© 2007 Heron Publishing—Victoria, Canada
Alleviation of dormancy in walnut kernels by moist chilling is independent from storage protein mobilization
Ali Reza Einali (1) and Hamid Reza Sadeghipour (1, 2)
1. Department of Biology, College of Science, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran / 2. Corresponding author (sadeghipour@gau.ac.ir) / Received February 20, 2006; accepted May 23, 2006; published online January 2, 2007
Summary
We studied the effects of moist chilling and warming on storage protein mobilization in walnut (Juglans regia L.) kernels to assess the metabolic inhibition theory, which states that dormant seeds are unable to utilize their own food
reserves and that cold conditions allow germination by activating hydrolases involved in reserve mobilization. Stratifying
kernels at 5 °C for 40 days enhanced their germination. During both cold stratification and warm incubation of kernels, storage
protein mobilization occurred in cotyledons rather than axes. Kernel amino acid concentration increased during protein mobilization,
with axes of warm-incubated kernels having particularly high amino acid concentrations. Polyacrylamide gel electrophoresis
in the presence of sodium dodecyl sulfate (SDS-PAGE) of the soluble protein fractions from both cold-stratified and warm-incubated
cotyledons revealed increased band intensities of putative glutelins (19–22 and 32–35 kDa). A very high molecular weight protease
was detected by gelatin SDS-PAGE that was most active at acid to neutral pHs in imbibed, cold stratified and germinated kernels
suggesting the protease(s) was synthesized earlier in the mature seeds. Thus, in dormant walnut kernels there is no block
to protein mobilization, and imbibition alone is sufficient to initiate proteolysis. Catalase activity was higher in warm-incubated
kernels than in cold-stratified kernels, suggesting that seed aging is hastened under warm conditions and that cold stratification
in walnut kernels might involve activation of cellular repair mechanisms.
Keywords:
amino acids, catalase, glutelin, Juglans regia, protease, stratification.
