Desiccation-sensitive Seeds Research Articles

Desiccation-induced ROS accumulation and lipid catabolism in recalcitrant Madhuca latifolia seeds.

Loss of viability in desiccation-sensitive seeds of Madhuca latifolia (Roxb.) J. F. Macbr., an important multipurpose tropical tree, was correlated with seed water content (WC). WC declined from 0.59 to 0.19gg-1 fresh mass, 35days after harvest from mother plant, at ambient conditions (temperature 25±2°C, relative humidity 50±2%). The desiccation-induced reduction in viability was related with an accumulation of reactive oxygen species (ROS) that promoted lipid peroxidation associated loss of membrane integrity. Conducted study revealed 1.6-19 folds rise in lipid peroxidized products in desiccated M. latifolia seeds, and was found to be linked inversely with WC and germination percentage. Additionally, increased activities (7 and 13 folds) of lipid hydrolyzing enzymes; lipase (EC 3.1.1.3) and lipoxygenase (EC 1.13.11.12) respectively, were discernible in desiccating M. latifolia seeds. In summary, increased ROS, lipid oxidation, lipase and lipoxygenase were strongly correlated with viability loss in desiccating M. latifolia seeds.

Uncovering the basis of viability loss in desiccation sensitive Trichilia dregeana seeds using differential quantitative protein expression profiling by iTRAQ

Recalcitrant seeds, unlike orthodox types, are desiccation sensitive and hence, cannot be stored using conventional seed storage methods In this study, relative changes of protein expression in T. dregeana seeds during desiccation and hydrated storage (a short- to medium-term storage method) were analysed to understand the basis of their desiccation- and storage-induced viability loss. Isobaric Tags for Relative and Absolute Quantitation (iTRAQ) were used to compare (selected) protein expression levels across fresh, partially dehydrated and stored seeds. A total of 114 proteins were significantly differentially expressed in embryonic axes of fresh seeds and those seeds exposed to dehydration and hydrated storage (which exposed seeds to a mild dehydration stress). Proteins involved in protein synthesis were up-regulated in stored and dehydrated seeds, possibly in response to dehydration-induced repair processes and/or germinative development. A range of proteins related to antioxidant protection were variably up- and down-regulated in stored and dehydrated seeds, respectively. Additionally, a class I heat shock protein was down-regulated in dehydrated and stored seeds; no late embryogenesis abundant proteins were identified in both stored and dehydrated seeds; and storage and dehydration up-regulated proteins involved in the provision of energy for cell survival. The results suggest that dehydration- and storage-induced viability loss in recalcitrant seeds may be based on proteomic changes that lead to cellular redox imbalance and increased cell energy demands. This, together with the absence/down-regulation of proteins associated with desiccation tolerance in plant tissues may form part of the proteomic footprint for desiccation sensitivity in seeds.

A comparison of partial dehydration and hydrated storage-induced changes in viability, reactive oxygen species production, and glutathione metabolism in two contrasting recalcitrant-seeded species

This study compared the responses of Avicennia marina and Trichilia dregeana seeds, both of which are recalcitrant, to partial dehydration and storage. Seeds of A. marina exhibited a faster rate of water and viability loss (± 50% viability loss in 4 days) during partial dehydration, compared with T. dregeana (± 50% viability loss in 14 days). In A. marina embryonic axes, reactive oxygen species (ROS) production peaked on 4 days of dehydration and was accompanied by an increase in the GSH:GSSG ratio; it appears that the glutathione system alone could not overcome dehydration-induced oxidative stress in this species. In A. marina, ROS and axis water content levels increased during hydrated storage and were accompanied by a decline in the GSH:GSSG ratio and rapid viability loss. In T. dregeana embryonic axes, ROS production (particularly hydrogen peroxide) initially increased and thereafter decreased during both partial dehydration and hydrated storage. Unlike in A. marina embryonic axes, this reduced ROS production was accompanied by a decline in the GSH:GSSG ratio. While T. dregeana seeds may have incurred some oxidative stress during storage, a delay in and/or suppression of the ROS-based trigger for germination may account for their significantly longer storage longevity compared with A. marina. Mechanisms of desiccation-induced seed viability loss may differ across recalcitrant-seeded species based on the rate and extent to which they lose water during partial drying and storage. While recalcitrant seed desiccation sensitivity and, by implication, storage longevity are modulated by redox metabolism, the specific ROS and antioxidants that contribute to this control may differ across species.

Tree seed traits' response to monsoon climate and altitude in Indian subcontinent with particular reference to the Himalayas.

Seed traits are related to several ecological attributes of a plant species, including its distribution. While the storage physiology of desiccation‐sensitive seeds has drawn considerable attention, their ecology has remained sidelined, particularly how the strong seasonality of precipitation in monsoonal climate affects their temporal and spatial distribution. We compiled data on seed mass, seed desiccation behavior, seed shedding, and germination periodicity in relation to monsoon and altitude for 198 native tree species of Indian Himalayas and adjoining plains to find out (1) the adaptive significance of seed mass and seed desiccation behavior in relation to monsoon and (2) the pattern of change in seed mass in relation to altitude, habitat moisture, and succession. The tree species fall into three categories with respect to seed shedding and germination periodicities: (1) species in which both seed shedding and germination are synchronized with monsoon, referred to as monsoon‐synchronized (MS, 46 species); (2) species in which seed germination is synchronized with monsoon, but seeds are shed several months before monsoon, referred to as partially monsoon‐synchronized (PMS, 112 species); and (3) species in which both shedding and germination occur outside of monsoon months, referred to as monsoon‐desynchronized (MD, 39 species). The seed mass of MS species (1,718 mg/seed) was greater than that of PMS (627 mg/seed) and MD (1,144 mg/seed). Of the 40 species with desiccation‐sensitive seeds, 45% belong to the MS category, almost similar (approx. 47%) to woody plants with desiccation‐sensitive seeds in evergreen rain forests. Seed mass differed significantly as per seed desiccation behavior and successional stage. No relationship of seed mass was found with altitude alone and on the basis of seed desiccation behavior. However, seed mass trend along the altitude differed among monsoon synchronization strategies. Based on our findings, we conclude that in the predicted climate change (warming and uncertain precipitation pattern) scenario, a delay or prolonged break‐spell of monsoon may adversely affect the regeneration ecology of desiccation‐sensitive seed‐bearing species dominant over large forest areas of monsoonal climate.

Predicting the global incidence of seed desiccation sensitivity

Summary The ability of seeds to tolerate desiccation plays an important role in plant regeneration ecology. Globally, the majority of species produce desiccation‐tolerant (orthodox) seeds, while comparatively few produce desiccation‐sensitive (recalcitrant) seeds that are unable to survive dehydration. The trait has important implications for species conservation, as desiccation‐sensitive species cannot be conserved using traditional seed banking techniques. In addition, these species may be less resilient to the increases in droughts predicted for some regions under climate change scenarios. The best available resource on seed desiccation tolerance is the Royal Botanic Gardens, Kew's Seed Information Database. This database contains seed desiccation‐sensitivity data for over 18 000 taxa, approximately 3% of which have desiccation‐sensitive seeds. However, this database is likely biased towards desiccation‐tolerant species. Previous attempts to estimate the proportion of seed plants with desiccation‐sensitive seeds have ranged from 7% to 50%. Here, we aimed to overcome sampling bias to derive a best estimate for the proportion of seed plants with desiccation‐sensitive seeds, based on current data. We used a recently developed method, based on taxonomic relatedness, to account for sampling bias and estimate the proportion of seed plants with desiccation‐sensitive seeds. As a comparison, given that seed desiccation sensitivity is strongly related to habitat, we repeated our analyses using habitat as a basis. The predictions from our taxonomy‐based models ranged between estimates of 7·5% and 19·6% of the world's seed‐plant species with desiccation‐sensitive seeds, depending on model type, while the habitat‐based models suggested a value of approximately 8%. Our evidence suggests that, based on current data, the best estimate of the proportion of species with desiccation‐sensitive seeds is likely to be approximately 8%. Tropical and subtropical moist broadleaf forests had the highest incidence of seed desiccation sensitivity, where an estimated 18·5% of the seed‐plant flora possessed the trait. Synthesis. Alongside our estimation of the numbers of species with desiccation‐sensitive seeds, we provide data on taxa and habitats where this trait may be most prevalent. These findings can be used to support conservation planning, particularly with respect to providing decision support for in and ex situ conservation techniques.

Osmotic and heat treatments on control of fungi associated with seeds of Eugenia brasiliensis and E. pyriformis (Myrtaceae)

Abstract: Desiccation sensitive seeds, such as those of Eugenia brasiliensis Lam. (grumixama) and E. pyriformis Cambess. (uvaia), also known as recalcitrant, need to be stored with high water content and temperatures above 0 °C. Such conditions keep these seeds with high metabolism, thus reducing their longevity, and allowing the development of microorganisms, especially fungi, accelerating their deterioration speed. Heat and osmotic treatments have shown some success for the control of some fungi associated with these seeds. However, to better measure the effectiveness of these treatments, the evaluation criteria needs to be refined, taking into account not only their incidence but also their intensity. Thus, in the present study, the percentage of seeds infected by the fungi (incidence) as well as the degree of infection on the seed surface (severity) of E. brasiliensis and E. pyriformis were evaluated after applying heat and osmotic treatments which controlled most fungi found in these seeds, except for Fusarium sp. and Penicillium sp. The evaluation of the severity showed that the effect of the treatments is not only quantitative, reducing the number of infected seeds; there was also a change in the development of the fungi, often reducing the severity of the infection, thus enabling the detection of differences between treatments that were not easily recognized when only using the incidence evaluation.

Fast-growing seeds and delayed rodent predatory activity in the seeding season: A combined mechanism to escape and survive rodent predation in Quercus ilex subsp. ballota L. acorns and seedlings

Holm-oak is a sclerophyllous Mediterranean species that presents relatively fast growing, non-dormant, desiccation-sensitive seeds. We investigated the importance of this trait for decreasing acorn predation risk and increasing seedling predation tolerance in combination with delaying the maximal predatory activity of rodents within the seeding season. The study was conducted in a Mediterranean savannah-like forest ecosystem. Temporal changes in acorn availability and predation by mice were studied during the acorn fall period. In a second experiment, propagules at different stages of development (acorns, rooted but un-emerged seedlings and emerged seedlings of different heights) were exposed to rodent predation at the end of the seeding season (end of winter). The results indicated that temporal changes in acorn availability (19–0.05acornsm−2) and predation rate (0–0.11acornsday−1) were negatively correlated; the lowest predation rate occurred when the food resource was at its highest (peak acorn fall). The developmental stage reached by propagules at the end of the seeding season significantly affected their ability to escape predation: 52–16% of emerged seedlings escaped predation by mice, but only 6% of rooted, un-emerged seedlings and 2% of acorns did so. Rodent predation of seedlings mostly consisted of cotyledon consumption and its effect on seedling survival was also significantly affected by developmental stage: 70% of emerged seedlings survived predation while only 17% of rooted, un-emerged seedling did so. The acorns did not survive at all. The results reinforce the ecological significance of non-dormancy and the associated rapid seed germination and seedling development facing early recruitment in holm-oak. We suggest that, in environments subject to high rodent predatory activity, early sowing of acorns during the seeding season should be considered in order to maximize the success of forest restoration.

English

Knowledge of the desiccation sensitivity of Alibertia edulis seeds is essential to provide adequate conditions for maintaining viability during storage. Thus, the objective of this study was to evaluate the effect of variations in the water content, environmental conditions, and storage periods on the conservation of A. edulis seeds. After processing, the seeds were dried under ambient conditions to water contents of 20, 15, 10 and 5±2%, and then subjected to storage under laboratory (25°C), cold chamber (16°C), refrigerator (8°C), and freezer (-18°C) conditions for zero, 30, 60, 90, 120, 150 and 180 days. To assess the physiological potential of the seeds, protrusion of the primary root, percentage of normal seedlings, germination speed index, total seedling length and total dry mass of seedlings were performed. A completely randomized factorial split-plot design (4 water contents × 4 temperature × 7 storage periods) was used for the experiment. A. edulis seeds tolerated water content reduction to 5% and storage under room temperature and cold chamber storage conditions for 150 days. Seeds with water content between 10 and 5% did not tolerate more than 60 days of freezing conditions, confirming their physiological behavior as intermediate. Key words: Brazilian savanna, conservation, drying, Rubiaceae.

Morphophysiological epicotyl dormancy in seeds of threePsychotriaspecies from Sri Lanka: first record for Rubiaceae

AbstractTo increase our knowledge of the diversity of seed dormancy and germination in Rubiaceae, we investigated seed desiccation sensitivity and germination of threePsychotriaspecies. Seeds ofP. gardneri, P. nigraandP. zeylanicagerminated to high percentages at <15% seed moisture content. Intact seeds ofP. zeylanicaandP. nigraimbibed water and thus do not have physical dormancy. More than 50% of the seeds ofP. zeylanica, P. nigraandP. gardneritook 33, 53 and 110 d, respectively, at 25°C for the radicle to emerge, and embryo growth occurred before and after radicle emergence. Thus, seeds have morphophysiological dormancy. Shoot emergence ofP. nigraandP. zeylanicaseeds was delayed 50 and 80 d after radical emergence, respectively; thus, seeds have epicotyl morphophysiological dormancy (eMPD). This is the first report of eMPD in Rubiaceae. Since warm stratification promoted both radicle and shoot emergence in seeds ofP. zeylanicaandP. nigra, the level of eMPD is non-deep simple. Hence, dormancy of the studiedPsychotriaspp. can be described as C1bBb(radicle)–C1bBb(epicotyl), i.e. the embryo is underdeveloped and grows prior to radicle emergence and epicotyl emergence under warm temperatures (Bb), and both the radicle and epicotyl have non-deep simple physiological dormancy broken by warm temperatures (C1b). In twoPsychotriaspecies studied in detail, radicle emergence occurs at the beginning of the rainy season and plumule emergence at the peak rainy season when conditions are most favourable for rapid seedling development.

Extensive Desiccation and Aging Stress Tolerance Characterize Gaillardia pulchella (Asteraceae) Seeds

We investigated the response of Gaillardia pulchella seeds to desiccation and aging stress to gain some perspective on the germplasm storage potential and seed vigor of this species. Seed–water relations of mature, freshly harvested G. pulchella seeds were characteristic of desiccation-tolerant species. For example, initial seed water potential (−53 MPa) was well below the lethal water potential limit (−15 MPa) for desiccation-sensitive seeds. Desiccation tolerance was confirmed by high (>70%), rapid (t50 range 4–7 days), and uniform germination following equilibration drying. Likewise, post–saturated salt accelerated aging (SSAA) germination tests indicated a high degree of vigor of fresh seeds. The substantial level of desiccation and aging-related stress tolerance in G. pulchella seeds suggests that these organs potentially display orthodox storage physiology and an ability to endure variable seed bed conditions.

Successful translocation of the threatened New Zealand root-holoparasite Dactylanthus taylorii (Mystropetalaceae)

The conservation and translocation of threatened holoparasitic flowering plants provide added challenges due to their complete host dependency and often large knowledge gaps of their autecology. Here, we present the first successful, quantified field trial to establish from seed populations of dactylanthus (Dactylanthus taylorii, Mystropetalaceae), a threatened New Zealand endemic root-holoparasitic angiosperm. Establishment was monitored at four sites at Waipapa, Pureora Forest Park. The impact of two different sowing methods (broad- and central-sown), canopy state (as a proxy for soil moisture levels) and three dominant host species were tested. Establishment of dactylanthus was confirmed in 22 out of 24 plots 10 years after sowing, with earliest emergence after 4 years. Average and maximum inflorescence numbers per plot were similar to those of protected wild populations. The only open-canopy site performed worse in comparison with a closed-canopy site sharing the same dominant host species; differences in root availability and survival of the desiccation-sensitive seeds were regarded as the most likely explanations. Host species dominance had a significant impact on inflorescence numbers, indicating host preference in the species despite a wide host range. In contrast to longer-established wild populations, most of which are male-biased, female inflorescences strongly outnumbered males, considered as evidence of environmental sex determination and sex-switching of individuals. Findings from this study have increased our knowledge of the biology of dactylanthus, confirmed translocation as an effective tool in the conservation of the species and should be applicable for the protection of threatened parasitic plants species elsewhere in the world.

Explanatory ecological factors for the persistence of desiccation-sensitive seeds in transient soil seed banks:Quercus ilexas a case study

Dominant tree species in northern temperate forests, for example oak and beech, produce desiccation-sensitive seeds. Despite the potentially major influence of this functional trait on the regeneration and distribution of species under climate change, little is currently known about the ecological determinants of the persistence of desiccation-sensitive seeds in transient soil seed banks. Knowing which key climatic and microsite factors favour seed survival will help define the regeneration niche for species whose seeds display extreme sensitivity to environmental stress Using the Mediterranean Holm oak (Quercus ilex) forest as a model system, an in situ time-course monitoring of seed water status and viability was performed during the unfavourable winter season in two years with contrasting rainfall, at an instrumented site with detailed climate records. In parallel, the characteristics of the microhabitat and their influence on the post-winter water status and viability of seeds were investigated in a regional survey of 33 woodlands representative of the French distribution of the species. Time-course monitoring of seed water status in natural conditions confirmed that in situ desiccation is the main abiotic cause of mortality in winter. Critical water contents could be reached in a few days during drought spells. Seed dehydration rates were satisfactorily estimated using integrative climate proxies including vapour pressure deficit and potential evapotranspiration. Seed water status was therefore determined by the balance between water uptake after a rainfall event and water loss during dry periods. Structural equation modelling of microhabitat factors highlighted the major influence of canopy openness and resulting incident radiation on the ground. This study provides part of the knowledge required to implement species distribution models which incorporate their regeneration niche. It is an important step forward in evaluating the ecological consequences of increasing winter drought and environmental filtering due to climate change on the regeneration of the most dominant Mediterranean tree species.

Understanding Poor Storage Potential of Recalcitrant Seeds

Trees producing recalcitrant seeds are dominant among Asian (89%) and neo-tropical species (44%), but are rare among African tree species (9%). Among the families, Dipterocarpaceae is the most populous with 98% of recalcitrant species, followed by Meliaceae (17%), Moraceae (14%), Malvaceae (8%), Rubiaceae (7%) and Bignoniaceae (3%). Since desiccationsensitive recalcitrant seeds are shed from the tree after maturation, with high moisture content, high metabolic activity and poor storage potential, it leads to significant challenge for ex situ conservation through seed-gene bank. A general understanding of the mechanisms underlying the poor viability potential of recalcitrant seeds is important to redefine our research programmes on these desiccation-intolerant seeds. There are three general categories of damage that may take place in recalcitrant seeds, eventually causing loss of viability: (i) mechanical damage, (ii) metabolism-induced damage, and (iii) macromolecular denaturation. This article discusses the occurrence of these three categories of damage, in the light of the various biochemical and structural changes reported in the different recalcitrant seeds, relative to (i) storage temperature, (ii) seed moisture content and (iii) rate of seed drying. Among these factors, maintenance of appropriate storage temperature is viewed as the most appropriate way to contain all the three types of damage. Storage of seeds in lowest suitable temperature is known to restrain the rate of moisture loss from seeds, thereby reducing mechanical damage and macromolecular denaturation; further, it can also minimize aberrant metabolism, eventually reducing metabolism- induced damage. Thus, the most practical way to extend the storage life of intact recalcitrant seeds is by storing them at lower temperatures, wherein the above damages can be reduced and at the same time chilling or freezing injury may not occur. Nevertheless, the 'lowest temperature' which is most suitable for seeds of a particular recalcitrant species should be standardized through dedicated research.

Methodology of the tetrazolium test for assessing the viability of seeds of Eugenia brasiliensis Lam., Eugenia uniflora L. and Eugenia pyriformis Cambess

Eugenia brasiliensis Lam. ("grumixameira"), Eugenia uniflora L. ("pitangueira") and Eugenia pyriformis Cambess. ("uvaieira") are forest and fruit species of pharmacological and gastronomic potential and have desiccation-sensitive seeds. The development of quick viability tests for the assessment of physiological quality of these seeds is needed. The tetrazolium test is an important method providing fast assessment of the seed physiological quality. Thus, this work aimed to develop a method for the tetrazolium test for determining viability of "grumixameira," "pitangueira" and "uvaieira" seeds. Initially the seeds of these species were soaked in water for 3 h at 25 ºC. Three concentrations of tetrazolium solutions were analyzed (0.100 %, 0.125 % and 0.250 %) for seed staining using three incubation periods (2, 3 and 6 h) at 35 ºC in the dark. After staining, seed viability was determined. Then, the seeds were subjected to different levels of controlled drying and were analyzed for their physiological quality by germination and electrical conductivity tests. The tetrazolium test is a suitable tool for determining viability after staining the seeds at 35 ºC using a 0.250 % concentration solution for 3 hours for "grumixameira" seeds, 0.125 % for 3 hours for "pitangueira" seeds and 0.100 % for 2 hours for "uvaieira" seeds.

Seed storage behaviour of 101 woody species from the tropical rainforest of southern China: a test of the seed-coat ratio–seed mass (SCR–SM) model for determination of desiccation sensitivity

The Xishuangbanna tropical rainforest in Yunnan Province is the greatest biodiversity hotspot in China. However, the biodiversity of this region is under threat, making seed conservation through seed and/or germplasm banking particularly urgent and crucial. Seed desiccation sensitivity limits the possibility of seed banking of 47% of tropical rainforest species. Thus, knowing if a species has desiccation-sensitive seeds is an important first step in seed banking; however, often resources are limited, making it difficult to determine storage behaviour for all the species in a region. Prediction of seed sensitivity using the SCR–SM model based on seed-coat ratio (SCR) and seed dry mass (SM) might be an alternative for determining desiccation sensitivity of seeds of each species. Here, seed-desiccation sensitivity of 101 woody species from the Xishuangbanna tropical forest were analysed using this model, and physiological determinations were made for a total of 25 species. Seed storage behaviour for 59 species was used for model validation, and storage behaviour of 88% of these species was successfully predicted. Seed storage behaviour of 83% of the 59 species was successfully predicted using the 1000-seed weigth–moisture content (TSW–MC) criteria, which include seeds with 1000-seed weight >500 g and seed moisture content at shedding of 30 –70%. The two predictive methods were subsequently used to predict seed desiccation sensitivity for another 42 species from Xishuangbanna whose storage behaviour was uncertain. Our results indicated that ~50% of the species in Xishuangbanna are likely to have desiccation-sensitive seeds.

The Role - Activity and/or Processing - Of (Re) Active Oxygen Species in Desiccation Sensitivity and/or Tolerance, Development, Dormancy and/or Germination in Seeds

The contents of cells may comprise and/or consist of up to 80% water. Removal of cellular water may be accompanied by and/or associated with disruptions and/or disturbances of normal cellular events and/or organization. Desiccation tolerance has evolved adaptations - mechanisms and/or processes - to deal with the situation. Dehydration, germination and ageing may lead to the generation and/or production of free radicals. (Re)active oxygen species may result in cellular damage and/or death. Antioxidants detoxify and/or process free radicals. Active oxygen species may also be involved and/or participate in an integrated intracellular signaling network. This paper attempts an overview and/or review of free radical processes – activity and/or processing - in seed desiccation sensitivity and/or tolerance in the context and/or light of the latter.

Physiology of Desiccation-Sensitive (Recalcitrant) Seeds and the Implications for Cryopreservation

Desiccation-tolerant (orthodox) seeds can survive in the dry state for considerable periods and so can be stored successfully at low water content and subzero temperatures. Orthodox seeds possess a variety of protective processes and mechanisms that confer desiccation tolerance, important among them being metabolic shutdown and intracellular dedifferentiation. In contrast, desiccation-sensitive (recalcitrant) seeds cannot tolerate water loss and so cannot be stored using conventional seed bank conditions. Particularly with respect to storage, recalcitrant seeds do not undergo intracellular dedifferentiation nor any significant metabolic shutdown. Embryos of recalcitrant seeds remain metabolically active, with little or no reduction in extent of the extensive intracellular membranes. At the water content at which they are shed, with the ongoing metabolism in recalcitrant seeds, developmental phenomena grade imperceptibly into those associated with germination. Thus, recalcitrant seeds can be stored intact ...

SEED FEATURES OF IMPORTANT TIMBER SPECIES FROM THE FLOODPLAIN VÁRZEA FOREST: IMPLICATIONS FOR EX SITU CONSERVATION PROGRAMS IN THE AMAZON

As an integral part of plant regeneration ecology, the ability of seeds to survive desiccation is an important functional feature. For the purpose of conservation, studies have investigated the responses of stored seeds to the desiccation process. In order to enhance the knowledge on seeds ecology of Amazonian floodplain trees, eight common tree species of the varzea floodplain forest with high economic value, were selected and their seeds classified according to their attributes. The selected species represent 80% of the number and total volume of the timber species selectively extracted from Mamiraua Sustainable Development Reserve, Central Amazon. Smaller seeds with lower water content ( Calycophyllum spruceanum (Benth.) Hook. f ex K. Schum., Hura crepitans L. and Piranhea trifoliata Baill.), which remained viable and germinated after desiccation and storage, were classified as tolerant to desiccation. The species Guarea guidonia (L.) Sleumer., Laetia corymbulosa Spruce ex Benth., Ocotea cymbarum Kunth., Tabebuia barbata (E. Mey.) Sandwith, and Sterculia apetala (Jacq.) H. Karst., were classified as sensitive to desiccation because their seeds did not germinate in the same treatment and thus cannot be effectively stored. The average dry mass was ten times higher in desiccation-sensitive seeds (82.22 g) than in desiccation-tolerant (8.58 g) seeds. The study suggests that if there are mechanisms to protect floodplain seeds, these would be more efficient as a form of conferring greater tolerance to flooding. Therefore, methods of storage in moist conditions should be investigated to desiccation-sensitive seeds.

LEA polypeptide profiling of recalcitrant and orthodox legume seeds reveals ABI3-regulated LEA protein abundance linked to desiccation tolerance

In contrast to orthodox seeds that acquire desiccation tolerance during maturation, recalcitrant seeds are unable to survive drying. These desiccation-sensitive seeds constitute an interesting model for comparative analysis with phylogenetically close species that are desiccation tolerant. Considering the importance of LEA (late embryogenesis abundant) proteins as protective molecules both in drought and in desiccation tolerance, the heat-stable proteome was characterized in cotyledons of the legume Castanospermum australe and it was compared with that of the orthodox model legume Medicago truncatula. RNA sequencing identified transcripts of 16 homologues out of 17 LEA genes for which polypeptides are detected in M. truncatula seeds. It is shown that for 12 LEA genes, polypeptides were either absent or strongly reduced in C. australe cotyledons compared with M. truncatula seeds. Instead, osmotically responsive, non-seed-specific dehydrins accumulated to high levels in the recalcitrant cotyledons compared with orthodox seeds. Next, M. truncatula mutants of the ABSCISIC ACID INSENSITIVE3 (ABI3) gene were characterized. Mature Mtabi3 seeds were found to be desiccation sensitive when dried below a critical water content of 0.4g H2O g DW–1. Characterization of the LEA proteome of the Mtabi3 seeds revealed a subset of LEA proteins with severely reduced abundance that were also found to be reduced or absent in C. australe cotyledons. Transcripts of these genes were indeed shown to be ABI3 responsive. The results highlight those LEA proteins that are critical to desiccation tolerance and suggest that comparable regulatory pathways responsible for their accumulation are missing in both desiccation-sensitive genotypes, revealing new insights into the mechanistic basis of the recalcitrant trait in seeds.

Desiccation sensitivity and successful cryopreservation of oil seeds of European hazelnut (Corylus avellana)

AbstractThe sensitivity of a Polish provenance of dormant Corylus avellana seeds to extreme desiccation and cryopreservation in liquid nitrogen (LN, −196°C) was investigated. No sensitivity to desiccation was observed as seeds readily germinated and exhibited seedling emergence, even when the critical water content (WC) of seeds (nuts devoid of pericarp) was reduced to 0.027 g H2O/g dry mass, g g−1 by drying. Results of germination and seedling emergence tests indicated that seeds tolerated cooling in LN when desiccated to a WC in the range of 0.05–0.10 and 0.08–0.10 g g−1, respectively. The results of this study demonstrate the feasibility of long‐term cryopreservation of European hazelnut seeds. As the seeds of this species have been classified in several different categories (orthodox, suborthodox and recalcitrant), based on their response to desiccation and low temperature, the assignment of the seeds of hazelnut to a specific category is provided and discussed.