Ranunculus glacialis L.: successful reproduction at the altitudinal limits of higher plant life

Biodiversity decreases with increasing altitude, mainly because of the increasingly adverse climate. In the European Alps, only a few plant species occur above 4,000 m a.s.l., among these is Ranunculus glacialis L. Current studies have shown that R. glacialis has a highly conservative growth strategy and low developmental plasticity in response to different dates of snowmelt. Therefore, it was of particular interest to observe whether this strategy is maintained at higher altitudes and to reveal the reproductive limits. We examined the effect of the date of snowmelt on reproductive development and reproductive success in R. glacialis over several years at two subnival sites (2,650 and 2,880 m a.s.l.) and at a nival site (3,440 m a.s.l.) in the Austrian Alps. At the subnival sites, reproductive performance was relatively stable (prefloration period, i.e. snowmelt to onset of anthesis, 2–3 weeks; postfloration period, i.e. onset of anthesis until fruit maturity, 4–5 weeks). Depending on the date of flowering, the mean seed/ovule (S/O) ratio was 0.5–0.8. The temporal safety margin between seed maturation and the onset of winter conditions was at least 1 month. The situation was quite different in the nival zone: the prefloration period usually lasted 1 month, anthesis up to 2 weeks, and seed development 6–7 weeks; when seeds matured in time, the S/O ratio was 0.4–0.6. Overall, R. glacialis shows a high developmental plasticity. At higher altitudes, R. glacialis can double the time taken for seed development but runs a high risk of seeds not maturing in time.     

Sexual reproduction of the high mountain plant Saxifraga moschata Wulfen at varying lengths of the growing season

Flowering phenology, dynamics of seed development and reproductive success of Saxifraga moschata Wulfen, occurring from the alpine to the nival zone, was investigated in three climatically varying years on early- and late-thawing sites at 2340 m a.s.l. in the Austrian Alps. The growing season was particularly short in 2001, about normal in 2002 and exceptionally long and warm in 2003. S. moschata is a mid-season flowering species, which started to bloom about 1 month after snowmelt. From onset of anthesis until seed maturity an individual flower required 6–7 weeks, and all individuals of a site 9–11 weeks. In 2001, late flowering individuals lost about 40% of the seed crop because of too early snowfalls in autumn. No clear relationship could be found between thermal time and the length of different reproductive phases, which indicates that temperature was not a limiting factor for reproductive development in the growing seasons 2001–2003.

Plants from the earliest-thawing site produced about double the reproductive structures (reproductive shoots per individual, number of flowers per inflorescence, number of ovules per ovary), and had a significantly higher reproductive output (number of fruits and mature seeds per inflorescence) compared with individuals from the late-thawing site. Reproductive success was additionally affected by the seasonal climate and was lowest in the warm and dry summer of 2003. Fruit/flower ratio ranged between 0.6 and 0.8, seed/ovule ratio between 0.4 and 0.5 and relative reproductive success (RRS) between 0.3 and 0.4, depending on the site and year.

Different from our expectations, it took S. moschata relatively long to undergo reproductive development; however, its phenological plasticity and ability to continue seed maturation even under snow are most advantageous for a life at higher altitudes.     

Dynamics of flower development and vegetative shoot growth in the high mountain plant Saxifraga bryoides L.

Saxifraga bryoides L. is an abundant species in the subnival and nival zone of the European mountains. First flowering occurs, at the earliest, 6 weeks after snowmelt. This is a remarkably long prefloration period in an environment with a short growing season. To gain more information about the developmental strategies of this species, the timing and the dynamics of flower bud formation and vegetative shoot growth were studied at sites with growing seasons of different lengths at two subnival locations (2650 and 2880 m a.s.l.) in the Tyrolean Alps. At an early, mid and late thawing site, individuals emerging from the winter snow were labelled. Reproductive and vegetative shoots were sampled at regular intervals throughout the growing season and analysed, using different microscopic techniques. Flower buds of S. bryoides develop in three cohorts. Provided the growing season is long enough, cohorts 1 and 2 come into flower, whereas cohort 3 buds remain primordial and continue to develop after winter. New flower primordia appear as day-length decreases from August on, which suggests a short-day requirement for floral initiation. At the end of the growing season, flower buds of different stages are present, but only primordial stages survive winter. Thus, flower buds of S. bryoides develop largely or even completely in the year of anthesis. Developmental dynamics were quite similar at the different sites. Time from flower initiation until anthesis took about 2 months, independently of whether flowers were formed within one or two seasons. All of the leaves on vegetative short-stem shoots turnover within a growing season. Leaves having passed winter continuously decline and are replaced by newly formed ones (21±3 at the mid-thawing site and 18±1 leaves at the short-season site). An individual leaf functions therefore, on average, about 12 months. In most years the seed crop of S. bryoides results mainly from the first cohort of flowers in an individual. In a changing climate with a prolonged growing season, the chance of two cohorts to develop mature seeds from flower cohorts 1 and 2 would increase.     

Natural selection favors rapid reproductive phenology in Potentilla pulcherrima (Rosaceae) at opposite ends of a subalpine snowmelt gradient

In high altitude plants, flowering quickly ensures reproductive success within a short snow-free period, but limits maturation time and fecundity. Natural selection on prefloration intervals may therefore vary in contrasting snowmelt environments and could influence the outcome of phenological responses to climatic change. This study investigated adaptive differentiation and plasticity of prefloration intervals in the subalpine perennial Potentilla pulcherrima. Three years of in situ field observations were combined with phenotypic selection analyses and a common garden experiment. Plants from high, intermediate, and low altitudes expressed similar prefloration intervals and plasticity when grown at common altitude, indicating no evidence for adaptive differentiation. Selection on the prefloration interval was negative at both low and high altitudes before and after accounting for strong positive selection on size. Environmental differences between high and low altitudes indicated that long, dry seasons and short, wet seasons both favored rapid reproduction. Therefore, quicker reproduction was adaptive in response to late snowmelt, but slower reproduction in response to earlier snowmelt appeared to be maladaptive. Selection differed marginally between late snowmelt years and dry ones. Plastic responses to future precipitation patterns may therefore have positive or negative effects on fitness within a single species, depending upon altitude and year.     

Timing of reproductive and vegetative development in Saxifraga oppositifolia in an alpine and a subnival climate

Morphogenesis of floral structures, dynamics of reproductive development from floral initiation until fruit maturation, and leaf turnover in vegetative short-stem shoots of Saxifraga oppositifolia were studied in three consecutive years at an alpine site (2300 m) and at an early- and late-thawing subnival site (2650 m) in the Austrian Alps. Marked differences in the timing and progression of reproductive and vegetative development occurred: individuals of the alpine population required a four-month growing season to complete reproductive development and initiate new flower buds, whereas later thawing individuals from the subnival sites attained the same structural and functional state within only two and a half months. Reproductive and vegetative development were not strictly correlated because timing of flowering, seed development, and shoot growth depended mainly on the date of snowmelt, whereas the initiation of flower primordia was evidently controlled by photoperiod. Floral induction occurred during June and July, from which a critical day length for primary floral induction of about 15 h could be inferred. Preformed flower buds overwinter in a pre-meiotic state and meiosis starts immediately after snowmelt in spring. Vegetative short-stem shoots performed a full leaf turnover within a growing season: 16 (+/-0.8 SE) new leaves per shoot developed in alpine and early-thawing subnival individuals and 12 (+/-1.2 SE) leaves in late-thawing subnival individuals. New leaf primordia emerged continuously from snowmelt until late autumn, even when plants were temporarily covered with snow. Differences in the developmental dynamics between the alpine and subnival population were independent of site temperatures, and are probably the result of ecotypic adaptation to differences in growing season length.     

Signals of range expansions and contractions of vascular plants in the high Alps: observations (1994–2004) at the GLORIA* master site Schrankogel,Tyrol, Austria

High mountain ecosystems are defined by low temperatures and are therefore considered to react sensitively to climate warming. Responding to observed changes in plant species richness on high peaks of the European Alps, an extensive setup of 1 m × 1 m permanent plots was established at the alpine‐nival ecotone (between 2900 and 3450 m) on Mount Schrankogel, a GLORIA master site in the central Tyrolean Alps, Austria, in 1994. Recording was repeated in a representative selection of 362 quadrats in 2004. Ten years after the first recording, we observed an average change in vascular plant species richness from 11.4 to 12.7 species per plot, an increase of 11.8% (or of at least 10.6% at a 95% confidence level). The increase in species richness involved 23 species (about 43% of all taxa found at the ecotone), comprising both alpine and nival species and was pronouncedly higher in plots with subnival/nival vegetation than in plots with alpine grassland vegetation. Only three species showed a decrease in plot occupancy: one was an annual species, one was rare, and one a common nival plant that decreased in one part of the area but increased in the uppermost part. Species cover changed in relation to altitudinal preferences of species, showing significant declines of all subnival to nival plants, whereas alpine pioneer species increased in cover. Recent climate warming in the Alps, which has been twice as high as the global average, is considered to be the primary driver of the observed differential changes in species cover. Our results indicate an ongoing range contraction of subnival to nival species at their rear (i.e. lower) edge and a concurrent expansion of alpine pioneer species at their leading edge. Although this was expected from predictive distribution models and different temperature‐related habitat preferences of alpine and nival species, we provide first evidence on – most likely – warming‐induced species declines in the high European Alps. The projected acceleration of climate warming raises concerns that this phenomenon could become the major threat to biodiversity in high mountains.     

Apomixis is not prevalent in subnival to nival plants of the European Alps

Background and Aims

High alpine environments are characterized by short growing seasons, stochastic climatic conditions and fluctuating pollinator visits. These conditions are rather unfavourable for sexual reproduction of flowering plants. Apomixis, asexual reproduction via seed, provides reproductive assurance without the need of pollinators and potentially accelerates seed development. Therefore, apomixis is expected to provide selective advantages in high-alpine biota. Indeed, apomictic species occur frequently in the subalpine to alpine grassland zone of the European Alps, but the mode of reproduction of the subnival to nival flora was largely unknown.

Methods

The mode of reproduction in 14 species belonging to seven families was investigated via flow cytometric seed screen. The sampling comprised 12 species typical for nival to subnival plant communities of the European Alps without any previous information on apomixis (Achillea atrata, Androsace alpina, Arabis caerulea, Erigeron uniflorus, Gnaphalium hoppeanum, Leucanthemopsis alpina, Oxyria digyna, Potentilla frigida, Ranunculus alpestris, R. glacialis, R. pygmaeus and Saxifraga bryoides), and two high-alpine species with apomixis reported from other geographical areas (Leontopodium alpinum and Potentilla crantzii).

Key Results

Flow cytometric data were clearly interpretable for all 46 population samples, confirming the utility of the method for broad screenings on non-model organisms. Formation of endosperm in all species of Asteraceae was documented. Ratios of endosperm : embryo showed pseudogamous apomixis for Potentilla crantzii (ratio approx. 3), but sexual reproduction for all other species (ratios approx. 1·5).

Conclusions

The occurrence of apomixis is not correlated to high altitudes, and cannot be readily explained by selective forces due to environmental conditions. The investigated species have probably other adaptations to high altitudes to maintain reproductive assurance via sexuality. We hypothesize that shifts to apomixis are rather connected to frequencies of polyploidization than to ecological conditions.     

How endangered is sexual reproduction of high-mountain plants by summer frosts? Frost resistance, frequency of frost events and risk assessment

In temperate-zone mountains, summer frosts usually occur during unpredictable cold spells with snow-falls. Earlier studies have shown that vegetative aboveground organs of most high-mountain plants tolerate extracellular ice in the active state. However, little is known about the impact of frost on reproductive development and reproductive success. In common plant species from the European Alps (Cerastium uniflorum, Loiseleuria procumbens, Ranunculus glacialis, Rhododendron ferrugineum, Saxifraga bryoides, S. moschata, S. caesia), differing in growth form, altitudinal distribution and phenology, frost resistance of reproductive and vegetative shoots was assessed in different reproductive stages. Intact plants were exposed to simulated night frosts between ?2 and ?14 °C in temperature-controlled freezers. Nucleation temperatures, freezing damage and subsequent reproductive success (fruit and seed set, seed germination) were determined. During all reproductive stages, reproductive shoots were significantly less frost resistant than vegetative shoots (mean difference for LT₅₀ ?4.2 ± 2.7 K). In most species, reproductive shoots were ice tolerant before bolting and during fruiting (mean LT₅₀ ?7 and ?5.7 °C), but were ice sensitive during bolting and anthesis (mean LT₅₀ around ?4 °C). Only R. glacialis remained ice tolerant during all reproductive stages. Frost injury in reproductive shoots usually led to full fruit loss. Reproductive success of frost-treated but undamaged shoots did not differ significantly from control values. Assessing the frost damage risk on the basis of summer frost frequency and frost resistance shows that, in the alpine zone, low-statured species are rarely endangered as long as they are protected by snow. The situation is different in the subnival and nival zone, where frost-sensitive reproductive shoots may become frost damaged even when covered by snow. Unprotected individuals are at high risk of suffering from frost damage, particularly at higher elevations. It appears that ice tolerance in reproductive structures is an advantage but not an absolute precondition for colonizing high altitudes with frequent frost events.     

Phenology,Seed Development,and Reproductive Success of an Alpine Population of Centianella germanica in Climatically Varying Years

During the growing seasons of 1994–1996, the reproductive fitness of an autumn flowering population of G. germanica was assessed at 1980 m in the Austrian Alps. The warmest year of the last two centuries in Austria was 1994, 1995 was a normal year, and the summer of 1996 was exceptionally cold. The Investigations were carried out on large, early-flowering individuals (L-plants) and on small, mainly late-flowering individuals (S-plants). In both size classes, the sequence of phenophases varied in response to the contrasting climatic conditions of these years. In 1994, peak flowering In L-plants occurred about one month earlier than in S-plants; in 1995 and 1996, the periods of full bloom overlapped partially and fully for the two size classes, respectively. Detailed analyses of seed development and thermal time revealed that low temperatures during histogenesis led to remarkable delays in the Initiation of seed and fruit development, whereas seed filling and seed maturation were largely Independent of temperature. Self-pollination resulted in high seed sets. Irrespective of weather conditions and dates of flowering. In both size classes, the seed: ovule ratio of mature fruits was about 0.9 and 0.75, in apical and basal positions of the stalks, respectively. The fruit: flower ratios, however, depended on temperature; the ratio was around 0.8 in 1994 and below 0.5 in 1996. In the cool year 1996, fruit development was so slow that in many individuals only the fruits in the apical positions of the stalks matured before the onset of winter conditions.     

Extended flowering in a Mediterranean shrub: Seasonal variability in seed quality and quantity

Fluctuating conditions throughout the year and changes in floral display may promote shifts in pollinator activity and predator pressure, influencing female reproductive output, especially for extended flowering species under seasonal climates. In this regard, flowering and fruit production were tracked in 2 different years in 2 populations of Ononis tridentata in Central Spain. Total fruit production was estimated, and fruits were harvested to obtain primary fruit investment, pollination success, predation incidence, seed production, seed weight and germination rates. Ononis tridentata combined spring mass flowering with a steady long flowering period across the summer and fall. The fewer flowers that are produced in fall were successfully pollinated, and produced fruits that were subject to minimal predation pressure relative to spring fruits. Moreover, fall fruits contained a higher number of heavier seeds and showed higher germination rates than those of spring seeds. Fall reproductive output represent 10% of annual viable seeds and thus may act as an important complement to the main spring reproductive investment. Extended flowering could be interpreted as a “bet-hedging strategy” for enduring Mediterranean unpredictable and changing environmental conditions.     

Response to simulated climatic change in an alpine and subarctic pollen-risk strategist, Silene acaulis

The aim of this study was to test if early flowering species respond with increased seed production to climate warming as is predicted for late-flowering seed-risk strategists. Experimental climate warming of about 3°C was applied to two populations of the cushion-forming plant Silene acaulis (L.) Jacq. The experiment was run at one subarctic site and one alpine site for 2 years and 1 year, respectively, using open-top chambers (OTC).
The 2-year temperature enhancement at the subarctic site had a marked effect on the flowering phenology. Cushions inside the OTC started flowering substantially earlier than control cushions. Both the male and female phases developed faster in the OTCs, and maturation of capsules occurred earlier. The cushions also responded positively in reproductive terms and produced more mature seeds and had a higher seed/ovule ratio. After 1 year temperature enhancement at the alpine site there was a weak trend for earlier flowering, but there was no significant difference in seed production or seed/ovule ratio.     

Development of the Potential for Cyanogenesis in Maturing Black Cherry (Prunus serotina Ehrh.) Fruits

Biochemical changes related to cyanogenesis (hydrogen cyanide production) were monitored during maturation of black cherry (Prunus serotina Ehrh.) fruits. At weekly intervals from flowering until maturity, fruits (or selected parts thereof) were analyzed for (a) fresh and dry weights, (b) prunasin and amygdalin levels, and (c) levels of the catabolic enzymes amygdalin hydrolase, prunasin hydrolase, and mandelonitrile lyase. During phase I (0-28 days after flowering [DAF]), immature fruits accumulated prunasin (mean: 3 micromoles/fruit) but were acyanogenic because they lacked the above enzymes. Concomitant with cotyledon development during mid-phase II, the seeds began accumulating both amygdalin (mean: 3 micromoles/seed) and the catabolic enzymes and were highly cyanogenic upon tissue disruption. Meanwhile, prunasin levels rapidly declined and were negligible by maturity. During phases II (29-65 DAF) and III (66-81 DAF), the pericarp also accumulated amygdalin, whereas its prunasin content declined toward maturity. Lacking the catabolic enzymes, the pericarp remained acyanogenic throughout all developmental stages.     

The subnival–nival vascular plant species of Iran: a unique high-mountain flora and its threat from climate warming

This study provides a first country-wide overview of the vertical distribution patterns and the chorology of vascular plant species that occur in the uppermost elevation zones in Iran. The current distribution patterns are discussed with respect to potential warming-induced species losses. Iran’s subnival and nival vegetation zones are found at elevations above 3600–3900 m in a highly fragmented distribution across Alborz, Zagros, and NW-Iran. Based on literature research and on field observations, all vascular plant species living in the subnival–nival zone of Iranian mountains were identified (151 species) and classified into three altitudinal groups: Group A comprises species that occur mainly in subnival–nival habitats (51 species). Group B are species being common in subnival–nival areas but are equally present in the alpine zone (56 species). Group C are species that can reach to subnival areas but also grow in alpine, subalpine and sometimes lower altitudes (44 species). The chorological patterns differ among the three groups. The percentage of species being endemic to Iran decreases from group A, to B and C, with 68, 53 and 20%, respectively. A narrow altitudinal distribution at high elevations is clearly related to a small-scaled geographical distribution range. The outstanding rate of high-altitude endemism appears to result mainly from orographic isolation of the country’s highly scattered cold areas and by the absence of extensive Pleistocene glaciations. The narrow distribution of most of Iran’s cold-adapted mountain flora and the low potential of alternative cold habitats render it highly vulnerable to climate change.     

Predispersal reproductive biology of female Osyris quadripartita (Santalaceae), a hemiparasitic dioecious shrub of Mediterranean scrublands

Female Osyris quadripartita plants exhibit uninterrupted reproductive activity throughout the year, due to the long duration of successive stages in the cycle and marked within-crop developmental asynchrony. Cycles corresponding to the flowering seasons of consecutive years overlap in each individual. Flowering takes place in spring, and fruits develop in the dry summer season and ripen at any time of the year. Variation in flowering time explains a negligible proportion of variation in ripening time. The greatest reproductive losses are incurred in the phase extending from closed flowers through unripe fruits, mostly due to ovary abortion. Only 30% of closed flowers eventually reach this latter stage. In contrast, 75% of unripe fruits complete their development, with subsequent dispersal of seeds. The probability of the setting of ripe fruit steadily decreases from early to late season flowers, due to increased ovary abortion rates. Resource limitation in the dry summer season seems responsible for this pattern of selective fruit maturation.     

Causes and consequences of frequent flowering on edges in the mast-seeding genus

Recent work has shown that resource accumulation is important in allowing mast-seeding plants to display occasional intense reproductive efforts. Anecdotal reports suggest that Chionochloa tussocks (bunchgrasses) on patch edges flower more frequently, and it has been proposed that this is due to greater resource availability. This study aimed to quantify any edge effect in flowering effort in Chionochloa populations at Mt Hutt in the Southern Alps of New Zealand, and to look for correlations with available soil nutrients. It also focused on how higher flowering along edges might affect seed predation rates in these plants, since seed predation is recognised as the likely cause of masting in this genus. As predicted, in a generally low-flowering year flowering was found to be most prolific on upslope edges across a range of altitudes with at least 43% of the flowering effort in the upslope plots being concentrated in the 20% of plot area within 2 m of the upper edge. Upslope edges also exhibited higher nitrate availability than did patch interiors or downslope edges. However, other measured nutrients did not show such a clear pattern. The elevated flowering effort on upslope edges does support the importance of a resource accumulation component in flowering effort. Higher edge-flowering did not significantly affect the distribution of the insect seed predators, suggesting the scale at which these insects move in search of oviposition sites is greater than the scale of the vegetation patches studied.     

Somatic and demographic costs under different temperature regimes in the late-flowering alpine perennial herb Saxifraga stellaris (Saxifragaceae)

If reproduction involves costs, preventing reproduction one year should result in increased growth and/or reproduction the next year. Costs of reproduction in the late-flowering perennial alpine herb Saxifraga stellaris were studied in an experimental field study. To determine whether cost of reproduction differed between two contrasting temperature regimes, I examined plants in Open Top Chambers (OTCs) and control plots. One year before measurements all flower buds on the experiment plants were removed. There was no impact of the flower bud removal or the interaction between flower removal and temperature on prefloration time or seed maturation time. However, cost of reproduction influenced growth (somatic cost), vegetative propagation, flowering frequency, number of stem per ramet, number of fruits, and seed mass (demographic cost). However, significant interaction effects of flower removal and temperature on growth and fruit production revealed that the cost of reproduction differed between the two temperature regimes. The warmed plants showed reduced cost of reproduction compared to plants growing under natural temperature.     

Selective fruit and seed maturation in Asphodelus albus Miller (Liliaceae)

The fruiting patterns of the rhizomatous perennial Asphodelus albus Miller (Liliaceae) were studied in five populations during 1989 and in one population over 3 years (1988–1990). Fruit/flower (Fr/Fl) ratio and seed/ovule (S/O) ratio varied markedly between populations. Although there were differences between years within the population studied over 3 years, these variations, although statistically signifcant, were less important than those between populations. Neither flowering phenology nor plant size influenced Fr/Fl or S/O ratios. Field experiments tested whether fruit and seed set were pollenor resource-limited. Hand-pollination had no effect on Fr/Fl or S/O ratios, but the reduction of resources by defoliation at the time of flowering decreased both relative components of fecundity. Manipulation of resources by hand-thinning flowers and tiny fruits had no demonstrable effect on these ratios, although brood size of individual fruits was significantly affected. It may be concluded that fruit maturation is resource-limited rather than pollen-limited. Most of the fruits aborted early in the fruiting season, and fruits with higher numbers of developing seeds had a lower probability of abortion than fruits with fewer seeds. Analyses of position effects revealed that the fruits in lower positions in the inflorescence matured preferentially. Furthermore, the two ovules in the same carpel tended either both to fail or both to develop into seeds. The plant's ability to selectively mature only high quality embryos may be limited.     

Promotion of flowering and reduction of a generation time in apple seedlings by ectopical expression of the Arabidopsis thaliana FT gene using the Apple latent spherical virus vector

Tree crops have a long juvenile period which is a serious constraint for genetic improvement and experimental research. For example, apple remains in a juvenile phase for more than five years after seed germination. Here, we report about induction of rapid flowering in apple seedlings using the Apple latent spherical virus (ALSV) vector expressing a FLOWERING LOCUS T (FT) gene from Arabidopsis thaliana. Apple seedlings could be flowered at 1.5-2?months after inoculation to cotyledons of seeds just after germination with ALSV expressing the FT gene. A half of precocious flowers was normal in appearance with sepals, petals, stamens, and pistils. Pollen from a precocious flower successfully pollinated flowers of 'Fuji' apple from which fruits developed normally and next-generation seeds were produced. Our system using the ALSV vector promoted flowering time of apple seedlings within two months after germination and shortened the generation time from seed germination to next-generation seed maturation to within 7?months when pollen from precocious flowers was used for pollination.     

开花时间与伴生种对鹤首马先蒿传粉和生殖成功的影响

开花物候是物种间相互作用的重要生活史特征和适合度因子,在全球气候变化的背景下而备受关注.为探讨开花时间如何存种内和种间水平上影响植物的传粉和生殖成功,我们连续3年(2003-2005)对不同花期和伴生种存在情况下的鹤首马先蒿(Pedicularis gruina)的传粉者访花忠实度、受粉率、坐果率、单果种子产量和果实被啃食频率进行了比较研究.结果表明鹤首马先蒿的坐果率主要受其传粉环境的影响:在没有伴生种时,不同时期鹤首马先蒿的坐果率没有显著差异,34-38％的花可以坐果;在有伴生种存在时既可以显著提高其坐果率,也可显著降低其坐果率,这取决于传粉者类型以及伴生种密穗马先蒿(P.densispica)花期的差异.密穗马先蒿具有花蜜和花粉双重报酬,在群落中可以作为主体物种吸引传粉者并间接促进与其伴生的鹤首马先蒿的传粉和生殖成功.同样无蜜的管花马先蒿(P.siphonantha)和鹤首马先蒿伴生,则是通过提高群落水平对传粉者的吸引力进而直接促进鹤首马先蒿的传粉和生殖成功.此外,研究结果也表明开花时间对坐果率没有显著影响,但是显著影响单果种子产量和果实被啃食的频率.在相同的传粉条件下早花期植株单果种子产量显著高于晚花期的种子产量,同时早花期的果实被啃食的频率显著增加.     

Changes in carbohydrates,amino acids and proteins in developing seed of chickpea

Developing seeds of chickpea cultivars G-130, L-550 and 850-3/27 grown under field conditions were sampled at different stages of maturity and analysed for soluble sugars, starch, soluble nitrogen, protein nitrogen and amino acids. Fr. wt of seeds of all three cultivars decreased after 28 days of flowering while the dry wt continued to increase. Rapid starch accumulation was observed between 14 and 28 days after flowering. Starch as per cent of seed dry wt started to decrease after 28 days, while starch per seed increased till maturity. The percentage of salt-soluble proteins decreased with maturation of seed. The electrophoretic pattern revealed that deposition of seed storage protein in cotyledons occurred 14 days after flowering. Most of the biochemical activity apparently occurred between 14 and 28 days after flowering.