Changes in Isoperoxidases during Cold Treatment of Dormant Pear Embryo

Abstract

The number of isoperoxidases and the intensity of certain isozymes increased with increasing periods of stratification of pear (Pyrus communis cv. Bartlett) embryos. The presence of GA3 or kinetin during stratification enhanced the activity of certain isoperoxidases, and these enhancements were blocked in the presence of ABA which by itself had an inhibitory effect. Enhancement in isoperoxidases of pear embryos during stratification was inhibited by 6-methylpurine and cycloheximide; and in the presence of either of these two inhibitors, stratification failed to release the dormancy. Pear embryos germinated for 3 days showed changes in the pattern of isoperoxidases depending on the length of stratification.Peroxidase may be important in the regulation of plant growth and development (2,3,12). Good correlation between seed viability and peroxidase activity was reported by MacLeod (9). Peroxidase activity increased during stratification in embryos of European mountain ash (1); however, no attempt has been made to study the isoperoxidase during stratification of seeds with a cold requirement. Rychter and Lewak (12) reported recently that the appearance of faster moving isoperoxidases in apple embryo was stimulated by stratification, GA3, and BA and inhibited by ABA or coumarin. Unfortunately, the peroxidases were isolated after 3 days of germination and the hormones were added at the beginning of germination. It is not certain whether the changes in isoperoxidases being measured were a result of growth alone, growth plus stratification, or growth plus hormonal treatment. The present study investigates the changes of isoperoxidases in pear embryos during stratification and germination. The data show changes in the isoperoxidase pattern during germination and stratification with or without the presence of hormones. MATERIALS AND METHODSPear seeds, Pyrus communis cv. Bartlett, were soaked at 5 C or 25 C on moist blotters for various lengths of time. Before and after the above treatments, seeds were soaked for 10 min in 2% sodium hypochlorite solution and then washed thoroughly with distilled H20. Embryos were then dissected out. In some experiments pear seeds were stratified (5 C) in the presence of 20 10 ungerminated embryos were ground in a mortar with 0.5 ml of phosphate buffer (50 mm, pH 7.8). The homogenate was centrifuged at 20,000g for 10 min. Saturated sucrose solution (0.1 ml) was added to each supernatant. All operations were carried out at 4 C.The electrophoresis was performed by a procedure adapted from McCown et al. (10). The 5.5% running gels with 4.4% spacer gels were prepared in glass tubes (0.6 x 7.8 cm) which were coated with diluted Photoflo solution. The gels were preelectrophoresed for I hr before applying 0.1 ml of supernatant (about 0.8 mg protein, except in germination experiment) on the top of each gel. The gel electrophoresis was conducted at 4 mamps/tube for approximately 2 hr in the 0.16 M tris-glycine buffer, pH 8.3, at 4 C. After electrophoresis, the gels were soaked in I M ace...

Peroxidases in Relation to Removal of Dormancy and Germination of Apple Embryos

“…Several authors have investigated the peroxidase activity and the isoperoxidase spectrum in embryos before their germination (Rychter and Lewak 1971, Thomas and Neucere 1974, Tao and Khan 1976, Gaspar et al, 1911, Their observations are in agreement with ours. The total peroxidase activity is always very low and results from some not very active isoperoxidases.…”

“…On the contrary, few authors have studied the possible role of the peroxidases in the breaking of dormancy. Nevertheless, one can deduce from the results by Tao and Khan (1976) that the synthesis of the isoperoxidases during the stratification of the pear embryo is not related to the elimination of dormancy. There are more data on the evolution of the peroxidase and isoperoxidase activity during the g-owth following germination (Siegel and Galston 1967, Mills and Crowden 1968, Mitra et al 1970, Ramaiah et al, 1971, Schopfer and Plachy 1973, Palmiano and Juliano 1973, Gaspar et al, 1974.…”

PHYSIOLOGICAL STUDY OF THE STRATIFICATION EFFECT ON THE DYNAMIC CHANGES IN ENDOGENOUS ABSCISIC ACID IN BITTER ALMOND SEEDS (Prunus amygdalus L.) AND ITS RELATION TO SEEDS GERMINATION.

“…Abscisic acid, is a naturally occurring material, and is one of a classes of growth inhibitors that play an important role in plant activities (Addicott, 1992 ;George, 1993). ABA is involved primarily in regulating seed germination, inducing storage, protein synthesis and modulating water stress of seeds and also in a potent germination inhibitor (Hopkins and Hüner,2004).Seeds stratification and changes in hormone levels during chilling stratification have been studied extensively in pear embryo (Tao and Khan, 1976), peach (Daize and Martin, 1972), and hawthorn (Qrunfleh, 1991). However, in Iraq there are a lot of information about the bitter almond specially on changes in ABA levels during chilling stratification of seeds of bitter almond (local variety) which grow under rain fed (unirrigation) conditions in north of Iraq.This research was initiated with the following objectives : a-study the effect of stratification periods on seed germination.…”

Effects of Stratification and Hormone Treatments on Germination and Physio-Biochemical Properties of <i>Taxus chinensis var. mairei</i> Seed

“…PP hypothesis of Roberts and Tao et al proposed that seed germination and dormancy were related to peroxidase and regulated by respiratory pathway in the EMP-TCA and the balance of PP [13,14]. The peroxidase activity of Taxus seeds increased gradually at the beginning of stratification, and then reached maximum point during stratification for 4 months in A1 and A2.…”