Recently, new materials have been introduced that minimize the loss of crosslink density and properties caused by overcure and/or high temperature applications. One of these new anti-reversion agents, 1,3-bis(citraconimidomethyl)benzene, compensates for the loss in crosslink density through the formation of new crosslinks. This paper evaluates various multifunctional acrylates to determine if they will function like 1.3-bis(citraconimidomethyl)benzene and reduce reversion through the formation of new crosslinks. The experimental data suggests that some of these acrylates form new crosslinks during overcure conditions and therefore are very effective at maintaining the modulus and tan delta values upon overcure.

Journal Article Plant Patterns and Culture Get access Pattern Formation in Plant Tissues. Sachs Tsvi. Cambridge University Press, Cambridge, 1991. 235 pp., illus. $75.00 (ISBN 0-521-248655 cloth). Plant Cell and Tissue Culture. Stafford Angela Warren Graham, eds. Open University Press, Buckingham, UK, 1991. 251 pp., illus. $90.00 (ISBN 0-335-15823-4 cloth), $45.00 (ISBN 0-335-15162-0 paper). J. E. Varner J. E. Varner Biology Department, Washington University, St. Louis, MO 63130 Search for other works by this author on: Oxford Academic Google Scholar BioScience, Volume 42, Issue 4, April 1992, Pages 305–306, https://doi.org/10.2307/1311685 Published: 01 April 1992

Good Tips on Tips Tip Growth in Plant and Fungal Cells. Health I. B., ed. Academic Press, New York, 1990. pp., illus. $85.00 (ISBN 0-12-335845-0 cloth). J. E. Varner J. E. Varner 1Department of Biology, Washington University, St. Louis, MO 63130 Search for other works by this author on: Oxford Academic Google Scholar BioScience, Volume 41, Issue 7, 1 August 1991, Page 514, https://doi.org/10.2307/1311813 Published: 01 August 1991

Journal Article Abscisic Acid Get access Abscisic Acid. Addicott Frederic T., ed. Praeger Publishers, New York, 1983. 586 pp., illus. $49.95. J. E. Varner J. E. Varner Department of Biology, Washington University, St. Louis, MO 63130 Search for other works by this author on: Oxford Academic Google Scholar BioScience, Volume 34, Issue 9, October 1984, Page 590, https://doi.org/10.2307/1309610 Published: 01 October 1984

Cordycepin, an inhibitor of RNA synthesis in barley (Hordeum vulgare L.) aleurone cells, does not inhibit the gibberellic acid-enhanced alpha-amylase (EC 3.2.1.1.) synthesis in barley aleurone layers if it is added 12 hours or more after the addition of the hormone. However, the accumulation of alpha-amylase activity after 12 hours of gibberellic acid can be decreased by abscisic acid. The accumulation of alpha-amylase activity is sustained or quickly restored when cordycepin is added simultaneously or some time after abscisic acid, indicating that the response of aleurone layers to abscisic acid depends on the continuous synthesis of a short lived RNA. By analysis of the newly synthesized proteins by gel electrophoresis with sodium dodecylsulfate, we observed that the synthesis of alpha-amylase is decreased in the presence of abscisic acid while the synthesis of most of the other proteins remains unchanged. From the rate of resumption of alpha-amylase production in the presence of cordycepin and abscisic acid, it appears that abscisic acid does not have a measurable effect on the stability of alpha-amylase mRNA.

Protease activity increased inattached cotyledons ofgermi- natedpeas(Pisum sativum L.cv.Alaska) asthestored proteins declined butdidnotincrease inexcised cotyledons incubated forthesamelength oftime.Cotyledons ofseeds germinated in thepresence ofa caseinhydrolysate solution developed less protease activity thandidthosegerminated on water. These results suggest thataccumulation ofaminoacids regulates the protease level inthecotyledons ofgerminating peas. Incontrast toprotease, a-and8-amylase increased during incubation ofexcised peacotyledons. Theirincrease wasin- hibited byabscisic acid. Abscisic aciddidnotinhibit "4C-leucine incorporation intoprotein orreducetherespiratory rateinthe cotyledons; hence, itseffect onamylase formation wasnotthe result ofageneral inhibition ofmetabolism. An ether-soluble acidfraction, whichwouldcontain anyabscisic acidpresent in thematerial, inhibited amylaseformation morewhenitwas obtained fromimbibedseedsthanwhenitwasobtained from cotyledons ofseedsgerminated for10days.Theseandother results suggest thatamylase formation ingerminating peasis regulated byabscisic acid.

In addition to releasing hydrolytic enzymes, isolated barley aleurone layers release large amounts of reserve protein. This protein release is only partially dependent on gibberellic acid (GA3). The addition of GA3 causes a shift in molecular weight distribution to lower molecular weight, and a change in the N-terminal profile of the released protein. Inhibition of proteolysis reduces protein release. When proteolysis is inhibited, amylase production can be made partially dependent on added amino acids.

The addition of gibberellic acid to isolated aleurone layers of barley (Hordeum vulgare L.) causes the production and secretion of four alpha-amylases. Two of these are stable at pH 3.7 and are not inactivated by ethylenediaminetetraacetate. The other two represent the classical barley alpha-amylases; i.e., they are inactivated at pH 3.7 and by reagents which from complexes with divalent metal ions. All four forms are synthesized de novo in response to the addition of gibberellic acid.

Density labeling with deuterium oxide, gel electrophoresis, and isopycnic equilibrium sedimentation were used to study the appearance and disappearance of individual peroxidases in the embryos of germinating barley. No detectable label was incorporated into those peroxidases which are present in the embryo of the dry seed and disappear during germination. Deuterium was incorporated into the additional peroxidases which appeared in the embryo during germination. This incorporation is not due to deuterium-hydrogen exchange into preformed proteins. The results indicate that the newly appearing peroxidases arise by synthesis during germination.

Starch, total alpha- and beta-amylase, and phosphorylase levels and the zymogram patterns of these 3 starch-degrading enzymes were determined in the cotyledons of smooth pea (Pisum sativum L.) during the first 15 days of germination. Starch is degraded slowly in the first 6 days; during this time, alpha-amylase is very low, beta-amylase is present at a constant level while phosphorylase gradually increases and reaches a peak on the fifth day. Beginning on the sixth day there is a more rapid degradation of starch which coincides with alpha-amylase production. One phosphorylase band and 2 beta-amylase bands are present in the zymogram of the imbibed cotyledon. An additional phosphorylase band and 1 alpha-amylase band appear during germination. Seeds imbibed in benzyladenine, chloramphenicol, and in cycloheximide show retarded growth and slower starch degradation and enzyme production than the controls. We conclude that alpha-amylase is the major enzyme involved in the initial degradation of starch into more soluble forms while phosphorylase and beta-amylase assist in the further conversion to free sugars.