摘要:

Aboriginal groups in the southwestern United States have grownProboscidea parviflorassp.parviflorafor basketry fiber. It has been hypothesized that cultivated plants of this subspecies with white seeds and long‐clawed fruit (which provide the fiber) have been domesticated. Cluster, multiple discriminant, and unvariate statistical analyses presented here show that the putative domesticate is indeed morphologically distinct from “wild” plants. It has clearly been domesticated, and has diverged from wild populations to the extent that a new variety, var.Hohokamiana, is proposed for the domesticate. Wild and domesticated varieties differ especially in seed color, rostrum, crest, style, and anther lengths. Most characteristics of the wild variety seem to be genetically dominant to those of the domesticate, which may account for absence of a weedy form intermediate between the wild and domesticated varieties. The wild variety is morphologically more variable than the domesticate, probably because of its broader geographical range and its intergradation with another subspecies. Ethnological data and the variational patterns reported here suggest that the domesticate originated in southern Arizonanorthern Sonora, but probably not north of that region.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1982.tb13404.x

出版商:Wiley    

年代:1982

数据来源: WILEY

摘要:

Gene flow in an experimental garden ofCucumis melo(Cucurbitaceae), the cultivated muskmelon, was measured by placing plants carrying a dominant gene (green cotyledons) in the center of an 18 × 18‐m field of recessive plants (yellow cotyledons). At the end of the growing season, all fruits were collected, and seeds planted for analysis of the progeny. The 123 fruits yielded 41,875 seedlings whose genotypes were recorded. Gene flow decreased with increasing distance from the central plot, while the variance increased. The decrease in frequency of the green gene did not follow a leptokurtic pattern over the distance measured, and there was a marked asymmetric and patchy pattern of gene flow in the field. The directionality contributed to a bimodal pattern of gene frequencies among fruits at the edges of the field, some fruits with no green seedlings, some with many. Bumblebee movements were recorded during 4,296 flower visits in an identically arrayed melon field. Bees usually moved to very nearby plants and visited only a few flowers on any one plant. This suggests that pollen carryover from the central patch out was quite high in the test garden. These findings show that local gene flow patterns in plant populations may be complex, and do not always follow regular and symmetrical models. The complex arrangement of progeny genotypes, when acted upon by local selective forces, may contribute to small‐scale differences often seen in plant populations.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1982.tb13405.x

出版商:Wiley    

年代:1982

数据来源: WILEY

摘要:

The cell wall of theNitellarhizoid was stripped to make wedges of various thicknesses. Polarizing and interference microscopes were used to examine the post‐deposition orientation of wall microfibrils. The fibrils appeared to maintain alignment after they were deposited. Since during growth the rhizoid wall elements are static in the cylindrical part or extend isotropically in the dome (Chen, 1973), these observations provide indirect evidence that the fibrillar reorientation observed in theNitellainternode is due to a passive reorientation during the predominant longitudinal cell elongation (Gertel and Green, 1977). The static microfibrils of the secondary wall of rhizoid, however, reoriented under the influence of colchicine, the alignment becoming almost random after 48 hrs. The disturbance of alignment started in the region adjacent to the plasma membrane, increasing in thickness with prolonged treatment.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1982.tb13406.x

出版商:Wiley    

年代:1982

数据来源: WILEY

摘要:

Needle leaves ofPinus longaevacan be accurately dated and remain alive on branches for 30 or more yrs, making this species ideal to study secondary growth in leaves. Field observations and regression analysis of needle age versus mean needle length both indicate primary (elongation) growth of needles is completed in the first year. Statistical analysis of cell counts for one‐ to 33‐yr‐old needles indicate production along the entire length of needles of 1.0‐1.7 cell layers per year of secondary phloem, but no secondary xylem. Microscopic measurements and cell counts reveal that with advancing needle age phloem increases radially and transfusion tissue buckles, but the number of endodermal cells and xylem width do not change.Livingphloem remains constant in amount (ca. 9 layers) with advancing needle age, indicating yearly replacement of old by new phloem. For comparison toP. longaeva, needle leaves were also studied for ten other conifer taxa with maximum needle longevities ranging from 3 to 19 yrs. In needles of each taxon no secondary xylem is produced, but secondary phloem production occurs throughout the post‐elongation lifespan of the needles regardless of maximum needle longevity.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1982.tb13407.x

出版商:Wiley    

年代:1982

数据来源: WILEY

摘要:

Past investigation of gametophyte ontogeny inGleichenia bifidaindicated that there was considerable plasticity in early developmental stages (spore germination to initiation of two‐dimensional growth). Recent examination has shown that this early ontogeny is not so plastic and can be defined by a characteristic series of developmental stages. Cell divisions following germination result in a three‐dimensional mass of cells which secondarily initiates the two‐dimensional thallus. Early development as a three‐dimensional mass correlates with other gametophyte and sporophyte features which indicateGleicheniato be phylogenetically primitive. This pattern of early ontogeny may also be of adaptive significance in enabling the gametophytes to survive the environmental fluctuations of the exposed, bare‐soil habitats which they colonize.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1982.tb13408.x

出版商:Wiley    

年代:1982

数据来源: WILEY

摘要:

Telangium pygmaeumGraham is known from Upper Pennsylvanian coal balls from the Calhoun coal mine (Illinois). The species was described as possessing radial synangia consisting of 3‐5 sporangia fused laterally for about f13 their length. Synangia were believed to be sessile and borne terminally or laterally on a branching rachis without lamina. Examination of new coal ball material of the same age indicates that the synangia are borne abaxially on the pinnules of a compound frond with the anatomy of aPsaroniusleaf (Marattiales). Synangia are sessile and borne in two rows, one on either side of the pinnule midrib, under the unbranched lateral veins. Synangia are radial, 0.6 mm in diam, and consist of a ring of thin‐walled sporangia fused to near their apices prior to dehiscence, but separating on dehiscence to release spores along their inner midline. Spores are spherical, trilete, 30‐48 μm in diam, with a granulate ornamentation. The new genusAraiangiumis proposed for this material based on the organization of the sessile thin‐walled synangia.Araiangiumis compared with other marattialean genera with sessile synangia (Acaulangium, Acitheca), and with the pedicellate synangia of various species ofScolecopteris.Criteria used in the delimitation of genera in Paleozoic anatomically preserved marattialean fertile foliage are discussed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1982.tb13409.x

出版商:Wiley    

年代:1982

数据来源: WILEY

摘要:

Techniques of horizontal starch gel electrophoresis were employed to estimate levels of genetic variation within and genetic differentiation among populations of the three Florida subspecies ofHelianthus debilis.The subspecies areH. d. debilis, H. d. vestitus, andH. d. tardiflorus.These taxa are very similar with respect to levels of genetic variability. The average values across all populations for proportion of polymorphic loci (25.5%) and number of alleles per polymorphic locus (2.35) are comparable to those found in other outcrossing plants. The average frequency of heterozygotes per locus (0.05) is lower than that found in other outcrossers. Local populations within each subspecies are genetically very similar. The average genetic distance between local populations is D = 0.010 ± 0.001. Subspeciesvestitusand subspeciestardiflorusare also genetically very similar (D = 0.015 ± 0.001). However, subspeciesdebilisis differentiated from both subspeciesvestitus(D = 0.121 ± 0.006) and subspeciestardiflorus(D = 0.103 ± 0.005). This genetic differentiation parallels morphological differentiation. The average genetic distance among all three subspecies is D = 0.080 ± 0.003. A moderate amount of genetic differentiation accompanies the process of subspeciation inHelianthus debilis.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1982.tb13410.x

出版商:Wiley    

年代:1982

数据来源: WILEY

摘要:

Structural changes accompanying the acclimation process were observed in leaves of sweetgum,Liquidambar styraciflua, using light and transmission electron microscopy (TEM). Comparisons were made of leaves obtained from tissue culture, plantlets acclimated after transfer from the in vitro environment to soil, and field grown trees. Leaves of cultured plantlets lacked a differentiated palisade parenchyma and had spongy parenchyma interspersed with large air spaces. Field grown leaves showed distinct palisade and spongy tissues and a high cell density. New leaves from acclimated plantlets showed an elongation of the upper mesophyll with fewer intercellular spaces than cultured plants. Cells from leaves from in vitro plantlets had large vacuoles, limited cytoplasmic content and flattened chloroplast with an irregularly arranged internal membrane system. Acclimated and field leaf cells had a greater cytoplasmic content than cultured leaves, with the former having more dominate vacuoles. Chloroplasts had evident grana. Acclimated and field leaves had a well developed cuticle unlike leaves from culture.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1982.tb13411.x

出版商:Wiley    

年代:1982

数据来源: WILEY

摘要:

Quantitative and qualitative features are reported for 23 collections of ten species ofIllicium, sole genus of Illiciaceae. Vessel elements are long, thin‐walled, and angular; perforation plates are scalariform and range from long to moderately long; vessel‐ray pitting is scalariform to opposite. Tracheids bear fully bordered pits. Axial parenchyma is sparse, abaxial to vessels with some diffuse cells also present. Rays are both multiseriate and uniseriate; the former are lacking near the pith in some species. No erect sheathing cells are present on multiseriate rays, and procumbent cells become more abundant as stems increase in size. Four species from montane subequatorial highlands lack growth rings and helical sculpture in vessels; the remainder ofIlliciumspecies have these features. Notably narrow vessels and large numbers of vessels per sq. mm characterize the temperate species from northern limits for the genus,I. anisatum, I. floridanum, andI.parviflorum.Greater vessel density offers redundancy and greater safety and is correlated with greater frost and possibly greater fluctuation in moisture availability. These two ecological features are probably also related to the narrow vessel diameter, which may retard entry of air embolisms (lowered air entry values) in accord with the physiological considerations of Slatyer. Reduction of number of bars per perforation plate withinIlliciumis also correlated with the more northerly climates. An additional hypothesis for evolution of shorter vessel elements in dicotyledons is introduced: if, as claimed by Slatyer, air embolisms in vessels tend to stop at ends of vessel elements and thus do not disable entire vessels, shorter vessel elements would maximally localize air embolisms. Presence of helical sculpture and other forms of relief within vessels has been difficult to explain in conifers and dicotyledons; such features might help resist cavitations by increasing adhesion of water molecules to cell walls (hydration).

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1982.tb13412.x

出版商:Wiley    

年代:1982

数据来源: WILEY

摘要:

The embryo ofRhizophora mangleL. is initially attached to the integument by a long multiseriate suspensor. Its basal cells lyse, and intrusive growth of the endosperm envelops the embryo, forces the micropyle open, and often carries the embryo out of the integument. Thus, “germination” is effected by growth of the endosperm rather than of the embryo. The surface of the endosperm differentiates into a layer of peculiar transfer cells. The cotyledonary body initiates as a toroidal primordium, which later becomes lobed; most of the free portions ultimately fuse. After “germination,” the axis of the viviparous seedling grows by a diffuse intercalary meristem below the cotyledonary node. Before seedling abscission, the shoot apex produces three pairs of leaves, the first of which aborts, leaving the rest of the plumule protected by their stipules. The (immersed) radicle apex is nearly inactive, but lateral roots arise early in seedling development; these are usually the first or only roots to grow during establishment. Ten provascular strands “differentiate” in the cotyledons; a hollow provascular cylinder develops in the hypocotyl. Initial vascular differentiation in the latter is of many alternate poles of xylem and phloem; later, de novo differentiation of metaxylem opposite the protophloem poles, and vice versa, produces collateral bundles. Xylem maturation is endarch over most of the length of the hypocotyl, but tangential and random series of metaxylem vessels occur in the radicle end.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1982.tb13413.x

出版商:Wiley    

年代:1982

数据来源: WILEY