Biochemical changes during embryogeny in Hordeum distichum

Changes in fr. and dry wt, soluble reducing sugars, protein. total carbohydrate, DNA, RNA, sucrose synthetase activity and invertase activity were recorded for the developing embryo of Hordeum distichum var Julia over the period 18–60 days after anthesis. Fresh wt increased until 45 days whereupon rapid dehydration commenced. Reducing sugar concentration remained low throughout development but total carbohydrate and protein accumulated rapidly over the initial period to reach maximum values at around 50 days. DNA concentration remained relatively constant throughout the middle and later stages of development, but RNA, on the other hand, increased rapidly to reach a maximum value at maturity. Sucrose synthetase (assayed in the direction of sucrose cleavage) was considerably more active with UDP than ADP and reached a maximum value around 35 days after anthesis. When assayed in the direction of sucrose synthesis the peak of activity was slightly later in development and doubled in value. Invertase activity was appreciable and was still present at maturity.     

Phosphorylase activity in relation to starch synthesis in developing Hordeum distichum grain

Activity, control and primer requirements of starch phosphorylase in developing barley endosperm were investigated. Phosphorylase was detected in endosperm extracts from 3 days after anthesis. Unprimed activity was predominant between 2 and 10 days after anthesis, when it constituted 70–80% of total activity, but this proportion declined rapidly as the grain developed. The existence of at least 2 isoenzymes was indicated by studies of pH dependence and phosphate inhibition, and was further supported by acrylamide gel electrophoresis and column chromatography using DEAE-cellulose. The two isoenzymes which ere possibly both glyco proteins, appear in barley endosperm soon after anthesis. One appears capable of unprimed activity, and may be associated with the initiation of a-1,2 glucans, which then serve as primers for starch synthetase. This disappears by 13–15 days after anthesis. The other isoenzyme is capable of some unprimed activity but undergoes modification between 15 and 20 days after anthesis, resulting in the loss of unprimed activity. The relevance of the results to initiation of starch synthesis and to starch synthetase in amyloplasts is discussed.     

Activity of enzymes of arginine metabolism in the cotyledons of developing and germinating pea seeds

Ornithine carbamoyltransferase, argininosuccinate synthetase, argininosuccinate lyase, and arginase activity were measured in extracts from cotyledons of developing and germinating seeds of Pisum sativum L. The course of activity of these four urea cycle enzymes showed a similar pattern during seed development. The activity per cotyledon increased sharply initially and reached a maximum about 5 weeks after anthesis, when the relative water content of the seeds was about 60%. About 8 weeks after anthesis, the seeds were mature (air-dry) and had enzyme activities which were much lower. The activities of the enzymes differed considerably. Ornithine carbamoyltransferase showed the highest activity, followed in order of decreasing activity by arginase, argininosuccinate lyase, and finally argininosuccinate synthetase.

The course of the activity of the four enzymes was different during germination. Arginase activity increased sharply 7 hours after the onset of germination and remained at a constant level during the following days. Argininosuccinate synthetase activity decreased; the other enzymes showed a small increase in activity and a subsequent decrease. Results are discussed in relation to the regulation of the arginine metabolism during pea seed development and germination.

     

Physicochemical properties and development of wheat large and small starch granules during endosperm development

Wheat mature seeds have large, lenticular A-type starch granules, and small, spherical B-type and irregular C-type starch granules. During endosperm development, large amyloplasts came from proplastid, divided and increased in number through binary fission from 4 to 12 days after flowering (DAF). Large starch granules formed and developed in the large amyloplast. One large amyloplast had only one large starch granule. Small amyloplasts came from the protrusion of large amyloplast envelope, divided and increased in number through envelope protrusion after 12 DAF. B-type starch granules formed and developed in small amyloplast from 12 to 18 DAF, C-type starch granules formed and developed in small amyloplast after 18 DAF. Many B- and C-type starch granules might form and develop in one small amyloplast. The amyloplast envelopes were asynchronously degraded and starch granules released into cell matrix when amyloplasts were full of starch granules. Apparent amylose contents of large starch granules were higher than that of small starch granules, and increased with endosperm development. The swelling powers and crystallinity of large starch granule were lower than that of small starch granules, and decreased with endosperm development. Small starch granules displayed broader gelatinization temperature ranges than did large starch granules.     

Changes in Amide-Linked and Ester Indole-3-Acetic Acid in Cotton Fruiting Forms during Their Development

The concentration of free indoleacetic acid (IAA) is high in cotton (Gossypium hirsutum L.) fruiting forms before anthesis, but is low at and for a few days after anthesis. Amide-linked and ester IAA were measured in fruiting forms at 9, 6, and 3 days before anthesis; at anthesis; and at 2, 4, 7, and 9 days after anthesis to determine if free IAA decreased because it was converted to a conjugated form. That did not appear to be the case. While the major decrease in free IAA occurred during the 6 days before anthesis, ester IAA increased only a small amount and amide-linked IAA decreased even more than free IAA. During the 6 days before anthesis free IAA decreased from 0.62 to 0.12 micrograms per gram and amide-linked IAA decreased from 19.14 to 1.16 micrograms per gram dry weight. No evidence was found that a large amount of amide-linked IAA was converted to an insoluble form; flowers contained less than 1 microgram per gram of insoluble IAA. The free and amide-linked IAA must have been converted to other forms, perhaps by oxidation. Soluble amide-linked IAA remained low after anthesis. No ester IAA was detected 6 days before anthesis and only 0.08 microgram per gram dry weight was measured at anthesis. The concentration of ester IAA increased thereafter to 4.43 micrograms per gram at 9 days after anthesis. Therefore, amide-linked IAA was the major form of IAA in flower buds and ester IAA was the major form in young fruits (bolls). Minimum concentrations of free and total IAA occurred during the 4 days after anthesis, a stage when cotton fruiting forms are most likely to abscise. The large decreases in free and amide-linked IAA during the 6 days before anthesis may indicate a rapid turnover of IAA in flower buds. But, the decrease in free IAA was not accompanied by a comparable increase in ester or amide-linked IAA.     

COORDINATED TIMETABLES FOR MEGAGAMETOPHYTE DEVELOPMENT AND POLLEN TUBE GROWTH IN RHODODENDRON NUTTALLII FROM ANTHESIS TO EARLY POSTFERTILIZATION

Rhododendron nuttallii T. W. Booth (Ericaceae) was used to derive concurrent timetables for megagametophyte, pollen tube and early postfertilization development from anthesis through 3 wk after pollination, based on timed collections of self-pollinated pistils. Stages of development were determined for over 33,500 cleared ovules, including, for selected collection dates, stages on different portions of the placenta. Pollen tube information was obtained by fluorescence microscopy of pistil squashes stained with aniline blue. Because of the very large number of ovules observed, it was possible to recognize a much more closely graded series of stages in megagametophyte development than is usually the case. While a range of stages occurred on all days, development progressed steadily from a majority of functional spores and 2-nucleate gametophytes on the day of anthesis to mostly a late zygote-primary endosperm stage at 18 days, and some 2-celled endosperm stages at 21 days, after pollination. At all times the most advanced stages, including first pollen tube entries, occurred on the outer surface of the lower half of the placenta, and the youngest on the inner surface of the uppermost portion. Fertilizable ovules were not found in any frequency until 8 days after pollination (then in only about 34% of the ovules); a few fertilized ones were seen after 10 days but constituted less than 5% until 12 days after pollination, thereafter increasing to about 60%. Fertilization occurred in any one of three morphologically recognizable stages distinguished by position and state of fusion of polar nuclei. Pollen germinated on the stigma 1–2 hr after pollination, and pollen tubes grew at a rate of about 1–1.25 cm/day, reaching the top of the ovary in 8–9 days with the first ovule entries seen after 10 days. There was a close correlation between megagametophyte development and pollen tube growth, with large numbers of functionally mature ovules not being found until pollen tubes had reached the ovary. While nuclei within ovules could not be distinguished in the squashes, three gametophyte stages that could be recognized—unelongated, elongated either without or with a pollen tube—were tallied for almost 29,000 ovules. The progression in these general stages corresponded well with that documented in more detail from cleared ovules. Unpollinated pistils showed a similar progression of gametophyte stages until the time fertilization would start to occur, after which there was continued accumulation of functionally mature ovules. A variety of abnormally developed and/or collapsing(ed) ovules or gametophytes were seen; collectively, they averaged over 8.6% of all ovules.     

Free amino Acid content and metabolic activities of setting and aborting soybean ovaries

Fruits of soybean (Glycine max [L.] Merr.) that are destined to abscise shortly after anthesis grow more slowly than fruits that will be retained. In this work, amino acid composition, protein metabolism, and nucleic acid metabolism were studied in setting and abscising soybean ovaries from anthesis to 6 days after anthesis to provide additional evidence of chemical processes associated with abscission. Principal free amino acids were asparagine, aspartic acid, glutamic acid, serine, and glutamine. Percent aspartate and glutamate declined as the ovaries grew, with aspartate declining more in abscising and glutamate more in setting ovaries. Percent glutamate was positively correlated to percent abscission throughout the period. Proline, serine, and leucine were positively correlated to abscission from 0 to 2 days after anthesis, whereas significant negative correlations were observed at these ages for ethanolamine and arginine. ⁷⁵Se fed as selenate and ¹⁴C fed as sucrose, glycine, and alanine were readily incorporated into soluble and insoluble proteins in a 24-hour in vitro incubation. Radioactivity of total proteins, expressed on a perovary basis, was negatively correlated with percent abscission and positively correlated with ovary weight. [¹⁴C]Glutamine and serine followed the opposite pattern, with greater protein labeling in abscising than in setting ovaries. When data were expressed as disintegrations per minute per milligram ovary fresh weight, protein labeling from alanine was seen to be significantly greater in abscising ovaries at anthesis and throughout the sampling period. Nucleic acid labeling from uridine was highly correlated to ovary weight; labeling from thymidine was greater in setting than abscising ovaries at anthesis and in abscising ovaries at later stages of development. It is concluded that abscising ovaries can continue amino acid metabolism almost up to the date of separation from the raceme, and that the involvement of alanine, glutamine, aspartate, glutamate, and other amino acids in soybean flower abortion deserves further study.     

Developmental Changes in the Amylose Content of Endosperm Starch of Barley (Hordeum vulgare L.) during the Grain Filling Period after Anthesis

Large and small starch granules were isolated and characterized from kernels of non-waxy (Bozu) and waxy (Yatomi mochi) barleys at their developmental stages of 8, 16, 28 and 40 days after flowering. The amylose content of the large and small granules of the non-waxy barley starch, as determined by the blue value and enzyme-chromatography, increased with the increasing age of the endosperm. Large granules of the non-waxy barley at any given developmental stage contained more amylose than small granules at the same stage, as in the case of mature non-waxy barley starches. Large granules of either the non-waxy or waxy barleys at any given developmental stage had a lower fraction III: fraction II ratio, one of the structural characteristics of amylopectin, than did small granules of the same cultivar at the same developmental stage. The amylose content in large granules of the waxy barley appeared to increase with the increasing age of the endosperm. The amylose content in small granules of the waxy barley at 8 days after flowering was 10%, although that at 16 and 28 days after flowering and at maturity was only 0~1%.     

OSMOPHORES OF STANHOPEA (ORCHIDACEAE)

Species of the Neotropical orchid genus Stanhopea produce a fragrance comprising terpenoids and aromatics which attracts euglossine bee pollinators. The secretory tissue, called an osmophore, is located in the adaxial region of a sac formed near the proximal portion of the floral lip. This region is easily recognized in Stanhopea oculata and S. wardii because it is papillate. The osmophore in these two species includes all the cells of the papillae and those directly below, that grade into fundamental tissue. Osmophore cells are more densely cytoplasmic than cells in the adjacent tissue. Numerous amyloplasts and mitochondria are seen in these cells from the earliest bud stages we examined through anthesis. Smooth and rough endoplasmic reticulum are abundant, but dictyosomes are uncommon. Mitochondria of osmophore cells appear to be distributed with no apparent pattern during bud stages, although they tend to be aligned near the plasmalemma at anthesis. Osmophore cells are highly vacuolate after anthesis.     

Metabolic pathways of the wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis>) endosperm amyloplast revealed by proteomics

Background  

By definition, amyloplasts are plastids specialized for starch production. However, a proteomic study of amyloplasts isolated from wheat (Triticum aestivum Butte 86) endosperm at 10 days after anthesis (DPA) detected enzymes from many other metabolic and biosynthetic pathways. To better understand the role of amyloplasts in food production, the data from that study were evaluated in detail and an amyloplast metabolic map was outlined.     

Phosphofructokinase from immature wheat grains

Levels of phosphofructokinase and metabolites known to affect its activity were monitored at different stages of wheat grain development. Phosphofructokinase activity peaked at 28 days after anthesis, declining thereafter. The amount of citrate increased up to 14 days after anthesis. PEP, ATP, ADP and AMP showed peak values at 28 days after anthesis. Phosphofructokinase from 28-day-old grains was purified × 23 with 49% recovery by ammonium sulphate fractionation and chromatography on DEAE-Sephadex A-50. A normal hyperbolic curve was observed with F-6-P. ATP inhibited the enzyme above 0.75 mM. ADP, citrate and 2-P-glycolate inhibited the enzyme noncooperatively; K_i values being 2.2, 1.6 and 5.0 mM, respectively. PEP and AMP failed to inhibit the enzyme activity     

Effects of Resistance in White Clover (Trifolium repens) on Heterodera trifolii

Clones of two partially resistant and two susceptible white clover, Trifolium repens, genotypes were exposed to eggs of Heterodera trifolii and nematode development in stained roots measured at 2, 4, 7, 11, 18, 23, and 37 days after inoculation. The differences in development between nematode populations in resistant and susceptible genotypes showed that resistance operated after infection during feeding and development. At 7 days after inoculation, counts of second-stage juveniles did not differ between genotypes, whereas at 37 days more adults had developed in the susceptible than in the resistant genotypes. In a separate experiment, cysts hosted by susceptible genotypes were larger and contained more eggs than those on resistant genotypes so that the product of the values for cysts per plant and for eggs per cyst resulted in a more sensitive measure of resistance than from using cysts per plant alone.     

小麦灌水时期与灌水量对花后果聚糖积累与转运及水分利用效率的影响

于2004-2005年和2005-2006年冬小麦生长季,在山东泰安和兖州进行田间试验,研究不同灌水时期和灌水量处理对冬小麦开花后倒二节间果聚糖积累与转运和水分利用效率的影响.结果表明：全生育期不灌水促进了灌浆后期倒二节间贮藏果聚糖向籽粒的转运.在拔节期和开花期各灌水60 mm,可提高开花后旗叶的光合速率和同化物输入籽粒量及其对籽粒的贡献率,拔节期、开花期和灌浆期各灌水60 mm或拔节期和开花期各灌水90 mm,灌浆后期旗叶的光合速率显著降低,营养器官花前贮藏同化物转运量及其对籽粒的贡献率升高,花后同化物输入籽粒量及其对籽粒的贡献率降低,灌浆后期倒二节间的聚合度（DP）≥4、DP=3果聚糖滞留量增加,不利于果聚糖向籽粒的转运.两个生长季中,拔节期和开花期各灌水60mm处理的小麦籽粒产量较高,水分利用效率最高.拔节期、开花期和灌浆期各灌水60 mm或拔节期和开花期各灌水90 mm,小麦籽粒产量无显著变化,水分利用效率降低.     

The Rest Period of Rhododendron Flower Buds: III. CYTOLOGICAL STUDIES ON THE ACCUMULATION AND BREAKDOWN OF PROTEIN BODIES AND AMYLOPLASTS DURING FLOWER DEVELOPMENT

Rhododendron flower development occurs in three easily definedstages: a pre-rest stage, during which petal growth is mainlyby cell elongation; an indeterminate rest period; and an after-reststage, that begins when the flowers resume growth and ends atanthesis. Early in the pre-rest stage of development, protein bodies andamyloplasts accumulate in the petals. The epidermal cells accumulateonly protein bodies and the mesophyll cells accumulate amyloplaststhat have a few small protein bodies around the periphery. Thesubepidermal cells and the cells around the vascular bundlesaccumulate both large protein bodies and amyloplasts. Duringthe rest period there is a cessation of cell elongation andthe reserve protein bodies and amyloplasts remain intact. The protein bodies in all of the cells including those aroundthe amyloplasts are proteolized early in the after-rest stageof development. Digestion of the starch granules occurs whenthe petals are about one-half their final size. Epidermal-cell expansion during after-rest is relatively uniform;the walls between adjacent epidermal cells remain attached toeach other. The mesophyll cells elongate irregularly and thewalls of adjacent cells separate giving rise to large intercellularspaces. At anthesis the petal cells consist of a cell wall, a parietalcytoplasm, and a large central vacuole.     

Effects of waterlogging on amyloplasts and programmed cell death in endosperm cells of Triticum aestivum L.

The effects of waterlogging on amyloplasts and programmed cell death (PCD) in endosperm cells in Chinese wheat (Triticum aestivum L.; cv: Hua mai 8) are here discussed. Four water treatments were established from anthesis to maturity: they were 3 days of waterlogging treatment (DWT), 7 DWT, 12 DWT, and moderate water supply (the control). Lugol staining and scanning electron microscopy showed decreases in the number of amyloplasts and partially filled circular cavities under the waterlogging treatments. These resulted in serious deformities in the endosperm cells. Evans blue staining analysis and terminal deoxynucleotidyl transferase-mediated fluorescein deoxyuridine triphosphate nick-end labeling assays indicated that the PCD progression of endosperm cells occurred earlier under waterlogging treatments than in the control, so did the internucleosomal DNA fragmentation, which accompanies PCD in endosperm cells. Electron transmission microscopy analysis showed similar results. Under waterlogging treatments, the following PCD characteristics appeared earlier and were more pronounced than in normal endosperm cells: chromatin condensation, degradation of the nuclear envelope, swelling, and degradation of the mitochondrial cristae. Our study concluded that under waterlogging conditions, the number of amyloplasts tended to decrease and PCD was likely to appear ahead of time.     

The pattern of amyloplast DNA accumulation during wheat endosperm development

The accumulation of amyloplast DNA during endosperm development was studied in two cultivars of spring wheat, Triticum aestivum L. Chinese Spring (CS) and Spica, small and relatively larger-grained cultivars, respectively. Endosperms were isolated between 9 and 45 days post anthesis (dpa) and the amyloplast DNA content of endosperm nucleic-acid extracts was measured by quantitative hybridisation with a homologous chloroplast-DNA probe. The endosperm cells of CS and Spica accumulated amyloplast DNA during development in a similar way. In both cultivars there was a large increase in the amount of plastid DNA (ptDNA) per endosperm between 9 and about 15 dpa, after which there was no further increase. Because nuclear DNA continued to accumulate until 24 dpa, the percentage contribution of amyloplast DNA to total DNA fluctuated in both cultivars during development, reaching maxima at 12 dpa of about 1.00% and 0.85%, and dropping to apparently constant levels of 0.60% and 0.52% in CS and Spica, respectively, by 24 dpa. In both cultivars, the average number of ptDNA copies per amyloplast was calculated to increase from about 10 copies at 9 dpa to about 50 copies in the mature amyloplasts at 31 dpa. However, the heavier endosperms of Spica contain more cells than those of CS and the varieties therefore differed in the amount of ptDNA that accumulated per endosperm: Spica endosperms accumulated 110 ng of ptDNA by 15 dpa, compared with only 85 ng in CS. The apparent accumulation of ptDNA copies in wheat amyloplasts during endosperm development contrasts with the decline in chloroplast-DNA copies in wheat chloroplasts during leaf development.Abbreviations CS Chinese Spring - ctDNA chloroplast DNA - dpa days post anthesis - kbp 10³ base pairs - nDNA nuclear DNA - ptDNA plastid DNA - mtDNA mitochondrial DNA     

Plastid differentiation during Cucurbita pepo (Cucurbitaceae) pollen grain development

The development of plastids in the pollen of Cucurbita pepo was followed from meiosis to pollen maturation by quantitative light and electron microscopy. Plastids are initially undifferentiated, then divide, and at late microspore stage differentiate into amyloplasts containing starch. Later the amyloplasts form lobes and divide. Amyloplasts containing a single starch grain are present from the early bicellular stage. Plastid development is considered in relation to such cytoembryological features as the pollen does not dehydrate at anthesis and germination begins 3 min after pollination.     

Development of seed coat-imposed dormancy during seed maturation in Cynoglossum officinale

The relationship between seed phenolics and appearance of seed coat–imposed dormancy during seed development in Cynoglossum officinale L. was studied. Up to 24 days after anthesis, seeds failed to germinate upon imbibition in Petri dishes at 25°C. At 44 days after anthesis, seeds were fully germinable; removal of seed coats did not improve their germination or O₂ uptake. At 72 days after anthesis, mature seeds at the base of the cyme did not germinate unless their coats were removed. Removal of seed coat also stimulated O₂ uptake at this harvest date. The methanol-soluble phenolic content of the seeds increased during the early stages of seed development, in both the seed coat and the embryo. As seed development continued, the methanol-soluble phenolic content of the embryo stabilized, but that of the seed coat declined. This decline was associated with an increase in the thioglycolic acid–soluble phenolics, presumably lignins, in the seed coat. These results suggest that polymerization of methanol–soluble phenolics into lignins in the seed coat during later stages of seed development renders the seed coat of C. officinale impermeable to 03, and thus keeps the seed dormant.     

几种水稻植株中血凝活性物质的分布与变化及其稻胚凝集素的比较

开花前的水稻旗叶提取液中不含有血凝活力,但开花后旗叶提取液中能测得血凝活力,并随着开花后天数增加而逐渐升高。雄蕊和成熟花药中无血凝活力,开花前和开花早期的子房提取液中有血凝活性,开花5d后子房或胚乳中测不到血凝活性,但胚中血凝活性随种子发育而明显增加。分别从“寒丰”和“双丰一号”水稻成熟胚中分离得到凝集素,用电泳、免疫学方法和血凝试验表明两者的分子特性和血凝性质完全相同。     

Effect of Water Stress on Expression of a 20 kD Cyclophilin-like Protein in Drought Susceptible and Tolerant Cultivars of Sorghum

Immunodetection studies revealed the presence of a 20 kD cyclophilin-like protein (designated as SorgCyp20) in leaves and seeds of sorghum (Sorghum bicolor L Moench). The expression of SorgCyp20 was temporally regulated in the leaves and after attaining maximum levels at either 60 or 70 days after sowing it declined after flowering. The effect of drought stress on SorgCyp20 levels in the leaves and seeds of sorghum was stage and cultivar dependent. The drought stress-induced enhancement in SorgCyp20 levels was many times higher in the leaves (3-fold increase at 30 days after sowing) and seeds (2.5-fold increase at 9 days post anthesis) of drought tolerant cv ICSV-272 than in the drought susceptible cv SPRU-94008B. The intercultivar differences in drought stress-induced changes in SorgCyp20 expression were not related to the difference in water potential thus suggesting differential regulation of SorgCyp20 in response to stress in the two sorghum cultivars.