Germination Ecology Research Articles

Acidity and availability of aluminum, iron and manganese as factors affecting germination in European acidic dry and alkaline xerothermic grasslands.

Germination ecology of 10 species from acidic dry grasslands and 10 species from alkaline xerothermic grasslands was studied. The seeds were subjected to different pH, iron (Fe), manganese (Mn) and aluminum (Al) treatments under controlled conditions. Effects of ionic (chlorides) and chelated forms (HBED chelates) of Fe and Mn were also compared. Final germination percentage (FGP) and index of germination velocity (IGV) were calculated. The results indicate that pH and extremely high availability of Al are the major edaphic filters regulating germination-based revegetation, while availability of Fe and Mn is of the secondary importance. Both chelates and ionic forms of Fe and Mn exerted similar effects on the ability of seeds to complete germination. It suggests that both chelates are not hazardous for early ontogenetic stages of plants. Neither group has group-specific adaptations pertaining to germination characteristics in the context of the studied chemical stimuli, which indicates a diversity of germination strategies and individual species-specific reactions to the tested factors.

Moisture content and oxidative damage determine longevity of the seeds of potential cash crop halophyte Haloxylon stocksii

Haloxylon stocksii is a succulent halophyte with high potential to become edible-oil and medicinal crop for the arid-saline lands. Studies about germination ecology and mechanisms of salinity tolerance during vegetative stage of this plant exist. However, information about longevity and biochemical changes in H. stocksii seeds during storage is absent. This study thus examined longevity, and physio-chemical attributes of the H. stocksii seeds under different storage conditions. Fresh seeds were non-dormant with ∼96% germination in water. Storage of seeds for four months had little effect on their germination in most conditions. However, storage for 8 or 12 months caused a complete germination inhibition in laboratory and field respectively. Seed moisture increased with the storage time and was positively correlated with mortality. Antioxidant activity of the seeds increased with time in all conditions, which however was inadequate to prevent oxidative damage as hydrogen peroxide and lipid peroxidation levels increased, especially with >4 months of storage. Hence, these data indicate the short longevity of the H. stocksii seeds resulting from moisture-induced oxidative damages during storage.

Seed germination ecology of leucaena (Leucaena leucocephala) as influenced by various environmental parameters

AbstractLeucaena [Leucaena leucocephala (Lam.) de Wit] is a perennial weed in more than 25 countries, including Australia. Knowledge regarding the seed biology of L. leucocephala could help in making weed management decisions. Experiments were conducted to study the effect of hot water (scarification), alternating temperatures, heat stress, salt stress, water stress, and burial depth on seed germination of two populations of L. leucocephala collected from Toowoomba and Gatton, Australia. The optimum duration of hot water treatment to break the hard seed coat dormancy was 2 min for both populations. The highest germination (92% to 98%) was recorded at 35/25 C for both populations, and similar germination occurred at 30/20 C. The Toowoomba population recorded greater germination at low temperature (15/5 to 25/15 C) than the Gatton population. Additionally, the Gatton population had higher germination than the Toowoomba population after 5 min of exposure to temperatures of up to 100 C, suggesting that the Gatton population may be more tolerant to heat stress. Germination was completely inhibited at pretreatment (5 min) temperatures of 150 to 250 C. The Toowoomba population recorded 17% greater germination than the Gatton population at a high salt concentration (160 mM NaCl), indicating its greater salt tolerance. At low moisture stress (−0.1 and −0.2 MPa), higher germination was observed in the Toowoomba population than in the Gatton population, whereas germination was similar for both populations at higher water stress levels (−0.4 MPa or lower). Germination was similar for both populations at shallow depths (0 and 1 cm) but higher emergence was recorded for the Toowoomba population at 2 to 8 cm than the Gatton population. Differential germination behaviors of both populations suggest that they adapted differently in their respective local environments. Knowledge gained from this study will help in formulating integrated management practices for L. leucocephala.

Seed size dimorphism in Hyptis suaveolens aids in differentiation of the germination niche.

Seed germination characteristics help predict the degree of invasive success of a species based on capacity of the seeds to germinate and recruit into novel habitats. Hyptis suaveolens (L.) Poit. (Bush mint, Pignut; Lamiaceae) is an invasive plant that is spreading throughout tropical and subtropical regions worldwide. We conducted a study to understand the role of seed size dimorphism in differentiation of germination niche in H. suaveolens. We subjected small and large seeds to varying environmental conditions of temperature (°C), photoperiod (light/dark), salt (NaCl; mM), pH, osmotic potential (MPa), different soil types and ratios (clay:sand) and burial depth (cm). Different germination indices were calculated and their interaction with seed dimorphism studied. There was a significant interaction (P < 0.001) between germination indices and seed dimorphism throughout the treatments. Large seeds had higher germination percentage and rate, indicating higher germination capacity. In addition, these displayed more asynchronous germination under various environments. Small seeds, on the other hand, required a longer germination time as compared to large seeds, indicating slower germination. Differential responses of the two seed morphs to varying environmental conditions, therefore, help H. suaveolens to differentiate its germination niche and establish in heterogeneous environments. These findings will help in devising appropriate management and eradication strategies based on germination ecology of seeds.

Germination and seed persistence of Amaranthus retroflexus and Amaranthus viridis: Two emerging weeds in Australian cotton and other summer crops.

Redroot pigweed (Amaranthus retroflexus L.) and slender amaranth (Amaranthus viridis L.) are becoming problematic weeds in summer crops, including cotton in Australia. A series of laboratory and field experiments were performed to examine the germination ecology, and seed persistence of two populations of A. retroflexus and A. viridis collected from the Goondiwindi and Gatton regions of Australia. Both populations of A. retroflexus and A. viridis behaved similarly to different environmental conditions. Initial dormancy was observed in fresh seeds of both species; however, germination reached maximum after an after-ripening period of two months at room temperature. Light was not a mandatory prerequisite for germination of both species as they could germinate under complete darkness. Although both species showed very low germination at the alternating day/night temperature of 15/5 C, these species germinated more than 40% between ranges of 25/15 C to 35/25 C. Maximum germination of A. retroflexus (93%) and A. viridis (86%) was observed at 35/25 C and 30/20, respectively. Germination of A. retroflexus and A. viridis was completely inhibited at osmotic potentials of -1.0 and -0.6 MPa, respectively. No germination was observed in both species at the sodium chloride concentration of 200 mM. A. retroflexus seedling emergence (87%) was maximum from the seeds buried at 1 cm while the maximum germination of A. viridis (72%) was observed at the soil surface. No seedling emergence was observed from a burial depth of 8 cm for both species. In both species, seed persistence increased with increasing burial depth. At 24 months after seed placement, seed depletion ranged from 75% (10 cm depth) to 94% (soil surface) for A. retroflexus, and ranged from 79% to 94% for A. viridis, respectively. Information gained from this study will contribute to an integrated control programs for A. retroflexus and A. viridis.

Reproductive biology of wild and domesticated Ensete ventricosum: Further evidence for maintenance of sexual reproductive capacity in a vegetatively propagated perennial crop.

Loss of sexual reproductive capacity has been proposed as a syndrome of domestication in vegetatively propagated crops, but there are relatively few examples from agricultural systems. In this study, we compare sexual reproductive capacity in wild (sexual) and domesticated (vegetative) populations of enset (Ensete ventricosum (Welw.) Cheesman), a tropical banana relative and Ethiopian food security crop.We examined floral and seed morphology and germination ecology across 35 wild and domesticated enset. We surveyed variation in floral and seed traits, including seed weight, viability and internal morphology, and germinated seeds across a range of constant and alternating temperature regimes to characterize optimum germination requirements.We report highly consistent floral allometry, seed viability, internal morphology and days to germination in wild and domesticated enset. However, seeds from domesticated plants responded to cooler temperatures with greater diurnal range. Shifts in germination behaviour appear concordant with a climatic envelope shift in the domesticated distribution.Our findings provide evidence that sexual reproductive capacity has been maintained despite long‐term near‐exclusive vegetative propagation in domesticated enset. Furthermore, certain traits such as germination behaviour and floral morphology may be under continued selection, presumably through rare sexually reproductive events. Compared to sexually propagated crops banked as seeds, vegetative crop diversity is typically conserved in living collections that are more costly and insecure. Improved understanding of sexual propagation in vegetative crops may have applications in germplasm conservation and plant breeding.

Germination ecology of cerejeira (Amburana acreana (Ducke) A. C. Sm.) seed as a function of temperature and photoperiod

The expansion of agricultural areas over the Amazon biome and illegal logging has caused a reduction in forest areas and the risk of extinction of several native species. Thus, cultivation in agroforestry or monoculture systems is essential for the economic and environmental sustainability of the sector. For this, it is necessary to understand the physiological parameters of seeds and establish protocols that help growers and nurseries during the seedling production phase. The objective of this work was to develop methods to evaluate the germination of Amburana acreana seeds at different temperatures and photoperiods. The seeds were submitted to germination tests, germination speed and average germination time at constant temperatures of 25 °C, 30 °C, 35 °C and 40 °C and two photoperiods, 12 and 24 hours of light. The temperature of 40°C inhibited germination. The germination process of A. acreana seeds is favored with a temperature of 30 °C under 24 h of light, promoting up to 100% germination.

Desiccation Tolerance and germination of Psidium guajava seeds from different regions of Brazil

Background: The germination ecology of P. guajava seeds collected in two regions of Brazil was investigated aiming to (1) characterize the seed batches; (2) determine the best temperature for germination; and (3) assess variations in seed desiccation tolerance (DT). For each batch, we determined seed water content and initial germination. To evaluate temperature effects, we tested seed germination. After, we generated the imbibition curves for the two provenance. To evaluate the loss of DT, the seeds were left to germinate along different time intervals. We monitored water loss by regularly weighing the seeds until achieving stabilization, keeping them under these conditions for 72 hours. After drying, the seeds were pre-hydrated and submitted to the germination test. Results:We identified variations in physiological characteristics between the seeds from north and southeast batches. At the temperature extremes, the seeds from both provenance failed to germinate. The highest germination percentages were observed at 20 and 25 °C (constant) and between 20-30 °C (alternating) for the two batches and, for the southeast batch specifically, at 30 °C. The imbibition curve displayed a triphasic pattern with a rapid increase in seed fresh weight in the first 48 hours. Conclusion: The southeast provenance seeds lost DT abruptly, until its complete loss after radicle protrusion, which occurred in both batches. The highest values of germination speed index (GSI) of both provenance were observed after a 9-day imbibition period, suggesting seed hydration memory. Drying resulted in necrosis of the root tissue and death of the seeds with visible roots.

Seed germination ecology of Conyza sumatrensis populations stemming from different habitats and implications for management.

Conyza sumatrensis (Retz.) E. H. Walker is an obnoxious weed, emerging as an invasive species globally. Seed germination biology of four populations of the species stemming from arid, semi-arid, temperate, and humid regions was determined in this study. Seed germination was recorded under six different environmental cues (i.e., light/dark periods, constant and alternating day and night temperatures, pH, salinity, and osmotic potential levels) in separate experiment for each cue. Populations were main factor, whereas levels of each environmental cue were considered as sub-factor. The impact of seed burial depths on seedling emergence was inferred in a greenhouse pot experiment. Seed germination was recorded daily and four germination indices, i.e., seed germination percentage, mean germination time, time to reach 50% germination, and mean daily germination were computed. Tested populations and levels of different environmental cues had significant impact on various seed germination indices. Overall, seeds stemming from arid and semi-arid regions had higher seed germination potential under stressful and benign environmental conditions compared to temperate and humid populations. Seed of all populations required a definite light period for germination and 12 hours alternating light and dark period resulted in the highest seed germination. Seed germination of all populations occurred under 5–30°C constant and all tested alternate day and night temperatures. However, the highest seed germination was recorded under 20°C. Seeds of arid and semi-arid populations exhibited higher germination under increased temperature, salinity and osmotic potential levels indicating that maternal environment strongly affected germination traits of the tested populations. The highest seed germination of the tested populations was noted under neutral pH, while higher and lower pH than neutral had negative impact on seed germination. Arid and semi-arid populations exhibited higher seed germination under increased pH compared to temperate and humid populations. Seed burial depth had a significant effect on the seedling emergence of all tested populations. An initial increase was noted in seedling emergence percentage with increasing soil depth. However, a steep decline was recorded after 2 cm seed burial depth. These results indicate that maternal environment strongly mediates germination traits of different populations. Lower emergence from >4 cm seed burial depth warrants that deep burial of seeds and subsequent zero or minimum soil disturbance could aid the management of the species in agricultural habitats. However, management strategies should be developed for other habitats to halt the spread of the species.

کمی‌سازی جوانه‌زنی بذر علف‌های‌هرز خانواده براسیکاسه (Brassicaceae) تحت شرایط شوری و خشکی

Introduction Knowledge on germination ecology of weeds in response to salinity and drought stresses can help to predict weeds population dynamics in the future. Among the family of weeds, the weeds of Brassicaceae family include many important species that contaminate crops and orchards. In addition to the presence of weeds, salinity and drought are also considered as limiting factors in agricultural production. Due to the increase in salinity and drought stresses in agricultural fields, it can be significant expansion and contamination of Brassicaceae weeds, because Physiological dormancy, abundant seed production and emergence at different time, leads to be persistent for long-term in soil. Therefore, the aim of this research was to compare the characteristics of seed germination of four weeds Brassicaceae family to salinity and drought stresses. Materials and methods In order to investigate the effects of salinity (0, 50, 100, 150, 200, 250, 300, 350 and 400 Mm) and drought stress (0, -0.2, -0.4, -0.6, -0.8, -1 and -1.2 MPa) on seed germination four Brassicaceae family weeds (Rocket (Eruca sativa), Hoary Mustard (Hirschfeldia incana), Wild Mustard (Sinapis arvensis) and Treacle Mustard (Erysimum repandum), two experiments as factorial based on completely randomized design (CRD) were conducted at agricultural sciences and natural resources university of Khuzestan in 2019 with three replications. Optimum Temperature for germination were selected 25°C for Rocket, Hoary Mustard, Wild Mustard and 15°C for Treacle Mustard. Duration of test for two experiments was considered 15 days. Criterion for germination was length radicle 2-3 mm. Results and discussion By increasing drought stress, germination, vigour index and germination rate were decreased and no germination was observed in drought stress of -1.2 MPa. 50% reduction for germination in four weeds Rocket, Hoary Mustard, Wild Mustard and Treacle Mustard were estimated in -1, -0.49, -0.76 and – 0.41 MPa of drought stress respectively. Drought stress required to reduce 50% of germination rate for Rocket, Hoary Mustard, Wild Mustard and Treacle Mustard were estimated -0.85, -0.35, -0.28 and 0.22 MPa respectively.The vigour index of Wild Mustard in conditions without drought stress treatment was more than other weeds. Rocket and Hoary Mustard were introduced as resistant and Wild Mustard was introduced as sensitive to salinity. The salinity required to reduce 50% of germination for Rocket, Hoary Mustard, Wild Mustard and Treacle Mustard were predicted 267, 162, 39 and 46 mM, while 50% reduction for germination rate were 174, 142, 27, 44 Mm respectively. By increasing salinity and drought stresses, mean germination time was increased and maximum mean germination time belonged to Treacle Mustard and the reason for this increase was the lag phase of germination. Germination rate in four weeds was more affected by salinity and drought stresses than germination percentage. Generally the germination rate of Treacle Mustard was much less than other weeds. So that the maximum germination rate of Treacle Mustard was 5 seed/day in control treatment while in Rocket Hoary Mustard, Wild Mustard were more than 30 seed /day. Conclusions According to the results, in saline lands, the spread of two weeds Rocket and Hoary Mustard is more expected and in the conditions of drought stress and in rainfed agriculture, presence of Rocket is more evident than Wild Mustard.

Smoke and heat accelerate and increase germination in fire‐prone temperate grassy ecosystems

AbstractFire increases seedling recruitment by reducing competition for space and resources. As such, many species in fire‐prone ecosystems germinate in response to fire cues such as smoke and heat. A notable exception is fire‐prone temperate grassy ecosystems, where &gt;20 yr of research has found that fire‐cued germination is rare. We tested the hypothesis that fire cues promote germination in temperate grassy ecosystems of south‐eastern Australia. We treated seeds of 55 common species with smoke, heat, and a combination of smoke and heat and tracked germination over time. We analyzed the effect of all combinations of treatments on germination speed and percent germination. Interestingly, we found that smoke and heat combined—which is more ecologically relevant to an actual fire than smoke and heat alone—was needed to increase germination speed, a mostly unstudied component of the germination ecology of grassy ecosystems. Smoke alone increased percent germination. Both plant family and seed traits influenced the germination response to smoke and heat. Poaceae species were the most responsive (in both speed and percent germination) to smoke alone. Water permeability of the seed coat was a key determinant of whether species responded to heat alone, smoke alone, or combined smoke and heat. Species with water‐impermeable seed coats responded to heat alone for both speed and percent germination. Species with water‐permeable seed coats germinated faster in response to combined smoke and heat and percent germination was increased by smoke alone. In contrast with more than two decades of research—our study of this large and representative group of species demonstrates that fire (via smoke and heat) is an important germination cue in fire‐prone temperate grassy ecosystems of south‐eastern Australia.

Morphophysiological dormancy and germination ecology in diaspores of the subtropical palmPhoenix canariensis

The timing of germination is a crucial event in a plant’s life cycle. Seed dormancy and germination mechanisms are important factors regulating seedling emergence. Since detailed experimental evidence of the germination pattern of Phoenix canariensis Chabaud colonizing sub-tropical climates is scarce, we investigated seed dormancy and germination ecology of P. canariensis. We found that the embryo is underdeveloped at the time of dispersal and doubles in size before the cotyledonary petiole (CP) protrudes through the operculum. The primary root and plumule emerge from the elongated CP outside the seed. In light/dark cycles of 30/25 °C, the CP emerged from 8% of the diaspores within 30 days and from 76% within 14 weeks. Thus, 8% of the diaspores have morphological dormancy and the others have morphophysiological dormancy. Removal of the pericarp and operculum resulted in 100% germination within five days in a light/dark cycle of 30/25 °C. Cold and warm stratification as well as treatment with GA3significantly increased the germination speed but the final germination percentage was not significantly increased. Seed germination was synchronized in early summer when seed dormancy was released by cold stratification in the soil over winter. A remote-tubular germination type and intricate root system provide an ecological advantage to seedling establishment.

Using seminatural and simulated habitats for seed germination ecology of banana wild relatives.

Ecologically meaningful seed germination experiments are constrained by access to seeds and relevant environments for testing at the same time. This is particularly the case when research is carried out far from the native area of the studied species.Here, we demonstrate an alternative—the use of glasshouses in botanic gardens as simulated‐natural habitats to extend the ecological interpretation of germination studies. Our focal taxa were banana crop wild relatives (Musa acuminata subsp. burmannica, Musa acuminata subsp. siamea, and Musa balbisiana), native to tropical and subtropical South‐East Asia. Tests were carried out in Belgium, where we performed germination tests in relation to foliage‐shading/exposure to solar radiation and seed burial depth, as well as seed survival and dormancy release in the soil. We calibrated the interpretation of these studies by also conducting an experiment in a seminatural habitat in a species native range (M. balbisiana—Los Baños, the Philippines), where we tested germination responses to exposure to sun/shade. Using temperature data loggers, we determined temperature dynamics suitable for germination in both these settings.In these seminatural and simulated‐natural habitats, seeds germinated in response to exposure to direct solar radiation. Seed burial depth had a significant but marginal effect by comparison, even when seeds were buried to 7 cm in the soil. Temperatures at sun‐exposed compared with shaded environments differed by only a few degrees Celsius. Maximum temperature of the period prior to germination was the most significant contributor to germination responses and germination increased linearly above a threshold of 23℃ to the maximum temperature in the soil (in simulated‐natural habitats) of 35℃.Glasshouses can provide useful environments to aid interpretation of seed germination responses to environmental niches.

Germination ecology of wild mustard (Sinapis arvensis) and its implications for weed management

AbstractWild mustard (Sinapis arvensis L.) is a widespread weed of the southeastern cropping region of Australia. Seed germination ecology of S. arvensis populations selected from different climatic regions may differ due to adaptative traits. Experiments were conducted to evaluate the effects of temperature, light, radiant heat, soil moisture, salt concentration, and burial depth on seed germination and seedling emergence of two populations (Queensland [Qld] population: tropical region; and Victoria [Vic] population: temperate region) of S. arvensis. Both populations germinated over a wide range of day/night (12-h/12-h) temperatures (15/5 to 35/25 C), and had the highest germination at 30/20 C. Under complete darkness, the Qld population (61%) had higher germination than the Vic population (21%); however, under the light/dark regime, both populations had similar germination (78% to 86%). At 100 C pretreatment for 5 min, the Qld population (44%) had higher germination than the Vic population (13%). Germination of both populations was nil when given pretreatment at 150 and 200 C. The Vic population was found tolerant to high osmotic and salt stress compared with the Qld population. At an osmotic potential of −0.4 MPa, germination of Qld and Vic populations was reduced by 85% and 42%, respectively, compared with their respective controls. At 40, 80, and 160 mM sodium chloride, germination was lower for the Qld population than the Vic population. Averaged over the populations, seedling emergence was highest (52%) from a burial depth of 1 cm and was nil from 8-cm depth. Differential germination behaviors of both populations to temperature, light, radiant heat, water stress, and salt stress suggest that populations of S. arvensis may have undergone differential adaptation. Knowledge gained from this study will assist in developing suitable control measures for this weed species to reduce the soil seedbank.

Seed germination ecology of Sumatran fleabane (Conyza sumatrensis) in relations to various environmental parameters

AbstractSumatran fleabane [Conyza sumatrensis (Retz.) Walker] is an emerging weed in the Australian cropping region. Populations resistant to glyphosate have evolved in Australia, creating the demand for information regarding the seed germination ecology of glyphosate-resistant (R) and glyphosate-susceptible (S) populations of C. sumatrensis. A study was conducted to examine the effects of temperature, light intensity, salt stress, osmotic stress, and burial depth on the germination and emergence of two populations (R and S) of C. sumatrensis. Both populations were able to germinate over a wide range of alternating day/night temperatures (15/5 to 35/25 C). In light/dark conditions, the R population had higher germination than the S population at 20/10 and 35/25 C. In the dark, the R population had higher germination than the S population at 25/15 C. In the dark, germination was inhibited at 30/20 C and above. Averaged over populations, seed germination of C. sumatrensis was reduced by 97% at zero light intensity (completely dark conditions) compared with full light intensity. Seed germination of C. sumatrensis was reduced by 17% and 85% at osmotic potentials of −0.4, and −0.8 MPa, respectively, compared with the control treatment. The R population had lower germination (57%) than the S population (72%) at a sodium chloride concentration of 80 mM. Seed germination was highest on the soil surface and emergence was reduced by 87% and 90% at burial depths of 0.5 and 1.0 cm, respectively. Knowledge gained from this study suggests that a shallow-tillage operation to bury weed seeds in conventional tillage systems and retention of high residue cover on the soil surface in zero-till systems may inhibit the germination of C. sumatrensis. This study also warrants that the R population may have a greater risk of invasion over a greater part of a year due to germination over a broader temperature range.

Septemeranthus(Loranthaceae), a new monotypic genus from the Andaman and Nicobar Islands, India and its relationship with allied genera

AbstractA new showy mistletoe genus,SeptemeranthusL.J. Singh with a type species,S. nicobaricusL.J. Singh sp. nov., is described and illustrated from the Andaman and Nicobar Islands, India. It is an aerial branch hemi‐parasite onHorsfieldia glabra(Blume) Warb. (Myrsticaceae). The conservation status, host inventory, germination ecology and remarks on its relationship with allied genera are given.Septemeranthusis distinct in vegetative morphology, inflorescence architecture and floral characters: leaves with long apex, camptodromous venation, coraceous, 5 bracts with brown margins, 3‐7 flowered racemose, 7 merous flowers, urceolate ovary, earthen pot shape fruits with prominent bracts and seeds with dark vertical streaks.

Effects of smoke and heat-shock on germination in eight perennial Reseda species (Resedaceae)

Reseda is an understudied genus regarding germination ecology. We studied the germination response of eight perennial Reseda species to fire related cues by performing a germination experiment including two aqueous smoke treatments (at 1:5 and 1:20 concentrations), one heat shock (100 °C for 5 min.) treatment, and two corresponding controls. Smoke slightly decreased germination percentage in R. aucheri ssp. rotundifolia and R. minoica, and the reduction in R. luteola was statistically significant (P &lt; 0.01). In contrary, smoke promoted germination in R. coodei, R. globulosa, and R. orientalis slightly, and markedly in R. anatolica (from 3 to 11%; P = 0.055). Heat shock treatment did not affect the germination in three of four species tested, but significantly increased germination percentage in R. luteola in comparison to the control (P = 0.046). Consequently, there was no consistent germination response to smoke or heat shock in Reseda species studied. This study is the most comprehensive study tested fire-related germination of several Reseda species and provides the first germination results on seven Reseda species. Further studies that include more species and treatments would show a more completed figure for fire-related germination patterns in the genus Reseda.

How fire history affects germination cues of three perennial grasses from the mountain steppes of Golestan National Park

Smoke and heat as germination cues are some of the most important drivers stimulating seed germination. However, the impact of germination factors from wildfire (i.e., smoke and heat) on the germination of species occurring in western Asia has rarely been investigated. We aimed to analyze the effects of different smoke and heat treatments on seed germination of three perennial grasses (Festuca valesiaca, Poa densa, and Stipa zalesskii) collected from two non-burned and burned environments of the mountain steppes in Golestan National Park, Iran. Seeds were germinated on filter paper following smoke (1:2000, 1:1000, and 1:500, v/v) or heat (50, 80, 100°C) treatments. Results showed that the germination of study species was reduced by heat treatments, whereas no particular response was observed with the smoke treatments.Interestingly, the fire history influenced magnitude of effects of fire-related germination cues, leading to slightly lower germination for F. valesiaca and P. densa and higher germination for S. zalesskii. Our results indicate that fire-related germination cues have different impacts on these grassland species. The consideration of the fire history of specific sites on germination ecology seems important to understand the effects of fire on the plant communities.

Germination ecology of four African mustard (Brassica tournefortii Gouan) populations in the eastern region of Australia

Abstract African mustard (Brassica tournefortii Gouan) is a problematic winter annual weed in Australia. Germination ecology of B. tournefortii may change in response to the maternal environments or habitats in which the plants grow. A study was conducted to evaluate the effect of environmental factors on germination and emergence of four populations of B. tournefortii that were collected from different fields. Averaged over populations, germination was stimulated by dark and was higher at 25/15 C (92%) compared with 15/5 C (76%) and 35/25 C (45%). Averaged over light/dark regimes, at the lowest temperature regime (15/5 C), population A had higher germination than population D; however, at the highest temperature regime (35/25 C), population D had higher germination than population A. Populations B and C had higher germination in the temperature range of 25/15 C and 30/20 C compared with 15/5 C, 20/10 C, and 35/25 C. Seeds germinated at a wide range of alternating day/night temperatures (15/5 to 35/25 C), suggesting that seeds can germinate throughout the year if other optimum conditions are available. Population A was more tolerant to water and salt stress than population D. The sodium chloride concentration and osmotic potential required to inhibit 50% germination of population A were 68 mM and −0.60 MPa, respectively. Averaged over populations, seeds placed at 1-cm soil depth had the highest emergence (54%), and burial depth of 8 cm resulted in 28% seedling emergence. Averaged over populations, wheat residue retention at 6,000 kg ha−1 resulted in greater seedling emergence than the residue amount of 1,000 kg ha−1. The results suggest that B. tournefortii will be favored in no-till systems and that the seedbank of B. tournefortii could be managed by tillage regimes that bury its seeds below 8-cm depths and restrict seedling emergence and growth of new plants.

A new species Dendrophthoe laljii (Loranthaceae) infesting Artocarpus heterophyllus Lam. (Moraceae) in Andaman and Nicobar Islands, India

Dendrophthoe laljii sp. nov. (Loranthaceae) from Andaman and Nicobar Islands, India, is described as an aerial branch hemiparasite on Artocarpus heterophyllus Lam. (Moraceae). The notes on conservation status and germination ecology were also depicted in this study. Apparently, this species resembles D. curvata (Blume) Miq, but strictly differs in vegetative morphology and floral characteristics. A taxonomic key to the species of Dendrophthoe Mart. in India is also provided. • D. laljii P. Sivaramakrishna, P. Yugandhar and G.A. Ekka from Andaman and Nicobar Islands is described and illustrated as new to science first time. • This species is described as an aerial branch hemiparasitic showy mistletoe on a specific host Artocarpus heterophyllus Lam. (Moraceae). • This new species differs from previously known species in respect to its morphology of vegetative and floral characteristics.