Germination of Seeds of Five Annual Species of Barley Grass

1981 ◽  
Vol 18 (2) ◽  
pp. 547 ◽  
Author(s):  
A. I. Popay
Keyword(s):  
Annual Species

scholarly journals Facilitation Effects of Haloxylon salicornicum Shrubs on Associated Understory Annuals, and a Modified “Stress-Gradient” Hypothesis for Droughty Times

Plants ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 1726
Author(s):  
Nasr H. Gomaa ◽  
Ahmad K. Hegazy ◽  
Arafat Abdel Hamed Abdel Latef
Keyword(s):  
Species Richness ◽  
Water Availability ◽  
Stress Gradient ◽  
Growing Season ◽  
Annual Species ◽  
Negative Effects ◽  
Growing Seasons ◽  
Dry Seasons ◽  
The Impact ◽  
Haloxylon Salicornicum

Perennial shrub-annual plant interactions play key roles in desert regions influencing the structure and dynamics of plant communities there. In the present study, carried out in northwestern Saudi Arabia, we examined the effect of Haloxylon salicornicum shrubs on their associated understory annual species across four consecutive growing seasons, along with a record of the seasonal rainfall patterns. We measured density and species richness of all the annual species in permanent quadrats located beneath individual shrubs, as well as in the spaces between shrubs. During wet growing season H. salicornicum shrubs significantly enhanced the density and species richness of sub-canopy species, whereas in the relatively dry seasons they exerted negative effects on the associated species. In all growing seasons, the presence of shrubs was associated with enhanced soil properties, including increased organic carbon content, silt + clay, and levels of nutrients (N, P and K). Shrubs improved soil moisture content beneath their canopies in the wet growing season, while in the dry seasons they had negative effects on water availability. Differences in effects of H. salicornicum on understory plants between growing seasons seem due to the temporal changes in the impact of shrubs on water availability. Our results suggest the facilitative effects of shrubs on sub-canopy annuals in arid ecosystems may switch to negative effects with increasing drought stress. We discuss the study in light of recent refinements of the well-known “stress-gradient hypothesis”.

Étude du développement hétéroblastique chez quelques espèces du genre Medicago

1983 ◽  
Vol 61 (8) ◽  
pp. 2212-2223 ◽  
Author(s):  
Catherine Damerval
Keyword(s):  
Environmental Conditions ◽  
Mean Value ◽  
Annual Species ◽  
The Mean ◽  
Shape Changes

Seven foliar types were defined for the first leaf in the heteroblastic development of seven annual species of Medicago L. Among the species, M. aculeata and M. murex have a typical foliar form. There is no relation between the first leaf and the succeeding trifoliolate one. The shape changes of the middle foliole of the trifoliolate leaves during the development allowed to establish a foliar sequence whose mean length was used to suggest an evolutive hierarchy among the taxa. Five quantitative variables were analysed on the first and on the sixth leaf for stability according to environmental conditions; the two stable variables (L/l and L/Pl) have a best discriminant value for the first leaf than for the sixth one. However, intraspecific heterogeneity is high in both cases. A relation between the flowering precocity and the mean value of one of the sixth leaf's variables (that is, the ratio of the length to the width of the foliole limb) was demonstrated in four species only. The heteroblastic development not only allows to establish a relation between foliar stage and physiologic age, but it itself constitutes a very good taxonomic and systematic criterium; it allowed to identify the seven species studied.

A taxonomic note of Pterocephalus (Caprifoliaceae) from N Iran

Phytotaxa ◽  
2021 ◽  
Vol 494 (1) ◽  
pp. 137-144
Author(s):  
MASSOUD RANJBAR ◽  
ZAHRA RANJBAR
Keyword(s):  
New Species ◽  
Annual Species ◽  
Taxonomic Note ◽  
Golestan Province ◽  
Well Differentiated ◽  
A New Species

Pterocephalus ramianensis (Caprifoliaceae) is described and illustrated as a new species from Golestan Province, north Iran. This species is morphologically and micromorphologically well-differentiated from P. plumosus. The characters that distinguish this new species from P. plumosus are provided along with a key to the Iranian annual species in Pterocephalus.

Presence and activity of Trypsin and chymotrypsin isoinhibitors in the annual species of Cicer

1981 ◽  
Vol 9 (1) ◽  
pp. 23-25 ◽  
Author(s):  
Patricia Smirnoff ◽  
Miriam Rotman ◽  
Gideon Ladizinsky
Keyword(s):  
Annual Species

Nuclear DNA content and minimum generation time in herbaceous plants

1972 ◽  
Vol 181 (1063) ◽  
pp. 109-135 ◽  
Keyword(s):  
Cell Cycle ◽  
Dna Content ◽  
Cycle Time ◽  
Generation Time ◽  
Nuclear Dna ◽  
Nuclear Dna Content ◽  
Annual Species ◽  
Cell Cycle Time ◽  
Developmental Processes ◽  
The Mean

Many components of cell and nuclear size and mass are correlated with nuclear DNA content in plants, as also are the durations and rates of such developmental processes as mitosis and meiosis. It is suggested that the multiple effects of the mass of nuclear DNA which affect all cells and apply throughout the life of the plant can together determine the minimum generation time for each species. The durations of mitosis and of meiosis are both positively correlated with nuclear DNA content and, therefore, species with a short minimum generation time might be expected to have a shorter mean cell cycle time and mean meiotic duration, and a lower mean nuclear DNA content, than species with a long mean minimum generation time. In tests of this hypothesis, using data collated from the literature, it is shown that the mean cell cycle time and the mean meiotic duration in annual species is significantly shorter than in perennial species. Furthermore, the mean nuclear DNA content of annual species is significantly lower than for perennial species both in dicotyledons and monocotyledons. Ephemeral species have a significantly lower mean nuclear DNA content than annual species. Among perennial monocotyledons the mean nuclear DNA content of species which can complete a life cycle within one year (facultative perennials) is significantly lower than the mean nuclear DNA content of those which cannot (obligate perennials). However, the mean nuclear DNA content of facultative perennials does not differ significantly from the mean for annual species. It is suggested that the effects of nuclear DNA content on the duration of developmental processes are most obvious during its determinant stages, and that the largest effects of nuclear DNA mass are expressed at times when development is slowest, for instance, during meiosis or at low temperature. It has been suggested that DNA influences development in two ways, directly through its informational content, and indirectly by the physical-mechanical effects of its mass. The term 'nucleotype' is used to describe those conditions of the nucleus which effect the phenotype independently of the informational content of the DNA. It is suggested that cell cycle time, meiotic duration, and minimum generation time are determined by the nucleotype. In addition, it may be that satellite DNA is significant in its nucleotypic effects on developmental processes.

scholarly journals Evaluation of Eastern Redcedar Substrate in the Production of Four Annual Species

2014 ◽  
Vol 32 (3) ◽  
pp. 167-173
Author(s):  
Lucy E. Edwards ◽  
Adam F. Newby ◽  
Charles H. Gilliam ◽  
Glenn B. Fain ◽  
Jeff L. Sibley ◽  
...  
Keyword(s):  
Petunia Hybrida ◽  
Weather Conditions ◽  
Environmental Concerns ◽  
Peat Moss ◽  
Juniperus Virginiana ◽  
Annual Species ◽  
Eastern Redcedar ◽  
Alternative Substrate ◽  
Greenhouse Production ◽  
Celosia Argentea

Peat moss and perlite have been major components in greenhouse substrates for over 50 years; however, shortages could occur due to restrictions from environmental concerns, fuel cost, and weather conditions. Due to these factors, research continues to seek available materials as alternative substrate components. These studies evaluated processed eastern redcedar (Juniperus virginiana L.) as an alternative substrate in the greenhouse production of four annual species: petunia (Petunia ×hybrida Juss.), annual vinca [Catharantus roseus (L.) G. Don], wax begonia (Begonia semperflorens-cultorum Hort.), and plumed cockscomb (Celosia argentea L.). Three screen sizes of hammer-milled eastern redcedar (ERC) were used including 0.64, 0.95, and 1.27 cm (0.25, 0.38, and 0.5 in). Plants were grown in peat moss amended with either 25 or 50% ERC (combinations of three screen sizes) and compared to a standard 80:20 peat:perlite mix. Plant growth was similar for petunia and vinca in 50% ERC (1.27 cm screen size) compared to those grown in 80:20 peat:perlite. Plants grown in 25% ERC were similar to plants grown in 80:20 peat:perlite mix for all species in all screen sizes. Root growth was similar to or greater for plants in substrates with 25% ERC when compared to the standard peat:perlite treatment. Amending peat with up to 25% eastern redcedar is an acceptable practice for the four annual species used in this study.

Sedum pyriseminum (Crassulaceae), a morphologically remarkable new annual species from the state of Durango, Mexico

Phytotaxa ◽  
2016 ◽  
Vol 255 (3) ◽  
pp. 297
Author(s):  
EMMANUEL PÉREZ-CALIX
Keyword(s):  
Conservation Status ◽  
The State ◽  
Annual Plant ◽  
Annual Species ◽  
Sympatric Distribution ◽  
Centre Of Diversity

Mexico is a proven centre of diversity and endemism for Sedum L. (Crassulaceae) and species new to science are continually being discovered. Sedum pyriseminum E. Pérez-Calix is described and illustrated based on specimens originating from the Mexiquillo region, Durango, Mexico. Sedum pyriseminum E. Pérez-Calix is a small annual plant, 2 cm or less in height. Although other Sedum species with this habit are known, S. pyriseminum does not closely resemble any of them. It is most similar to S. vinicolor S. Watson (= S. forreri E. L. Greene), with which it could be confused as a consequence of their similar size and sympatric distribution. The conservation status of Sedum pyriseminum is assessed as Vulnerable (VU).

Impact of Alien Plants on Grant Basin Rangelands

1996 ◽  
Vol 10 (2) ◽  
pp. 384-391 ◽  
Author(s):  
James A. Young ◽  
William S. Longland
Keyword(s):  
North America ◽  
Great Basin ◽  
Alien Plants ◽  
Western North America ◽  
Biological Functions ◽  
Annual Species ◽  
Weed Species ◽  
Model Ecosystem ◽  
Alien Weed ◽  
The Impact

Our purpose is to discuss the impact of alien plants on rangeland ecosystems of the Great Basin in terms of their effects on biological functions. The sagebrush/bunchgrass ranges of western North America are used as a model ecosystem for the impact of alien plants. Alien weed species have been introduced in successive waves, with the success of each new introduction dependent on how well adapted to the environment and how competitive the new weed is with those previously introduced. Annual species have been successful across extensive areas of Great Basin rangelands. Biennial and short- and long-lived perennial introductions have been restricted to much more specific habitats. Alien plants impact rangelands through stand renewal and successional processes. Alien weeds can cause such processes to be accelerated and/or truncated depending on the species and range site.

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