Fruit and seed ontogeny related to the seed behaviour of two tropical species of Caesalpinia (Leguminosae)

Caesalpinia echinata and C. ferrea var. ferrea have different seed behaviours and seed and fruit types. Comparison of the seed ontogeny and anatomy partly explained the differences in seed behaviour between these two species of Brazilian legumes; some differences were also related to fruit development. The seed coat in C. ferrea consisted of two layers of osteosclereids, as well as macrosclereids and fibres, to form a typical legume seed coat, whereas C. echinata had only macrosclereids and fibres. In C. echinata , the developing seed coat had paracytic stomata, a feature rarely found in legume seeds. These seed coat features may account for the low longevity of C. echinata seeds. The embryogeny was similar in both species, with no differences in the relationship between embryo growth and seed growth. The seeds of both species behaved as typical endospermic seeds, despite their different morphological classification (exendospermic orthodox seeds were described for C. echinata and endospermic orthodox seeds for C. ferrea ). Embryo growth in C. ferrea accelerated when the sclerenchyma of the pericarp was developing, whereas embryonic growth in C. echinata was associated with the conclusion of spine and secretory reservoir development in the pericarp. Other features observed included an endothelial layer that secreted mucilage in both species, a nucellar summit, which grew up into the micropyle, and a placental obturator that connected the ovarian tissue to the ovule in C. ferrea . © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 146 , 57–70.     

α-d-galactosidase deficiency in coconut endosperm: its possible pleiotropic effects in makapuno

α-d-galactosidase (α-d-galactoside galactohydrolase, EC 3.2.1.22) activity in the normal endosperm increased with age continually up to endosperm maturity. In contrast, makapuno α-d-galactosidase was hardly detected in almost all stages of development except the last, where its activity was 8300-fold lower as compared to the normal. The possible role of α-d-galactosidase in the formation of the makapuno endosperm is discussed.     

Ageing of isolated embryos and endosperms of durum wheat: An analysis of chromosome damage

Embryos (EM) and endosperms (END) were isolated from durum wheat seeds and aged separately for 3 years. Analysis of chromosome damage was carried out on root tip meristems of transplants in which aged (a) embryos and/or endosperms were used. The aim of the experiments was to investigate the ageing process when embryos and endosperms age separately and to evaluate the possible influence of the endosperm during storage of the seed.The results obtained indicate that (i) both aged embryo and endosperm produce mutagenic substances capable of inducing nuclear damage in the radicle meristem and (ii) age-induced damage in the embryo is not the consequence of endosperm ageing. The relationships between chromosome damage produced by aged embryos and endosperms in the transplants are discussed.     

Enzymes of carbohydrate metabolism in developing Hordeum distichum grain

Variations in activity of several enzymes associated with carbohydrate metabolism were recorded during the development of barley endosperm. The enzymes investigated were: sucrose-UDP (ADP) glucosyl transferase; invertase; UDPG (ADPG) pyrophosphorylase; hexokinase; glucose-6-phosphate ketoisomerase; phosphoglucomutase, and nucleosidediphosphokinase.     

Morphological Studies on Circaeaster agrestis Maxim. (1) Process of Embryolo gical Development

The present paper aims at discovering the characters of embryological development of Circaeaster agrestis, which makes up a monotypic genus, Circaeaster, to establish the phylogenetic relationships of the genus. The different opinions on its systematic position among botanists are briefly explained. The embryological studies show that the most important advanced characters of the genus are as follows. The ovule is amphitropous, unitegmic and tenuinucelar; the embryo sac formation is in accordance with the Polygonum type; endosperm formation is of the cellular type, the primary endosperm nucleus dividing to form two cells and the first wall vertical; embryo formation follows the variation of the Caryophyllad type; at the early stage of development of embryo, the integument has been already atrophied and at last disappeared, so that the seed coat is absent in the mature fruit. On the basis of the embryological and some morphological evidence, the authors consider that a close relationship between the genus and Ranunculaceae and its related families seems to be unlikely. The affinities of the genus Circaeaster are still uncertain.     

一种有效地提高银杉人工菌根苗诱导率的方法

 银杉（Cathaya argyrophylla）是一种极其珍稀的濒危松科植物。该研究建立了一种有效的银杉人工菌根诱导技术。通过将银杉种子播种于琼脂培养基7 d后,切除1/5～1/3的 种皮以及胚乳,从而使银杉种子的发芽率达到60％以上;同时筛选出既适合外生菌根菌土生空团菌（Cenococcum geophilum）平铺扩展生长的要求,又能满足银杉幼苗生长的培养基 RM, 使银杉的侧根能最大程度地与菌丝接触,确保了菌根的诱导率;通过紫外线照射加70％酒精 或0.05%NaOCl的表面消毒的双重处理,使不能高压灭菌的容器达到表面消毒效果,同时验证了用该灭菌法既能达到完全的灭菌效果又不会对植物的生长产生不良影响,而且银杉小苗的菌根形成率达到87.5%。该方法对于银杉的菌根学研究以及其它基础研究具有实际应用价值     

The role of hybrid seed inviability in angiosperm speciation

Understanding which reproductive barriers contribute to speciation is essential to understanding the diversity of life on earth. Several contemporary examples of strong hybrid seed inviability (HSI) between recently diverged species suggest that HSI may play a fundamental role in plant speciation. Yet, a broader synthesis of HSI is needed to clarify its role in diversification. Here, I review the incidence and evolution of HSI. Hybrid seed inviability is common and evolves rapidly, suggesting that it may play an important role early in speciation. The developmental mechanisms that underlie HSI involve similar developmental trajectories in endosperm, even between evolutionarily deeply diverged incidents of HSI. In hybrid endosperm, HSI is often accompanied by whole-scale gene misexpression, including misexpression of imprinted genes which have a key role in endosperm development. I explore how an evolutionary perspective can clarify the repeated and rapid evolution of HSI. In particular, I evaluate the evidence for conflict between maternal and paternal interests in resource allocation to offspring (i.e., parental conflict). I highlight that parental conflict theory generates explicit predictions regarding the expected hybrid phenotypes and genes responsible for HSI. While much phenotypic evidence supports a role of parental conflict in the evolution of HSI, an understanding of the underlying molecular mechanisms of this barrier is essential to test parental conflict theory. Lastly, I explore what factors may influence the strength of parental conflict in natural plant populations as an explanation for why rates of HSI may differ between plant groups and the consequences of strong HSI in secondary contact.     

The endosperm development and the variations of structures of embryo sacs: unravelling the low fecundity of Zephyranthes candida (Amaryllidaceae)

To unravel a low fecundity in Zephyranthes candida (Lindl.) Herb., the development of the endosperm was studied using conventional paraplast section technique. The results show that the endosperm develops normally and comprises four major stages viz. syncytial, cellularization, differentiation and maturation. Both proliferation of antipodal cells and their close contact with the primary endosperm nucleus were observed, which should favor transportation of nutrients and accelerate development of embryo and endosperm. In Z. candida, at least four events of nuclear migration occurred during the course of embryogenesis and endosperm development. The 12.7% structurally and functionally abnormal ovules, along with the 22.3% collapsed and aborted ovules observed accounts for the low fecundity to some extent.     

Protein phosphorylation regulates maize endosperm starch synthase IIa activity and protein−protein interactions

Starch synthesis is an elaborate process employing several isoforms of starch synthases (SSs), starch branching enzymes (SBEs) and debranching enzymes (DBEs). In cereals, some starch biosynthetic enzymes can form heteromeric complexes whose assembly is controlled by protein phosphorylation. Previous studies suggested that SSIIa forms a trimeric complex with SBEIIb, SSI, in which SBEIIb is phosphorylated. This study investigates the post-translational modification of SSIIa, and its interactions with SSI and SBEIIb in maize amyloplast stroma. SSIIa, immunopurified and shown to be free from other soluble starch synthases, was shown to be readily phosphorylated, affecting V_max but with minor effects on substrate K_d and K_m values, resulting in a 12-fold increase in activity compared with the dephosphorylated enzyme. This ATP-dependent stimulation of activity was associated with interaction with SBEIIb, suggesting that the availability of glucan branching limits SSIIa and is enhanced by physical interaction of the two enzymes. Immunoblotting of maize amyloplast extracts following non-denaturing polyacrylamide gel electrophoresis identified multiple bands of SSIIa, the electrophoretic mobilities of which were markedly altered by conditions that affected protein phosphorylation, including protein kinase inhibitors. Separation of heteromeric enzyme complexes by GPC, following alteration of protein phosphorylation states, indicated that such complexes are stable and may partition into larger and smaller complexes. The results suggest a dual role for protein phosphorylation in promoting association and dissociation of SSIIa-containing heteromeric enzyme complexes in the maize amyloplast stroma, providing new insights into the regulation of starch biosynthesis in plants.     

Global analysis of canola genes targeted by SHORT HYPOCOTYL UNDER BLUE 1 during endosperm and embryo development

Seed development in dicots includes early endosperm proliferation followed by growth of the embryo to replace the endosperm. Endosperm proliferation in dicots not only provides nutrient supplies for subsequent embryo development but also enforces a space limitation, influencing final seed size. Overexpression of Arabidopsis SHORT HYPOCOTYL UNDER BLUE1::uidA (SHB1:uidA) in canola produces large seeds. We performed global analysis of the canola genes that were expressed and influenced by SHB1 during early endosperm proliferation at 8 days after pollination (DAP) and late embryo development at 13 DAP. Overexpression of SHB1 altered the expression of 973 genes at 8 DAP and 1035 genes at 13 DAP. We also surveyed the global SHB1 association sites, and merging of these sites with the RNA sequencing data identified a set of canola genes targeted by SHB1. The 8‐DAP list includes positive and negative genes that influence endosperm proliferation and are homologous to Arabidopsis MINI3, IKU2, SHB1, AGL62, FIE and AP2. We revealed a major role for SHB1 in canola endosperm development based on the dynamics of SHB1‐altered gene expression, the magnitude of SHB1 chromatin immunoprecipitation enrichment and the over‐representation of eight regulatory genes for endosperm development. Our studies focus on an important agronomic trait in a major crop for global agriculture. The datasets on stage‐specific and SHB1‐induced gene expression and genes targeted by SHB1 also provide a useful resource in the field of endosperm development and seed size engineering. Our practices in an allotetraploid species will impact similar studies in other crop species.