摘要:

Date seeds were sampled at regular intervals from pollination (March) to mature fruit (September) and processed for light microscopy and SDS‐PAGE. Seed fresh weight rose until early June and then declined slightly through September due to a continuous decrease in water content. Cell wall formation started in May in the free nuclear endosperm and proceeded centripetally from the inner integument to the seed center. Wall thickening in each cell started in cell corners and showed a layered appearance with calcofluor white staining. It started in early June in the center of the seed and proceeded centrifugally such that the outer cells showed cell wall thickening in late June. Thickened cell walls were soft and PAS positive at inception, but staining disappeared and hardness increased during wall maturation. Cell elongation in the radial direction accompanied wall thickening. Protein body formation started after cell wall thickening and followed the same centrifugal developmental pattern. Mature protein bodies occurred in even the outermost cells by early July. No further structural changes occurred after this time. The high molecular weight storage proteins appeared in late June, which is when protein bodies had formed in all but the outer endosperm cells; however, these proteins did not appear simultaneously and minor changes in protein bands continued until maturation.α‐Galactosidase activity was present in the developing endosperm and peaked at 13 wk after pollination. The data suggest that the thickened wall is deposited as a highly substituted galactomannan, but that most of the galactose side branches are clipped off presumably byα‐galactosidase during cell wall polymerization.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1989.tb15107.x

出版商:Wiley    

年代:1989

数据来源: WILEY

摘要:

Transmission electron microscopy of serial thin sections was used to reconstruct several early developmental stages of the blepharoplast inColeochaete pulvinataspermatids. These were compared to published studies of blepharoplast development in Charales and the closest relatives of charophycean green algae among embryophytes, i.e., hornworts and liverworts. Bicentriolar centrosomes such as occur in bryophytes and fern allies were not observed inColeochaete.Centriole replication inC. pulvinatawas orthogonal as in Charales. The resulting two daughter centrioles were oriented perpendicularly and joined proximally by electron‐dense material. Their orthogonal relationship was maintained throughout blepharoplast development by a massive, banded connective which appeared early. In spermatids of hornworts and liverworts, a multilayered structure (MLS) develops in association with two centrioles destined to become flagellar basal bodies. When the MLS of these lower land plants is sectioned at right angles to the long axis of the microtubular layer, the MLS is observed to lie beneath cross sections of both centrioles. In contrast, when developing MLSs ofC. pulvinataand Charales are similarly sectioned, they occur beside a cross section of just one of the two centrioles. InC. pulvinata(as in other charophytes), MLS lamellae are oriented at a 90‐degree angle to the long axis of the S1microtubules from the beginning. This contrasts with the 40–45 degree angle between the MLS lamellae and S1microtubules universally reported for archegoniates. In earlyC. pulvinataspermatids, spline microtubules are closely associated with an anterior mitochondrion having a low stromal density and few cristae. An anterior mitochondrion is typically associated with blepharoplast development in hornworts and liverworts, but has not previously been reported to occur inColeochaeteor any other charophycean alga. InColeochaete, as in hornworts and liverworts, but unlike Charales, structure of mature blepharoplasts reflects early blepharoplast ontogeny. Very little change in positional relationships among blepharoplast components (flagella, connective, MLS) occurs during development. These character‐state differences are of importance in cladistic analyses of charophycean algae and lower land plants.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1989.tb15108.x

出版商:Wiley    

年代:1989

数据来源: WILEY

摘要:

Flowers ofDalechampia magnoliifoliain eastern Peru were pollinated primarily by maleEulaema merianaandE. cingulata, which collected fragrance from the secretory gland borne in the staminate cymule. The fragrance contains carvone oxide, benzyl acetate, limonene,α‐pinene, myrcine,β‐pinene/camphene, and carvone.Trigonacf.pallenswas the most abundant visitor, but was primarily a pollen thief. The rate of contact with the stigmas byTrigona, and hence the bee's efficacy as a pollinator, was highly variable and was determined by variation in the separation of anthers and stigmas.Dalechampia magnoliifoliaco‐occurred with a congeneric species,D. cissifolia, but did not share pollinators with it.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1989.tb15109.x

出版商:Wiley    

年代:1989

数据来源: WILEY

摘要:

All water and nutrients required for the growth of the huge viviparous seedlings ofRhizophora manglemust be transported from the inner surface of the integument (maternal tissue), across a layer of persistent endosperm cells (seedling tissue), and to the surface of the cylindrical cotyledonary body. We describe the ultrastructure of these tissues at two functionally different stages of embryo and seedling development (i.e., 2–3 wk and 2–3 mo postgermination, respectively). Integumentary cells adjacent to the endosperm have unique plastids and divide more frequently than cells further away from the endosperm/integument interface. Later, fibrillar inclusions develop in vacuoles of the integument cells. The outermost layer of endosperm cells differentiates into transfer cells with wall ingrowths on the external walls, and the remainder of the endosperm degenerates during the embryo to seedling transition. The wall ingrowths gradually occlude the lumena of the transfer cells, a process which is complete long before the seedling abscises; therefore, the seedling may be photosynthetically independent throughout most of its development. The outer surface of the seedling cotyledonary body is minimally papillate and exhibits several ultrastructural specializations: centripetal degeneration of external walls which are bounded by electron‐dense deposits; numerous mitochondria; and plastids of unusual structure with many plastoglobuli, and which contain unique yellow pigments having absorption spectra characteristic of carotenoids. HPLC residence times of these pigments are unlike those ofβ‐carotene or other common carotenoids. Transfer tissues ofRhizophoramay have functions not found in other plants, such as salt exclusion and facilitating viviparous germination, but the ultrastuctural correlates of these functions remain uncertain.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1989.tb15110.x

出版商:Wiley    

年代:1989

数据来源: WILEY

摘要:

Evolsoniais a new gigantopterid genus (type‐species:E. texana), based on leaf impressions from 3 widely separated localities in north‐central Texas. The leaves are associated with terrestrial vertebrates in floodplain sediments of the Vale Formation in the Clear Fork Group, of late Leonardian (Early Permian) age.Evolsonialeaves are simple, with very large elliptic laminae reaching 27 cm in width and 80 cm, possibly more, in length. Leaf margins are sinuate to crenate, with mostly shallow concavities. Venation is pinnate, in 4 orders; all but the ultimate veins are very thick and protrude below the lamina, creating deep impressions in the matrix. The secondary and tertiary veins form a precise herringbone pattern, with the secondaries and exmedial tertiaries ending at the leaf margin between concavities. The other tertiary veins are either simple or divided into 2 nearly equal divisions; they produce simple or variously divided quaternary veins that end at a thin sutural vein, forming a dense reticulum; some of the terminally branched tertiaries delimit areolelike areas that enclose several quaternaries and meshes. One of 6 presently known American gigantopterids,Evolsoniamost closely resembles the youngerDelnorteain gross architecture; with its sutures and dichotomously divided veins, however,Evolsoniais architecturally intermediate betweenDelnorteaand the older American gigantopterids with forked leaves. Sedimentary features indicate deposition under alternating periods of flooding and drought. Their huge size invites comparison ofEvolsonialeaves with those of modern tropical plants, whereas their thick veins and preservational features suggest thick, coriaceous texture.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1989.tb15111.x

出版商:Wiley    

年代:1989

数据来源: WILEY

摘要:

Pyritized axes of the vegetative branching system ofRellimia thomsonii, from the Givetian of New York were described with emphasis on the presence and position of the secondary tissues in relation to the known axis orders. The morphology and anatomy of four axis orders (N, N + 1, N + 2, N + 3) was described using two well‐preserved specimens. One specimen showed the largest known (N) axis order, with spirally attached N + 1 axes. The other specimen, from a more distal portion of the plant, showed the N + 2 axis order with spirally arranged N + 3 axes. The shape of the primary xylem, discernible in three of the axis orders (N + 1, N + 2, N + 3), was a three‐lobed protostele with mesarch maturation of the primary xylem. The protostele of the N + 3 axis order, with only primary growth, was identical to that of fertile N + 3 axes. The other axis orders (N + 2, N + 1, N) had wood surrounding the primary xylem. The wood of the N+2 axis was limited, and occurred only in the basal portion of the axis, but that of the N+1 and N axes was extensively developed with two and three growth layers, respectively. This wood was pycnoxylic with narrow rays similar to other aneurophytalean progymnosperms. Surrounding the secondary xylem was secondary phloem indicating the vascular cambium inRellimiawas bifacial. The presence of growth layers was discussed in relation to the climatic interpretation placed on their presence and how it correlates with paleogeographic reconstructions of the Devonian.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1989.tb15112.x

出版商:Wiley    

年代:1989

数据来源: WILEY

摘要:

Anisophyllea distichais characterized by strong shoot dimorphism. Orthotropic shoots with helically arranged scale leaves produce tiers of plagiotropic shoots, while plagiotropic shoots are anisophyllous and bear dorsal scale and ventral foliage leaves arranged in a unique tetrastichous system. In this study we compare the patterns of leaf development and primary vascular organization in the two types of shoots. Orthotropic shoots have an open vascular system with five sympodia. Expansion of orthotropic shoot scale leaves occurs from P1 to P10–12, and leaf tissues mature precociously. Plagiotropic shoots have a closed vascular system with six sympodia. Leaves in ventral and dorsal orthostichies do not differ significantly in size until ca. P15, but ventral leaves are distinct histologically from the second node in an orthostichy, P4–6. Ventral foliage leaves have a diffuse plate meristem, and leaf expansion continues until ca. P30. Differentiation of ventral and dorsal leaf trace procambium parallels the divergent patterns of leaf expansion. These observations demonstrate the strong correlation among shoot symmetry, leaf development, and vascular differentiation within dimorphic shoots of one species.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1989.tb15113.x

出版商:Wiley    

年代:1989

数据来源: WILEY

摘要:

The initiation and development of the flower ofBixa orellanaL. andCochlospermum tinctoriumA. Rich, were investigated using the scanning electron microscope to elucidate the nature of the androecial development and the relationships of both taxa. Initiation of floral buds starts with the inception of five sepals in a 2/5 sequence between two bracteoles. The petals are formed successively on the irregular pentagonal apex in a phyllotactic pattern different from that of the calyx. Stamen development proceeds centrifugally on a broad circular primordium or ringwall, which attains its final size at the time of initiation of individual stamens. Stamen primordia arise in successive whorls without connection to the perianth. The residue of the apex is differentiated into a gynoecial circular primordium. InCochlospermum3 to 4 carpels are initiated; inBixano individual carpels are visible. The origin of the androecial circular primordium is discussed in relation to other types of androecial development. A comparison is made with existing theories of the evolution of multistaminate androecia. Few differences were found in the floral development ofBixaandCochlospermum, except in the gynoecium. It is proposed to retain them in a single family Bixaceae for a number of reasons. The floral development supports a thealean, dillenialean, or violalean affinity rather than a malvalean. The inception of a broad androecial circular primordium is highly different from the development in Malvales, where more space for stamens is provided by the continuous growth of a tube.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1989.tb15114.x

出版商:Wiley    

年代:1989

数据来源: WILEY

摘要:

This study documents the comparative success of seeds and seedlings of the perennial gynodioecious‐gynomonoecious weed,Silene vulgaris, in the greenhouse. The importance of experimental design is stressed by comparing two different statistical analyses of the data. Seeds were obtained from artificial pollinations in the field: self‐fertilization of hermaphrodites, and cross‐fertilizations of both hermaphrodites and females. One‐way analysis of variance using progeny type (selfed hermaphrodites, outcrossed hermaphrodites, and outcrossed females) as the treatment effect for each seed and seedling variable showed statistically discernable differences among progeny from different cross types. The significance of this type of ANOVA resulted from a reduced error term and positively‐biasedFratios. A factorial design showed no significant differences due to type of progeny in seed mass, days to germination, leaf number, area, or biomass at six weeks of age. There were, however, significant differences among seeds attributable to maternal parent for all seed and seedling variables. A higher proportion of seeds from outcrossed individuals germinated compared to that from self‐fertilization. When the data were analyzed to include and partition all sources of variation, differences among offspring appeared during germination, rather than during later development. Seed mass, cross type, and sex of maternal parent all significantly affected the likelihood of germination; however, they had decreasing predictive power, respectively. Inbreeding depression inSilene vulgarismay help maintain gynodioecy; however, the pleiotropic effects of both nuclear and cytoplasmic genes for sex expression also may affect fitness and the maintenance of females.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1989.tb15115.x

出版商:Wiley    

年代:1989

数据来源: WILEY

摘要:

Agropyron smithiiandBouteloua gracilisplants from intensively grazed prairie dog colonies and from a grazing exclosure in Wind Cave National Park, South Dakota, were used to compare responses of conspecific populations with different histories of exposure to grazing and to competition for light. In separate experiments for each species, plants grown in monocultures and two‐population replacement‐series mixtures were used to examine effects of defoliation, frequency‐dependent competition, and population on biomass and morphology.Colony and exclosure plants frequently responded differently. Defoliation more often adversely affected exclosure plants than colony plants, while interpopulation competition more often adversely affected colony plants. Defoliation frequently negated the competitive advantage of exclosure plants. Intrapopulation competition appeared to be greater among exclosure than colony plants. Our results indicate that conclusions based on studies of plants in long‐term exclosures may not apply to plant populations having long histories of intensive grazing. While there were differences between species, in both, these experiments provide evidence of population differentiation, resulting in morphologically dissimilar populations which responded differently to defoliation and to inter‐ and intrapopulation competition.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1989.tb15116.x

出版商:Wiley    

年代:1989

数据来源: WILEY