Acorn mass and seedling growth in Quercus rubra in response to elevated CO2

Abstract. In order to explore whether seed size affects plant response to elevated CO₂, plants grown from red oak (Quercus rubra L.) acorns were studied for differences in their first year response to CO₂ concentrations of 350 and 700 μl/l. Overall, at final harvest, total biomass of plants grown in elevated CO₂ were 47 % larger than that of plants grown in ambient CO₂. There were significant interactions between CO₂ treatments and initial acorn mass for total biomass, as well as for root, leaf, and stem biomass. Although total biomass increased with increasing initial acorn mass for both high and ambient CO₂ plants, high CO₂ plants exhibited a greater increase than ambient CO₂ plants, as indicated by a steeper slope in high CO₂ plants. However, CO₂ levels did not affect biomass partitioning traits, such as root/shoot ratio, leaf, stem, and root weight ratios, and leaf area ratio. These results suggest that variation in seed size or initial plant size can cause intraspecific variation in response to elevated CO₂.     

Homology between the seed cytolysin enterolobin and bacterial aerolysins

Enterolobin, a 55-kDa cytolytic, inflammatory, and insecticidal protein isolated from seeds of the Brazilian treeEnterolobium contortisiliquum (Leguminosae-Mimosoideae) has been further purified and partially sequenced by using both manual and automated methods. A computational search of enterolobin partial amino acid sequence against the PIR database revealed possible sequence similarities with aerolysins, cytolytic proteins fromAeromonas species. An alignment of enterolobin partial sequence to the amino acid sequences ofA. hydrophila andA. sobria aerolysins showed several similar regions with many residue identites. The seed protein enterolobin and the bacterial aerolysins may be homologous proteins despite the distant phylogenetic relationship.     

Nuclear replication activities during imbibition of abscisic acid- and gibberellin-deficient tomato (Lycopersicon esculentum Mill.) seeds

The role of cis-abscisic acid (ABA) and gibberellins (GAs) in the induction of cell-cycle activities has been studied during imbibition and subsequent germination of tomato seeds. Using flow cytometry, nuclear replication activity was investigated in embryo root tips isolated from seeds of the ABA-deficient mutant sit ^w , the GA-deficient mutant gib-1, and the wild-type (MM) tomato (Lycopersicon esculentum Mill. cv. Moneymaker) upon imbibition in water, 10 μM GA₄₊₇, 5 μM ABA or 5 μM ABA+10 μM GA₄₊₇. The nuclei of fully matured dry MM, sit ^w and gib-1 seeds predominantly showed 2C DNA signals, indicating that the cell-cycle activity of most root-tip cells had been arrested at the G₁ phase of nuclear division. However, ABA-deficient sit ^w seeds contained a significantly higher amount of G₂ cells (4C DNA) compared with the other genotypes, suggesting that, during maturation, cell-cycle activity in sit ^w seeds is less efficiently arrested in G₁. Upon imbibition in water, an induction of the 4C signal, indicating nuclear replication, was observed in the root tip cells of both MM and sit ^w embroys. The augmentation in the 4C signal occurred before visible germination. Gib-1 seeds did not show cell-cycle activity and did not germinate in water. Upon imbibition in GA₄₊₇, both cell-cycle activity and subsequent germination were enhanced in MM and sit ^w seeds, and were induced in gib-1. In ABA, the germination of MM and sit ^w seeds was inhibited while nuclear replication of these seeds was not affected. It is concluded that GA influences germination by acting upon processes that precede cell-cycle activation, while ABA affects growth by acting upon processes that follow cell-cycle activation.     

The glycinin box: a soybean embryo factor binding motif within the quantitative regulatory region of the 11S seed storage globulin promoter

The soybean embryo factor binding sequence in the glycinin A₂B_1a gene promoter was delimited to an A/T-rich 9 bp sequence, 5-TAATAATTT-3, designated as the glycinin box, by DNA footprinting and gel mobility shift assay using synthetic oligonucleotides. It was shown that the interaction with the factor takes place at a defined DNA sequence rather than at random A/T-rich sequence blocks in the glycinin 5 flanking region. There are four glycinin boxes in the quantitative regulatory region between positions – 545 and – 378 of the glycinin A₂B_1a promoter. Multiple nonamer motifs similar to the glycinin box were also found in the equivalent regions of other glycinin and legumin promoters, suggesting that they must be conserved as a binding site for the embryo factor that activates the differential and stage-specific expression of seed 11S globulin genes in leguminous plants.     

Tropical tree species diversity: a test of the Janzen-Connell model

To test the premises and predictions of the Janzen-Connell model (Janzen's spacing mechanism), seeds of the rainforest canopy tree, Brosimum alicastrum, were placed at different distances from the parent tree and their removal observed over 3 weeks. The number and density of naturally occurring seeds at different distances from the parent tree were also estimated. Predation was not greater near the parent tree, except on the very small spatial scale: the proportion of experimental seeds removed was greater 1 m from the trunk than it was 5–25 m from the trunk. Predation was negatively correlated with seed density, not positively as the Janzen-Connell model assumes-presumably due to predator satiation. The density of seeds after predation peaked 5 m from the tree trunk, but this is well within the crown radius of the parent tree. There is a peak in the number of potential recruits at a distance of 10 m from the parent tree, due to the peaked initial distribution of seeds. This peak is caused by the interaction between the seed density curve and the increasing area of an annulus around the parent tree at increasing distances, not by the product of the density curve and the predation curve. However, it is important to realize that it is not the presence of a peak in recruitment away from the parent that is essential to maintaining tropical tree species diversity, but frequency-dependent recruitment induced by poor recruitment near conspecifics. Predator satiation seems to be an important factor in the survival of B. alicastrum seeds, possibly at several spatial scales. The number of seeds produced by the tree is negatively correlated with the loss to predators, and trees that have a fruiting conspecific nearby also suffer lower levels of predation. Seed predation increases as one moves from the forest edge into the interior, creating an edge effect that may have long-term effects on the forest composition and tree species diversity. More studies are needed, for other species, other localities, and larger spatial and temporal scales, on both the Janzen-Connell mechanism and this edge effect.     

Oleate from triacylglycerols is desaturated in cold-induced developing sunflower (Helianthus annuus L.) seeds

For the first time, an active fatty-acid metabolism is indicated for triacylglycerols (TAG) of developing sunflower (Helianthus annuus L.) seeds. When the developing seeds were transferred to low temperature, the total amount of oleate found in TAG decreased as that of linoleate increased, while the contents of total lipids and TAG remained unchanged. These results suggest that oleate from TAG was used for desaturation. This occurred first in microsomal TAG, but after a long cold period it was observed mainly in the oil-body fraction. Thesn-2 position of TAG was preferentially enriched in linoleate. Apparently, more linoleate than necesary for the maintenance of membrane fluidity was synthesized at the expense of TAG oleate.     

Molecular heterogeneity of Cowpea (Vigna unguiculata Fabaceae) seed storage proteins

81 wild forms and 110 cultivated cowpea,Vigna unguiculata, accessions from 21 countries of Africa were screened for variability in seed storage proteins. Total seed proteins, albumin and globulin fractions were investigated by means of sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and isoelectric focusing (IEF) of nonreduced and/or reduced samples in one- and two-dimensional procedures. The globulin fraction is heterogeneous in molecular weight and contains both legumin-like components and three to six nondisulfide-linked subunits. Three globulin subunits, with molecular weights 110, 76, and 41 kD were found to be composed of disulfide-linked polypeptides. In the nondisulfide-linked fraction, both cultivated and wild forms exhibited patterns of four types (A–D). This fraction contains polypeptide subunits of molecular weights 62, 56, and 52 kD for A type, 62, 56, 54, and 52 kD for B type, 62, 56, 52, and 50 kD for C type, and at least 62, 56, 54, 52, 50, and 49 kD for D type. These subunits present similar multiple charge forms but C and D types possess more basic specific 50 and 49 kD nondisulfide linked components. Major albumin fraction contains subunits of 94, 86, 32, and 24kD. No infraspecific variation was observed in albumin or legumin-like fractions. The discussion is focussed on the relations between genetic variability assessed by storage protein coding genes and phenotypic variability.     

长江三峡库区种子植物的中国特有分布

报道了分布于长江三峡库区的中国种子植物特有属及特有植物在库区的水平与垂直分布概况,对库区的特有分布的特点也进行了简要的分析和探讨。     

铅锌矿尾矿场植被重建的生态学研究Ⅰ.尾矿对种子萌发的影响

在实验条件下,供试的林木、农作物及牧草种子均能在铅锌矿尾矿中萌发,其中萌发率与非污染土壤中的相近,多数种子的萌发速率低于对照组。供试植物幼苗出土30天内没有死苗现象,但与对照相比,株高下降28.4%,复叶数减少34.1%,生物量下降52.6%.     

Suppression of phaseolin and lectin in seeds of common bean, Phaseolus vulgaris L.: increased accumulation of 54 kDa polypeptides is not associated with higher seed methionine concentrations

Suppression of phaseolin and lectin accumulation in common bean resulted in higher concentrations of bean seed polypeptides with apparent molecular weights of 54 kDa and from 70 to 84 kDa on SDS-polyacrylamide gel electrophoresis. Polypeptides of 54 and 56 kDa segregated as products of different alleles. Genes for the 54/56 kDa bands and phaseolin were estimated to be 26.2±3.7 map units apart. The 54 kDa band phenotype manifested by SDS-PAGE consisted of from one to three polypeptides of 54 kDa MW on 2D gels, and the 56 kDa phenotype consisted of one polypeptide of 56 kDa plus two minor polypeptides of 54-54.5 kDa molecular weight. The pK_I of these polypeptides was approximately 5.25. The methionine content of the 54 kDa polypeptides of the cultivar Great Northern Star was 1.6±0.1 g/100 g protein, which was not statistically different from the value (1.5±0.1%) obtained for phaseolin isolated by the same procedure. F₂ seeds deficient for phaseolin and lectin contained as much total N per g as wild-type seeds and were not shrunken, but contained 50% more free amino acids. F₂ seeds from two of the three populations contained from 8 to 13% less methionine per mg total N.