Subnivean embryo development in the alpine herb Caltha leptosepala (Ranunculaceae)

2001 ◽  
Vol 79 (5) ◽  
pp. 635-642 ◽  
Author(s):  
Tara A Forbis ◽  
Pamela K Diggle
Keyword(s):  
Embryo Development ◽  
Low Temperatures ◽  
Histological Analysis ◽  
Growing Season ◽  
Perennial Herb ◽  
Wet Meadow ◽  
Morphophysiological Dormancy ◽  
Time Period ◽  
Embryo Dormancy ◽  
Further Development

Caltha leptosepala D.C. (Ranunculaceae) is a perennial herb of alpine wet meadows. Seeds of this species have morphophysiological dormancy; they contain a rudimentary embryo that must undergo further development prior to germination. The embryo itself is also dormant and requires a physiological cue for resumption of development. We ask how C. leptosepala can break embryo dormancy and complete embryo development, germination, and seedling growth under the constraint of the extremely short alpine wet meadow growing season. Seeds were stratified at 2.5°C and collected at regular intervals for germination trials and histological analysis. At dispersal, the embryo occupies approximately 7% of the length of the seed and is dormant. Embryo development resumes within 1 month of stratification. Embryos grow to fill the seed over a 4- to 7-month period. Germination rates are positively correlated with stratification time and reach 50% at 4 months and 70% at 7 months. Because embryo development requires a time period longer than the snow-free period prior to germination in the alpine wet meadow, we conclude that embryo development in C. leptosepala takes place beneath alpine snowbanks. Morphophysiological dormancy in Caltha is not uniquely derived, but the ability of Caltha embryos to develop and germinate at low temperatures may be an adaptation to their environment.Key words: alpine, rudimentary embryo, Ranunculaceae, seed, dormancy, germination.

Embryo dormancy responses to temperature in capeweed (Arctotheca calendula) seeds

2002 ◽  
Vol 12 (3) ◽  
pp. 181-191 ◽  
Author(s):  
Amanda J. Ellery
Keyword(s):  
Soil Temperature ◽  
Water Potential ◽  
Low Temperatures ◽  
Seasonal Changes ◽  
Temperature Fluctuation ◽  
Soil Surface ◽  
Seed Collection ◽  
Embryo Dormancy ◽  
Response To Temperature ◽  
Dormancy Cycles

Changes in embryo dormancy of capeweed [Arctotheca calendula (L.) Levyns.] seeds in response to temperature were investigated to determine the nature of seasonal dormancy cycles. Primary embryo dormancy persisted for 2–3 months after seed collection and was then rapidly relieved when seeds were maintained at temperatures simulating summer soil surface temperatures. Embryo dormancy was also rapidly relieved in seeds maintained at constant temperatures, indicating that a daily temperature fluctuation was not necessary for the relief of embryo dormancy in capeweed. Dormancy relief was maximal at 40°C. Secondary dormancy was induced when seeds were maintained at low temperatures and a water potential of –1.5 MPa, suggesting that the onset of winter may postpone germination until a subsequent autumn. These results indicate that the dormancy cycles observed in capeweed seeds maintained on the soil surface are probably driven by seasonal changes in soil temperature.

scholarly journals ACCUMULATION BEHAVIOUR OF ALLANTOIN IN THE UNDERGROUND PHYTOMASS OF THE BORAGINACEAE FAMILY AND ITS ROLE IN ADAPTING THE PLANTS TO ADVERSE ENVIRONMENTAL FACTORS

2019 ◽  
Vol 14 (1) ◽  
pp. 126-136
Author(s):  
A. Ya. Tamakhina ◽  
A. A. Akhkubekova ◽  
A. B. Ittiev
Keyword(s):  
Solar Radiation ◽  
Sea Level ◽  
Low Temperatures ◽  
High Performance ◽  
Growing Season ◽  
Stress Factors ◽  
Adaptation To Stress ◽  
Plant Adaptation ◽  
The Family

Aim.The aim of the work described herein was to study the dynamics of allantoin accumulation in the underground phytomass ofEchium vulgareL.,Symphytum caucasicumM. Bieb. andS. asperumLepech. as well as to clarify the role of allantoin in plant adaptation to stress factors.Methods.We studied the roots of plants growing in the foothill (Nalchik, 490–512 m above sea level) and the mountain zones of the Kabardino-Balkarian Republic (Terskol village, 2530 m above sea level; Verkhnyaya Balkaria village, 2680 m above sea level). The roots were collected at the stages of rosetting, flowering, fruiting and at the end of the growing season. Aqueous-alcoholic extracts of shredded roots were analyzed by high-performance liquid chromatography.Results.The highest content of allantoin in the roots ofEchium vulgare,Symphytum caucasicum,S. asperumplants was noted at the end of the growing season, respectively 0.915; 0.342–0.658; 2,842–3,426%. Under conditions of low temperatures and increased solar radiation, the content of allantoin in the roots increases 1.2–1.9 times as compared with the plants of the foothill zone.Conclusion.Allantoin plays an important role in the process of adapting species of the family Boraginaceae to oxidative stress caused by hypothermia and increased solar radiation.

scholarly journals Rainfall in growing season determines the size of an annual-dominated soil seed bank in a desert ecosystem

2020 ◽  
Author(s):  
Ya-Fei Shi ◽  
Zengru Wang ◽  
Bing-Xin Xu ◽  
Jian-Qiang Huo ◽  
Rui Hu ◽  
...  
Keyword(s):  
Environmental Factors ◽  
Species Composition ◽  
Seed Bank ◽  
Soil Seed Bank ◽  
Growing Season ◽  
Seed Banks ◽  
Desert Ecosystem ◽  
Perennial Herb ◽  
Desert Ecosystems ◽  
Soil Seed Banks

Soil seed banks may offer great potential for restoring and maintaining desert ecosystems that have been degraded by climate change and anthropogenic disturbance. However, few studies have explored the annual dynamics in the composition and relative abundance of these soil seed banks. We conducted a long-term observational study to assess the effects of environmental factors (meteorology and microtopography) and aboveground vegetation on the soil seed bank of the Tengger Desert, China. The desert seed bank was dominated by annual herbs. We found that more rainfall in the growing season increased the number of seeds in the soil seed bank, and that quadrats at relatively higher elevations had fewer seeds. The species composition had more similarity in the seed bank than in the aboveground vegetation, though the seed bank and aboveground vegetation did change synchronously due to the rapid propagation of annuals. Together, our findings suggest that the combined effects of environmental factors and plant life forms determine the species composition and size of soil seed banks in deserts. Thus, if degraded desert ecosystems are left to regenerate naturally, the lack of shrub and perennial herb seeds could crucially limit their restoration. Human intervention and management may have to be applied to enhance the seed abundance of longer-lived lifeforms in degraded deserts.

Controls on Decomposition Processes in Alpine Tundra

2001 ◽  
Author(s):  
Timothy R. Seastedt ◽  
Marilyn D. Walker
Keyword(s):  
Low Temperatures ◽  
Lignin Content ◽  
Research Effort ◽  
Arctic Tundra ◽  
Decay Rates ◽  
Wet Meadow ◽  
Substrate Quality ◽  
Decomposition Processes ◽  
1960S And 1970S ◽  
The 1960S

The snowpack gradient in the alpine generates a temperature and moisture gradient that largely controls organic matter decomposition. While low temperatures constrain decomposition and mineralization (chapter 12), moisture appears to be the strongest source of landscape variation in the alpine, with surface decay rates of plant materials highest in moist and wet meadow habitats. Despite a longer snow-free season and higher surface temperatures in dry meadows, decay in these areas is substantially lower than in moist meadows. Studies of decay rates of roots within the soil indicate that decay is uniformly low in all habitats and is limited by low temperatures and perhaps by the absence of certain groups of decomposer invertebrates. As in other ecosystems, substrate quality indices such as nitrogen and lignin content can be shown to be important factors influencing the rate of decay of specific substrates. Alpine ecosystems were overlooked during the flurry of activity associated with the extensive ecosystem science programs of the 1960s and 1970s. With the few exceptions to be discussed here, decomposition studies in cold regions were conducted in arctic tundra or northern temperate and boreal forests. The need for this information in conjunction with efforts to understand carbon cycling in the alpine stimulated a substantial research effort in the 1990s. Studies have included both the effects of landscape location on decay (O’Lear and Seastedt 1994; Bryant et al. 1998), information on the importance of substrate chemistry on decomposition processes (Bryant et al. 1998), and preliminary information on some of the decomposer organisms (O'Lear and Seastedt 1994; Addington and Seastedt 1999). Niwot Ridge researchers also participated in the Long-term Intersite Decomposition Experiment Team (LIDET) study, which involved placement of a dozen different litter types in the alpine and in 27 other sites from the tropics to the arctic tundra (Harmon 1995). All but one of the plant species used in the LIDET experiments were exotic to the alpine. Collectively these studies have provided sufficient information to represent the alpine in global decomposition modeling efforts.

Effect of time of sowing on flowering and growth of Townsville stylo (Stylosanthes humilis)

1974 ◽  
Vol 14 (67) ◽  
pp. 182 ◽  
Author(s):  
Mannetje L t ◽  
KHLvan Bennekom
Keyword(s):  
Low Temperatures ◽  
Dry Matter ◽  
Late Summer ◽  
Growing Season ◽  
Sowing Date ◽  
Stylosanthes Humilis ◽  
Maturity Type ◽  
Townsville Stylo ◽  
Late Start ◽  
Spring Sowing

A midseason maturity type of Townsville stylo sown at monthly intervals throughout a year in a glasshouse in Brisbane (27�30' south) started flowering from 42 to 76 days after sowing between February and September, with dry matter yields at flowering ranging from 0.05 to 5.82 g/per plant. Sowings between October and January resulted in flowering after 98 to 157 days, with yields ranging from 26.41 to 54.75 g/per plant. Flowering was mainly determined by daylength, although low temperatures during winter delayed inflorescence elongation. Growth after onset of flowering was measured in plants sown in winter, spring and late summer. Plant weights increased after flowering in all sowings. In the spring sowing this consisted entirely of stem and inflorescence, but in the other sowings leaf was formed after onset of flowering as well. Winter and spring sowings gave the highest, late summer sowing the lowest final yields. The main agronomic implication is that sowing early in the growing season is necessary for obtaining a good first year's yield, but that seed production is little affected by sowing date, ensuring good regeneration even in years with a late start of the growing season.

Enhancement by Low Temperatures of the Anaerobic Induction of Cocklebur Seed Germination

1977 ◽  
Vol 4 (6) ◽  
pp. 849 ◽  
Author(s):  
Y Esashi ◽  
Y Ohhara
Keyword(s):  
Seed Germination ◽  
Low Temperature ◽  
Gibberellic Acid ◽  
Low Temperatures ◽  
Anaerobic Treatment ◽  
Maximal Response ◽  
Benzyl Adenine ◽  
Anaerobic Induction ◽  
Time Period ◽  
Proportional Increase

Non-dormant, upper cocklebur (Xanthium pensylvanicum Wallr.) seeds, incapable of germinating under ordinary conditions, can germinate when previously subjected to anaerobiosis; this has been termed the anaerobic induction of seed germination. Aerobic presoaking of the seeds was also required for successful anaerobic induction, and exerted two counter-acting effects on seed germination. When the time period of aerobic presoaking was sufficiently prolonged, the increasing duration of an anaerobic treatment resulted in proportional increase of germination potential but, when it was short, the effect of the anaerobiosis was saturated in a few days. Prolonging the aerobic presoaking period caused less response of the seed to the anaerobic induction, suggesting the development of some germination-inhibiting system during the aerobic presoaking period. This system could not develop in the absence of O2 or at low temperature. Thus, low temperature during prolonged presoaking produced a maximal response to anaerobic induction. Various germination stimulants, CO2, ethylene, gibberellic acid and benzyl adenine, did not significantly alter the effects of the presoaking.

The ecology of Sminthurus viridis (Collembola) III. The influence ofclimate andl land use on its distribution and that of an important predator, Bdellodea lapidaria (Acari : Bdellidae)

1971 ◽  
Vol 19 (2) ◽  
pp. 177 ◽  
Author(s):  
MMH Wallace ◽  
JA Mahon
Keyword(s):  
Land Use ◽  
Low Temperatures ◽  
New South ◽  
New South Wales ◽  
Summer Rainfall ◽  
Growing Season ◽  
Predatory Mite ◽  
South Wales ◽  
Important Predator ◽  
Distribution Limits

The lucerne flea, S. viridis, is restricted to the southern parts of Australia and, apart from a few isolated occurrences in eastern New South Wales, occurs only in areas with an essentially Mediterranean-type climate. The northern inland limit to its distribution agrees closely with the 250-mm isohyet for the growing season of May-October inclusive. The eastern limit to distribution in New South Wales and Victoria agrees with a December-March isohyet of 225 mm. Areas east of this line receive predominantly summer rainfall, and the pastures contain a high proportion of perennial plants which probably do not provide the nutritional stimulus for the development of aestivating diapause eggs in S. viridis essential for oversummering. The predatory mite B. lapidaria requires slightly moister conditions than S. viridis and the limit of its inland distribution agrees reasonably well with the 260-mm isohyet for the May-October period. Low temperatures (mean maximum < 17.5'C) also seem necessary during this period. The eastern distribution limits in Victoria are similar to those of S. viridis.

scholarly journals Temporal Patterns of Sporulation Potential of Phomopsis viticola on Infected Grape Shoots, Canes, and Rachises

Plant Disease ◽  
2012 ◽  
Vol 96 (9) ◽  
pp. 1297-1302 ◽  
Author(s):  
D. J. Anco ◽  
L. V. Madden ◽  
M. A. Ellis
Keyword(s):  
Leaf Spot ◽  
Temporal Pattern ◽  
Growing Season ◽  
First Year ◽  
Bud Break ◽  
Optimal Conditions ◽  
Phomopsis Viticola ◽  
Time Period ◽  
Dormant Season ◽  
Vitis Spp

Phomopsis cane and leaf spot on Vitis spp. (grape) is currently understood to be monocyclic, with primary inoculum only being produced early in the growing season. However, of the few published studies pertaining to sporulation of Phomopsis viticola, none specifically examined rachises, and none were designed to determine when infected tissues become capable of sporulation. The objective of these studies was to determine when grape shoots, canes, and rachises infected with P. viticola develop the capacity to sporulate, and to determine the time period during which those tissues remain capable of sporulation. Starting in 2009 and 2010, infected first-year shoots and rachises were collected biweekly throughout the growing season, into the dormant season, and into the following growing season. Tissues were collected from ‘Catawba,’ ‘Concord,’ and ‘Reliance’ vineyards. Samples were observed for sporulation after 48 h of incubation in a moist chamber at 23°C; the magnitude of the conidia production under these optimal conditions was considered the sporulation potential. For infections that occurred in 2009 and 2010, the production of conidia was not observed until after harvest. In the year following infection, sporulation potential was found from about bud break until shortly after the end of bloom. There was a generally consistent temporal pattern to relative sporulation potential across sampled vineyards, years, and grape tissues (rachises and canes), described by a modified β model, with peak sporulation potential occurring around 16 May. These results confirmed that Phomopsis cane and leaf spot is a monocyclic disease and support control recommendations for use of fungicides in spring.

scholarly journals Temperature-related Variables Associated with Yield of ‘Kerman’ Pistachio in the San Joaquin Valley of California

HortScience ◽  
2017 ◽  
Vol 52 (4) ◽  
pp. 598-605 ◽  
Author(s):  
Craig E. Kallsen
Keyword(s):  
Crop Yield ◽  
Air Temperature ◽  
Growing Season ◽  
San Joaquin Valley ◽  
Efficient Allocation ◽  
Time Period ◽  
Processing Facility ◽  
Time Periods ◽  
Advance Knowledge ◽  
Facility Capacity

Information on how annual pistachio yield is affected by air temperature (Ta) during the winter and growing season is lacking. Timely advance knowledge of the magnitude of the yield of the California pistachio harvest would be beneficial for the pistachio industry for efficient allocation of harvest and postharvest resources, such as personnel, harvesting machinery, trucks, processing facility capacity, crop storage facilities, and for making marketing decisions. The objective of this study was to identify parameters, especially Ta variables and time periods, calculated from Ta data during the previous fall, winter, spring, and summer, that were associated most closely with fall nut-crop yield. The premise of this study was that sequential, historical yield records could be regressed against a number of Ta-derived variables to identify Ta thresholds and accumulations that have value in explaining past and predicting subsequent nut yield. Of the 27 regression variables examined in this study, the following, which were all negatively correlated with subsequent yield, explained the greatest proportion of the variability present in predicting yield of ‘Kerman’ pistachio: yield of the previous-year harvest, hourly Ta accumulations above 26.7 or 29.4 °C from the time period between 20 Mar. and 25 Apr., hourly Ta accumulations below 7.2 °C from 15 Nov. to 15 Feb., and hourly Ta accumulations above 18.3 °C from 15 Nov. to 15 Feb.

Influence of nutrients enrichment on ecosystem functioning in a subpolar seagrass meadow

2020 ◽  
Author(s):  
Ludovic Pascal ◽  
Gwénaëlle Chaillou ◽  
Pascal Bernatchez ◽  
Christian Nozais ◽  
Philippe Archambault
Keyword(s):  
Nutrient Enrichment ◽  
Ecosystem Functioning ◽  
Anthropogenic Activities ◽  
Growing Season ◽  
Benthic Fluxes ◽  
Seagrass Meadows ◽  
Time Period ◽  
Mesocosm Experiments ◽  
Functional Consequences ◽  
Summer Time

&lt;p&gt;Seagrass meadows are among the most productive ecosystems in the world: they store a large amount of carbon and host highly&amp;#160;diverse macrobenthic communities. They also play a key role in biogeochemistry at the sediment-water interface. The light requirements of seagrasses limit their development to shallow coastal areas where they are facing various natural and anthropogenic disturbances, which has induced a global loss of these ecosystems over the last decades. Nutrient enrichment of coastal waters, resulting from anthropogenic activities is one of the leading causes of this decline. Subpolar seagrass meadows present a strong seasonal dynamic, with a long winter when seagrasses rely on carbon reserves that they build up during the short growing season (limited to two to three months during summer time). Hence, it has been hypothesized that the effects of nutrient enrichment on seagrass ecosystem functioning depend on seasonal dynamics. In this study, we performed a series of mesocosm experiments over a month period to investigate the effects of the timing, duration and intensity of disturbance on macrofauna bioturbation, oxygen and nutrients porewater concentration profiles and benthic fluxes using three levels (including control) of realistic nutrient enrichments at the beginning (June) and at the end (August) of the growing season. In May, effects of intermediate level of nutrient enrichment were only visible on total oxygen uptake by the sediment at day 30 of disturbance while it affected oxygen and nutrients benthic fluxes at day 15 in August. The highest level of nutrient enrichment affected oxygen and nutrients benthic fluxes in May and August. Overall, our results highlight the importance of considering the time (period and duration) in the assessment of the functional consequences of disturbances.&lt;/p&gt;

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