摘要:

Legume fruits from the Eocene of Tennessee and Wyoming and the Miocene of Idaho are described and assigned toCaesalpiniasubgenusMezoneuron(Caesalpinioideae), an extant Paleotropical taxon that does not occur in North or South America today. Morphological and anatomical details of the fruits are used in evaluating their systematic relationships. The features of the fossil fruits are accommodated only within this extant subgenus. These fossils represent the only reliable known occurrence ofC.subgenusMezoneuronin the paleobotanical record. These fossils suggest that subgenusMezoneuronwas distinct from subgenusCaesalpiniaby the Middle Eocene. Further, they document the widespread occurrence of this currently Paleotropical group for at least 30 million years in North America.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1991.tb12566.x

出版商:Wiley    

年代:1991

数据来源: WILEY

摘要:

InChamaecrista fasciculata,fruit abortion levels are high and seed mass is highly variable, necessary preconditions for differential resource allocation of the female to seed and fruit sired by different males. This study investigated the relative role of pollen donor and seed parent on the allocation of resouces to developing seed and fruit, and assessed the role of genetic relatedness in contributing to any observed paternal effect inC. fasciculata.In addition, pollen donor effects were contrasted to within‐seed parent sources of variation in resource allocation due to pollination date and ovule position in the pod. Plants collected from the field were brought to a greenhouse where single‐donor crosses were conducted controlling for pollen donor source and interplant distance, a measure of genetic relatedness. Seed mass, number of seed/fruit, fruit maturation time, and fruit abortion rate were measured as indicators of resource allocation to developing seed and fruit. Variation in resource allocation was largely determined by the seed parent. Pollen donor effects were limited to differences between self vs. non‐self pollinations, suggesting that inbreeding depression following mating events between related individuals is the source of any variation among pollen donors on differential resource allocation to developing seed and fruit. Once the effect of inbreeding was removed, however, pollination date and ovule position played larger roles than pollen source. Since there was no detectable variation among male pollen donors in their ability to accrue resources from the female seed parent apart from inbreeding effects, it is concluded that the opportunity for postzygotic mate choice is limited inC. fasciculata.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1991.tb12567.x

出版商:Wiley    

年代:1991

数据来源: WILEY

摘要:

Spore wall morphogenesis ofLycopodium clavatumwas observed by transmission electron microscopy. The spore plasma membrane indicates the reticulate spore sculpture shortly after meiosis. The mature spore wall of this species consists of two layers, inner endospore and outer exospore. There is no perispore in the sporoderm of this species. The exospore formation begins during the tetrad stage; and this layer is divided into two distinct sublayers, an outer lamellar layer and an inner granular layer. The lamellar layer is formed on the sculptured spore plasma membrane. Additional lamellae attach to this layer in a centripetal direction. For that reason, this layer may be derived from spore cytoplasm. The granular layer is formed only in the proximal region following lamellar layer formation, and it also may be derived from spore cytoplasm. The endospore is formed lastly and seems to be derived from spore cytoplasm as well. Accordingly, the spore sculpture of this species may be under the genetic control of the spore nucleus.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1991.tb12568.x

出版商:Wiley    

年代:1991

数据来源: WILEY

摘要:

A new dimension to the well‐known phenotypic plasticity inScenedesmusis presented. Large colony typeScenedesmus communisHegew. reproduced in a typical fashion in batch culture in standard media but produced small colonies (SCT) resemblingS. komarekiiHegew. andS. subspicatusChod. at low cell densities in dilute media. Highest frequency of production occurred after cells had been pretreated in a concentrated (inorganic nutrients) medium. Examples of both cyclic and noncyclic behavior in the life history ofScenedesmus arepresented. The noncyclic behavior resembles previous reports on induced heritable changes in flax and tobacco due to different treatment applications of fertilizers. An analysis of gross morphological features using scanning electron microscopy showed that isolated strain SCT1 was similar toS. komarekii(strain UTEX 1236) and isolated strain SCT2 was similar toS. subspicatus(strain UTEX 1358). Growth and morphological expression of the induced SCT strains were highly similar to those of the respective UTEX species. The current state of taxonomy and the implications of phenotypic plasticity on taxonomy inScenedesmusare discussed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1991.tb12569.x

出版商:Wiley    

年代:1991

数据来源: WILEY

摘要:

Histochemical and morphometric analyses were used to identify and define an early stage of procambial differentiation in 1.5–2.0‐cm‐long (48 hr after germination) primary roots ofTrifolium pratenseL. Esterase activity was used as a histochemical marker for early differentiation of procambium. Morphometric analysis of cell length and width as a function of distance from the root cap junction was performed on the same tissue using brightfield and Nomarski DIC optics. This combination of techniques allowed the identification of esterase activity in both the cell wall and cytoplasm and permitted the determination of the exact location, size, and shape of the histochemically stained cells within the apex. Esterase activity identified the proendodermis and procambial cylinder (six to seven cells in diameter) two to three cells proximal to the root cap junction. In this system, esterase activity proved to be an earlier marker for procambial differentiation than morphometric or cytological changes. It is suggested that these techniques will be useful in characterizing procambial pattern development in more complex shoot systems.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1991.tb12570.x

出版商:Wiley    

年代:1991

数据来源: WILEY

摘要:

Contrary to taxonomic descriptions, female flowers ofSuckleya suckleyanahave four perianth segments rather than two bracts. Consequently,Suckleya suckleyanabelongs in the tribeChenopodieae,family Chenopodiaceae, instead of tribeAtripliceae.Since it is the only member of tribeChenopodieaewith unisexual flowers and superior radicles, it is proposed that it be assigned to a new subtribe,Suckleyinae.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1991.tb12571.x

出版商:Wiley    

年代:1991

数据来源: WILEY

摘要:

Japanese honeysuckle (Lonicera japonicaThunb.), introduced to the United States, and the native coral honeysuckle (Lonicera sempervirensL.) were compared to determine how intrinsic differences in their growth characteristics would affect their response to atmospheric carbon dioxide enrichment. Plants of both species grown from cuttings were harvested after 54 days of growth in controlled environment growth chambers at 350, 675, or 1,000 μl/liter CO2. The biomass of Japanese honeysuckle was increased 135% at 675 μ∗∗∗l/liter CO2and 76% at 1,000 μl/liter CO2after 54 days. Morphologically, the main effect of CO2enrichment was to triple the number of branches and to increase total branch length six times. Enhanced and accelerated branchingalso increased total leaf area 50% at elevated CO2concentrations. In coral honeysuckle, total biomass was only 40% greater in the elevated CO2treatments. Branching was quadrupled but had not proceeded long enough to affect total leaf area. Main stem height was increased 36% at 1,000 μl/liter CO2. The much less significant height response of other woody erect growth forms suggests that vines may increase in importance during competition if atmospheric CO2concentrations increase as predicted. The impact of Japanese honeysuckle in the United States may become more serious.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1991.tb12572.x

出版商:Wiley    

年代:1991

数据来源: WILEY

摘要:

Adaptation to high light intensity inAmbrosia cordifolia(Compositae) involved an increase in leaf thickness, photosynthetic capacity, and maximum stomatal conductance. In addition, leaves produced at high light intensities were amphistomatous, but those produced at low light intensities were hypostomatous. Although stomatal density on the upper surface was increased with increasing light intensity, the total stomatal density (upper + lower surfaces) was not substantially affected by light intensity because the density of stomata on the lower surface was reduced at high light intensities. The possible value of amphistomy in reducing diffusional limitations to photosynthesis in thick, high photosynthetic‐capacity leaves is discussed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1991.tb12573.x

出版商:Wiley    

年代:1991

数据来源: WILEY

摘要:

The order, rate, and extent with which plant tissues dehydrate during water stress and rehydrate remains largely unknown. In vivo magnetic resonance imaging was used at seven Tesla to measure changes in degree of water binding and relative water content (through T1 and N[H] changes) ofBlechnum unilateralestem regions as water stress developed and was relieved. Spin‐lattice relaxation times (T1s) ofB. unilateralestem regions were found to be positively linearly correlated with water potential. In the well‐watered state, the longest T1s were associated with the stem margin, followed by cortical parenchyma, pith parenchyma, and vascular bundles. During water stress, T1 values of the stem margin, cortical parenchyma, and pith parenchyma converged. After rehydration, T1s returned nearly to initial values. As indicated by a decrease in relative spin density (N[H]), the stem margin and cortical parenchyma began to lose water first during dehydration with the rate and extent of water loss being greatest for the stem margin. Later, water loss occurred from all regions; most rapidly and to a greater extent from the stem margin and vascular bundles. During water stress, N(H) of stem regions converged to a common value. Order of rehydration of stem regions was the same as order of dehydration. This study demonstrates that MR imaging can be used as a noninvasive tool for examining changes in the degree of water binding and water content of stem regions in live plants.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1991.tb12574.x

出版商:Wiley    

年代:1991

数据来源: WILEY

摘要:

Trees ofSassafras albidum(Nuttall) Nees. display leaves that fall into discrete categories of form. Unlobed leaves, with undissected margins, predominate at proximal and distal nodes of shoots, while lobed leaves are most common at intermediate nodes. In this study we investigated the hypothesis that shoots of sassafras respond to environmental changes over the growing season by generating predictable nodal patterns for leaf morphology and physiology. We recorded leaf shape category and measured leaf surface area, node number, chlorophyll content, nitrogen content, and photosynthesis in four trees. Over 1,000 measurements of photosynthesis were made in situ, using the LI‐Cor LI 6200 portable photosynthesis system. The two trees growing under heavy shade had few lobed leaves (2.0% and 18.8%) and often had negative carbon balance, with positive net photosynthesis occurring during sun flecks. The two trees growing in more open conditions had many more lobed leaves (56.3% and 61.0%) and higher, less variable net photosynthetic rates. As indicated by chlorophyll and nitrogen contents, the highest leaf photosynthetic rates occurred at intermediate nodes (nodes six to nine), and this was shifted distally along the shoot during the growing season. Leaves at intermediate nodes also had the largest surface areas and the greatest frequency of lobing. In comparative experiments with models, lobing was shown to enhance free‐convectional heat loss relative to unlobed leaves of the same surface area. Due to their large surface area, these leaves also have the highest rates of whole leaf photosynthesis. Under conditions of equivalent photosynthetically active radiation, lobed leaves had higher rates of net photosynthesis than did unlobed leaves. We conclude that shoots of sassafras produce groups of leaves with predictably different morphological and physiological specializations.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1991.tb12575.x

出版商:Wiley    

年代:1991

数据来源: WILEY