摘要:

The pattern and sequence of zein degradation in the endosperm of germinating maize seeds were investigated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS‐PAGE) and by immunostaining Western blots with a monoclonal antibody toα‐zein and polyclonal antibodies toβ‐, γ‐, andδ‐zeins. The results indicated: 1) the degradation of the predominantα‐zein fraction (23.8 and 26.7 kD) started on the 5th day after germination (DAG) and continued gradually until the 10th DAG with a small amount remaining undegraded up to the 26th DAG; 2)β‐zein (17 kD) began to be degraded on the 2d DAG, and the degradation of the 17 kD polypeptide was completed by the 7th DAG; 3)γ‐zeins (27 and 18 kD) were the first zeins to be degraded, and the degradations ofγ‐zeinl (27 kD) andγ‐zein2 (18 kD) were complete by the 3rd and 4th DAG, respectively; and 4) the degradation ofδ‐zein (10 kD) began on the 4th DAG and was complete by the 7th DAG. Based on these results, the following arrangement of zein polypeptides within the protein bodies is postulated, assuming that the proteolytic events start at the periphery and processed towards the core of the protein body: 1)γ‐zeins are situated around the periphery of the protein bodies and are possibly a structural component of the protein body membrane or directly anchored in the membrane; 2)β‐zein would be internal toγ‐zeins; and 3)α‐zein andδ‐zein would be in the protein body core. This arrangement is largely consistent with published data on the immunocytochemical localization of zeins, and it indicates that the different classes of zein are not randomly organized within the matrix of the protein body.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1990.tb13591.x

出版商:Wiley    

年代:1990

数据来源: WILEY

摘要:

Cycles of development in several male shoots ofCycas circinaliswere studied by counting sequences of foliage leaves, scale leaves, and cones by observation of either their scar patterns or vascular remains. Although male cones are always produced subsequent to a cycle of foliage leaves and are fairly regularly spaced there is no obvious correlation between their presence and the previous cycles of leaves. Ratios of foliage leaves to scale leaves in each cycle are variable. The primary diameter of the axis is obconical, but a conical stem form results from secondary growth. The result of concentric development of xylem and phloem is positively correlated with stem diameter rather than stem age.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1990.tb13592.x

出版商:Wiley    

年代:1990

数据来源: WILEY

摘要:

Most plants in Mediterranean ecosystems are insect pollinated, with pollen being the main reward to pollinators. The great majority of pollinators (70%) are bees and flies. We measured the energy content of pollen from 40 plant species in these ecosystems that represent abiotic and biotic pollination modes as well as the number of species of their pollinators. Pollen energy content correlates with pollinator diversity. Pollen of wind‐pollinated plants contained less energy than that of insect‐pollinated plants; there was no difference between insect‐pollinated dicots and insect‐pollinated monocots. The median date of flowering (from 1 January) estimated for each of the plant species did not vary significantly either with the number of pollinator species or with the energy content of pollen. The reasons for the differing values of pollen energy content are discussed; in particular, its relation to the type of pollen reserves, length of the flower style, and pollination enhancement.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1990.tb13593.x

出版商:Wiley    

年代:1990

数据来源: WILEY

摘要:

Growth chamber experiments with rapid‐cyclingBrassica rapawere designed to estimate the signs and magnitudes of the genetic correlations for plant performance in each of three conditions: no‐competition (isolated plants), intraspecific competition, and interspecific competition withRaphanus sativa.Biomass and flower number were highest in the no‐competition treatment, intermediate under intraspecific competition, and lowest under interspecific competition. Significant among‐family variation in biomass and flower number was found under each regime. The mean family performance (biomass or flower number) in the no‐competition treatment was significantly positively correlated with the performance in only one of the competitive treatments (for biomass in the intraspecific treatment). For both biomass and flower number there was a significant positive correlation between family means in the intra‐ and interspecific regimes. These correlations were greater in magnitude than those for the comparison between no‐competition and competition (intra‐ or interspecific) treatments. Our results suggest that the importance of traits affecting plant performance is environment‐dependent; the performance of a family grown without competition was a poor predictor of performance with competition, while the performance of families grown under intra‐ and interspecific competition was positively correlated.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1990.tb13594.x

出版商:Wiley    

年代:1990

数据来源: WILEY

摘要:

We report the photosynthetic characteristics of a C3shade plant native to the tropical rain forest understory. It was shown thatElatostema repensLour. (Hall) f. (Urticaceae) presents a large light adjustment capacity. The effects of several lightfleck sequences on photoinhibition of photosynthesis and carbon gain are analyzed. Photoinhibition is measured both as a decrease in leaf net CO2uptake in limiting light (shown to be linearly correlated to quantum yield of O2evolution measured at saturating CO2) and as a decrease of the ratio of variable fluorescence (Fv) to maximum fluorescence (Fmax) measured in liquid nitrogen. It is shown that lightflecks (from 10 to 30 min in duration) of 700μmol m–2s–1(high light) induce photoinhibition, and that the effects of those successive high light periods are additive; there is apparently no recovery from photoinhibition during the low light periods (from 10 to 45 min in duration). In contrast, the Fv/Fmax ratio, though decreasing similarly to quantum yield of net CO2uptake on leaves submitted to a continuous illumination of 700μmol m–2s–1, is only decreased a little on leaves submitted to lightfleck sequences of the same photon flux density. Lightflecks of 250μmol m–2s–1are not photoinhibitory. Compared to the control maintained under light growth condition (40μmol m–2s–1) carbon gain is increased on leaves submitted to lightflecks; this gain remains high throughout the light cycles on leaves submitted to nonphotoinhibitory lightflecks and to the photoinhibitory lightflecks followed by the shortest low light period. In the other cases, carbon gain, higher than that of the control at the beginning of the treatments, decreases and becomes lower than the control carbon gain. Finally, the relevance of photoinhibition in the tropical rain forest understory environment is discussed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1990.tb13595.x

出版商:Wiley    

年代:1990

数据来源: WILEY

摘要:

Stem and leaf photosynthesis were measured inGlycine maxvar.essex(soybean) andSparteum junceum(Spanish broom). The significance of stem photosynthesis to whole plant growth was evaluated by blocking stem photosynthesis with black straw sections. The growth ofS. junceumwas reduced by 18% when black straws were used in comparison to clear straws. The whole plant growth ofG. maxwas not influenced by blocking the stem carbon contribution. Mean midday leaf photosynthesis was 12μmol CO2m–2s–1and 17μmol CO2m–2s–1forG. maxand 5.junceum, respectively. Mean midday stem photosynthesis ofS. junceumwas 6.5μmol CO2m–2s–1; however, positive net photosynthesis did not occur inG. maxstems. Water stress caused a proportionally greater decrease in leaf photosynthesis compared to that of stems during diurnal cycles of photosynthesis inS. junceum.As a result the contribution to canopy carbon gain by stem photosynthesis increased from 38% to 48% of the total plant carbon gain under reduced water availability.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1990.tb13596.x

出版商:Wiley    

年代:1990

数据来源: WILEY

摘要:

Chromosome numbers and karyotypes of species from four American Zamiaceae (Cycadales) are reported.Zamiashows interspecific and intraspecific chromosome variation, whereasMicrocycas, Ceratozamia, andDioonhave constant karyotypes within each genus. InZamia, all karyotypes have the same number of submetacentric and acrocentric chromosomes, but they differ in the number of metacentric and telocentric chromosomes. Centric fission of metacentric chromosomes is proposed to explain the karyotypic variation in this genus.Zamiashows karyological relationships withMicrocycasandCeratozamia, whereasDioonappears very distinct from the other American cycad genera. Affinity amongZamia, Ceratozamia, andMicrocycaskaryotypes and distinctiveness ofDioonkaryotypes are supported by comparative analysis of phenotypic characters in the four genera.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1990.tb13597.x

出版商:Wiley    

年代:1990

数据来源: WILEY

摘要:

Brownea arizaBenth. (Leguminosae: Caesalpinioideae) shows early shoot tip abortion and subsequent renewal growth from the pseudoterminal bud. This species is unusual in that the entire shoot system is formed before flushing from the bud occurs, shoot tip abortion occurs during flushing, and the aborting portion contains three to six leaves as well as primordial structures varying from hood to peg shape. This study focused on the morphological changes from initiation of scale and foliage leaf primordia in the “resting” renewal bud through bud elongation to flushing and bud abortion. Scanning electron microscopy revealed that embryonic scale leaves are hood‐shaped while foliage leaf primordia show early segmentation into leaflets and stipules. No transitional stages were observed. Bud scales and foliage leaves show opposite developmental trends. In bud scales, length at maturity increases from first to last formed, while length decreases in sequentially formed foliage leaves. Early in leaf development the stipules keep pace with the elongation of the rachis. When the bud reaches about one half of its final length the leaf rachis begins to exceed the lengths of its stipules. This young rachis terminates in a distinct mucro that persists until maturity at which time it abscises. Growth patterns indicate that mucro and rachis are a single developmental unit. The early abortion of a shoot tip containing several leaves cannot be easily rationalized. Previous suggestions have involved maintenance of form and ecological adaptation. We add the possibility of elimination of cell progeny encumbered by mutations. From this and other studies of this group, it is clear that at maturity leaves of different species may look alike, e.g.,HymenaeaandColophospermumare bifoliolate;Brownea, Saraca, and others are multifoliolate. However, early stages of leaf ontogeny are quite diverse and may be of systematic value, since these early differences are lost or masked by later development.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1990.tb13598.x

出版商:Wiley    

年代:1990

数据来源: WILEY

摘要:

Leaf growth and spore release inDanaea wendlandiiwere monitored under temperate greenhouse conditions and in a rain forest at the La Selva Biological Station in Costa Rica. Sterile leaf (trophophyll) growth occurs in four phases, and fertile leaf (sporophyll) growth occurs in five phases. Trophophylls show an initial rapid increase in length for a 4‐week period, attain full maturity at 8 weeks, and remain on the plant for about 3 years. There appears to be a seasonal pattern of trophophyll growth, with crozier emergence rates in May and June three times higher than the mean annual rate. Sporophyll growth shows a double sigmoid pattern. For about 3 weeks after crozier emergence, there is a rapid increase in length. This phase is followed by a 10‐week period with no appreciable change in length. Rapid elongation over a 2‐week period precedes spore release; this is followed within 2 weeks by disappearance of the sporophyll. Sporophylls in the rain forest are subject to 14% mortality prior to maturation, with most mortality occurring in later stages of growth. A projected phenology based on the sporophyll growth curve shows peaks in spore release late in the wet season with a concomitant peak in sporophyll emergence early in the wet season during the 15‐month period from June 1986 through September 1987.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1990.tb13599.x

出版商:Wiley    

年代:1990

数据来源: WILEY

摘要:

Fertile leaves (sporophylls) of the eusporangiate herbaceous layer fernDanaea wendlandiiemerge from the shoot apex with a horizontal orientation. Croziers of sterile leaves (trophophylls) emerge from the terminal bud oriented vertically. Sporophylls maintain a horizontal orientation as the leaflets uncoil and the rachis unrolls. This is followed by formation of a petiolar hook and vertical reorientation of the mature sporophyll. Both the vertical orientation of young trophophylls and the horizontal orientation of young sporophylls are gravitropic responses. Neither type of leaf responds to directional light stimulus. Negative gravitropism causing downward curvature of young sporophylls occurs only in the light, and in the absence of light, sporophyll croziers curve upward. Amyloplast sedimentation patterns in cells of the petiole and rachis indicate that a statolith mechanism may be involved in the orientation of young leaves ofD. wendlandii.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1990.tb13600.x

出版商:Wiley    

年代:1990

数据来源: WILEY