Callose deposition during gravitropism ofZea mays andPisum sativum and its inhibition by 2-deoxy-D-glucose

In etiolated corn (Zea mays L.) and etiolated pea (Pisum sativum L.) seedlings, a gravitropic stimulation induces the deposition of callose. In the corn coleoptiles this occurs within 5 min of gravity stimulation, and prior to the beginning of curvature. Both gravitropic curvature and callose deposition reach their maxima by 12 h. Within the first 2 h more callose is deposited on the upper (concave) side, but after 2–3 h, this deposition pattern is reversed. An inhibitor of protein glycosylation, 2-deoxy-d-glucose (DDG), inhibits callose production and considerably retards gravitropic bending in both species of plants. Mannose can relieve the inhibition of gravitropic bending by DDG. The pea mutant Ageotropum, which does not respond to gravity when etiolated, also fails to produce callose in response to a gravitic stimulus. These correlations indicate that callose deposition may be a biochemical component of gravitropism in plant shoots.Abbreviation DDG 2-deoxy-d-glucose     

Temperature effects on soybean imbibition and leakage

As a part of an analysis of the nature of chilling injury to seeds, measurements were made of the initial linear rates of water entry into and solute leakage out of cotyledons of soybean at various temperatures. Arrhenius plots were approximately linear for water entry into both living and dead cotyledons, with the slope (and activation energy) for entry into living cells being insignificantly higher than for dead cells, suggesting little effect of membrane barriers on water entry. The plots for solute leakage showed 10-fold lower leakage rates from living than from dead tissues; a reversal of slope in the Arrhenius plot at temperatures below 15 C reflected increasing leakage rates, interpreted as a quantitative disruption of membrane reorganization at the temperatures associated with chilling injury.     

On the mechanism of aging in soybean seeds

Changes in seeds of soybeans (Glycine max [L.] Merr. var. Wayne) which occur during accelerated aging (41 C, 100% relative humidity) showed subsequent loss of vigor, a decline in early respiratory activity, increased leakage of electrolytes, losses of as much as 10% dry weight from imbibing cotyledons, and a decrease in the swelling response of the imbibing system (seed plus H₂O). Each of these changes with aging is interpreted as resulting from deteriorative changes in membranes.     

Purification and partial characterization of the 17 kDa sperm coating protein from boar seminal plasma.

Sperm coating proteins of 16, 17, and 19 kDa have been purified from boar seminal plasma. The 17 kDa protein has been identified as an antigen recognized by monoclonal antibody ACR.3 and is thus identical to low molecular mass zona pellucida binding protein from boar spermatozoa (Moos et al., 1990). The 17 and 19 kDa proteins are glycosylated and tend to form hetero-complexes. The 17 kDa ACR.3 antigen is sequentially released from the sperm cell surface during capacitation and, after induction of the acrosome reaction, the 16 kDa form was also observed. Immunocytochemical studies on boar reproductive tissues have suggested that the seminal vesicle epithelium may be the source of these proteins.     

Hydrostatic pressure mimics gravitational pressure in characean cells

Summary Hydrostatic pressure applied to one end of a horizontalChara cell induces a polarity of cytoplasmic streaming, thus mimicking the effect of gravity. A positive hydrostatic pressure induces a more rapid streaming away from the applied pressure and a slower streaming toward the applied pressure. In contrast, a negative pressure induces a more rapid streaming toward and a slower streaming away from the applied pressure. Both the hydrostatic pressure-induced and gravity-induced polarity of cytoplasmic streaming respond identically to cell ligation, UV microbeam irradiation, external Ca²⁺ concentrations, osmotic pressure, neutral red, TEA Cl^–, and the Ca²⁺ channel blockers nifedipine and LaCl₃. In addition, hydrostatic pressure applied to the bottom of a vertically-oriented cell can abolish and even reverse the gravity-induced polarity of cytoplasmic streaming. These data indicate that both gravity and hydrostatic pressure act at the same point of the signal transduction chain leading to the induction of a polarity of cytoplasmic streaming and support the hypothesis that characean cells respond to gravity by sensing a gravity-induced pressure differential between the cell ends.     

An assessment of phase transitions in soybean membranes

Phase transitions were measured in vesicles of phospholipids, alone and in various combinations, and in pelleted mitochondrial membranes, using thermal (DSC) and optical methods. The objective was to consider their possible involvement in chilling injury of soybeans (Glycine max [L.] Merr. cv Wayne 1977). Saturated phospholipids showed clear transitions in the temperature range of 50°C to near 0°C. When mixtures of two phospholipids were examined, there was a marked lowering and broadening of the transition peaks, and a shift in the transition temperatures to intermediate temperatures. The unsaturated phospholipids that occur naturally in soybeans showed no detectable phase transitions in this temperature range, alone or in combinations. Examination of the polar lipids from soybean asolectin revealed no transitions in the biological temperature range; the additions of cations such as Ca²⁺ and La³⁺ did not evoke a detectable phase transition in them. Mitochondrial membrane pellets likewise showed no transitions. The application of these two direct methods of examination of membrane components without the addition of foreign agents did not support the suggested occurrence of a bulk phase transition which could be related to chilling injury in soybeans.     

Solute leakage resulting from leaf desiccation

The leakage of solutes from foliar tissue is utilized as a dynamic measure of apparent changes in membrane integrity in response to desiccation. It is found that rehydrating leaf discs of cowpea (Vigna sinensis [L.] Endl.) show increasing leakiness in proportion to the extent of prior desiccation, whereas Selaginella lepidophylla Spring., a resurrection plant, does not. The elevated leakage rate of cowpea after desiccation recovers with time, and the passage of time in the stressed condition results in reduced subsequent leakiness. These characteristics are interpreted as suggesting that the leakage of solute reflects the condition of cellular membranes, and that desiccation stress leads to lesions in the membranes. The kinetics of solute leakage is suggested as a simple means of following changes in membrane lesions and associated features of membrane repair and hardening.     

Effects of inorganic solutes on the binding of auxin

The binding of α-naphthaleneacetic acid (¹⁴C-NAA) to pelletable particulates from corn (Zea mays) coleoptiles was found to be influenced by inorganic solutes. La³⁺, Ca²⁺, and Mg²⁺ increased the binding whereas monovalent cations did not. The concentrations of CaCl₂ which increased auxin binding were similar to those which inhibited coleoptile elongation in the presence of auxin. These results are interpreted as suggesting that the alteration of hormonal effectiveness by some inorganic solutes involves alterations in the attachment of the hormone to binding sites in the cell.     

Effects of inorganic salts on tissue permeability

Inorganic solutes are shown to alter the permeability of root and leaf tissues. Experiments with beet root tissues reveal that CaCl(2) decreases leakage of betacyanin from the tissue, that (NH(4))(2)SO(4) increases leakage, and that each salt can relieve the effects of the other. A comparison of cations and anions shows a range of effects with the various solutes. Experiments with Rumex obtusifolius L. leaf discs reveal that whereas CaCl(2) defers the development of senescence, (NH(4))(2)SO(4) hastens senescence and increases the leakage of materials out of the leaf discs. The solute effect on Rumex obtusifolius L. is prevented by gibberellin. CaCl(2) can relieve the (NH(4))(2)SO(4) effect. The results are interpreted as indicating that the inorganic solutes may serve to alter the permeability of membranes through alterations of interactions between water and macromolecules in the tissues; the interpretation is consistent with the evidence for opposite effects of Ca and NH(4), the effective concentrations being about 10(-3)m, and the reversibility of the effects of one solute by another of opposite stabilization-destabilization effect.     

Genetics of house flies. Variability studies with North Dakota, Texas, and Florida populations.

Genetic data were used to compare the structure of native house fly populations collected in North Dakota, Texas, and Florida. Recombination studies with mutant markers on chromosomes 3 and 4 indicated a lack of inversion polymorphism among the three populations in those areas of the genetic map studied. Significant differences were observed among flies from the three regions with regard to the frequency of 1) females that produced only male progeny, and 2) male-determining 3rd chromosomes (IIIm chromosomes). However, the North Dakota and Texas flies were more similar to each other than to the Florida flies since populations from the two former areas possessed a low frequency of both male-producing females and IIIm chromosomes; in contrast, the Florida population was void of females that produced males only and a high percentage if not all Florida males appeared to possess the IIIm male-determining mechanism. Tests for recessive lethal 3rd chromosomes showed that there was no significant difference in the frequency of lethal factors recovered from the North Dakota and Texas flies; the presence of IIIm chromosomes in Florida males precluded the recovery of lethal factors from this population by the method employed. The data suggest that house fly strains to be employed in genetic control programs should 1) originate from target control areas to avoid possible behavioral differences existing among flies from different locales, 2) be initiated with as many flies as possible to provide a background for the maintenance of variability, and 3) be renewed periodically with field-collected material since the genotype may be capable of rapid reorganization in response to laboratory selection pressures.