On the relative role of the scutellum and aleurone in the production of hydrolases during germination of barley

Abstract

The relative roles of the scutellum and the aleurone layer in the production and mediation of both germination-specific a-amylase and cell wall breakdown hydrolases has been examined in vivo following treatment of barley seeds with the plant hormones gibberellic acid and abscisic acid. To facilitate entry of these exogenous hormones, a technique is presented where multiple incisions b~nicks~0 are made in the outer layers of the seed prior to germination. Treatment of seeds with gibberellic acid and abscisic acid effected major changes on the pattern of hydrolase transport. The nature of the changes were such that it is concluded that the scutellum alone is capable of producing and mediating up to 50To of germination specific hydrolases in a commercial European malting barley, germinating at the conventional European malting temperature of 15 ~

The effects of oxygen, nitrogen, and carbon dioxide steeping regimes on endosperm modification and embryo growth of germinating barley seeds

“…Water uptake in seeds of Tokak barley steeped for 1 day at 15 *C under the conditions described in Figure 1. ments resulted in a similar pattern of modification for Nordal as seen with unsteeped seeds of this variety in earlier experiments (8,9), and the O2-treatment showed a slightly lower rate of initial modification.…”

“…balance between oxygen and carbon dioxide tensions in the microenvironment of the grain, temperature, final moisture content) play an important role in the quality of the final malt after germination (4,5,6,7,15,16,18,19,20). The development of fluorescence staining techniques specially designed to measure the extent of endosperm modification in individual germinating seeds and populations of these (3,8,9,10,11,17), prompted therefore a study of changes occurring both inside germinating seeds 0105-1938/83/0048/0035/$ 04.40 G. C. GIBBONS: O2/NE/COflAir and Steeping and in their embryos as a result of different treatments during steeping. The present communication describes the effects of oxygen, nitrogen, carbon dioxide, and air during steeping on endosperm modification, water uptake, and embryo growth as measured by root and shoot development.…”

Development of (1→3,1→4)-β-d-Glucan Endohydrolase Isoenzymes in Isolated Scutella and Aleurone Layers of Barley (Hordeum vulgare)

“…Similarly, aamylase is now known to be secreted from both tissues (6,8,13,16) although, in contrast to the (1--3,1-+4).q3-glucanases, no major differences in a-amylase isoenzyme patterns are apparent (8). The preferential disappearance of (1-+3,1-4)-f3-glucanase isoenzymes II and III from aleurone and scutellar secretions when Ca2" is withdrawn from the medium may be compared with the disappearance of a-amylase group B isoenzymes following Ca2+ withdrawal from isolated aleurone layers (7).…”

“…Cells of the scutellar epithelial layer also appear to secrete hydrolytic enzymes which participate in the degradation of barley endosperm (4,6,8,13,16), although this has been disputed on the basis that the aleurone cells which adhere tightly to the periphery of the scutellum complicate interpretation of experimental data (2,14). Two (1--3, 1 -4)-f3-glucan 4-glucanohydrolases (EC 3.2.1.73), which specifically depolymerize (1--3,1-4)-#-glucans of endosperm cell walls, have been purified from germinating barley and characterized (20,21).…”

Changes in Levels of α-Amylase Components in Barley Tissues during Germination and Early Seedling Growth

“…A larger proportion of scutellar a-amylase was excreted into the endosperm compared to aleurone synthesized a-amylase. Aleurone cells appeared to synthesize appreciably more a-amylase than did scutellar tissue.There has been much discussion recently on the relative importance of aleurone and scutellar tissues in the production of hydrolytic enzymes during germination and early seedling growth of cereal grains (3,4,11,23,24). a-Amylase synthesis in barley has received particular attention because ofthe technological importance of this enzyme in malting and brewing and also because synthesis of the enzyme in aleurone cells from barley kernels has been used as a model system to study hormonal action on protein synthesis (7,13).…”