摘要:

The ontogeny of tassels and ears in two annual Mexican teosintes,Zea mayssubsp.mexicanaandZ. mayssubsp.parviglumis, was examined using scanning electron microscopy and light microscopy. Ear development in these annual teosintes follows a pattern previously described as leading to the bisexual mixed inflorescence inZ. diploperennis.Common bud primordia are initiated in the axils of distichously arranged bracts along the ear axis. These common primordia bifurcate to form paired sessile and pedicellate spikelet primordia. Development of pedicellate spikelets is arrested leaving the sessile spikelets, along with the adjoining rachis segment, to form solitary grains enclosed within cupulate fruitcases. Development of the central tassel spike is similar to that previously described in theZ. diploperennistassel, except that the first formed axillary bud primordia form precocious tassel branches. The origin of these tassel branches suggests a possible mechanism for the transition from a distichous spike, characteristic of teosinte, to a polystichous spike, typical of maize.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1990.tb13541.x

出版商:Wiley    

年代:1990

数据来源: WILEY

摘要:

Starch grain morphology in laticifer amyloplasts ofEuphorbia pulcherrimaWilld. (poinsettia) was examined for evidence of starch metabolism in vegetative and flowering plants. Laticifer starch grains in vegetative plants were rod shaped with lengths ranging from 3 to 60μm. Average grain size was significantly larger in stems than leaves, and in older than younger tissues. Starch grain length frequency was unimodal and approximated a normal probability distribution in stems, but was skewed positively toward smaller grains in leaves. Frequency distributions were shifted toward larger grains in older tissues. Under short‐day photoperiod (flowering) conditions, round starch grains formed in latex of stems, and the average length of rod‐shaped grains decreased in latex of stems and leaves. Round grains did not occur in laticifers of leaves or bracts. Round starch grains often occurred in aggregates of two or more subunits. Changes in size and shape of latex starch grains indicate that amyloplasts in fully differentiated laticifers metabolize starch. Identification of metabolically active amyloplasts in differentiated laticifers suggests that the function of these organelles may involve starch mobilization under certain physiological conditions.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1990.tb13542.x

出版商:Wiley    

年代:1990

数据来源: WILEY

摘要:

Pollen of the 27 genera presently recognized as comprising the family Lythraceae have been surveyed with light microscopy and scanning and transmission electron microscopy. Results for five genera (Physocalymma, Pleurophora, Rotala, Tetrataxis, Woodfordia), in addition toDuabanga, Sonneratia, andPunica(assigned to the Lythraceae in some classifications), are presented here; the remaining genera were treated previously in the series. The family is revealed as the most diverse palynologically of the order Myrtales. The most simple pollen type and the one common to the largest number of genera is prolate‐spheroidal to prolate; tricolporate, without pseudocolpi; psilate, scabrate or finely verrucate; and 16–28μm or less in length. Specializations include oblate grains, development of pseudocolpi (three or six in number), diversification of exine sculpturing, broadening of the colpal and pseudocolpal areas, and reduction in the conspicuousness of the colpi. Pollen evidence provides qualified support for inclusion ofPunicain the Lythraceae, the generalized nature of the pollen tempering the conclusion, and little support for inclusion ofSonneratiaandDuabangain the family. Completion of the survey provides a data base of pollen characters that will be integrated in future studies with other evidence into an overall phenetic and cladistic assessment of the family leading to production of a more natural classification.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1990.tb13543.x

出版商:Wiley    

年代:1990

数据来源: WILEY

摘要:

I examined effects of pollination intensity on fruit, seed and seedling characteristics inCampsis radicans, and joint effects of pollen donor and pollination intensity on fruit production. Large pollen loads were more likely to initiate fruit production than small pollen loads, and the former fruits contained more seeds and a greater total seed mass. No further increases in seed number or mass occurred for pollen loads above 4,000 grains. The weight of individual seeds was unaffected by pollen load. Effects of pollen donor were generally larger than effects of pollen load, and fruit production from small loads of pollen from one donor were sometimes equal to fruit production from larger pollen loads from another donor. The ratio of pollen grains deposited to resultant seeds increased with pollen load, and several explanations are proposed. Seeds from heavy pollinations emerged better than seeds from light pollinations, but did not differ in speed of germination or in the performance of seedlings up to 126 days. The emergence differences are probably due to differing intensities of pollen tube competition.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1990.tb13544.x

出版商:Wiley    

年代:1990

数据来源: WILEY

摘要:

Germinating seeds and developing seedlings ofPhalaenopsisHabsburg andPhalaenopsisRuth Burton × (PhalaenopsisAbendrot ×PhalaenopsisAbendrot) can utilize glucose, maltose, maltotriose, maltotetraose, maltopentaose, maltohexaose, and maltoheptaose as carbon sources. Fresh weight decreased significantly with increased polymerization from glucose through maltoheptaose. Seedling survival declined on higher molecular weight sugars reaching levels which were significantly different from those on glucose. Sugar uptake increased moderately with increasing molecular weight of oligomers. The maltooligosaccharides used in these experiments are hydrolyzed by the orchid seedlings and of the sugars which can support good growth glucose, but not maltose accumulate in culture media. As a result, media which supported seedlings contained substantial levels of glucose, the starting sugars, and decreasing amounts of the next shorter oligomers. This suggests enzymatic endwise hydrolysis of these maltooligosaccharides. Similar results were obtained withPhalaenopsisseedlings produced from seeds which were germinated on sugar‐free medium and transferred to a solution containing the same oligomers. Sugars in media which did not support seedlings were not hydrolyzed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1990.tb13545.x

出版商:Wiley    

年代:1990

数据来源: WILEY

摘要:

The three‐dimensional structure of the endothecial thickenings in the anthers was investigated in 87 species from 70 genera, chosen to provide representative coverage of the families Cyperaceae, Restionaceae, Anarthriaceae, Ecdeiocoleaceae, Centrolepidaceae, Joinvilleaceae, Flagellariaceae, Poaceae, Xyridaceae, and Eriocaulaceae. There is complex variation in the patterns of endothecial thickening: the Eriocaulaceae, Flagellariaceae, and most Poaceae have thickenings with a complete baseplate; the Cyperaceae and most of the Restionaceae are characterized by helical thickenings; some genera in the Bambusoideae have annular thickenings; and U‐shaped thickenings occur in the Xyridaceae and Eriocaulaceae and in some Poaceae and Restionaceae.JoinvilleaandEcdeiocoleahave unique thickening types. Endothecial characters were subjected to cladistic analysis. Including endothecial characters in an existing cladogram of the group indicates that there is no single, well‐corroborated cladogram available for the Poales/Restionales.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1990.tb13546.x

出版商:Wiley    

年代:1990

数据来源: WILEY

摘要:

Isozymatic data taken from 67 Guatemalan collections of maize were subjected to numerical taxonomic analyses to elucidate systematic relationships among the 19 maize races and subraces described for Guatemala by Wellhausen et al. As with Bolivian and Mexican races, isozymatic variation in Guatemalan maize was strongly associated with altitude. Guatemalan lowland races were in general isozymatically distinct from races of higher elevations. Two middle elevation Guatemalan races proved difficult to place taxonomically. As a group, Guatemalan highland races were isozymatically more diverse than races from lower elevations, and were rather weakly differentiated from Mexican highland races. Notably, variational patterns evident from phenetic analyses of isozyme data were generally congruent with those apparent in phylogenetic analyses. The data reported here, and in earlier studies, suggested that divergent combinations of isozymatic, karyotypic, and morphological features have evolved in local maize races from Mexico, Guatemala, and Bolivia, perhaps as the result of the different selective regimens indigenous cultivators have imposed on different regional phylogenetic lineages.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1990.tb13547.x

出版商:Wiley    

年代:1990

数据来源: WILEY

摘要:

Gas exchange was measured in two subalpine herbs during alternating periods of sun and shade that simulated natural cloud patterns. Stomatal conductance (g) in the subalpine herbHelianthella quinquenerviswas reduced by as much as 75% during 5‐min shade periods that ranged in photosynthetic photon flux density (PPFD) from 100 to 1,100μmol m–2sec–1. In contrast, responses in g in another herb,Frasera speciosa, to fluctuations in sunlight were small, apparently due to slower stomatal responses. Based on an earlier hypothesis that water stress may strongly influence nonsteady state gas exchange responses to fluctuations in PPFD, net photosynthesis and g were measured in these herbs as seasonal water stress increased and compared with responses in irrigated plants. Stomatal conductance was relatively unresponsive to changes in PPFD inF. speciosaregardless of water stress. In contrast, substantial decreases in g occurred forH. quinquenervisduring shade only when this species experienced water stress later in the season. Little response in g was measured early in the season or in irrigated plants. The seasonal shift in nonsteady state responses inH. quinquenervisfrom little response in g to shade when plants were nonstressed to more rapid reductions in g as water stress increased would maximize carbon gain early in the season when soil water was abundant while conserving water during periods of soil drought.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1990.tb13548.x

出版商:Wiley    

年代:1990

数据来源: WILEY

摘要:

Diploid and autotetraploid populations ofHeuchera grossulariifoliaoccur throughout mountainous regions of the Pacific Northwest. Controlled greenhouse crosses indicated that the two cytotypes are largely reproductively isolated. Fourteen diploid and 11 tetraploid populations were analyzed electrophoretically. Individual tetraploid plants expressed up to four alleles per isozyme locus, and tetraploid populations had significantly higher levels of heterozygosity than diploids. Mean observed heterozygosity was 0.159 for tetraploid populations and 0.058 for diploid populations. The patterns of allelic distribution between cytotypes suggested multiple origins of autotetraploids. This hypothesis was supported by restriction‐site analysis of chloroplast‐DNA (cpDNA) variation which indicated that there had been at least three independent origins of tetraploids. Electrophoretic data, in conjunction with a cpDNA‐based phylogeny and geographic distribution of populations, suggest that autopolyploid populations evolved several times as migration of diploids occurred down river systems. This study further supports the contention that autopolyploidy can be a common and successful speciation process in some groups of plants.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1990.tb13549.x

出版商:Wiley    

年代:1990

数据来源: WILEY

摘要:

The apical meristems of one‐year‐old container‐grown seedlings of coastal Douglas fir were studied in two years during embryonic shoot development, dormancy, and dormancy release by light and electron microscopy. Apical zonation was evident at all times but prominence of some zones varied. Vacuolation was an important zone‐characteristic and was not an artifact created by lipid extraction. During late summer and fall the plasma membrane was relatively smooth, ER not abundant, nuclear membranes irregular, and lipid bodies sparse. Numerous autophagic vacuoles occurred in apical cells. These diminished after bud scale initiation was completed in September and reappeared again in midwinter. Maximum starch accumulation was in the fall then it decreased during the winter and remained low during cold storage. The number of lipid bodies gradually increased in late fall and was large in winter. A single night of –1 C caused an increase in the number of lipid bodies. Plastids contained electron‐dense material which accumulated further under subfreezing temperatures and eventually appeared to be released during winter into the cytoplasm and arranged into small globules along the cisternae of the ER. Granular protein bodies were observed at this time as well as deposits of electron‐dense material on the outer surface of the plasma membrane and in cell walls. During winter, the plasma membrane became convoluted, short cisternae of the ER abundant, the nuclear membranes evenly separated, and nucleolar components aggregated. At the end of dormancy, ribosomes and starch grains became very abundant. Most lipid bodies diminished by budbreak.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1990.tb13550.x

出版商:Wiley    

年代:1990

数据来源: WILEY