摘要:

Sexual systems of tropical lowland rain forest trees were investigated to estimate the relative proportions of hermaphroditic, monoecious, and dioecious species. Controlled hand pollinations were performed on hermaphroditic species to determine the proportions of self‐compatible and self‐incompatible species. A total of 333 species was examined; 65.5% species were found to be hermaphroditic, 11.4% monoecious, and 23.1% dioecious. There were no differences between canopy and subcanopy habitats in the distribution of various sexual systems. Out of the 28 species subjected to controlled pollinations, 24 showed the presence of self‐incompatibility. The site of the incompatibility barrier in distylous species was either in the stigma or in the style. In most of the monomorphic species, the incompatibility barrier was in the ovary. Although a majority of tree species in the rain forest appear to be obligate outcrossers (xenogamons), the potential for inbreeding due to small effective population size still remains to be explored.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb05357.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

The reproductive biology of tree species of a tropical rain forest was investigated to determine the relative frequency and spatial distribution of different types of pollination mechanisms. Species pollinated by medium‐sized to large bees were most frequent, followed by those pollinated by moths, small diverse insects and small bees, in that order. Almost one half the total species were found to have pollinators with wide foraging ranges. Species pollinated by various groups of pollinators were distributed non‐randomly. The greatest diversity of pollination systems was found in the subcanopy. As compared to the subcanopy, pollination mechanisms in the canopy were monotonous, consisting primarily of species pollinated by bees and small diverse insects. The hummingbird‐ and sphingid moth‐pollinated species were found mainly in the subcanopy. The factors underlying the non‐random distribution of pollinators are discussed and the potential implications of such distribution on the forest structure are explored.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb05358.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

The small‐scale distribution of an understory herb,Heracleum lanatum, was evaluated in terms of leaf temperature and water relations limitations due to a large leaf size (630 cm2). Diurnal variations in transpiration (4 to 60 mg m−2s−1) were influenced by fluctuations in solar irradiance, wind speed, leaf temperature and stomatal conductance. Computer simulations indicated that leaf temperatures in a forest clearing would be>12 C above air temperature, with maximum transpiration rates of 140 mg m−2s−1, and daily water loss to be over 200% greater than values at natural understory locations. Simulations of nocturnal temperature relations indicated ~100 W m−2less incident longwave irradiance in the forest clearing as compared to the understory (560 vs. 660 W m−2at 400 hr). This difference led to predicted leaf temperatures being as low as 6 C below air temperature in the forest clearing while measured leaf temperatures in the forest understory were within 1.5 C of air temperature throughout the night. Furthermore, minimum air temperatures were at or below 6 C on 36% of the nights during the summer growth period indicating that in open areas leaves ofH. lanatumwould frequently be below 0 C and subject to possible freeze damage.Heracleum lanatummay be more abundant in the shaded understory of the subalpine forest because exposure in open environments would result in high leaf temperatures and increased transpirational water loss during the day, as well as low leaf temperatures with the possibility of freeze damage at night.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb05359.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

At the end of mitosis in the lily pollen microspore, the fan‐shaped cell plate gives rise to a cell wall delineating a hemispherical cell. At first, the cell wall of the newly formed generative cell and the intine‐3 layer of the pollen grain wall are inseparable. Gradually, the wall of the generative cell near the pollen grain wall becomes thicker and wall segments are formed between the thickened zones, and these make a network system by which the generative cell becomes suspended and separated from the pollen grain wall. After the separation, the intine‐3 layer is formed inside the intine 2. The generative cell wall and the intine‐3 layer are formed by coated vesicles, polysaccharide particles and rough ER.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb05360.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

Ultrastructure of spore maturation in the myxomyceteDidymium iridiswas investigated using morphometric analytical techniques. Changes in actual volume (μm3) and relative volume (Vv) of nuclei, autophagic vacuoles, mitochondria, microbodies, lipid droplets, and spore wall were described for spores in three stages of development. Stage I spores were newly formed, surrounded only by the cell membrane. Stage II spores were approximately 1 hr older than Stage I spores and possessed surface spines, but little if any additional wall material. Stage III spores were 24 hr old and possessed a fully formed, multilayered wall. The results of this study indicate that spore maturation inD. iridisis a multistep process involving a decrease in spore volume and coordinated changes in specific organelle compartments. From Stage I to Stage III, mean spore volume decreased by more than 50%. Percent volume data (Vv) showed that Stage I spores allocated volume equally to all measured organelles except microbodies and the spore wall, the latter of which had not yet begun to develop. By Stage II, only the nucleus and spore wall showed significant changes in Vv values, both increasing. In terms of actual volume, the nucleus, autophagic vacuole and spore wall increased by Stage II. Between Stages II and III the cell wall was the only component to increase in volume, all others decreased in volume. Our data indicate a close relationship between a decrease in organelle volume and an increase in cell wall volume in the Stage III spore. The autophagic vacuole and the cell wall dominated the volume of the Stage III spore while the remaining volume was allocated unequally to the other components.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb05361.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

In this paper we describe the phenology, fruiting ecology, and colonization ability of a widespread neotropical pioneer tree,Muntingia calabura(Eleocarpaceae), in Costa Rican dry tropical forest. Individuals ofM. calaburagrow rapidly, flower at<2 yr age, and produce juicy red fruits containing thousands of tiny seeds that are eaten by a variety of frugivorous birds, bats, and monkeys. Although most individuals produce some flowers and fruit year‐round, peak flowering occurs in the late dry season (April–May), and peak fruit availability occurs early in the wet season (May–June). Bats and parakeets are the major seed dispersers ofM. calaburaat our study site, and they concentrate their attention on this species at its fruit peak when few alternate fruits are available. GerminableM. calaburaseeds accumulate in the forest soil in relatively high density in areas of high frugivore activity.M. calaburacan quickly invade large disturbed areas with a high density of seedlings. Adult densities decline from thousands of individuals/ha to a few individuals/ha in a relatively few years. Clumps ofM. calaburatrees are replaced by later successional species in<30 yr.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb05362.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

Leaves of the Princeton and a variegated clone ofColeus blumeiBenth. were examined with the light microscope to determine the course of their vasculature and the spatial relationship between the mesophyll, bundle sheath, and vascular tissues. In Princeton clone leaves two leaf traces enter the petiole at the node and quickly branch to form an arc of bundles which undergo further divisions as well as fusions in the distal half of the petiole. The anastomosing arc of bundles reaches its greatest complexity in the base of the midvein, where its lateral‐most bundles unite and diverge outward to form secondary veins. As the midvein bundles continue acropetally, they gradually fuse more and divide less until only a single bundle remains, from which secondaries and smaller veins branch. Major (ribbed) veins include not only the midvein and secondaries but also tertiary and quaternary veins. Decreasing vein size is accompanied by increasing direct contact between vascular and photosynthetic tissues. Minor veins, which make up 86% of the total vein length, are completely surrounded by photosynthetic bundle sheaths and mesophyll consisting of palisade and spongy parenchyma. Statoliths occur in a layer of cells just outside the phloem of the petiole‐midrib axis and secondary veins. Functional hydathodes are present at the apices of the marginal teeth. The overall organization of tissues in variegated leaves differs little in either the green or albuminous areas from corresponding (but always green) regions of Princeton leaves. Chloroplasts are lacking in mesophyll, bundle‐sheath, and most guard cells of the albuminous region but are present in guard cells which are within 1 mm of green areas.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb05363.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

Threadlike structures were observed on many pollen grains ofJacqueshuberia amplifoliola, J. purpurea, andJ. quinquangulataof the Leguminosae/Caesalpinioideae. Each end was attached to the highly reticulate polar exine surface of different grains. The consistency of this observation, hence, the absence of free thread ends, is interpreted to mean that they should be considered as either exine bridges or exinial connections rather than viscin threads, although, most likely functionally homologous to viscin threads. Other significant morphological characters were the tricolporate apertures and strikingly lamellate foot layer and endexine.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb05364.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

Seminal root tissue ofHordeum vulgareL. var. Barsoy was fixed in glutaraldehyde and osmium tetroxide and studied with the light and electron microscopes. The roots consist of an epidermis, 6–7 layers of cortical cells, a uniseriate endodermis and a central vascular cylinder. Cytologically, the cortical and endodermal cells are similar except for the presence of tubular‐like invaginations of the plasmalemma, especially near the plasmodesmata, in the former. The vascular cylinder consists of a uniseriate pericycle surrounding 6–9 phloem strands occurring on alternating radii with an equal number of xylem bundles. The center of the root contains a single, late maturing metaxylem vessel element. Each phloem strand consists of one protophloem sieve element, two companion cells and 1–3 metaphloem sieve elements. The protophloem element and companion cells are contiguous with the pericycle. Metaphloem sieve elements are contiguous with companion cells and are separated from tracheary elements by xylem parenchyma cells. The protoplasts of contiguous cells of the root are joined by various numbers of cytoplasmic connections. With the exception of the pore‐plasmodesmata connections between sieve‐tube members and parenchymatic elements, the plasmodesmata between various cell types are similar in structure. The distribution of plasmodesmata supports a symplastic pathway for organic solute unloading and transport from the phloem to the cortex. Based on the arrangement of cell types and plasmodesmatal frequencies between various cell types of the root, the major symplastic pathway from sieve elements to cortex appears to be via the companion and xylem parenchyma cells.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb05365.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

In bumblebee visits to flowers ofErythronium grandiflorum(Liliaceae), the ratio of self‐ to nonself‐ (“outcross”) pollen grains deposited on the stigma is positively correlated with the degree of stylar exsertion beyond the anthers. Natural populations show substantial, continuous variation in stylar exsertion.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb05366.x

出版商:Wiley    

年代:1985

数据来源: WILEY