摘要:

Sterigmal initiation inBoletus rubinellusresembled hyphal tip growth. Four stages in early basidiospore development have been delineated based on gross morphology, and changes in wall layers and cytoplasm. Changes in wall layers and cytoplasm during spore development were stage‐specific. During Stage 1 the spore wall consisted of two layers identical to those of the sterigmal wall with occasional pellicle remnants on the outer surface. The onset of wall differentiation began in Stage 2, and during Stage 3 wall layers characteristic of the mature spore developed. At Stage 4 there was a pronounced gradient in wall thickness from the apex to the base of the spore. Small vesicles (30–60 nm diam) were uniformly distributed in the cytoplasm of spherically enlarging spores (Stage 2), but during spore elongation (Stages 3 and 4) numerous larger vesicles as well as small vesicles aggregated at the spore apex. A variety of cytoplasmic organelles entered the spore during Stage 3; however, migration of storage materials and the nucleus to the spore did not occur until late basidiospore development. The hilar appendix body developed in the earliest spore primordium and persisted until Stage 3. Development of wall layers and their differential thickening, distribution of vesicles, and probable function of the hilar appendix body are discussed with reference to the control of spore shape. Systematic implications of the data are considered.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1984.tb12488.x

出版商:Wiley    

年代:1984

数据来源: WILEY

摘要:

Seedlings ofSpartina alternifloraLoisel. from Oregon Inlet, North Carolina were generally taller and produced significantly more culms and total dry weight than those ofS. foliosaTrin. from two California populations (Alameda Beach and Marin County) in eight photoperiod‐temperature treatments over a 17‐wk period. Seedlings ofS. alternifloraproduced maximal biomass in 30–26 C whereas those ofS. foliosaproduced maximal biomass in 22–18 C, both under long‐day conditions. The average photosynthesis rate forS. alterniflora(3.0 mg C g dry wt−‐hr−‐1) was 1.6 times higher than that for S.foliosa(1.9 mg C g dry wt−‐1hr−‐1), but the dark respiration rates (0.3 and 0.4 mg C g dry wt−‐1hr−‐1, respectively) were not significantly different. The proportion of rhizomes was greater under short than long‐day conditions for both species in most temperature regimes. The average shoot soluble carbohydrate and starch concentrations were higher forS. foliosa(8.4 and 0.9%, respectively) than those forS. alterniflora(6.0 and 0.4%, respectively). The average rhizome soluble carbohydrate concentration (18%) forS. alternifloraunder long‐day conditions was significantly lower than that under short‐day conditions (28%) and also lower than those for S.foliosaunder both long (26%) and short‐day (25%) conditions. Rhizome starch concentrations ofS. alterniflorawere significantly higher in the short than in most long‐day temperatures and were generally higher forS. alterniflorathan forS. foliosaunder short‐day conditions. The root starch concentration ofS. alternifloraunder short‐day conditions (1.3%) was higher than that under long‐day conditions (0.2%) and also higher than those ofS. foliosaunder both long (0.2%) and short‐day (0.7%) conditions. The two species exhibited similar patterns of carbohydrate storage in belowground organs, similar flower initiation processes not under strict photoperiod control, and similar respiration rates, but significantly different photosynthetic rates and growth responses withS. alterniflorahaving the potential to be the more productive species.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1984.tb12489.x

出版商:Wiley    

年代:1984

数据来源: WILEY

摘要:

Electron microscopy was used to investigate early development of latex ducts inMammillaria heyderi(Cactaceae). Numerous vesicles (secondary vacuoles) form from invaginations of the plasmalemma near sites of wall thinning, from endoplasmic reticulum (ER), and from vesiculate grana of degenerate plastids. Dictyosomes, though they occur in young duct cells, do not seem to be responsible for the formation of vesicles. Cytoplasmic vesicles may contain fibrillar, globular, or crystalline materials, or may be devoid of any type of particulate matter. They may be responsible for storage of numerous laticiferous components. Lysosomal materials could be stored in some vesicles and contribute to the degradation of the protoplast. Some nuclei contain condensed chromatin and are subject to deformation and collapse. Mitochondria and lipid bodies are common in young duct cells but ER is rare. When ducts form in young tissues, plastids in the lumen do not produce starch grains or extensive membranous networks. The plastids eventually degenerate to become a part of latex. If ducts form in older, established tissues having mature plastids, the plastids undergo extreme modification.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1984.tb12490.x

出版商:Wiley    

年代:1984

数据来源: WILEY

摘要:

We have examined the motile cell ultrastructural features of several green algal species having filamentous or foliose thallus morphology and probable affinities with the Ulvophyceae, and compared them with the structural, reproductive, and life history features known for these taxa. We separate the algae studied into the orders Ulotrichales and Ulvales on the basis of consistent variations in terminal cap and proximal sheath structure that correlate well with life history patterns and certain features of sporangial and gametangial structure and development. Body scales are present only in certain members of the Ulotrichales. Both orders encompass a variety of thallus forms, demonstrating parallel evolution of thallus morphology. Flagellar apparatus features common to all the motile cells examined include 180° rotational symmetry, counterclockwise absolute orientation, the positioning of the basal bodies in an apical papilla, and the presence of one or more sets of striated bands associated with the X rootlets. Additional features that are usually present include basal body overlap and orientation roughly perpendicular to the long axis of the cell during forward swimming, striated distal fibers, and a single, striated, microtuble‐associated component underlying each two‐membered rootlet. These similarities indicate to us that the two groups are closely related members of the Ulvophyceae. We suggest that the Ulotrichales is the most primitive ulvophyceous assemblage known, but that all groups studied have advanced features relative to those supposed to have been present in the ancestral members of the Ulvophyceae.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1984.tb12491.x

出版商:Wiley    

年代:1984

数据来源: WILEY

摘要:

The endemic Hawaiian species ofScaevolaandEuphorbiagrow in a wide variety of native habitats and exhibit a wide range of variation in photosynthetic responses. Light‐saturated photosynthetic capacities range from 12.0 to 24.7 μmol CO2m−‐2s−‐1in theScaevolaspecies and from 18.2 to 51.4 μmol CO2m−‐2s−‐1in theEuphorbiaspecies. Within each genus, differences in light‐saturated photosynthetic capacity are paralleled by differences in mesophyll and leaf conductances to CO2. Within each habitat, the C4Euphorbiaspecies exhibits a significantly higher photosynthetic capacity and a significantly higher mesophyll conductance than the corresponding C3Scaevolaspecies. These differences are greatest in the dry scrub habitat and least in the wet forest habitat. One photosynthetic characteristic that exhibits little variation among the species within each genus, yet that exhibits a consistently large difference between the species within each habitat, is photosynthetic water‐use efficiency. The C4Euphorbiaspecies possess water‐use efficiencies that are 2–3½ times as high as those of the C3Scaevolaspecies, regardless of whether these species are native to very dry or very wet habitats. At present, the ecological significance of this large inherent difference in photosynthetic water‐use efficiency is unknown. Indeed, it appears that neither photosynthetic pathway has imposed any major inherent constraints on the ability of theScaevolaandEuphorbiaspecies to diversify into a wide variety of habitats.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1984.tb12492.x

出版商:Wiley    

年代:1984

数据来源: WILEY

摘要:

Productivity ofPodostemum ceratophyllum,the dominant aquatic macrophyte in the New River, was measured at four sites representing soft‐ and hardwater reaches of the river. Available dissolved inorganic carbon (DIC) was 4–5 times greater in the hardwater reach. The difference in available DIC was reflected in standing crop and productivity ofP. ceratophyllum.Maximum standing crops ofP. ceratophyllumat the two hardwater sites (Sites 1 and 2) were 244.8 ± 30.7 g ash‐free dry wt (AFDW) m−‐2and 193.8 ± 18.7 g AFDW m−‐2compared to 128.5 ± 14.9 g AFDW m−‐2and 101.3 ± 6.9 g AFDW m−‐2for the softwater sites (Sites 3 and 4). Productivity, based on differences in standing crops, was: Site 1, 1.08 ± 0.12 g C m−‐2d−‐1; Site 2, 0.86 ± 0.08 g Cm−‐2d−‐1; Site 3,0.58 ± 0.06 g C m−‐2d−‐1; Site 4,0.45 ± 0.03 g C m−‐2d−‐1. Corresponding values for productivity as14C uptake were: 2.77 ± 0.44 g C m−‐2d−‐1; 2.10 ± 0.45 g C m−‐2d−‐1; 0.34 ± 0.04 g C m−‐2d−‐1; 0.28 ± 0.03 g C m−‐2d−‐1. Productivity/biomass (P/B) based on14C uptake and standing crop revealed thatP. ceratophyllumproductivity was inhibited at the softwater sites perhaps due to carbon limitation. Because of its abundance and its high productivity,P. ceratophyllumis hypothesized to contribute significantly to the New River organic matter budget.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1984.tb12493.x

出版商:Wiley    

年代:1984

数据来源: WILEY

摘要:

A starch‐agar gel assay was developed for the localization of enzyme activity in the cotyledons and hypocotyls of beans. The four major starch hydrolyzing enzymes, α‐amylase, β‐amylase, debranching enzyme and phosphorylase, were assayed with this technique using gels containing different substrates and buffers. Hypocotyls and cotyledons were sectioned by hand and the sections were incubated on the gel for varying lengths of time. Only α‐amylase was observed to increase significantly. While virtually absent in ungerminated axes and hypocotyls from young seedlings, it increased first in the basal region and subsequently in progressively higher portions of the hypocotyl. High activities were first observed in the pith and later in the cortex. The increased activity was most obviously associated with the degradation of the pith, suggesting a regulation relative to cellular autolysis.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1984.tb12494.x

出版商:Wiley    

年代:1984

数据来源: WILEY

摘要:

Secondary growth begins in the nodal regions before the internodal regions inColeus,so that longitudinally discontinuous vascular cambia are formed in the 6th through the 9th or 10th nodes, where the internodal cambium becomes continuous between nodal cambia. The nodal cambia are identifiable by radial seriation in interfascicular regions, typical cytology of fusiform initials, and the presence of a ray system. Anatomical features distinct from the primary plant body are shared by the nodal and internodal cambia. Branching of primary vascular strands, restricted to procambium and phloem, is virtually confined to nodal regions. In secondary growth, vascular branching of xylem and phloem occurs in both nodes and internodes. Xylem strand branches are formed only from derivatives of vascular cambia. It is proposed that the cambium provides the secondary plant body an efficient channel for lateral auxin transport, by which branching across interfascicular regions is facilitated.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1984.tb12495.x

出版商:Wiley    

年代:1984

数据来源: WILEY

摘要:

All xylem strands inColeusare initiated and differentiated discontinuously and bidirectionally from each nodal region along the lengths of the strands. Within nodes, the strands are larger in transsectional area and contain a greater number of vessels, a greater proportion of vessel elements vs. xylary parenchyma cells, and vessels in more advanced stages of differentiation than in adjacent internodes. When xylem develops in bundles that initially are composed only of phloem, or in short, isolated strands, it is initiated within nodal regions. The increased xylogenesis in the nodal regions is suggestive of locally enhanced auxin levels. Experiments were conducted to determine whether the advanced state of nodal vessel differentiation is a function of auxin import to the node from the leaf pair inserted at that node or whether it is due to an effect in the node of auxin transport from another (distal) source. A combined result was indicated, as removal of a leaf pair led to a decline in nodal xylem differentiation in the side bundles but not the corner traces passing through the node from younger leaves. The effect of a leaf pair on side bundle xylem differentiation at the same node was replaceable by exogenous IAA application to the cut leaf sites.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1984.tb12496.x

出版商:Wiley    

年代:1984

数据来源: WILEY

摘要:

Long‐term (1 yr), soft, embryogenic callus tissue cultures were established from excised immature embryos of a commercial cultivar of hybrid maize (Zea maysL.). Plant regeneration occurred by the formation of somatic embryos, and the regenerated plants were morphologically normal with 2n= 20 chromosomes. Such cultures may be useful for the isolation of mutants and the establishment of embryogenic cell suspension cultures.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1984.tb12497.x

出版商:Wiley    

年代:1984

数据来源: WILEY