A role for fruit structure in seed survival and germination of Swartzia langsdorffii Raddi beyond dispersal

• Diaspore structure has been hypothesised to play a role in seed viability and/or germination of recalcitrant seeds, especially for Swartzia langsdorffii. Thus, this work aims to (i) investigate the in situ contribution of pericarp and aril on seed viability and germination, and (ii) identify morphoanatomical traits of S. langsdorffii diaspores that allow its desiccation‐sensitive seeds to remain viable.
• The role of the pericarp and aril in seed survival and germination was investigated by placing the whole fruit, whole seeds (arillate seed) and bare seeds (without aril) in soil in the forest understorey, assessing germination, emergence, dead, firm and predated seeds, and water content of pericarps, arils and seeds. Correlation analysis was performed between environmental variables and physiological parameters. Histochemical features of diaspores were also investigated.
• Pericarp water content fell after several months, while the aril maintained its water content. Seeds did not lose water even without the presence of the pericarp and aril. However, presence of the pericarp promoted seed water content, viability and germination long after dispersal. The embryo had a thickened outer periclinal cell wall.
• Pericarp and aril are not essential to prevent water loss in seeds, but do help to retain seed moisture, favouring viability maintenance and promoting germination during the rainy season. Morphoanatomical features of seeds are suggested as main factors that reduce water loss. Survival of these desiccation‐sensitive seeds upon dispersal during the dry season appears to be facilitated by multiple diaspore features that prevent viability loss.

     

Seed traits and germination behaviour of four Sardinian populations of Helichrysum microphyllum subsp. tyrrhenicum (Asteraceae) along an altitudinal gradient

• Helichrysum microphyllum subsp. tyrrhenicum (Asteraceae) is an endemic taxon of Sardinia and Corsica, where it grows at different altitudes. The objective of this study was to investigate the seed traits and germination behaviour of four Sardinian populations of this taxon located at different altitudes.
• Seed traits were evaluated, and germination tests were carried out by incubating seeds at a range of constant (5–30 °C) and alternating (25/10 °C) temperatures. The dry after‐ripening (DAR) pre‐treatment was also applied by storing seed in dry conditions for 3 months at 25 °C. Seed traits and germination behaviour data were statistically analysed to identify if there was a correlation with altitude.
• Differences in seed size, area and mass among populations were recorded, however, no relationship was found with altitude. High germination percentages were obtained in all populations, both in untreated and DAR seeds, and were positively affected by alternating temperatures. The final germination percentage and time required to reach 50% final germination (T₅₀) showed no relationship with altitude.
• The differences in seed traits and germination detected among the studied populations of H. microphyllum subsp. tyrrhenicum were not correlated with altitude. This study provides new and important knowledge for this taxon. H. microphyllum subsp. tyrrhenicum is characterised by high germination percentages and low T₅₀ values and does not seem to require any dormancy‐breaking treatment. This species represents a high‐potential native plant species that should be considered within environmental management plans.

     

Seed ecology of the geophyte Conopodium majus (Apiaceae), indicator species of ancient woodland understories and oligotrophic meadows

• Conopodium majus is a geophyte with pseudomonocotyly, distributed in Atlantic Europe. It is an indicator of two declining European habitats: ancient woodland understories and oligotrophic hay meadows. Attempts to reintroduce it by seed have been hindered by scarce seedling emergence and limited knowledge of its seed biology.
• Micro‐CT scanning was used to assess pseudomonocotyly. Embryo growth and germination were studied in the laboratory and the field, using dissection and image analysis. The effects of temperature, light, nitrate and GA₃ on germination were tested. Seed desiccation tolerance was investigated by storage at different RHs and by drying seeds at different stages of embryo growth.
• Seeds possess morphological but not physiological dormancy. Embryo growth and germination were promoted by temperatures between 0 and 5 °C, arrested above 10 °C, and indifferent to alternating temperatures, light, nitrate and GA₃. Pseudomonocotyly appears to result from cotyledon fusion. While seeds tolerated drying to 15% RH and storage for 1 year at 20 °C, viability was lost when storage was at 60% RH. Seeds imbibed at 5 °C for 84 days had significant internal embryo growth but were still able to tolerate drying to 15% RH.
• Reproduction by seed in C. majus follows a strategy shared by geophytes adapted to deciduous temperate forests. The evolution of fused cotyledons may enable the radicle and the hypocotyl to reach deeper into the soil where a tuber can develop. The embryo is capable of growth within the seed at low temperatures so that germination is timed for early spring.

     

An Intermediate Category of Seed Storage Behaviour?: I. COFFEE

Seeds of four cultivars of arabica coffee (Coffea arabica L.)were tested for germination following hermetic storage for upto 12 months at several different combinations of temperaturesbetween –20 °C and 15 °C and moisture contentsbetween 5% and 10% (wet basis). Most of the seeds from one cultivarwithstood desiccation to between 5% and 6% moisture content,a seed water potential of approximately –250 MPa, butthose of the remaining three cultivars were much more sensitiveto desiccation damage. Moreover, in all four cultivars, seedlongevity at cool and sub-zero temperatures, and at low moisturecontents did not conform with orthodox seed storage behaviour:viability was lost more rapidly under these conditions thanat either warmer temperatures or higher moisture contents. Theresults confirm that coffee seeds fail to satisfy the definitionsof either typical orthodox or recalcitrant seed storage behaviour.These results, therefore, point to the possibility of a thirdcategory of storage behaviour intermediate between those oforthodox and recalcitrant seeds. One of the main features ofthis category is that dry seeds are injured by low temperatures. Key words: coffee, Coffea arabica L., seed storage, seed longevity, desiccation, temperature     

Evidence for physiological seed dormancy cycling in the woody shrub Asterolasia buxifolia and its ecological significance in fire‐prone systems

• Dormancy cycling is a key mechanism that contributes to the maintenance of long‐term persistent soil seed banks, but has not been recorded in long‐lived woody shrub species from fire‐prone environments. Such species rely on seed banks and dormancy break as important processes for post‐fire recruitment and recovery.
• We used germination experiments with smoke treatments on fresh seeds and those buried for 1 year (retrieved in spring) and 1.5 years (retrieved the following late autumn) to investigate whether Asterolasia buxifolia, a shrub from fire‐prone south‐eastern Australia with physiologically dormant seeds, exhibited dormancy cycling.
• All seeds had an obligation for winter seasonal temperatures and smoke to promote germination, even after ageing in the soil. A high proportion of germination was recorded from fresh seeds. but germination after the first retrieval was significantly lower, despite high seed viability. After the second retrieval, germination returned to the initial level. This indicates a pattern of annual dormancy cycling; one of the few observations, to our knowledge, for a perennial species. Additionally, A. buxifolia’s winter temperature and smoke requirements did not change over time, highlighting the potential for seeds to remain conditionally dormant (i.e. restricted to a narrow range of germination conditions) for long periods.
• For physiologically dormant species, such as A. buxifolia, we conclude that dormancy cycling is an important driver of successful regeneration, allowing seed bank persistence, sometimes for decades, during fire‐free periods unsuitable for successful recruitment, while ensuring that a large proportion of seeds are available for recruitment when a fire occurs.

     

Hydrothermal thresholds for seed germination in winter annual forbs from old‐field Mediterranean landscapes

• Under Mediterranean climates with dry‐hot summers and cool‐wet winters, many forbs with potential for habitat restoration are winter annuals, but there is little information about their germination.
• We performed laboratory germination experiments on 13 ruderal dicots native to Andalusia (southern Spain). We measured the germination of recently harvested seeds from natural populations across nine temperature treatments (from 5 to 35 °C, constant and alternate); two storage periods; and eight water stress treatments (from 0 to ?1.0 MPa). We then calculated the hydrothermal thresholds for seed germination.
• Final germination ranged from 0–100% and results were mixed in response to temperature. Base temperature was below 6 °C, optimal temperature was around 14 °C and the ceiling temperature around 23 °C. For five species, 10 months of storage improved total germination, indicating a dormancy‐breaking effect, but the other species did not respond or had their germination reduced. All species were relatively tolerant to water stress, with base water potential ranging from ?0.8 to ?1.8 MPa.
• Our results suggest that hydrothermal germination thresholds, rather than physiological dormancy, are the main drivers of germination phenology in annual forbs from Mediterranean semi‐dry environments. The variation in germination responses of these forb species differs from winter annual grasses, but their seeds are all suitable for being stored before restoration.

     

Linking seed germination and plant height: a case study of a wetland community on the eastern Tibet Plateau

• Seed germination is the earliest trait expressed in a plant's life history, and it can directly affect the expression of post‐germination traits. Plant height is central to plant ecological strategies, because it is a major determinant of the ability of a species to compete for light. Thus, linking seed germination and plant height at the community level is very important to understanding plant fitness and community structure.
• Here, we tested storage condition and temperature requirements for germination of 31 species from a wetland plant community on the eastern Tibet Plateau and analysed correlation of germination traits with plant height in relation to storage condition.
• Germination percentage was positively related to plant height, and this relationship disappeared when seeds were incubated at a low temperature (i.e. 5 °C) or after they were stored under wet‐cold conditions. The response of seeds to dry+wet–cold storage was negatively related to plant height. Based on the scores of each species on the first two principal components derived from PCA, species were classified into two categories by hierarchical clustering, and there was a significant difference between germination and plant height of species in these two categories.
• These results suggest that the requirements for seed germination together with seasonal change in environmental conditions determine the window for germination and, in turn, plant growth season and resource utilisation and ultimately plant height.

     

Seed viability and fatty acid profiles of five orchid species before and after ageing

• Changes in seed lipid composition during ageing are associated with seed viability loss in many plant species. However, due to their small seed size, this has not been previously explored in orchids. We characterized and compared the seed viability and fatty acid profiles of five orchid species before and after ageing: one tropical epiphytic orchid from Indonesia (Dendrobium strebloceras), and four temperate species from New Zealand, D. cunninghamii (epiphytic), and Gastrodia cunninghamii, Pterostylis banksii and Thelymitra nervosa (terrestrial).
• Seeds were aged under controlled laboratory conditions (3-month storage at 60% RH and 20 °C). Seed viability was tested before and after ageing using tetrazolium chloride staining. Fatty acid methyl esters from fresh and aged seeds were extracted through trans-esterification, and then analysed using gas chromatography–mass spectrometry.
• All species had high initial viability (>80%) and experienced significant viability loss after ageing. The saturated, polyunsaturated, monounsaturated and total fatty acid content decreased with ageing in all species, but this reduction was only significant for D. strebloceras, D. cunninghamii and G. cunninghamii.
• Our results suggest that fatty acid degradation is a typical response to ageing in orchids, albeit with species variation in magnitude, but the link between fatty acid degradation and viability was not elucidated. Pterostylis banksii exemplified this variation; it showed marked viability loss despite not having a significant reduction in its fatty acid content after ageing. More research is required to identify the effect of ageing on fatty acid composition in orchids, and its contribution to seed viability loss.

     

Biotypes of the seed beetle Callosobruchus maculatus have differing effects on the germination and growth of their legume hosts

• 1 Populations of the seed beetle Callosobruchus maculatus (F.) exhibit considerable differences in body size and larval behaviour. We examined whether such variation modifies the relationship between beetle infestation and host plant performance.
• 2 Larvae from African and Asian biotypes were reared in seeds of four hosts that represented an almost four‐fold variation in seed mass. We estimated mass lost to larval consumption, and compared germination rates and seedling growth between infested and control seeds.
• 3 In seeds bearing a single larva, the larger‐bodied, contest‐competing larvae of the Asian biotype caused a 38–47% greater reduction in seed mass compared with the smaller‐bodied, scramble‐competing larvae of the African biotype. The amount of seed mass lost per larva remained similar in seeds with one or two scramble‐competing larvae but decreased significantly in seeds bearing two contest‐competing Asian larvae.
• 4 Differences in larval consumption and behaviour produced striking differences in the frequency of germination. Germination of singly‐infested mung bean (i.e. the smallest host) was 71% for African‐infested seeds versus 11% for Asian‐infested seeds. In cowpea (i.e. the largest host), 76% of Asian‐infested seeds germinated, whereas the germination rate of African‐infested cowpeas (92%) was similar to that of uninfested seeds.
• 5 Effects of beetle origin persisted after germination. Seedlings derived from Asian‐infested seeds had greater cotyledon damage 7 days after germination, and displayed lower height and less biomass 15 days after germination. Cotyledon damage was a good predictor of seedling performance (i.e. better than seed mass consumed) 15 days after germination.
• 6 Previous studies have suggested that population differences in larval size and burrowing behaviour (‘centripetal tendency’) reflect adaptation to different‐sized seeds. The present study demonstrates that these differences in turn influence the impact of larval feeding on host viability. Strong biotypic variation makes it difficult to generalize about pest impacts at the level of pest species.

     

Phospholipase Dα1‐mediated phosphatidic acid change is a key determinant of desiccation‐induced viability loss in seeds

High sensitivity of seeds to water loss is a widespread phenomenon in the world's plant species. The molecular basis of this trait is poorly understood but thought to be associated with critical changes in membrane function. We profiled membrane lipids of seeds in eight species with varying levels of desiccation tolerance and found a close association between reducing seed viability and increasing phosphatidic acid (PA). We applied hydration–dehydration cycles to Arabidopsis seeds, which are normally desiccation tolerant, to mimic the onset of desiccation sensitivity with progression towards germination and examined the role of phospholipase D (PLD) in desiccation stress‐induced production of PA. We found that PLDα1 became more abundant and migrated from the cytosol to the membrane during desiccation, whereas PLDδ did not change, and that all desiccation‐induced PA was derived from PLDα1 hydrolysis. When PLDα1 was suppressed, the germination level after each hydration–dehydration cycle improved significantly. We further demonstrated that PLDα1‐mediated PA formation modulates desiccation sensitivity as applying its inhibitor improved seed desiccation tolerance and its suppression in protoplasts enhanced survival under dehydration. The insights provided by comparative lipidomics enable us to propose a new membrane‐based model for seed desiccation stress and survival.     

Diversity of epicotyl dormancy among tropical montane forest species in Sri Lanka

• Fruiting season of many Sri Lankan tropical montane species is not synchronised and may not occur when conditions are favourable for seedling establishment. We hypothesised that species with different fruiting seasons have different seed dormancy mechanisms to synchronise timing of germination with a favourable season for establishment. Using six species with different fruiting seasons, we tested this hypothesis.
• Germination and imbibition of intact and manually scarified seeds were studied. Effect of GA₃ on germination was examined. Embryo length:seed length (E:S) ratio of freshly matured seeds and of those with a split seed coat was determined. Time taken for radicle and plumule emergence and morphological changes of the embryos were recorded.
• The radicle emerged from Ardisia missionis, Bheza nitidissima and Gaetnera walkeri seeds within 30 days, whereas it took >30 days in other species. Embryos grew in seeds of B. nitidissima and G. walkeri prior to radicle emergence but not in Microtropis wallichiana, Nothapodytes nimmoniana and Symplocos cochinchinensis. A considerable delay was observed between radicle and plumule emergence in all six species. Warm stratification and/or GA₃ promoted germination of all species.
• All the tested species have epicotyl dormancy. Seeds of B. nitidissima and G. walkeri have non‐deep simple morphophysiological epicotyl dormancy, and the other four species have non‐deep physiological epicotyl dormancy. Differences in radicle and epicotyl dormancy promote synchronisation of germination to a favourable time for seedling development. Therefore, information on dormancy‐breaking and germination requirements of both radicle and epicotyl are needed to determine the kind of dormancy of a particular species.

     

Sensitivity cycling in physically dormant seeds of the Neotropical tree Senna multijuga (Fabaceae)

• Cycling of sensitivity to physical dormancy (PY) break has been documented in herbaceous species. However, it has not been reported in tree seeds, nor has the effect of seed size on sensitivity to PY‐breaking been evaluated in any species. Thus, the aims of this study were to investigate how PY is broken in seeds of the tropical legume tree Senna multijuga, if seeds exhibit sensitivity cycling and if seed size affects induction into sensitivity.
• Dormancy and germination were evaluated in intact and scarified seeds from two collections of S. multijuga. The effects of temperature, moisture and seed size on induction of sensitivity to dormancy‐breaking were assessed, and seasonal changes in germination and persistence of buried seeds were determined. Reversal of sensitivity was also investigated.
• Fresh seeds were insensitive to dormancy break at wet–high temperatures, and an increase in sensitivity occurred in buried seeds after they experienced low temperatures during winter (dry season). Temperatures ≤20 °C increased sensitivity, whereas temperatures ≥30 °C decreased it regardless of moisture conditions. Dormancy was broken in sensitive seeds by incubating them at 35 °C. Sensitivity could be reversed, and large seeds were more sensitive than small seeds to sensitivity induction.
• Seeds of S. multijuga exhibit sensitivity cycling to PY‐breaking. Seeds become sensitive during winter and can germinate with the onset of the spring–summer rainy season in Brazil. Small seeds are slower to become sensitive than large ones, and this may be a mechanism by which germination is spread over time. Sensitive seeds that fail to germinate become insensitive during exposure to drought during summer. This is the first report of sensitivity cycling in a tree species.

     

Effects of Moisture Content on Germination of Seeds of Hancornia speciosa Gom. (Apocynaceae)

Seeds of Hancornia speciosa germinated best at a temperatureof 20–30 °C. The viability of the seeds during storagewas short and the best storage conditions for viability entailedkeeping the seeds in polyethylene bags. Seed viability was maintainedonly when the seeds were stored at a moisture content above30%; storage conditions which allowed dehydration resulted ina rapid loss of viability (the seeds showed recalcitrant behaviour). Low temperature during storage did not improve longevity. Arelationship between germination and moisture content was established,but when the moisture content fell below 25% there was a drasticreduction of germination. After 9 weeks of storage, even athigh moisture content, seeds lost viability. Loss of seed viability during seed dehydration was associatedwith increased leakage of electrolytes and organic solutes,and reduced tetrazolium staining during subsequent imbibition. Hancornia speciosa, germination, recalcitrant seeds, storage, moisture     

Physiological characteristics underpinning successful cryopreservation of endemic and endangered species of Bromeliaceae from the Brazilian Atlantic Forest

The germination requirements and the basis of the optimal water content before and after cryopreservation were studied for ten endangered Brazilian species of Bromeliaceae. Constant and alternating temperature regimes were used to determine the best conditions for seed germination. The relationship between seed water content and relative humidity was evaluated using water sorption isotherms at 15 °C. Seeds were cryostored at four water contents (3, 5, 7 and 9%) and three storage periods (0, 180 and 365 days), and loss in viability and vigour were estimated. Fresh seeds of all species showed maximum germination in < 30 days at temperatures between 20 and 30 °C, indicating the absence of a physical/morphological dormancy. A sigmoidal relationship between seed water content and relative humidity was observed with no apparent differences in sorption characteristics among the species. The optimum water content for cryopreservation of most of these species was c. 7%. Ultra‐drying (3% seed water content) had a detrimental effect on seed viability and vigour. Our experiments suggested orthodox storage behaviour for all species of Bromeliaceae examined as they are able to survive desiccation and freezing. This study has shown the feasibility of ex situ conservation in seed cryobanks of endangered bromeliads from the Brazilian Atlantic Forest to support future reintroduction of these species in nature. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176 , 567–576.     

Diaspore dispersal season influences root growth and seed traits,but not germination responses,of sympatric Piper species in a seasonal forest

• Seeds may differ in terms of dormancy, longevity, sensitivity to desiccation and dry mass, according to the timing (dry season/rainy season) of diaspore dispersal. In addition, seasonal variations in temperature and water availability can act as signals of the season during seed development, influencing germination responses and root growth. We evaluated the effects of temperature variations and water availability on germination parameters, root growth and seed traits of four coexisting Piper species in seasonal vegetation that differed in diaspore dispersal timing.
• Eight temperature treatments (15, 20, 23, 25, 28, 30, 35 °C, and alternate 30 °C–20 °C) and four induced water potentials (0, −0.3, −0.6 and −1.2 MPa) were used. The parameters germination onset, germination percentage (G%), mean germination time (MGT), root elongation, seed longevity during ex situ storage and dry mass of seeds were evaluated.
• Germination responses observed were independent of the diaspore dispersal timing, such as variations in germination onset, G% and MGT, both in temperature and water availability treatments. In contrast, root elongation, longevity and dry mass of seeds varied according to the time of diaspore dispersal.
• Our results corroborate the hypothesis that the timing of diaspore dispersal is an important factor in controlling the initial development of seedlings in seasonal vegetation, but not in germination responses. The predominance of negative effects of temperature increases and water deficit on root growth shows that the initial stages of plant development can be strongly impacted by these environmental factors.

     

Ecology of seed germination of eight non-pioneer tree species from a tropical seasonal rain forest in southwest China

We compared various aspects of the seed biology of eight non-pioneer tree species from a tropical seasonal rain forest in Xishuangbanna, SW China, that differ in time of dispersal, size and fresh seed moisture content (MC). Seeds were tested for germination under laboratory conditions after dehydration to different moisture levels and under 3.5, 10 and 30% solar irradiances in neutral-shade houses. For six species, germination was also compared in forest understory (3.5% light) and center of a forest gap (32.5% light). Under continuous dehydration over activated silica gel, 100% of seeds of four species had lost the ability to germinate after 48 h, and those of all species except Castanopsis hystrix (decreased from >90 to 30% germination) had lost the ability to germinate after 120 h. Four species did not differ in final germination percentages at the three irradiances (i.e. uniform germination). However, final germination percentages of Horsfieldia pandurifolia and Litsea pierrei var. szemaois were significantly lower in 30% than in 10 or 3.5% light, and seeds of Antiaris toxicaria and C. hystrix germinated to higher percentages in 30 and 10% than in 3.5% light. Mean time to germination (MTG) of the eight species (forest and shade house data combined) ranged from 5–5 days for Pometia tomentosa to 72–207days for L. pierrei; MTG for four species was ≤21 days. There was no obvious relationship between relative desiccation resistance and either time of dispersal, MTG or uniformity of germination at the three light levels, or between seed size and MC or MTG. However, the relationship between seed MC at maturity (25–60% fresh mass basis) and MC at 50% loss of seed viability (12.4–42.5%) was significant. Seven of the species fit Garwood’s (Ecol Monogr 53:159–181, 1983) rapid-rainy germination syndrome and one, L. pierrei, either her delayed-rainy or intermediate-dry germination syndrome. However, fresh, non-dehydrated seeds of all eight species germinated in ≤30 days at constant 30°C in light.     

Dormancy cycles in buried seeds of three perennial Xyris (Xyridaceae) species from the Brazilian campo rupestre

• Dormancy cycles are an important mechanism for avoiding seed germination under unfavourable periods for seedling establishment. This mechanism has been scarcely studied in tropical species. Here, we studied three tropical and perennial species of Xyris, X. asperula, X. subsetigera and X. trachyphylla, to investigate in situ longevity and the existence of seasonal seed dormancy cycles.
• Seeds of three species of Xyris were buried in their natural habitat, with samples exhumed bimonthly for 18 months. Germination of exhumed seeds was assessed under a 12‐h photoperiod over a broad range of temperatures. Seeds of X. trachyphylla were also subjected to treatments to overcome secondary dormancy.
• Seeds of all species are able to form a persistent seed bank and exhibit seasonal changes in germinability. Secondary dormancy was acquired during the rainy summer and was overcome during the subsequent dry season (autumn/winter). Desiccation partially overcomes secondary dormancy in X. trachyphylla seeds.
• Soil seed bank persistence and synchronisation of seed germination under favourable conditions for seedling establishment contribute to the persistence and regeneration of X. asperula, X. subsetigera and X. trachyphylla in their natural environment.

     

Osmoconditioning prevents the onset of microtubular cytoskeleton and activation of cell cycle and is detrimental for germination of Jatropha curcas L. seeds

• Jatropha curcas is an oilseed crop renowned for its tolerance to a diverse range of environmental stresses. In Brazil, this species is grown in semiarid regions where crop establishment requires a better understanding of the mechanisms underlying appropriate seed, seedling and plant behaviour under water restriction conditions. In this context, the objective of this study was to investigate the physiological and cytological profiles of J. curcas seeds in response to imbibition in water (control) and in polyethylene glycol solution (osmoticum).
• Seed germinability and reactivation of cell cycle events were assessed by means of different germination parameters and immunohistochemical detection of tubulin and microtubules, i.e. tubulin accumulation and microtubular cytoskeleton configurations in water imbibed seeds (control) and in seeds imbibed in the osmoticum.
• Immunohistochemical analysis revealed increasing accumulation of tubulin and appearance of microtubular cytoskeleton in seed embryo radicles imbibed in water from 48 h onwards. Mitotic microtubules were only visible in seeds imbibed in water, after radicle protrusion, as an indication of cell cycle reactivation and cell proliferation, with subsequent root development. Imbibition in osmoticum prevented accumulation of microtubules, i.e. activation of cell cycle, therefore germination could not be resumed.
• Osmoconditioned seeds were able to survive re‐drying and could resume germination after re‐imbibition in water, however, with lower germination performance, possibly due to acquisition of secondary dormancy. This study provides important insights into understanding of the physiological aspects of J. curcas seed germination in response to water restriction conditions.

     

Variation in seed germination between populations of five sub-alpine woody species from eastern Qinghai-Tibet Plateau following dry storage at low temperatures

Effects of cold-dry storage on dormancy break and viability were determined for seeds of the five sub-alpine woody species Philadelphus incanus, Berberis vernae, Berberis dubia, Betula utilis, and Picea purpurea collected along an altitudinal gradient on the eastern part of the Qinghai-Tibet Plateau in China. Germination tests were conducted at 20/5°C for seeds stored dry at ambient room temperature for 4 weeks and then at 3–4°C for 0, 6, 12, and 24 weeks. Dormancy break during dry storage, i.e., afterripening, was indicated by an increase in germination percentages and rates. Duration of cold-dry storage and altitude of seed collection had significant effects on germination. With an increase in duration of storage, germination percentages and rates of P. incanus and B. vernae increased with a decrease in altitude of seed collection, while they increased with an increase in altitude for seeds of B. utilis and P. purpurea. Seeds of B. dubia did not exhibit changes in germination percentages and rates with altitude because a high number of seeds remained dormant during storage. Seed viability after 24 weeks of storage ranged from high (88, 93.3, 92.7%) for B. utilis to low (15% for high altitude) for P. incanus. The potential for dormancy break to occur during cold-dry storage should be considered when studies on basic seed dormancy are conducted or when seeds from various locations are stored prior to propagating plants from them.     

White‐tailed deer as the last megafauna dispersing seeds in Neotropical dry forests: the role of fruit and seed traits

Endozoochory is a prominent form of seed dispersal in tropical dry forests. Most extant megafauna that perform such seed dispersal are ungulates, which can also be seed predators. White‐tailed deer (Odocoileus virginianus) is one of the last extant megafauna of Neotropical dry forests, but whether it serves as a legitimate seed disperser is poorly understood. We studied seed dispersal patterns and germination after white‐tailed deer gut passage in a tropical dry forest in southwest Ecuador. Over 23 mo, we recorded ca 2000 seeds of 11 species in 385 fecal samples. Most seeds belonged to four species of Fabaceae: Chloroleucon mangense, Senna mollissima, Piptadenia flava, and Caesalpinia glabrata. Seeds from eight of the 11 species dispersed by white‐tailed deer germinated under controlled conditions. Ingestion did not affect germination of C. mangense and S. mollissima, whereas C. glabrata showed reduced germination. Nevertheless, the removal of fruit pulp resulting from ingestion by white‐tailed deer could have a deinhibition effect on germination due to seed release. Thus, white‐tailed deer play an important role as legitimate seed dispersers of woody species formerly considered autochorous. Our results suggest that more research is needed to fully understand the ecological and evolutionary effects of the remaining extant megafauna on plant regeneration dynamics in the dry Neotropics.