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Induction of phenylalanine ammonia‐lyase (PAL) in germinating lettuce seeds ( Lactuca sativa )
Author(s) -
Daines Richard J.,
Minocha Subhash C.,
Kudakasseril G. Jose
Publication year - 1983
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1983.tb06584.x
Subject(s) - radicle , lactuca , germination , phenylalanine ammonia lyase , gibberellic acid , imbibition , biology , botany , phytochrome , horticulture , phenylalanine , biochemistry , amino acid , red light
Dry lettuce seeds (achenes of Lactuca sativa L. cv. Grand Rapids) contain no detectable phenylalanine ammonia‐lyase (PAL, EC 4.3.1.5) activity. Enzyme activity could be detected in these seeds within 4 h of imbibition under white light. The specific activity of PAL increased rapidly during the next 12–16 h of imbibition. Far‐red light completely suppressed germination as well as the development of PAL. Gibberellic acid (GA 3 , 0.1 m M ), although effective in causing almost 100% germination in dark, did not induce proportionate increases in PAL. Seed germination as well as PAL activity were substantially inhibited by cis ‐4‐cyclohexene‐l, 2‐dicarboximide (CHDC, 1.0 m M ) both in light and dark. Both GA 3 and benzyladenine (BA, 0.1 m M ) retarded radicle elongation in light. Concomitantly, a decrease in PAL activity was observed. Benzyladenine was able to reverse the effects of CHDC on germination but PAL activity was still highly reduced, probably due to the inhibitory effects of BA on elongation of the radicle. More than 95% of the extractable PAL was found to be present in the radicle. When seeds incubated in white light for 10 h were transferred to FR, further increases in PAL activity as well as the growth of the radicle were severely inhibited. It is suggested that the induction of PAL in light‐sensitive lettuce seeds is coincidental with the germination of seeds, and the amount of PAL per germinated seed is related to the extent of elongation of the embryonic axes.