Indole-3-acetic acid content and glutamine synthetase activity in the pericarp, and peroxidase activity and isoenzymes in the meso- and exocarp of growing peach fruits

The indole-3-acetic acid (IAA) content in peach pericarp (Prunus persica L. Batsch cv. Merry) was highest at early stage I of development (200 ng/g fresh wt), decreased to the lowest level during stage II, and rose again at stage III to 60–70 ng/g fresh wt. High activity of glutamine synthetase was found in the pericarp during stage I. The soluble peroxidase activity was highest in the meso- and exocarp at stage II, and isoenzymatic changes in this fraction corresponded to the transition from cationic isoenzymes, predominant at stage I, to anionic isoenzymes at stage III. The ionically bound peroxidase activity in these tissues was highest at stage I. The three developmental stages showed marked differences in auxin content and enzyme activities; for peroxidases these changes reflect a developmental expression pattern for the isoenzymes.     

A HISTOCHEMICAL STUDY OF ABSCISSION LAYER FORMATION IN THE BEAN

In debladed bean petioles calcium and dry weight increased in the abscission zone during an induction period of 14 hr. Before the microscopic appearance of the abscission layer calcium decreased in the abscission zone and increased in the petiole. Dry matter began to decrease in both the abscission zone and the petiole 24 hr after deblading. The first visual change in the cells of the abscission zone was a swelling of the pectic materials of the cell walls. This was followed by breakdown of other cell wall components, i.e., non-cellulosic polysaccharides and cellulose. The cellulose of the cell walls adjacent and distal to the abscission layer was found to be altered; however, no lignin was present during abscission layer development. The alteration of pectic materials, coupled with breakdown of cell wall components, resulted in the collapse of cells of the abscission layer just prior to separation. Auxin delayed abscission and also delayed the initial increase in calcium, the movement of calcium from the abscission zone to the petiole, and the decrease in dry weight.     

Histochemical changes in the developing abscission layer in fruits of Prunus cerasus L.

Summary Abscission layer formation in the sour cherry (Prunus cerasus L.) during fruit maturation occurred in the transition zone between the fruit and the pedicel. The abscission layer, consisting of 5–8 rows of cells, was first identified by its low affinity for haematoxylin. The walls of cells in the abscission layer contained less total polysaccharides than adjacent cells. The pectins were degraded and the cellulose was partially broken down resulting in cell separation. The Ca level in the abscission zone decreased and Ca and Mg were lost from the walls of cells in the layer during abscission. After the abscission layer formed, cells associated with the layer had a lower capacity to bind ⁴⁵Ca than cells distal or proximal to the layer.Michigan Agricultural Experiment Station Journal Article No. 4607     

Purification of an anionic isoperoxidase from peach seeds and its immunological comparison with other anionic isoperoxidases

A soluble anionic isoperoxidase (EC 1,11,1,7) was purified from peach ( Prunus persica L. Batsch cv. Merry) seeds. Purification was achieved by DEAE-Sephacel, Sephacryl S-300 and CM-cellulose chromatography. The purified isoperoxidase de-carboxylated indole-3-acetic acid (S_0.5 0.13 m M , Hill coefficient 1.7). Molecular mass, determined by gel filtration and sodium dodecyl sulfate polyacrylamide gel electrophoresis, was ca 60 kDa. Polyclonal antibodies were raised in rabbit against this isoperoxidase. Using immunoprecipitation this isoenzyme was found to be immunologically different from other soluble anionic isoperoxidases isolated from peach seeds.     

Endogenous Plant Growth Substances in Developing Fruit of Prunus cerasus L: VII. Isolation of Gibberellin A(32)

A polar gibberellin active in the dwarf rice (Oryza sativa L.) seedling and barley (Hordeum vulgare L.) half-seed assays was extracted from immature sour cherry (Prunus cerasus L.) seed and identified as gibberellin A₃₂ by gas-liquid chromatography and selected ion monitoring.     

A single site in human beta-hexosaminidase A binds both 6-sulfate-groups on hexosamines and the sialic acid moiety of GM2 ganglioside

Human beta-hexosaminidase A (Hex A) (alphabeta) is composed of two subunits whose primary structures are approximately 60% identical. Deficiency of either subunit results in severe neurological disease due to the storage of GM2 ganglioside; Tay-Sachs disease, alpha deficiency, and Sandhoff disease, beta deficiency. Whereas both subunits contain active sites only the alpha-site can efficiently bind negatively charged 6-sulfated hexosamine substrates and GM2 ganglioside. We have recently identified the alphaArg(424) as playing a critical role in the binding of 6-sulfate-containing substrates, and betaAsp(452) as actively inhibiting their binding. To determine if these same residues affect the binding of the sialic acid moiety of GM2 ganglioside, an alphaArg(424)Gln form of Hex A was expressed and its kinetics analyzed using the GM2 activator protein:[3H]-GM2 ganglioside complex as a substrate. The mutant showed a approximately 3-fold increase in its K(m) for the complex. Next a form of Hex B (betabeta) containing a double mutation, betaAspLeu(453)AsnArg (duplicating the alpha-aligning sequences), was expressed. As compared to the wild type (WT), the mutant exhibited a >30-fold increase in its ability to hydrolyze a 6-sulfated substrate and was now able to hydrolyze GM2 ganglioside when the GM2 activator protein was replaced by sodium taurocholate. Thus, this alpha-site is critical for binding both types of negatively charge substrates.     

Absorption and distribution of sodium,phosphorus, chlorine,calcium and zinc in some selected woody ornamentals

Byla sledována absorpce listy a následající rozmístění sodíku, fosforu, chloru, vápníku, zinku u jednoletých zako?eněných ?ízk?Forsythia intermedia ZABEL, A, ko?enová absorpce fosforu uTaxus cuspidata SIEB. and Zucc. Podíl ?ivin, který byl p?emístěn z list?, na ně? byl aplikován, byl pou?it jako kritérium jejich pohyblivosti. Z toho hlediska bylo zji?těno, ?e sodík a chlor jsou velmi pohyblivé, vápník nepohyblivý a zinek mírně pohyblivý. Méně ne? 1 procento fosforu, který byl uTaxus cuspidata aplikován jak na rostliny aktivně rostoueí, tak na rostliny v ?áste?ně kldovém stadiu, se objevilo v ko?enech po dvanácti dnech od aplikace. ?est procent z celkového fosforu, zji?těného po 12 dnech v nadzemní ?ásti, pocházelo z jediné dávky ve vodě rozpu?těného fosfore?ného hnojiva p?idané ho do p?dy, a?koliv bylo z něho absorbováno méně ne? 0,5 % fosforu.     

Studies on water transport through the sweet cherry fruit surface: II. Conductance of the cuticle in relation to fruit development

Water conductance of the cuticular membrane (CM) of sweet cherry (Prunus avium L. cv. Sam) fruit during stages II and III (31-78 days after full bloom, DAFB) was investigated by gravimetrically monitoring water loss through segments of the exocarp. Segments were mounted in stainless-steel diffusion cells, filled with 0.5 ml of deionized water and incubated for 8 h at 25 +/- 2 degrees C over dry silica. Conductance was calculated by dividing the amount of water transpired per unit surface area and time by the difference in water vapor concentration across the segment (23.07 g m(-3) at 25 degrees C). Fruit mass and fruit surface area increased 4.9- and 2.8-fold between 31 and 78 DAFB, respectively. However, CM mass per unit area decreased from 3.9 to 1.5 g m(-2) and percentage of total wax content remained constant at about 31%. Stomatal density decreased from 0.8 to 0.2 mm(-2) (31-78 DAFB). Total conductance of the CM on the fruit cheek (gtot.) remained constant during stage II of development (approx. 1.38 x 10(-4) m s(-1) from 31 to 37 DAFB), increased to 1.73 x 10(-4) m s(-1) during early stage III of fruit growth (43-64 DAFB) then decreased to 0.95 x 10(-4) m s(-1) at maturity (78 DAFB). Partitioning gtot. into cuticular (gcut.) and stomatal conductance (gsto.) revealed that the relative contribution of gcut. to gtot. increased linearly from 30% to 87% of gtot. between 31 and 78 DAFB. respectively. On a whole-fruit basis, g,tot. and gcut. consistently increased up to 64 DAFB, and decreased thereafter. A significant negative linear relationship was obtained between gcut. and CM thickness, but not between the permeability coefficient (p) and CM thickness. Further, p was positively related to strain rate, suggesting that strain associated with expansion of the fruit surface increased p.     

BINDING SITES FOR INORGANIC IONS AND UREA ON ISOLATED CUTICULAR MEMBRANE SURFACES

Binding sites for calcium and chloride ions, and urea on cuticular membrane surfaces were identified by microautoradiography. There was no localization of binding on either the smooth outer or irregular inner surfaces of the astomatous tomato fruit cuticle, and urea was bound to a lesser degree than inorganic ions. Calcium and chloride binding sites on surfaces of green onion leaf cuticles were closely associated with stomatal pores and above the periclinal cell walls. Binding of calcium was more pronounced than of chloride. These results are discussed in light of possible sites of entry for foliar applied nutrients.     

Mechanism of Indole-3-acetic Acid Conjugation: No Induction by Ethylene

Formation of indole-3-acetic acid-aspartate in detached primary leaves of cowpea (Vigna sinensis Endl.) floating on (14)C-indole-3-acetic acid (3 muc; 3.15 mum, phosphate-citrate buffer, pH 4.75), almost doubled when leaves were pretreated with 31.5 mum(12)C-indole-3-acetic acid for 17 hr and then transferred to (14)C-indole-3-acetic acid for 4 hours as compared with leaves preincubated in buffer only. When leaves were preincubated with ethylene (11.0 and 104 mul/l) instead of (12)C-indole-3-acetic acid, no induction of indole-3-acetylaspartic acid formation was observed, and the rate of indole-3-acetylaspartic acid formation decreased as compared with control leaves. Rhizobitoxine (1.87 mum) inhibited indole-3-acetic acid-induced ethylene production but did not prevent the formation of indole-3-acetylaspartic acid. In view of the similarity of these results and those previously obtained with alpha-naphthaleneacetic acid, it is concluded that ethylene has no role in the auxin-induced indole-3-acetylaspartic acid formation in cowpea leaves.