How do enzymes speeds up seed germination?

How do enzymes speeds up seed germination?

I assume that the organic cellulase (wood attacking) type enzyme drain cleaners dissolve (attack) the seed coat and possibly the glue that holds the 2 parts of the shell together (the suture).

I say “possibly the glue” because I have not been able to find any studies that have determined the chemical composition of the glue (suture).

Bromelain is a different type of enzyme than the cellulase type. It attacks proteins (proteolytic enzyme). I assume that the reason that overexposure to Bromelain does not kill rose seeds while overexposure to a cellulase type does is because of this distinction. So how does a proteolytic enzyme increase the germination rate? One possibility is that the suture contains protein type bonds. A second possibility is that the Bromelain hydrolyzes something that is required to terminate dormancy. There is some evidence to support this second possibility from studies of other seeds:

Title: Changes in activity of proteolytic enzymes (BAPAases) in germinating buckwheat and rye seeds.

Authors: Dunaevskii la E; Belozerskii M A

Published in: BIOKHIMIIA, volumn 45, pages 908-911, (1980).

Abstract: “The interrelationship between the activity of proteolytic enzymes (BAPAases) from buckwheat and rye seeds hydrolyzing Nalpha-benzoyl-DL-arginine-p-nitroanilide (BAPA) and the amount of the antiserum to these enzymes necessary to obtain a certain inhibition level has been studied at different stages of seed germination. The data obtained show that the increase of the BAPAase activity in germinating rye seeds is due to de novo synthesis of this enzyme. During this process antigenically identical enzyme molecules are synthesized in roots and shoots of the developing plant.”

Title: Proteolytic enzymes in germinating rye grains.

Authors: Brijs, Kristof; Trogh, Isabel; Jones, Beme L.; Delcour, Jan A.

Authors affiliation: Laboratory of Food Chemistry, Katholieke Universiteit Leuven, Louvain, Beig.

Published in: Cereal Chemistry, volumn 79, pages 423-428, (2002).

Abstract: “The proteolytic activities during rye (Secale cereale L. “Humbolt”) grain germination were monitored using in-soln. methods and one- and two-dimensional PAGE with gels that contained incorporated substrate proteins. The total proteolytic activity increased during the first three days of germination, but not after that. The proteinase activity was measured at pH 3.8, 6.0, and 8.0 in the presence and absence of class-specific proteinase inhibitors. This indicated that enzymes from all four proteinase classes were present during the germination process. Germinated rye grain contained mainly aspartic and cysteine proteinase activities that are esp. active at pH 3.8. Serine- and metallo-proteinases were less abundant. Overall, the pattern of hydrolysis was very similar to that obsd. during barley and wheat germination.”

Title: Protease inhibitors of pigeonpea (Cajanus cajan ) and its wild relatives.

Authors: Pichare, M. M.;Kachole, M. S.

Published in: Physiologia Plantarum, volumn 98, pages 845-851, (1996).

Abstract: “Seed extracts from pigeonpeas and its wild relatives were analysed for protease inhibitor activities by caseinolytic assay, and the number of protease inhibitors determined by polyacrylamide gel electrophoresis. Besides trypsin and chymotrypsin inhibitors, seed extracts contained weak papain inhibitor(s) but no bromelain inhibitor. Treatment of seed extracts with bromelain generated new active forms of trypsin inhibitors. The relative amounts of different trypsin inhibitors and the total trypsin inhibitor activity varied with different extraction media. Trypsin inhibitors were not detectable in pigeonpea leaves. The profiles of trypsin and chymotrypsin inhibitors in almost all the cultivars of pigeonpea analysed were similar; however, those in wild relatives were quite variable.”

Another thought completely: The following paper reports that “All shell splitting occurred at the ventral suture with apprx 80% of the splits occurring at the site of the degenerating funiculus leading to the aborted or secondary ovule.” I do not have access to the full paper at this time.

Title: Shell seal breakdown in almond is associated with the site of secondary ovule abortion

Authors: Gradziel, T. M.; Martinez-Gomez, P.

Authors affiliation: Department of Pomology, University of California, Davis, CA, 95616, USA.

Published in: Journal of the American Society for Horticultural Science, volumn 127, pages 69-74, (2002).

Abstract: “California almonds (Prunus dulcis, syn. P. amygdalus, P. communis) possess a moderately lignified ‘paper’ shell rather than the stony, peach-pit type shells common to European and Asian cultivars. At nut maturity, more than 70% of shells of the principal California cultivar Nonpareil can be split. Use of a mechanical shaker to harvest nuts increased the proportion of nuts with split shells by 40% when compared to hand harvest. All shell splitting occurred at the ventral suture with apprx 80% of the splits occurring at the site of the degenerating funiculus leading to the aborted or secondary ovule. Remaining splits occurred near the site of the funiculus feeding the viable ovule, and only rarely at the suture line. Abortion of one of the two ovules in the almond ovary is often initiated at or shortly after bloom, and so the final site of shell splitting appears to be predetermined early in fruit development. Measurements of the strength of the inner endocarp wall at 50 days after flowering showed distinct weaknesses in the areas of the developing funiculi. Similarly, damage to the developing kernel at 60 days after flowering by the leaffooted bug (Leptoglossus clypealis Heiderman) occurred along the ventral suture, with 80% of the damage located at the point of attachment of the secondary funiculus.”