenesis processes in meristems tissues are limited by winter temperatures.

Molecular Identification and Pathogenicity of Fusarium Species Associated with Wood Canker, Root and Basal Rot in Turkish Grapevine Nurseries.

Fusarium species are agriculturally important fungi with a broad host range and can be found as endophytic, pathogenic, or opportunistic parasites in many crop plants. This study aimed to identify Fusarium species in bare-rooted, dormant plants in Turkish grapevine nurseries using molecular identification methods and assess their pathogenicity. Asymptomatic dormant plants were sampled from grapevine nurseries (43) in different regions of the country, and fungi were isolated from plant roots and internal basal tissues. The Fusarium strains were identified by performing gene sequencing (TEF1-α, RPB2) and phylogenetic analyses. Pathogenicity tests were carried out by inoculating mycelial agar pieces of strains onto the stem or conidial suspensions into the rhizosphere of vines (1103 Paulsen rootstock). Laboratory tests revealed that Fusarium species were highly prevalent in Turkish grapevine nurseries (41 out of 43). Gene sequencing and phylogenetic analyses unraveled that 12 Fusarium species (F. annulatum, F. brachygibbosum, F. clavum, F. curvatum, F. falciforme, F. fredkrugeri, F. glycines, F. nanum, F. nematophilum, F. nirenbergiae, F. solani, and Fusarium spp.) existed in the ready-to-sale plants. Some of these species (F. annulatum, F. curvatum and F. nirenbergiae) consistently caused wood necrosis of seedling stems, rotting of the basal zone and roots, and reduced root biomass. Although the other nine species also caused some root rot and root reduction, their virulence was not as severe as the pathogenic ones, and they were considered opportunistic parasites or endophytic species. This study suggests that Fusarium species might play an important role in root-basal rot, wood canker symptoms, and young vine decline in Turkish grapevine nurseries and that these species need to be considered for healthy seedling production.

Molecular advances in bud dormancy in trees.

Seasonal bud dormancy in perennial woody plants is a crucial and intricate process that is vital for the survival and development of plants. Over the past few decades, significant advancements have been made in understanding many features of bud dormancy, particularly in model species, where certain molecular mechanisms underlying this process have been elucidated. We provide an overview of recent molecular progress in understanding bud dormancy in trees, with a specific emphasis on the integration of common signaling and molecular mechanisms identified across different tree species. Additionally, we address some challenges that have emerged from our current understanding of bud dormancy and offer insights for future studies.

MIKC type MADS-box transcription factor LcSVP2 is involved in dormancy regulation of the terminal buds in evergreen perennial litchi (Litchi chinensis Sonn.).

SHORT VEGETATIVE PHASE (SVP), a member of the MADS-box transcription factor family, has been reported to regulate bud dormancy in deciduous perennial plants. Previously, three LcSVPs (LcSVP1, LcSVP2 and LcSVP3) were identified from litchi genome, and LcSVP2 was highly expressed in the terminal buds of litchi during growth cessation or dormancy stages and down-regulated during growth stages. In this study, the role of LcSVP2 in governing litchi bud dormancy was examined. LcSVP2 was highly expressed in the shoots, especially in the terminal buds at growth cessation stage, whereas low expression was showed in roots, female flowers and seeds. LcSVP2 was found to be located in the nucleus and have transcription inhibitory activity. Overexpression of LcSVP2 in Arabidopsis thaliana resulted in a later flowering phenotype compared to the wild-type control. Silencing LcSVP2 in growing litchi terminal buds delayed re-entry of dormancy, resulting in significantly lower dormancy rate. The treatment also significantly up-regulated litchi FLOWERING LOCUS T2 (LcFT2). Further study indicates that LcSVP2 interacts with an AP2-type transcription factor, SMALL ORGAN SIZE1 (LcSMOS1). Silencing LcSMOS1 promoted budbreak and delayed bud dormancy. Abscisic acid (200mg/L), which enforced bud dormancy, induced a short-term increase in the expression of LcSVP2 and LcSMOS1. Our study reveals that LcSVP2 may play a crucial role, likely together with LcSMOS1, in dormancy onset of the terminal bud and may also serve as a flowering repressor in evergreen perennial litchi.

Factors controlling spatiotemporal variability of soil carbon accumulation and stock estimates in a tidal salt marsh

Abstract. Tidal salt marshes are important contributors to soil carbon (C) stocks despite their relatively small land surface area. Although it is well understood that salt marshes have soil C burial rates orders of magnitude greater than those of terrestrial ecosystems, there is a wide range in accrual rates among spatially distributed marshes. In addition, wide ranges in C accrual rates also exist within a single marsh ecosystem. Tidal marshes often contain multiple species of cordgrass due to variations in hydrology and soil biogeochemistry caused by microtopography and distance from tidal creeks, creating distinct subsites. Our overarching objective was to observe how soil C concentration and dissolved organic carbon (DOC) vary across four plant phenophases and across three subsites categorized by unique vegetation and hydrology. We also investigated the dominant biogeochemical controls on the spatiotemporal variability of soil C and DOC concentrations. We hypothesized that subsite biogeochemistry drives spatial heterogeneity in soil C concentration, and this causes variability in total soil C and DOC concentrations at the marsh scale. In addition, we hypothesized that soil C concentration and porewater biogeochemistry vary temporally across the four plant phenophases (i.e., senescence, dormancy, green-up, maturity). To test these interrelated hypotheses, we quantified soil C and DOC concentrations in 12 cm sections of soil cores (0–48 cm depth) across time (i.e., phenophase) and space (i.e., subsite), alongside several other porewater biogeochemical variables. Soil C concentration varied significantly (p < 0.05) among the three subsites and was significantly greater during plant dormancy. Soil S, porewater sulfide, redox potential, and depth predicted 44 % of the variability in soil C concentration. There were also significant spatial differences in the optical characterization properties of DOC across subsites. Our results show that soil C varied spatially across a marsh ecosystem by up to 63 % and across plant phenophase by 26 %, causing variability in soil C accrual rates and stocks depending on where and when samples are taken. This shows that hydrology, biogeochemistry, and plant phenology are major controls on salt marsh C content. It is critical to consider spatiotemporal heterogeneity in soil C concentration and porewater biogeochemistry to account for these sources of uncertainty in C stock estimates. We recommend that multiple locations and sampling time points are sampled when conducting blue C assessments to account for ecosystem-scale variability.

Seed permeability: an essential trait for classifying seed dormancy type

Abstract Seed dormancy in plants can have a significant impact on their ecology. Recent work by Rojas-Villa and Quijano-Abril (2023) classified the seed dormancy class in 14 plant species from the Andean forests of Colombia by using germination trials and several microscopy techniques to describe seed anatomy and morphology. The authors conclude that Cecropia species have both physical and physiological dormancy (of which they call physiophysical dormancy) based on seed morphology and mean germination times of over 30 days. Here, we present seed permeability and germination data from neotropical pioneer tree species: Ochroma pyramidale, Cecropia longipes, and Cecropia insignis, as well as Cecropia peltata (present in Rojas-Villa and Quijano-Abril, 2023), to demonstrate that Cecropia species do not exhibit dormancy and also have high levels of seed permeability. We find that the mean germination time for all three Cecropia species in our study was less than 30 days. This suggests a need for reporting the conditions in which germination trials take place to allow for comparability among studies and using seed permeability tests to accurately identify the physical dormancy class of seeds. Further, we present data from the literature that suggests that dormancy is not a requirement for seed persistence in the seed bank.

Histone modifications affecting plant dormancy and dormancy release: common regulatory effects on hormone metabolism.

As sessile organisms, plants enter periods of dormancy in response to environmental stresses to ensure continued growth and reproduction in the future. During dormancy, plant growth is suppressed, adaptive/survival mechanisms are exerted, and stress tolerance increases over a prolonged period until the plants resume their development or reproduction under favorable conditions. In this review, we focus on seed dormancy and bud dormancy, which are critical for adaptation to fluctuating environmental conditions. We provide an overview of the physiological characteristics of both types of dormancy as well as the importance of the phytohormones abscisic acid and gibberellin for establishing and releasing dormancy, respectively. Additionally, recent epigenetic analyses have revealed that dormancy establishment and release are associated with the removal and deposition of histone modifications at the loci of key regulatory genes influencing phytohormone metabolism and signaling, including DELAY OF GERMINATION 1 and DORMANCY-ASSOCIATED MADS-box genes. We discuss our current understanding of the physiological and molecular mechanisms required to establish and release seed dormancy and bud dormancy, while also describing how environmental conditions control dormancy depth, with a focus on the effects of histone modifications.

Autochthonous grape varieties in the Lower Don Region

This article describes modifi cation changes in the phenotypic traits of grape varieties, including the number of normally developed shoots and infl orescences, the average bunch weight, and grape yield under the infl uence of unstable weather conditions. The research was carried out in the moderate continental climate of the Lower Don region in the period from 2013 to 2022. The average annual air temperature ranged from +10.2 to +11.6 °C, with the climatic norm being +10.4 °C. In the period of active vegetation (May–September), the temperature ranged from +21.2 to +22.7 °C, with the norm being 18.1 °C. The maximum temperature ranged from +37.2 to +40.0 °C, with the norm being +40.0 °C. In winter, during the plant dormancy period (December–February), the average air temperature varied from 0.6 to minus 2.6 °С, with the norm being about minus 2.4 °С. The annual precipitation varied from 292 to 693 mm, with the norm being 548 mm. During the vegetation period of grapes, atmospheric precipitation by the years of observation varied from 99 to 359 mm, with the norm being 177 mm. The aim was to establish the limits of modifi cation variability of phenotypic traits under the infl uence of the unstable moderate continental climate of the Lower Don Region. The research objects were autochthonous grape varieties, including ‘Varyushkin’, ‘Krasnostop’ ‘Zolotovsky’, ‘Kumshatsky Belyi’, ‘Plechistik’, ‘Sibirkovy’, and ‘Tsimlyansky Chernyi’. The reaction norm and modifi cation changes of the phenotypic traits of grape plants under the infl uence of natural conditions in their habitats were studied. The autochthonous grape varieties in contrasting weather conditions exhibited individual and varietal specifi city in terms of reaction norm and adaptability. According to the variability of phenotypic traits and adaptive potential, the varieties were ranked in the following descending order: ‘Plechistik’, ‘Krasnostop Zolotovsky’, ‘Varyushkin’, ‘Kumshatsky Belyi’, ‘Sibirkovy’, and ‘Tsimlyansky Chernyi’. The genotypes ‘Plechistik’, ‘Krasnostop Zolotovsky’, ‘Varyushkin’, and ‘Kumshatsky Belyi’ with their high adaptive potential for formation of stable vine plantations are recommended for developing stable grape plantations in the conditions of the Lower Don region.

ELONGATED HYPOCOTYL 5a modulates FLOWERING LOCUS T2 and gibberellin levels to control dormancy and bud break in poplar.

Photoperiod is a crucial environmental cue for phenological responses, including growth cessation and winter dormancy in perennial woody plants. Two regulatory modules within the photoperiod pathway explain bud dormancy induction in poplar (Populus spp.): the circadian oscillator LATE ELONGATED HYPOCOTYL 2 (LHY2) and GIGANTEA-like genes (GIs) both regulate the key target for winter dormancy induction FLOWERING LOCUS T2 (FT2). However, modification of LHY2 and GIs cannot completely prevent growth cessation and bud set under short-day (SD) conditions, indicating that additional regulatory modules are likely involved. We identified PtoHY5a, an orthologs of the photomorphogenesis regulatory factor ELONGATED HYPOCOTYL 5 (HY5) in poplar (Populus tomentosa), that directly activates PtoFT2 expression and represses the circadian oscillation of LHY2, indirectly activating PtoFT2 expression. Thus, PtoHY5a suppresses SD-induced growth cessation and bud set. Accordingly, PtoHY5a knockout facilitates dormancy induction. PtoHY5a also inhibits bud-break in poplar by controlling gibberellic acid (GA) levels in apical buds. Additionally, PtoHY5a regulates the photoperiodic control of seasonal growth downstream of phytochrome PHYB2. Thus, PtoHY5a modulates seasonal growth in poplar by regulating the PtoPHYB2-PtoHY5a-PtoFT2 module to determine the onset of winter dormancy, and by fine-tuning GA levels to control bud-break.

Genetic, Epigenetic, and Environmental Control of Seed Dormancy and Germination.

Seed germination is controlled by a combination of the seed dormancy level and environmental conditions such as light, temperature, moisture, and nitrate levels. Seed dormancy is programed genetically, but it is also sensitive to maternal environmental conditions before and after anthesis. Recent developments in molecular genetics and bioinformatics have greatly enhanced our understanding of the molecular mechanisms of seed dormancy and germination in model plants and economically important crop species. This chapter focuses on temperature as an environmental factor and discusses the genetic and epigenetic mechanisms of dormancy and germination.

Quality Characteristics of Raspberry Fruits from Dormancy Plants and Their Feasibility as Food Ingredients.

The raspberry (Rubus idaeus L.) is a soft red fruit consumed worldwide due to its bitter-sweet taste and phenolics-associated health benefits. During plant dormancy, raspberry fruits are discarded. However, this work hypothesised that these fruits have the chemical quality to be valorised, which would mitigate their waste if adequately stabilised. This can be achieved by drying. The Pacific Deluxe and Versailles varieties were dried by freeze- and convective-drying (30 °C and 40 °C). The freeze-dried fruits preserved their colour, drupelets structure, and phenolic content. Convective-drying promoted a significant fruit darkening, which was more evident at 30 °C due to the longer drying process, and a loss of drupelets structure. Both temperatures promoted a similar decrease in phenolic content, as determined by HPLC, although the ABTS●+ antioxidant activity at 40 °C was lower (IC50 = 9 compared to 13 μg AAE/mg dry weight). To incorporate dried raspberries into muffin formulations, while keeping their red colour, it was necessary to change the raising agent from sodium bicarbonate to baker's yeast. Sensory analysis by a non-trained panel revealed good acceptance, showing that fresh or dried raspberry fruits from dormancy had suitable characteristics for use as food ingredients.

Dynamically Downscaled Projections of Phenological Changes across the Contiguous United States

Abstract Phenological indicators (PI) are used to study changes to animal and plant behavior in response to seasonal cycles, and they can be useful to quantify the potential impacts of climate change on ecosystems. Here, multiple global climate models and emission scenarios are used to drive dynamically downscaled simulations using the WRF Model over the contiguous United States (CONUS). The wintertime dormancy of plants [chilling units (CU)], timing of spring onset [extended spring indices (SI)], and frequency of proceeding false springs are calculated from regional climate simulations covering historical (1995–2005) and future periods (2025–2100). Southern parts of the CONUS show projected CU decreases (inhibiting some plants from flowering or fruiting), while the northern CONUS experiences an increase (possibly causing plants to break dormancy too early, becoming vulnerable to disease or freezing). Spring advancement (earlier SI dates) is projected, with decadal trends ranging from approximately 1–4 days per decade over the CONUS, comparable to or exceeding those found in observational studies. Projected changes in risk of false spring (hard freezes following spring onset) vary across members of the ensemble and regions of the CONUS, but generally western parts of the CONUS are projected to experience increased risk of false springs. These projected changes to PI connote significant effects on cycles of plants, animals, and ecosystems, highlighting the importance of examining temperature changes during transitional seasons. Significance Statement This study examines how phenological indicators, which track the life cycles of plants and animals, could change from 2025 to 2100 as simulated in a regional climate model over the contiguous United States. Chilling units quantify the presence of cooler weather that can benefit plants prior to their growing season. They are projected to decrease in the southern United States, possibly inhibiting agricultural production. Spring onset is projected to occur earlier in the year, advancing by 1–4 days on average over each future decade. Risk of false springs (damaging hard freezes after spring onset) increases in the western United States. Our findings highlight the need to understand effects of climate change during transitional seasons, which can impact agriculture and ecosystems.

Time to budbreak is not enough: cold hardiness evaluation is necessary in dormancy and spring phenology studies.

Dormancy of buds is an important phase in the life cycle of perennial plants growing in environments where unsuitable growth conditions occur seasonally. In regions where low temperature defines these unsuitable conditions, the attainment of cold hardiness is also required for survival. The end of the dormant period culminates in budbreak and flower emergence, or spring phenology, one of the most appreciated and studied phenological events - a time also understood to be most sensitive to low-temperature damage. Despite this, we have a limited physiological and molecular understanding of dormancy, which has negatively affected our ability to model budbreak. This is also true for cold hardiness. Here we highlight the importance of including cold hardiness in dormancy studies that typically only characterize time to budbreak. We show how different temperature treatments may lead to increases in cold hardiness, and by doing so also (potentially inadvertently) increase time to budbreak. We present a theory that describes evaluation of cold hardiness as being key to clarifying physiological changes throughout the dormant period, delineating dormancy statuses, and improving both chill and phenology models. Erroneous interpretations of budbreak datasets are possible by not phenotyping cold hardiness. Changes in cold hardiness were very probably present in previous experiments that studied dormancy, especially when those included below-freezing temperature treatments. Separating the effects between chilling accumulation and cold acclimation in future studies will be essential for increasing our understanding of dormancy and spring phenology in plants.

Towards a Physiological Modeling of Sweet Cherry Blossom

For several years, there has been a need in phenological modeling to better account for physiological processes during the winter dormancy of woody plants, which is here addressed to the sweet cherry cultivar ‘Summit’ (Prunus avium L.). This study compares three sequential phenology models (M1–M3) for the beginning of ‘Summit’ blossom in the experimental sweet cherry orchard in Berlin-Dahlem (Germany) between 2011/12–2019/20 (model development) and 2020/21–2022/23 (model validation). M1 represents an inverse modeling approach where the chilling and forcing requirements of ‘Summit’ were optimized solely from observed flowering data. In contrast, M2 and M3 are more physiologically based as they already incorporate biological knowledge, so that the model parameters were calculated directly within the specified developmental phases. Here, M2 is a two-phase model that considers experimental data for the date of endodormancy release (t1) of nine years (2011/12–2019/20) to calculate the chilling and forcing requirements. Finally, M3 is a newly developed three-phase model that additionally includes the onset of ontogenetic development (t1*) and the abscisic acid (ABA) content of ‘Summit’ flower buds during the ecodormancy phase (t1 − t1*). The results indicate that the inclusion of ABA-related heat weighting during ecodormancy significantly improves the performance of M3 compared to M1 and M2. While M1 gives satisfactory results in terms of fit and validation, it is considered physiologically unacceptable as it greatly overestimates the chilling requirement of ‘Summit’ by ignoring the ecodormancy phase. M2 accumulates too much heat during ecodormancy as it does not include control by the bud ABA content. The results highlight the need for parameters such as t1, t1*, and the bud ABA content for the physiological modeling of ‘Summit’ blossom. To the best of our knowledge, this is the first study to provide a pathway towards a physiologically based modeling approach.

Impact of de-icing salt runoff in spring on bioretention efficiency

Abstract We investigated the effect of de-icing salt in stormwater runoff on bioretention system hydrology and filtration of contaminants. Salt runoffs during the snow melt period were simulated in 20 mesocosms planted with 1 of 3 plant species (Cornus sericea, Juncus effusus and Iris versicolor) or left unplanted, and then watered with semi-synthetic stormwater runoffs supplemented with 4 NaCl concentrations (0, 250, 1,000 or 4,000 mg Cl/L). All bioretention mesocosms, irrespective of treatment, were efficient in reducing water volume, flow and pollution level. There was no phytotoxic effect of NaCl on plants, even at the highest NaCl concentration tested. Water volume reduction and flow rate were influenced by plant species, but salt concentration had no effect. Salt runoffs significantly increased the removal of some metals, such as Cr, Ni, Pb and Zn, but had no effect on nutrient removal. Because snowmelt laden with de-icing salt is of short duration and occurs during plant dormancy, plants in bioretention may be less affected by de-icing salt than previously thought, provided that salinity decreases rapidly to normal levels in the soil water. The long-term effects of de-icing salt and general performance of bioretention should be further studied under full-scale conditions.

Forcing Temperature Effects on Plant Development for Containerized Blackberry Grown Using Long-Cane Techniques

Dormant containerized blackberry plants grown as long canes are forced into protected environments, such as plastic tunnels or greenhouses, to schedule harvesting for important market weeks. The time needed to produce a crop is mainly a function of temperature. In this study, the objectives were to quantify the effects of temperature on plant development rates for long-cane blackberry and develop simple models predicting the time from forcing dormant plants to first open flowers and ripe fruit as a function of average daily temperature (ADT). The crop time and ADT at the first-flower and -fruit stages were measured for the cultivars ‘Loch Ness’, ‘Osage’, ‘Ponca’, and ‘Prime-Ark® 45′ grown as long canes during a greenhouse and high-tunnel experiment, and the days to flowering and fruiting were converted to rates by calculating the reciprocal. Nonlinear models relating flowering and fruiting rates to ADT were developed for each cultivar using a combination of the experimental data and base (6 °C), optimum (25 °C), and maximum (35 °C) temperature parameters derived from a previous blackberry heat unit study. Model accuracy was evaluated by comparing the predicted to observed times to first flower and fruit per cultivar. Average daily temperature was shown to have a main influence on crop timing, as shown by a strongly positive and near 1:1 relationship between predicted and observed days to flowering/fruiting. However, there was significant variability depending on the cultivar and model accuracy within ±7 days, ranging from 50% (‘Prime-Ark® 45) to 90% (‘Loch Ness’) for the flower models and from 60% (‘Prime-Ark® 45) to 100% (‘Loch Ness’) for the fruit models. To the best of our knowledge, this study is the first to characterize the relationship between temperature and crop timing for soilless long-cane blackberry, and it provides a framework for modeling temperature effects on crop timing for these systems. The authors discuss further methods to improve model accuracy and precision for commercial use. These models can also be used for general training purposes to help educate growers on how temperature influences crop scheduling during long-cane blackberry production.