摘要:

Caulogenic callus cultures were established from vegetative short shoot buds collected from cuttings from a ca. 12‐year‐old tree ofLarix × eurolepis.Schenk and Hildebrandt basal medium supplemented with various concentrations of 6‐benzylaminopurine (BAP, 2.5 × 10–7to 1.0 × 10–5M) or BAP (5.0 × 10–6M) + indolebutyric acid (IBA, 1.0 × 10–6M) was used. Subcultures were carried out on the same medium as used for initiation. Shoot formation resulted mostly from adventitious organogenesis on callus tissue, but adventitious organogenesis and axillary shoot development were occasionally observed on neoformed shoots. Series initiated in December 1984, June 1985, and August 1985 were still very productive after 32, 26, and 24 months respectively in culture. Sampling date of the primary explants had a pronounced effect on i) initial survival rate, ii) number of subcultures before establishment of continuous, vigorous cultures, and iii) number of subcultures before attaining a high percentage of caulogenic calli and good productivity. Browning of callus tissue with time during each subculture was concomitant with an increase in shoot productivity. Most neoformed shoots did not show pronounced elongation of the stem in vitro. Some shoots entered dormancy, and either stayed dormant upon subculture or resumed growth. Depending on the concentration of growth regulators used during callus culture, between 4 and 22% of excised shoots rooted when transferred first on DCR medium without growth regulator (Gupta and Durzan, 1985) and then twice on DCR‐1 medium (Gupta and Durzan, 1985). Rooted shoots elongated after a few weeks in greenhouse conditions.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb13499.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

The megagametophyte ofPlumbagella micrantha, consisting of three cells: an egg, a central cell, and a single antipodal, represents the most structurally reduced female gametophyte of the flowering plants. In the absence of synergids, the pollen tube enters the megagametophyte through a filiform apparatus at the base of the egg, continues growth for 40μm through the egg‐central cell wall, until reaching a region of strong curvature near the chalazal end of the egg. A terminal pollen tube aperture then forms, the sperm cells and vegetative nucleus are released between the egg and central cell, and the sperm undergo gametic fusion, thereby effecting double fertilization. The mode of fertilization inPlumbagellais therefore similar to that ofPlumbagothat has been described elsewhere.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb13500.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

A competition experiment was carried out in a greenhouse withSchizachyrium scoparium(Michx.) Nash (little bluestem) and seedlings ofProsopis glandulosaTorr. (honey mesquite). The effect ofS. scopariumdensity on the growth ofP. glandulosaand the effect of a singleP. glandulosaseedling on the growth of various densities ofS. scopariumwere examined. WhenP. glandulosawas grown withS. scoparium, there was a significant decrease inP. glandulosaabove‐, belowground, and total dry weight at allS. scopariumdensities tested. In contrast,P. glandulosadid not cause a significant reduction inS. scopariumdry weight. Root: shoot ratios for bothP. glandulosaandS. scopariumincreased almost three times from lowest to highest grass density. The number and length of flowering stalks ofS. scopariumper plant decreased with increasing density. The presence ofP. glandulosacaused a slight nonsignificant reduction of the number and length ofS. scopariumflowering stalks. Establishment ofP. glandulosaand other woody legumes would probably be low in high glass density and highly productive grasslands.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb13501.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

Observations based on new preparations confirm the presence of four cells in parallel alignment inA. sullivantistomata but not with two flanking subsidiary cells as in paracytic stomata. Rather, each guard cell contains in its interior a smaller inner cell. The stomatal pore is formed by walls of the larger cells and it is not known what role, if any, the interior cells may have played in opening and closing the pore. This cell‐within‐a‐cell arrangement is unknown among stornata elsewhere in the plant kingdom. The inner cells have the appearance of guard cells, especially when the poral walls of the larger cells are removed, and were so designated by Oestry Stidd and Stidd (1976). Cuticle preparations (Reihman and Schabilion, 1985) leave most of the cell structure of the stomatal apparatus intact among other leaf tissues (are not removed with the cuticle) and therefore do not reveal essential features.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb13502.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

The life history biology of the fernLorinseria areolatawas studied at three sites adjacent to the Escambia River, Florida, which represented part of its habitat diversity in the Gulf Coastal Plain. Site 1 was dominated byPinus elliottiiand was flooded only during hurricanes. Site 2 was dominated byMagnolia virginianaandGordonia lasianthusand was flooded for 3–5 months of the year. Site 3 was dominated byNyssa sylvaticavar.bifloraandTaxodium distichumand was flooded for 9–12 months of the year.Lorinseria areolatacoverage was 92, 61, and 16% of total understory at sites 1, 2, and 3. Rhizome length varied 5‐fold between sites. Microtopography varied little at site 1. Microtopography at sites 2 and 3 consisted of distinctive hummocks and hollows. Association analysis documented thatL. areolatawas distributed randomly with regard to microtopography at site 1, and was strongly associated with hummocks at sites 2 and 3. Seven life history classes (LHCs) forL. areolatawere discriminated based on field collections and seasonal observations over three years. Density of LHCs decreased logarithmically, with the exception of older LHCs whose age could not be determined beyond 30 months. Spore storage in dead erect sporophylls allowed the establishment of gametophytes throughout the year. Up to 25% of the gametophyte population survived the cold and relative drought of winter. More than half of field collected gametophytes were small males, and up to a third were larger bisexual gametophytes. Safe sites for completion of the life cycle were limited to decayed pine stumps and twigs at site 1, and to hummocks at sites 2 and 3. It was hypothesized that the acidifying action ofPinus elliottiilitter on soil contributed to the abundance ofLorinseria areolataat site 1, and that parts of the microhabitat mosaic at sites 2 and 3 which most closely approached edaphic characteristics of site 1 provided safe sites for the fern.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb13503.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

Scanning electron microscopy (SEM) observations of seed samples of 75 species representing fourteen Pitcairnioideae genera combined with some seed developmental and germination data revealed six classes of seed morphology (the Dyckia type, Puya ferruginea type, Puya hamata type, Fosterella type, Navia type and the Brocchinia type). Overall seed shape, nature of the appendage, presence or absence of visible demarcation between the body and appendage, surface cellular pattern and the permanency of the appendage were especially useful for distinguishing the seed types. Taxonomically, seed characteristics are correlated with other features in indicating a close relationship between i)EncholiriumandDyckia, ii)Fosterellaand the Guayana Highland generic group (Ayensua, ConnelliaandCottendorfia) and iii)PepiniaandPuya, and within the species of Puya hamata complex. Seed morphology suggests an isolated position forBrocchiniawithin the subfamily. Phylogenetically, seeds of the Fosterella and Puya ferruginea types represent putative homoplasies due to the reversals and parallelisms in different groups. Other seed types are unique to their lineages. Some putative phyletic transformations of the Brocchinia and Navia type seeds correspond with those of the Tillandsioideae and Bromelioideae, respectively.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb13504.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

Alvimiais a new genus of climbing bamboo that occurs in a relatively small area of restinga of coastal Bahia, Brazil. It is easily distinguished from other genera of the New World by a combination of several features: fleshy fruits, flowers with two stamens arranged in pseudospikelets, and the climbing habit. The BrazilianAlvimia, MexicanOlmeca, and one Peruvian species ofGuaduaare the only bamboos from America with fleshy fruits, a feature also found in a few Asiatic bamboos such asDinochloa, Melocalamus, Melocanna, andOchlandra.Three new species inAlvimiaare described:A. auriculata, A. gracilis, andA. lancifolia.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb13505.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

The vascular architecture of plants may constrain the pattern of resource movement among organs, resulting in morphological subunits that behave relatively autonomously, particularly with respect to carbon. Systematic and random patterns of leaf removal were imposed onCapsicum annuumplants to examine how architectural constraints may affect the development of sympodial branch systems. Removing leaves within a branch system resulted in a significant decrease in further sympodial growth by that branch, compared to a random pattern of leaf removal or to no removal at all. Data are consistent with the hypothesis that individual branch systems ofCapsicumfunction as integrated physiological units (IPUs). Developmental potential appears to be controlled within these IPUs.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb13506.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

Through a combination of field and greenhouse experiments, I examined the factors contributing to the maintenance of female individuals in natural populations of the gynodioecious alpine plantSilene acaulis(Caryophyllaceae). Hand‐pollinated female plants produced 3.8 times as many seeds as did either self‐ or outcross‐pollinated hermaphrodites, and open‐pollinated females produced 2.9 times as many seeds as open‐pollinated hermaphrodites. Females and hermaphrodites produce seeds of similar mass, and the same number of seeds per fruit, but females set fruit from a higher proportion of their flowers. This fecundity difference alone is sufficient to sustain equilibrium frequencies of females in natural populations. Greenhouse germination trials revealed no difference in the timing or probability of germination among seeds produced from females, selfed, and outcrossed hermaphrodites. Seedlings produced by females had the highest juvenile survivorship followed by those from outcrossed hermaphrodites and then those from selfed hermaphrodites. Differences between selfed hermaphrodites and the other treatments provide evidence for inbreeding depression at the establishment stage. The discrepancy between success of seedlings from female plants and those from outcrossed hermaphrodites suggests either that superior resources are allocated to seeds by females (maternal effect) or that seedlings of females are genetically superior to those of hermaphrodites.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb13507.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

Daily cloudcover is a frequent and persistent environmental feature of subalpine habitats. Response patterns in net photosynthesis (A), stomatal conductance to water vapor diffusion (g), transpiration (E), and water use efficiency (WUE = A/E) to intermittent cloudcover were evaluated for two subalpine species to determine if their responses supported the hypothesis that species that undergo water stress during sunlit intervals may have more rapid and greater stomatal responses to irradiance fluctuations than species under little apparent water stress. InHelianthella quinquenervis, a herbaceous perennial with midday xylem pressure potential<–2.0 MPa, responses in both A and g to simulated changes in natural irradiance occurred almost simultaneously and were relatively rapid. Although A was reduced by 22% during periods of shade compared with full sunlight periods, E was similarly reduced, and thus, no reduction in WUE occurred. In contrast, the riparian herbSenecio triangulariswas under little apparent water stress and g was relatively insensitive to fluctuations in irradiance. As a result, periods of cloudcover led to a smaller reduction in A of only 15% relative to full sunlight with little concurrent reduction in E, leading to a corresponding 12% decrease in WUE compared with steady state values under full sunlight. These data suggest that species that experience apparent water stress during sunlit intervals may maintain higher WUE during intermittent cloudcover through water conservation at the expense of carbon gain. In contrast, species in which water stress does not occur during sunlit intervals can maximize carbon gain at the expense of reduced WUE. The degree of competition for water and sunlight in a habitat may determine the particular physiological response pattern expressed during natural cloudcover regimes.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb13508.x

出版商:Wiley    

年代:1988

数据来源: WILEY