摘要:

For several years it has been recognized that introduction of plant cells into culture results in genetic changes. These genetic alterations have been recovered in the plants regenerated from cell cultures. More recently it has been recognized that this method of introducing genetic changes into crop plants could be used to develop new breeding lines. The technology of introducing genetic variation by using cell culture has been termed somaclonal and gametoclonal variation. This paper reviews the history of this technology and offers genetic documentation of somaclonal variation in tomato. As this variation represents a new tool for the plant breeder, breeding strategies for the use of this variation are presented and discussed. Somaclonal and gametoclonal variation are new tools for the geneticist and plant breeder that permit reduction in the time period for new variety development and that permit access to new classes of genetic variation.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1984.tb14141.x

出版商:Wiley    

年代:1984

数据来源: WILEY

摘要:

Gynodioecy in two populations ofLimnanthes douglasiivar.roseawas studied for its maintenance requirements, role in population structure and its influence on the levels of outbreeding. The mode of inheritance of male sterility appeared to be nucleo‐cytoplasmic, although the precise number of nuclear genes and dominance relationships could not be ascertained. Measurements on the plants sampled from natural stands and controlled experiments showed that male‐steriles and their progeny had greater biomass and more flowers per plant than hermaphrodites, though these results varied with the environmental conditions. The hermaphrodites of gynodioecious populations had higher rates of selfing than the hermaphrodite individuals in populations lacking male sterility. Estimates of the inbreeding depression and homozygosity levels were also higher in gynodioecious populations. Variation in these parameters of breeding system and relative heterozygosis among populations may explain why male sterility has a restricted distribution, as theoretical models also predict rather specific conditions for this stable polymorphism. These data suggest that the advantage of male sterility is associated with lowered inbreeding depression. However, the potential ecological resource reallocation to the female function needs to be investigated. The fitness differences observed in this study between male‐steriles and hermaphrodites appear inadequate to maintain the nucleo‐cytoplasmic male sterility but could account for the observed frequencies (10–20%) of male‐steriles in nature if the genetic system has evolved from a cytoplasmic system.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1984.tb14142.x

出版商:Wiley    

年代:1984

数据来源: WILEY

摘要:

Study plots with ten types of disturbances were established in aSolidago‐Astercommunity in western Pennsylvania. One year after disturbance, 93% of all species had vesicular‐arbuscular mycorrhizae (VAM) and accounted for 92% of all plant cover. After 3 yr, 96% of the species had VAM and 96% canopy coverage. An adjacent 10‐yrSolidago‐Astercommunity had 100% VAM species. The VAM annuals,Ambrosia artemisiifoliaandSetaria glauca,were major first year dominants while VAM perennials,Agropyron repens, Solidago canadensis,andAster ericoides,dominated at 3 yr. The mean percent mycorrhizae of all dominants at 1 yr was 39% and 34% at 3 yr. Four disturbed sites had 100% VAM colonization after 1 yr and six sites after 3 yr. Severe physical disturbances (topsoil removed and topsoil‐subsoil removed) resulted in complete colonization by VAM species and mean mycorrhizal infections of more than 75%. The plowed‐disked‐prometone and plowed‐disked‐vapam disturbances resulted in low levels of mycorrhizae after 3 yr. The plowed‐disked‐atrazine plot showed an initial severe decrease in percentage of mycorrhizae, but doubled its infection rate by 3 yr. Three non‐mycorrhizal species (Chenopodium album, Rumex acetosella,andPolygonuspersicaria) were observed during the 3‐yr period.C. albumwas the major dominant after 1 yr in the plowed‐disked‐fertilized site andR. acetosellaa dominant in the plowed‐disked‐prometone plot.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1984.tb14143.x

出版商:Wiley    

年代:1984

数据来源: WILEY

摘要:

Pastinaca sativa(wild parsnip) produces seeds on the primary, secondary, and tertiary umbels of the flowering stalk. Within plants, variation in seed weight is about twofold. Secondary and tertiary seed weight is 73% and 50% of primary seed weight, respectively. Maximum variation in seed weight between plants is sixfold when tertiary seeds from a small plant are compared to primary seeds from a large plant. Within an umbel order, variation in seed weight between plants is correlated with plant size. Under autumn germinating conditions in the laboratory, final germination of seeds from different umbel orders does not differ but smaller seeds germinate more rapidly than larger seeds. Under spring germination conditions in the laboratory, significantly more primary and secondary seeds germinate than tertiary seeds and the rate of germination is independent of seed weight. Field germination of seeds from different umbel orders produces similar results except that in the spring both secondary and tertiary seed germination is lower than that of primary seeds. These results suggest that with respect to seed germination characteristics small seeds may have a competitive advantage over large seeds in the autumn because they germinate more quickly, but in the spring small seeds are at a disadvantage because they have lower overall germination. Because most germination in the field occurs in the spring, population recruitment from small seeds is likely to be substanially less than that from large seeds.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1984.tb14144.x

出版商:Wiley    

年代:1984

数据来源: WILEY

摘要:

In parasitic angiosperms the haustorium, an organ specialized for attachment and penetration of host tissue, functions in the transport of water and nutrients from the host to the parasite. InAgalinis purpurea(L.) Raf. (Scrophulariaceae) these organs are initiated laterally along its roots, opposite a primary xylem pole. Analyses of haustoria distribution and cellular root profiles show that the portion of the root which is most sensitive to haustorial elicitor molecules is the area distal to the zone of elongation and near the root meristem. Sectioned material supports this finding and, further, indicates that the cells which are the first to respond to haustorial elicitors are located in the inner cortex. Haustoria develop rapidly in response to a host root or to isolated chemical elicitors (xenognosins) normally contained in host root exudate. By 6 hr, vacuolation and radial cellular enlargement are observed in the cortex, and a lateral swelling along the root is visible. By 12 hr, cells of the epidermis divide anticlinally to establish a group of densely cytoplasmic cells at the apex of the haustorial swelling. Accompanying these divisions is the differentiation of specialized hair cells which elongate from epidermal cells flanking the presumptive haustorial apex. Next, the internal, radially enlarged cortical cells divide periclinally. Periclinal divisions are subsequently initiated in the pericycle as early as 18 hr post‐induction. Cellular division and enlargement continue so that by 24–36 hr a mature pre‐contact haustorium is formed. There is a reduction in root elongation concomitant with haustorial initiation. Depending upon the number of haustoria produced, elongation typically returns to the preinduction level within 2 or 3 days.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1984.tb14145.x

出版商:Wiley    

年代:1984

数据来源: WILEY

摘要:

Physalis viscosavar.cinerascensis a self‐incompatible, herbaceous perennial which occurs in disturbed or open habitats in the south‐central United States and eastern Mexico. The plants are low‐growing and the pendant blossoms are often obscured by the foliage. In Oklahoma the species blooms from April through October. The flowers are yellow with dark purple or brown maculations in the center and a mat of white hairs in the throat. Nectar is produced in small quantities at the base of the ovary and pollen is present in copious amounts. The pollinators are solitary bees which visit the flowers for nectar and pollen.Perdita halictoidesis the primary pollinator and is oligolectic onPhysalis.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1984.tb14146.x

出版商:Wiley    

年代:1984

数据来源: WILEY

摘要:

Trichostema lanceolatumBenth. (vinegar weed), an annual herb of the California grassland, contains 2.9 ml of volatile essential oil per 100 g of fresh foliage. Vapors from leaves and extracted oil inhibited growth of other plants in laboratory tests. Volatiles from 0.12–0.15 g greenTrichostemaleaf caused a 50% reduction in radicle elongation ofBromus mollisL. andHordeum vulgareL. seeds in petri dishes. Vapors from 1.5 and 3.2 μl essential oil in sealed and non‐sealed dishes, respectively, had a similar effect onHordeumseeds. Exposure of dryBromusseeds for 1 day, and dryHordeumseeds for 3 days, to volatiles fromTrichostemafoliage inhibited growth when the seeds were later moistened. The toxic volatiles had a high affinity for vegetable oil and were not readily removed from seeds by rinsing with water. The major volatile inhibitor fromTrichostemawas terpinen‐4‐ol. This monoterpene alcohol was about 0.3 and 1.9 times as inhibitory as camphor and 1,8‐cineole, terpenes that have previously been shown to influence vegetation patterning nearSalvia leucophyllaGreene shrubs. These results suggestTrichostema lanceolatummay also have allelopathic potential.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1984.tb14147.x

出版商:Wiley    

年代:1984

数据来源: WILEY

摘要:

Seeds from 37 species ofNama(Hydrophyllaceae) were examined by scanning electron microscopy in order to assess systematic implications of seed coat structure. Generally, seed coat morphology is species specific. Nevertheless, similarities among species in seed coat organization, particularly, outer testa anatomy and wall thickening‐pitting patterns allow the recognition of six groups among examined taxa; furthermore, seed coat features often suggest both intra‐group and inter‐group relationships. Recognized groupings do not correspond well with the more classicial treatments ofNama;rather, they suggest that a restructuring of the infrageneric and even the generic taxonomy ofNamais in order.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1984.tb14148.x

出版商:Wiley    

年代:1984

数据来源: WILEY

摘要:

The aerobiology of the skunk cabbage,Symplocarpus foetidus(l.) Nutt., is examined as a factor contributing to efficient pollination and temperature regulation around the spadix. Field measurements show that the compass orientation of the asymmetrical opening of the spathe is random, while wind tunnel studies reveal that similar patterns of airflow are generated around the spadix regardless of the orientation of the spathe opening to the direction of airflow. Temperature measurements within a model of the inflorescence reveal that airflow around the spathe effectively maintains heat generated by the spadix, even at airflow speeds of 1.5 m/s. These results are discussed as exaptations of the spathe for pollination and for temperature regulation in sub‐freezing weather.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1984.tb14149.x

出版商:Wiley    

年代:1984

数据来源: WILEY

摘要:

The development of jack pine (Pinus banksianaLamb.) microsporangia from October to April was investigated with a microdensitometer and a transmission electron microscope. DNA, RNA, and protein content of sporogenous cells was measured at monthly intervals. DNA was unreplicated (2C) until March when DNA synthesis was first noted, coinciding with a loss of heterochromatin. Protein content doubled in April. RNA staining increased in December and then decreased. Numerous whorls and stacks of rough endoplasmic reticulum and ribonucleoprotein‐like granules appeared in December and may be related to the RNA increase. A fibrillar, light‐staining region was found in the cytoplasm of the sporogenous cells from November to March. It was hydrolyzed in the presence of protease and may be a winter morphology of microfilament bundles or dictyosomes. Lipid bodies and vacuoles were abundant in the tapetum and sporangial wall cells during the winter. Observations substantiate reports that winter is not a time for cessation of development.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1984.tb14150.x

出版商:Wiley    

年代:1984

数据来源: WILEY