Diversities in morphological characteristics and seed germination behavior in fruits ofSalsola komarovii Iljin

Two different types of dispersal units (called fruits in this study) were observed inSalsola komarovii Iljin. One is a fruit which has dark brown lignified tepals with long wings and a green seed and falls easily from the mother plant (long-winged type). Another has light brown lignified tepals with short wings and a yellow seed and attaches tightly to the mother plant (short-winged type). This difference of fruit type appeared independently from maturity of fruit. Seeds in the short-winged fruits were in dormancy for a longer period of time than those in the long-winged fruits. The germination rate was significantly higher in the seeds of long-winged fruits. The dormancy in seeds of the long-winged fruits was effectively terminated by reducing the temperature but the effect of chilling was very weak in seeds of the short-winged fruits. It was concluded from these observations that there exists a dimorphism in the fruits of, or a heterocarpy in,S. komarovii. The plants grown under water stress produced mostly short-winged fruits and those grown under well-watered conditions bore fruits of both types. Exogenously applied abscisic acid (ABA) tended to produce the short-winged fruits, suggesting that the heterocarpy was, at least partly, regulated by ABA.     

Seed dispersal by pygmy chimpanzees (Pan paniscus): A preliminary report

The role in seed dispersal played by the pygmy chimpanzees (Pan paniscus) inhabiting Wamba, Republic of Zaïre, was studied. Germination was tested for seeds of 17 plant species recovered from the feces of pygmy chimpanzees at Wamba. The fecal seeds of 13 species germinated, and in six of the species the germination rate for the fecal seeds was higher than that of control seeds. Although five other species showed a higher germination rate in the control seeds than in the fecal seeds, the remaining two species revealed no difference in germination rate between the fecal and control seeds. There was no great difference in germination velocity between the fecal and control seeds of the same species. For comparison, seeds of four plant species collected from the feces of common chimpanzees (Pan troglodytes) and gibbons (Hylobates lar) in captivity in Okinawa were tested for their germinability. In this test, although the seeds had passed through the digestive tract, their germinability demonstrated little change. Based on the behavioral characteristics of the pygmy chimpanzee at Wamba and observations of the captive primates on Okinawa, it seems that pygmy chimpanzees may play an important role in the seed dispersal of fruit plant species at Wamba.     

Effects of salt,alkali and salt–alkali mixed stresses on seed germination of the halophyte Salsola ferganica (Chenopodiaceae)

Salsola ferganica L. (Chenopodianceae) is an annual halophytic species. Experiments were carried out in laboratory to determine the effects of temperature, perianths and various types of salinity on seed germination and germination recovery. Seeds were germinated at 6 levels of temperature with perianths, plus perianths and removed perianths in complete darkness for 9 days. The germination responses of the seeds without perianths at 25 °C were determined over a wide range of NaCl, NaHCO₃ or NaCl–NaHCO₃ mixed stress for 13 days. Perianths seriously affected germination as a barrier for seed germination and the optimal temperature was at 25 °C. Highest germination percentage was obtained under control and seed germination was progressively inhibited with the increase of salinity concentration. The negative effect of NaHCO₃ at the same concentration on germination was stronger than that of NaCl and NaCl–NaHCO₃ mixed. When substrate salinity was removed, seeds exposed to a high NaCl concentration (400–800 mM), NaHCO₃ (50–200 mM) and NaCl–NaHCO₃ mixed (100–400 mM) germinated well. Final germination of Salsola ferganica seeds was significantly affected by types of salt at the low salinity (?200 mM) and with increased salinity it was influenced mainly by salinity concentration for various proportion of salt–alkali mixed stress.     

Dormancy Release,Germination, and Electrolyte Leakage from Apple Embryos during Stratification in the Presence of Sucrose

The dynamics of dormancy release during the stratification of apple (Malus domestica Borkh.) seeds was quantitatively described by three characteristics of seeds germination: the percentage of seeds that germinated by the tenth day, mean germination time, and the sum of seeds germinated in each of ten days (Timson's parameter), which allowed the assessment of the viability, the rate of dormancy release, and seed heterogeneity. We showed that apple seeds were characterized by a combined (physical and physiological) type of dormancy, with the seed coat and the embryo envelope being involved in the maintenance of physical dormancy. The addition of sucrose to the stratification medium accelerated the release of seed dormancy and improved all characteristics that determine seed germinability. Electrolyte leakage from embryos hardly changed during stratification, which agrees with the fact that all seeds remained viable throughout the entire period of dormancy. We assume that the release of seed dormancy is not a single-stage process.     

散枝猪毛菜的种子多型性及其萌发行为

散枝猪毛菜(Salsola bracchita)主要分布于新疆准噶尔荒漠,具有很强的抗干旱和抗盐碱能力。该文对散枝猪毛菜的果实进行了观察,表明散枝猪毛菜具有4种类型的散布单位和果实,这4种果实在形状、大小、颜色和着生方式上均有显著差异。A型果实绿色、球形、大,着生方式为横生,宿存花被革质,背部有紫红色翅状附属物,直径为(2.161±0.138) mm,单粒重为(3.810±0.113) mg;B型果实绿色、大、扁平、长圆形,着生方式为直立,宿存花被革质,背部有翅状附属物,长为(2.062±0.188) mm,宽为(1.720±0.148) mm,单粒重为(2.665±0.113) mg;C型果实绿色、大、扁平、长圆形,着生方式为直立,宿存花被膜质,背部无翅状附属物,长为(2.239±0.277) mm,宽为(1.844±0.150) mm,单粒重为(2.723±0.559) mg;D型果实黄色、小、扁平、长卵形,着生方式为直立,宿存花被膜质,背部无翅状附属物,长为(1.678±0.163) mm,宽为(1.390±0.110) mm,单粒重为(0.928±0.025) mg。A型、B型和C型种子(果实)在5 ℃/15 ℃、5 ℃/25 ℃、15 ℃/25 ℃(暗12 h/光12 h)变温条件下萌发率>68%,且B型和C型种子比A型种子有较高的萌发率和萌发速率。D型种子在3种变温条件下萌发缓慢,最终萌发率始终维持在较低水平(<20%),划破果皮和种皮能够显著提高D型种子的萌发率和萌发指数,表明D型种子处于生理休眠状态。散枝猪毛菜的种子多型性是对荒漠异质环境的一种适应。     

Reproductive ecology of Thymelaea velutina (Thymelaeaceae)- Factors contributing to the maintenance of heterocarpy

Thymelaea velutina (Thymelaeaceae) is a dioecious shrub that presents a unique type of heterocarpy which consists of the simultaneous production of dry and fleshy fruits. It is endemic to the Balearic Islands (Western Mediterranean) and is found both in dunes and mountain areas. The goal of this study was to identify which factors influence the production of both fruit types, examining the variation of their effects at a spatio-temporal scale (comparing two localities in different years). Specifically, we investigated (1) whether pollen limitation influences the type of fruit produced, and (2) the possible differences in seed size, mass, dispersal capacity, seed predation, germination patterns and seedling survival between fruit types. We also examined if the production of fleshy fruits was modified with the application of gibberellins to reproductive branches. Although fleshy fruits were consistently more abundant than dry ones at both populations, their proportion was significantly higher at the site with greater precipitation. The addition of either pollen or gibberellins did not affect the proportion of each fruit type. Seeds in fleshy fruits are consistently larger, heavier and more likely to be dispersed than seeds in dry fruits, but germinability, germination rate and seedling survival was similar among fruit types. Heterocarpy in this species is currently maintained as there is no apparent factor that exerts any strong selective pressure on either fruit type. The two fruit types might even have different `functions', one serving especially for dispersal and population expansion and the other for producing a seed bank that ensures an eventual germination.     

Non-native mammals are weak candidates to substitute ecological function of native avian seed dispersers in an island ecosystem

Although prominent examples exist of non-native species causing substantial ecological harm, many have neutral or positive effects, including filling surrogate roles once performed by extinct native organisms. We tested the ecological roles of two non-native mammals as seed dispersers or seed predators in Guåhan, which, due to invasive brown tree snakes (Boiga irregularis), is devoid of native seed dispersers–birds and bats. We conducted feeding trials with captive rats (Rattus spp.), which are present but uncommon due to predation by snakes, and pigs (Sus scrofa), which are abundant. We examined if and how they interacted with common forest fruits. We then compared how any gut-passed or animal-handled seeds germinated compared to seeds left in whole fruit or depulped seeds. Rats and pigs interacted with most of the fruits and seeds (>80%) that they were fed. Of those, most seeds were destroyed—78% for rats and 90% for pigs, across both native and non-native plant species. Compared to seeds germinating within whole fruits, rats improved germination of the seeds that they handled without ingesting, while pigs diminished the germination of seeds that they handled. The small percentage of seeds (approximately 1.5% for rats and 5% for pigs) that survived gut passage germinated in higher proportions than those in whole fruits. Percentages of seed survival to germination are lower than found in similar studies with native avian frugivores. Our results indicate that pigs and rats have mixed effects on seeds, but are not suitable surrogates for native seed dispersers.     

棕果蝠取食对两种榕树种子萌发行为的影响

在实验室利用聚果榕（Fieus racemosa）和对叶榕（Fieus hispida）成熟的果实饲喂笼养棕果蝠（Rousettus leschenaulti）,比较了不同处理的3组种子的萌发行为：（1）棕果蝠粪便中的种子;（2）被吐出的果渣中的种子;（3）成熟果实中的种子（对照）。棕果蝠取食行为显著影响了两种榕树种子的萌发过程,3种不同处理的种子萌发过程及最终萌发率（GP）之间都存在显著的差异。聚果榕种子经过棕果蝠消化道后GP显著降低,而对叶榕种子的GP显著提高。棕果蝠粪便中的聚果榕种子萌发开始（GS）和最短萌发时间（Tmin）均比对照种子延迟了2d,但其粪便中的对叶榕种子G5比对照种子提前了1d,Tmin提前了2d;与之相似,前者种子萌发比果实中种子提前2d达到萌发总量的50％（T50）,但后者没有改变T50。不同种榕果果渣中的种子萌发行为也有重大差异：聚果榕果渣中种子的Tmin和T50均比对照种子延迟1d,GS没发生改变;而对叶榕果渣中种子的Tmin比对照种子提前了3d,GS提前1d,T50没有改变。棕果蝠取食两种榕果后在飞行过程中排泄,进而有效的散布种子;而且通过消化明显改变了种子萌发行为,使种子萌发类型更为多样,增加了种子在不同时空条件下萌发的可能性。     

Does perianth colour affect the seed germination of two desert shrubs under different storage periods and conditions?

Haloxylon salicornicum and Salsola vermiculata (Amaranthaceae) are two perennial shrubs producing fruits with differently coloured perianths (yellow vs pink) on separate individuals. To test the impact of different storage periods (four, eight and twelve months) and temperature conditions (freezing, room temperature and natural field temperatures) on the seed germination of the two seed categories, germination tests were carried out on both species. For both species, collected from wild plants in the Arabian desert (Qatar), seed germination was tested under two photoperiods (light 12/12; dark 24 hours) at 20/30°C for winged (intact) and de‐winged seeds. For each species, all the considered factors (perianth colour, wing presence, photoperiod, storage period and storage conditions) had significant effects on seed germination (p < 0.001), while the interactions among factors varied in their level of significance depending on the species. In both species, yellow seeds germinated considerably better than the pink ones, the presence of wings slowed the germination, and both storage period and temperature conditions highly influenced their germination ability. Our results indicate that seeds from different perianth colours have different germination strategies to delay their germination and distribute the species through time by escaping germination time by imposing some kind of after‐ripening or seed dormancy. The variation in storage time and storage conditions might help in extending their germination period, where one set of seeds germinate immediately, and the other set of seeds becomes dormant and thus contributes to the formation of a soil seed bank for the long‐term recruitment of seedlings. This study highlights an ecological advantageous strategy for these two species growing in the unpredictable desert habitat.     

THE EFFECT OF SALINITY AND TEMPERATURE ON THE GERMINATION OF POLYMORPHIC SEEDS AND GROWTH OF ATRIPLEX TRIANGULARIS WILLD.

Polymorphic seeds of Atriplex triangularis were germinated at various temperatures (5–15 C, 5–25 C, 10–20 C, 20–30 C) and salinity regimes (0 to 1.5% NaCl) in order to determine their germinability and early seedling growth under these conditions. Larger seeds generally had a higher germination percentage in saline medium. The rate and percentage of germination decreased with increased salinity stress. A thermoperiod of 25 C day and 5 C night, 12 hr/12 hr, temperature enhanced germination of seeds. Early seedling growth is promoted in larger seeds at lower salinity, and at high-day and low-night temperatures. Polymorphic seeds have different physiological requirements which provide alternative situations for seed germination in natural habitats.     

不同年际间异子蓬种子大小、萌发能力及结实格局

异子蓬(Borszczowia aralocaspica)为中亚荒漠特有种,在我国仅分布于新疆,其果实具有二型性。对同一生长地2006、2007、2008年异子蓬种子的大小、萌发特性及结实格局进行比较,结果表明:(1)年份和种子类型对种子大小和重量均有显著影响(P<0.05)。(2)2种类型种子具有不同的萌发行为,褐色种子萌发率高(>90%),萌发速度快,而黑色种子萌发率低(2006年的萌发率为31%),萌发速度慢;2种类型种子的萌发指数在不同年际间均差异显著。(3)不同年际间,种子总数、褐色种子数、黑色种子数均具有极显著差异(P<0.001),且随个体的增大黑色种子的比例逐渐减小,褐色种子的比例逐渐增大,并且黑色种子数目均高于褐色种子数目。该研究为深入认识异型种子的生态适应对策提供理论基础。     

Factors influencing seed germination of Salsola affinis (Chenopodiaceae), a dominant annual halophyte inhabiting the deserts of Xinjiang, China

Salsola affinis is a dominant annual inhabiting saline deserts of Xinjiang, China. Experiments were conducted to determine the effects of temperature, winged perianths and NaCl on seed germination and on germination recovery from the effects of saline conditions after transfer to distilled water. Freshly harvested seeds could germinate equally well in light and darkness at 5–30 °C. Attached winged perianths significantly inhibited germination, removal enhanced germination. However, germination was not inhibited in the presence of detached winged perianths in any of the temperature treatments. We suggest that the winged perianth is a mechanical barrier for radicle emergence, not a barrier for water uptake; hence, it inhibited germination. Germination of seeds from which the perianth had been removed was not affected by NaCl at concentrations below 0.4 mol/l, but it was significantly decreased by NaCl at concentrations of 0.6–2.0 mol/l. No seeds germinated at 4.0 mol/l NaCl. Seeds incubated in NaCl at concentrations of 0.05–4.0 mol/l for 14 days recovered after being transferred to distilled water. However, germination was lower than that in the non-saline control, indicating that a portion of the NaCl-treated seeds may lose their ability to germinate.     

Seed dispersal by the Florida box turtle (<Emphasis Type="Italic">Terrapene carolina bauri</Emphasis>) in pine rockland forests of the lower Florida Keys,United States

Seed dispersal by animals is one of the most important plant-animal mutualisms, but saurochory, the dispersal of seeds by reptiles, has received little attention. We investigated the role of the Florida box turtle (Terrapene carolina bauri) as a seed dispersal agent in pine rockland forests of the lower Florida Keys and examined the effect of turtle digestion on seed germination. We obtained seeds of 11 species with fleshy fruits and 2 species with non-fleshy fruits (a grass and legume) from the feces of 145 box turtles collected on Key Deer National Wildlife Refuge from 1999 to 2000. We planted the seeds of nine species and germination percentage (percentage of seeds that germinated during the experiment) varied from 10% to 80%. Comparative germination experiments were conducted with Thrinax morrissii, Serenoa repens, and Byrsonima lucida. We compared the germination percentage and germination rate (number of days from planting to seedling emergence) of seeds from three treatments (seeds recovered from feces, control seeds with pulp, and control seeds without pulp) and continued these experiments for up to 2 years. Passage through the box turtle digestive tract greatly enhanced the germination percentage and germination rate of S. repens, but decreased the germination percentage of B. lucida and T. morrissii, and decreased germination rate for T. morrissii. Subsequent destructive seed viability tests revealed that many ungerminated T. morrissii seeds remained viable, suggesting long-term seed dormancy may occur, even after passage through the turtle digestive system. In addition, the proportion of ungerminated seeds which remained viable was greater for seeds recovered from turtle feces than from control seeds with pulp. Furthermore, removal of fleshy pulp either manually or by the turtle digestive system may allow T. morrissii to escape insect predation.     

Seed germination and seedling fitness in Mesua ferrea L. in relation to fruit size and seed number per fruit

Effect of fruit size and seediness (seed number per fruit) was examined on germination and early growth of seedlings in Mesua ferrea L. Fruiting incidence (number of fruited trees in a population) and fruit loading (number of fruits per tree) vary from one year to the other, and were greater in 1997 than in 1998. Seeds from large fruits (> 40 g) are preferred for forestry plantations and those from small fruits (< 40 g) are discarded, despite a greater proportion of small fruits (63.2 %) than large fruits (36.8 %). A fruit, large or small in size, may contain one, two, three or four seeds. The germination percentage of seeds increased from 1-seeded through 4-seeded fruits both in laboratory and greenhouse conditions, and both in case of large and small fruits. Conversely, the mean seed weight and germination time decreased along this gradient, i.e. seeds from 1-seeded fruits were the heaviest and required maximum time for germination, and the seeds from 4-seeded fruits were the lightest and required minimum time for germination. The seeds from small fruits were lighter in weight, achieved lower germination percentages and required greater germination time than the seeds from large fruits in all four seeded categories. Seedlings from seeds from 1-seeded fruits survived better and with stronger vigour after 1 year of growth than seedlings from 2-, 3- and 4-seeded fruits. Further, seedling survival and vigour were greater for seeds from large rather than small fruits.     

Frugivory and the effects of ingestion by bats on the seed germination of three pioneering plants

The dispersion and seedling establishment of pioneering plants can be favoured by the presence of frugivorous bats because the bats usually improve seed germination after ingestion. Although seed germinability is known to vary greatly after ingestion by different bats, the relative contribution of each bat species to seed germination within plant communities is poorly understood. In this study, we first determined the fauna of frugivorous bats in a semideciduous seasonal forest remnant in southern Brazil and subsequently identified the plant species of the seeds passed through their guts. Second, the germination performance (i.e., germination percentage and speed) of the seeds of three pioneering plants (Piper aduncum, Piper hispidinervum and Solanum granuloso-leprosum) ingested by the most abundant bats was compared with that of the non-ingested seeds (seeds collected from fruits). Additionally, the effects on seed germination of different bat species were compared. During one year, five species of frugivorous bats were caught, and the seeds of eleven identifiable plant species (not counting those of undetermined species) were found in their faeces. We found that the germination performance of the seeds of Piper species was significantly enhanced after ingestion by bats, whereas S. granuloso-leprosum seeds had neutral or reduced germinability when seeds in faeces were compared with pulp-removed seeds. Our results revealed that the bat species that were captured exerted different effects upon seed germination; such a disparity is expected to result in different rates of early establishment of these pioneer plants in tropical forests, most likely affecting forest composition and structure, particularly during the initial stages of succession.     

紫翅猪毛菜的种子多型性及其结实格局

紫翅猪毛菜(Salsola affinis)主要分布于新疆准噶尔荒漠, 具有很强的抗干旱和耐盐碱能力, 其种子具有多型现象。我们对紫翅猪毛菜的种子形态、萌发特性及结实格局进行了观测研究。结果表明: (1) 紫翅猪毛菜3种类型的种子在形状、大小、颜色、着生方式及包被其花被片背部是否具翅方面均有明显不同; (2) 3种类型的种子具有不同的散布特性和萌发行为: A型种子容易从母体脱落, 发达的果翅能够借助风进行远距离传播; B、C型种子成熟时紧连母体, 不易脱落。在变温下A型种子和B型种子能够快速萌发, 且B型种子比A型种子的萌发速度快; 而C型种子萌发缓慢, 最终萌发率小于10%, 表明其处于休眠状态; (3)随植株个体的增大, A型种子所占比例逐渐增多, 由0.43%增加到51.07%; B型种子所占比例逐渐减少, 由65.80%减少到18.06%; C型种子所占比例没有显著变化, 约为30–35%。紫翅猪毛菜的种子多型性以及种子输出的灵活性有利于其在荒漠异质环境中成功定居。对种子多型性及其结实格局的研究将为探讨其生态适应机制及生活史进化研究提供科学依据。     

Germination ofRubus palmatus var.coptophyllus andR. microphyllus seeds buried in soil for 7.5 years

Seeds of twoRubus species,R. palmatus var.coptophyllus andR. microphyllus, buried for 7.5 years in soil were subjected to germination tests to investigate their germinability and germination traits. Most of the retrieved seeds were viable, and germinated at the alternating temperatures of 20/30°C in both light and dark. The twoRubus species showed similar responses of germination to temperature and light, although the final percentages of germination were slightly higher inR. palmatus var.coptophyllus. These characteristics of seed dormancy and germination would be involved in the species' utilization of ephemeral habitats created by unpredictable and infrequent disturbances.     

The role of frugivorous birds in fruit removal and seed germination of the invasive alien Cotoneaster franchetii in central Argentina

Many invasive plant species have fleshy fruits that are eaten by native frugivorous birds which disperse their seeds and may facilitate their germination, playing an important role in plant invasion success. The fleshy‐fruited shrub Cotoneaster franchetii (Rosaceae) is an important invasive alien in the mountainous regions of central Argentina. To determine the role of avian frugivorous in fruit removal of this species, we conducted a frugivore exclusion experiment including bagged and unbagged branches in 75 plants of C. franchetii. At the end of the dispersal period, we compared the percentage of missing fruits (removed by birds + naturally dropped) in unbagged branches with the percentage of naturally dropped fruits in bagged branches. To assess whether any mechanism acting on seeds during their passage through bird guts (de‐inhibition by pulp removal and/or seed scarification) affects seed germination of this species, we compared percentage and speed of germination among seeds obtained from faeces of the native frugivorous Turdus chiguanco, from manually de‐pulped fruits, and from intact fruits. The percentage of missing fruits per shrub in unbagged branches was significantly higher than the percentage of naturally dropped fruits in bagged branches, suggesting that frugivorous birds play an important role in fruit removal of C. franchetii in the study area. Seeds from bird faeces and from manually de‐pulped fruits germinated in higher percentage and faster than seeds from intact fruits. Germination percentage and speed of seeds from manually de‐pulped fruits were significantly higher than those of gut‐passed seeds. These results indicate that T. chiguanco increases and accelerates seed germination of C. franchetii through pulp removal, but not through seed scarification. Overall, our findings indicate that native frugivorous birds facilitate the dispersal and germination success of C. franchetii, likely playing an important role in its invasion throughout the mountainous region of central Argentina.     

Effects of seed colour heterogeneity on germination behaviour of the desert plant Lotononis platycarpa (Fabaceae)

We aimed to determine the ecological role of three seed morphs observed for the first time in a desert population of Lotononis platycarpa (Fabaceae), with respect to their germination requirements. Seeds sorted by seed coat colour (olive green, orange and brown) were germinated under laboratory conditions under two photoperiods (12/12‐h light and continuous dark) and three alternating temperature regimes (15/25, 20/30, 25/35°C). We found that the three distinct seed types differ in their seed mass, germination percentage and speed of germination. Overall, the light‐incubated seeds germinated with higher percentages than seeds in the total darkness. Furthermore, seeds with orange coat germinated with higher percentages at 15/25 and 25/35°C (up to 60%, for both) and significantly faster than the other two colour morphs. Our results suggest an adaptive significance of seed colour heterogeneity in the harsh desert habitat inhabited by the study species.     

新疆干旱区植物藜的种子异型性及其萌发机理

新疆干旱区分布的植物藜(Chenopodium album)的种子有黑色和褐色两种类型。对藜的异型性种子从形态结构、不同环境因素及激素或化学物质对萌发的影响以及同工酶谱等方面进行了研究,并对其萌发及适应异质环境的机理进行了讨论。结果表明:(1)藜的异型性种子在形态结构、萌发休眠特性等方面都存在明显差异:黑色种子种皮厚且硬,休眠,萌发慢,萌发率低;褐色种子种皮薄而软,不休眠,萌发快且萌发率高;(2)黑色种子的休眠可通过切除胚根外缘种皮得以完全解除;(3)赤霉素、乙烯利对黑色种子的萌发无明显促进作用;KNO3可较显著促进黑色种子的萌发;协同使用乙烯利和KNO3时,可显著提高黑种子萌发率,完全打破休眠;(4)黑色种子和褐色种子的酯酶、过氧化物酶及过氧化氢酶同工酶谱带存在差异;(5)黑色种子的萌发需要光照,而褐色种子则对光不敏感;低温贮藏对二者的萌发均无显著影响,尽管黑色种子的萌发率有波动。研究结果初步显示黑色种子的休眠是内源(胚)和外源(种皮)因素共同所致。藜的种子异型性及其萌发机理的形成是其对新疆干旱区异质化环境的高度适应。