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Articles by Toshiyuki Matsui
Total Records ( 24 ) for Toshiyuki Matsui
  Pankaj Kumar Bhowmik , Toshiyuki Matsui , Haruo Suzuki and Yusuke Kosugi
  The tip region of asparagus (Asparagus officinalis L.) spear, comprising immature, rapidly developing tissues, is particularly susceptible to harvest stress and is usually the first part of the spear to show several detrimental changes during storage. In order to define the factors contributing to postharvest deterioration, a 1-aminocyclopropane-1-carboxylate oxidase (ACC oxidase, pAS-ACO) cDNA clone was isolated from a cDNA library prepared from the tip section (apex to 33 mm) of the spears using reverse transcriptase-polymerase chain reaction. The partial cDNA clone encodes an mRNA of 832 bp and the derived amino acid sequence is highly homologous to ACC oxidase from rice, pea and cucumber. Northern blot analysis showed increase level of pAS-ACO mRNA until 3 d at 20oC, which coincided with ethylene production and the ACC oxidase activity, suggesting that the increase might be a response to the wounding associated with harvest.
  Pankaj Kumar Bhowmik , Toshiyuki Matsui , Haruo Suzuki and Yusuke Kosugi
  Glutamine synthetase (GS; EC 6.3.1.2.) has a central role in plant nitrogen metabolism and is a key enzyme in the assimilation of ammonia. Asparagus (Asparagus officinalis L.) spear quality deteriorates rapidly after harvest and is associated with an increase in the ammonia content of the spear tip. In order to define the factors contributing to postharvest deterioration of asparagus spears, the changes in GS activity and gene expression in the top and bottom portions of asparagus spears were examined during storage. GS enzyme activity declined throughout the 96 h postharvest period in both top and bottom portion. Northern blot analysis showed that the level of transcript of GS decreased in top and bottom portion during storage. Expression of GS gene in top portion was observed more clearly but it was barely detectable in bottom portion that might be due to the lower activity of GS in bottom portion.
  Pankaj Kumar Bhowmik , Toshiyuki Matsui , Haruo Suzuki and Yusuke Kosugi
  An asparagus (Asparagus officinalis L. cv. Welcome) cDNA clone coding the enzyme phenylalanine ammonia-lyase (PAL) was isolated from a cDNA library prepared from asparagus spears using reverse transcription- polymerase chain reaction (RT-PCR). The partial cDNA clone encodes an mRNA of 527 bp and the derived amino acid sequence is highly homologous to PAL from rice, maize and barley. Northern blot analysis showed increase level of pAS-ACO mRNA until 24 hour at 200C, which coincided well with PAL activity and fiber development, suggesting that the increase might be a response to the wounding associated with harvest.
  Pankaj Kumar Bhowmik , Toshiyuki Matsui and A.K.M. Shameem Alam
  A 1-aminocyclopropane-1-carboxylate (ACC) synthase cDNA from Asparagus spears was isolated and sequenced as a continuation after cloning, sequencing and expression analysis of ACC oxidase. The partial cDNA clone encoded an mRNA of 968 bp and the derived amino acid sequence was highly homologous to ACC synthase from bamboo banana, rice and wheat. Northern blot analysis showed increase level of pAS-ACS mRNA until 8 h at 20°C, which coincided with ethylene production and the ACC synthase activity, suggesting that the increase might be a response to the wounding associated with harvest.
  Pankaj Kumar Bhowmik , Toshiyuki Matsui , Masayuki Fujita , Md. Zakir Hossain and Eizou Miki
  Two inhibitors of the first enzyme phenylalanine ammonia lyase (PAL) in the phenylpropanoid pathway were used to investigate the role of phenolic metabolism in lignification and toughness of Asparagus spears. Spears were soaked for 1 h at 20°C in aqueous solution of α-aminooxi-β-phenylpropionic acid (AOPP) at 0, 100, 300 and 600 μM. Liquid 2,5-Norbornadiene (NBD) was applied with a micropipette onto a sheet of filter paper in a 6.4 liter big jar which was immediately sealed with a cover. Liquid NBD readily volatilized at 25°C in a closed chamber. The amount of liquid applied was calculated to give the desired gaseous concentration (6000 μl L-1) in the jar. Both AOPP and NBD inhibited PAL activity and significantly decreased fiber content in both top and bottom portions of the spears. Northern blot analysis showed that expression in mRNA level coincided well with the changes in PAL activity and fiber content. These results confirm the view that AOPP and NBD, inhibitors of PAL enzyme activity, reduce PAL gene expression and decrease the fiber content of Asparagus spears, suggesting that downstream products of PAL enzyme activity may have a regulatory role in the lignification process.
  Dewoowoogen Porras Baclayon , Toshiyuki Matsui , Haruo Suzuki and Yusuke Kosugi
  This study investigated the physiological and biochemical changes during postharvest senescence of two broccoli (Brassica oleracea L.) cultivars (‘Hartland’ and ‘Sairin’). A parallel trend in weight loss, color change and respiration rate was observed in both cultivars. However, ‘Sairin’ exhibited higher total weight loss and rate of respiration and lower hue angle value. Glutamine synthetase (GS, EC 6.3.1.2) activity decreased in the florets of both cultivars while an increasing glutamate dehydrogenase (GDH, EC 1.4.1.2) activity was noted in the florets of ‘Hartland’. On the other hand, GDH activity was not detected in the floret of ‘Sairin’. In the branchlet portion of both cultivars, GS activity was nearly unchanged except for a transient increase during the first 24 h of storage. Initial GDH-aminating and deaminating activities were significantly higher in this portion but were not maintained until the end of the storage period. Ammonia accumulated largely in the floret portion which accounted for about 87 and 93% of initial contents in ‘Hartland’ and ‘Sairin’, respectively. On the contrary, ammonia concentration in the branchlet portion of both cultivars remained almost unchanged. Total amino acid in all portions of both cultivars increased as storage progressed. A highly significant negative correlation was observed between GS activity and ammonia and total amino acid accumulations while a highly significant positive correlation was evident between GDH activity and ammonia and total amino acid accumulations in the florets of ‘Hartland’. In the branchlet portions, only GDH-deamination showed significant negative and highly significant negative correlations with ammonia and total amino acid accumulations, respectively. Comparing the two cultivars, ‘Hartland’ has longer shelf life than ‘Sairin’. The shorter shelf life of ‘Sairin’ could be attributed to higher respiration rate and the deficiency of GDH activity.
  Bimal Kumar Pramanik , Toshiyuki Matsui , Haruo Suzuki and Yusuke Kosugi
  Changes in sucrose synthase (SS) and sucrose phosphate synthase (SPS) activities and sugar content during postharvest senescence in broccoli (Brassica oleracea L. cvs. `Hartland` and `Sairin`) were studied. The first change in color became apparent between 2 and 3 d but whole head yellowed after 5 d of storage. The SS activity increased gradually in all portions although with few fluctuations in branchlets of both cultivars at the end of the storage time. In case of SPS, there was no inclining or declining pattern of the activity in any portion of the two cultivars at the end of the storage period. In both cultivars, branchlets showed higher SS and SPS activity than florets. Sucrose content gradually decreased in both portions of the two cultivars with time. Fructose content was higher than glucose and sucrose in the florets as well as branchlets of both cultivars. There was a highly significant negative correlation observed between the SS activity and sucrose content in the florets and branchlets of both cultivars. There was no significant correlation between sugar contents and SPS activity in any portions of both cultivars.
  Bimal Kumar Pramanik , Toshiyuki Matsui , Haruo Suzuki and Yusuke Kosugi
  This study investigated the changes in carbohydrate content and activities of invertase, sucrose synthase and sucrose phosphate synthase in two broccoli cultivar (Brassica oleracea L. Cvs. ‘Hartland’ and ‘Sairin’) stored at 5°C. Respiration rate rapidly declined after 1 day of storage and gradually decreased at the end of the storage period. Color did not change significantly at the end of the storage period. In both cultivars and portions, the invertase activity increased gradually at the end of the storage time. The acid invertase in cell wall-bound fraction (CWBF) showed a higher activity than that in soluble fraction (SF). Again, the branchlets showed a significantly higher invertase activity than that of florets. In both cultivars, sucrose synthase (SS) activity gradually increased in the florets with some fluctuations in the branchlets at the end of the storage time. Sucrose phosphate synthase activity (SPS) activity did not change markedly in any portion of the two cultivars at the end of the storage period. Sucrose content gradually decreased in both portions of the two cultivars with time. It was negatively correlated with the acid invertase and SS activities in both portions accounting well for the relation between the substrate and the activity. Fructose and glucose content were higher than sucrose in the florets as well as branchlets in both cultivars.
  Sitthiwong Kassinee , Toshiyuki Matsui and Nobuyuki Okuda
  This study investigated the changes in acid invertase activity and sugar distribution during postharvest senescence in vegetable soybean (Glycine max (L.) Merr. vars. ‘Ajigen’ and ‘Huuki’) stored at 5°C for 10 days. Percent weight loss of the pods decreased with few fluctuations until the end of the experimental period. The degree of yellowing gradually increased with time. Respiration rate rapidly declined in both cultivars after 2 days of storage. The acid invertase activity of soluble and cell wall-bound fractions increased with some fluctuations throughout the storage period in both cultivars. During storage, acid invertase activity of cell wall-bound fraction showed higher activity than that of soluble fraction. There was a significant negative correlation between invertase activity (soluble and cell wall-bound fractions) and soluble sugars (sucrose, fructose and glucose). Among the three sugars, sucrose constitute the highest concentration. Glucose was present but in smaller amount than that of sucrose and fructose. Comparing the two cultivars, ‘Huuki’ showed higher percentage of weight loss, degree of yellowing, enzyme activities and sucrose content than ‘Ajigen’.
  Bimal Kumar Pramanik , Toshiyuki Matsui , Haruo Suzuki , Yusuke Kusugi and Matsuzaki Tomohiro
  This study investigated the seasonal fluctuations in invertase, sucrose synthase (SS) and sucrose phosphate synthase (SPS) activities and sugar and organic acid contents in the florets and branchlets of two broccoli cultivars ‘Hartland’ and ‘Sairin’ harvested from October to April. In both, cultivars and portions, invertase (soluble and cell wall-bound fraction) and SS activities were high in October thereafter decreasing until January and once again gradually increasing up to April. In both cultivars, there was no specific change in SPS activity throughout the harvest season but the activity was high in January. Organic acids (malic and citric) and sugar (specially, sucrose) concentrations increased from October to a maximum in January and again decreased up to April. However, no significant change was observed in glucose and fructose. There was a highly significant negative correlation observed between invertase and SS activities and sucrose content in the florets and branchlets of both cultivars. ‘Sairin’ showed higher invertase, SS and SPS activities in both florets and branchlets than ‘Hartland’.
  Dewoowoogen Porras Baclayon , Toshiyuki Matsui , Haruo Suzuki , Yusuke Kosugi and Matsuzaki Tomohiro
  Temperature changes during growth and development influence various metabolic processes in plants. To determine its influence in broccoli (Brassica oleracea L.) at harvest, we examined the activities of some ammonia-assimilating enzymes and ammonia content in the floret and branchlet portions of two cultivars (Hartland and Sairin) harvested from October to April. Glutamine synthetase (GS; EC 6.3.1.2) in the two portions showed decreasing and increasing activity in the florets and branchlets, respectively with decrease in temperature. Asparagine synthetase (AS; EC 6.3.5.4) activity did not show significant variation in both cultivars throughout the experimental period except the branchlet portion wherein activity reached a peak in January and then fluctuated until April. AS activity was significantly higher in the floret than in the branchlet portion in both cultivars. Glutamate dehydrogenase (GDH; EC 1.4.1.2) aminating activity was higher during warmer harvest months while no distinct declining or inclining trend was found in the deaminating activity throughout the experimental period. GDH activities were significantly higher in the branchlet than in the floret portion except for GDH-amination in Hartland harvested in October and December. In the floret portion GDH activity was not detected in Sairin and Hartland after December and February harvests, respectively. The results of this study may provide insights in obtaining optimum yield and product quality of broccoli.
  Wanraya Suthumchai , Toshiyuki Matsui , Kazuhide Kawada and Yusuke Kosugi
  This study investigated the changes in acid invertase activity and sugar contents in lettuce (Lactuca sativa L. cvs. ‘Shizuka’ and ‘Shisuko’) during storage at 20°C. Percent weight loss of the heads was highest after 2 days of storage. In both cultivars, the degree of greenness continuously declined with time. Respiration rate decreased in ‘Shisuko’, whereas the rate in ‘Shizuka’ increased at the end of storage. The activity of acid invertase in soluble and cell wall-bound fractions decreased with few fluctuations throughout the storage period in both cultivars and portions. The acid invertase in the cell wall-bound fraction showed a higher activity than the soluble fraction. The soluble sugar contents gradually decreased in both cultivars and portions as storage progressed. Fructose content was higher than glucose and sucrose in the leaves of two cultivars. In the leaves of ‘Shisuko’, there was a significant positive correlation between the acid invertase activity and the soluble sugars. Comparing the two cultivars, #Shisuko’ showed higher percentage of weight loss, degree of yellowing, respiration rate and has low sugar contents than ‘Shizuka’.
  Teerasak Pongsa-Anutin , Haruo Suzuki and Toshiyuki Matsui
  The effects of mulching on soil moisture and temperature and sugar metabolism in Japanese radish (Raphanus sativus L.) were studied. Soil moisture content and temperature were higher in mulched plots than the none-mulched plots throughout the experimental period. Radish roots grown in plots with mulch were heavier than those without one. Acid invertase activities in soluble fraction (SF) and cell wall-bound fraction (CWBF) of the roots grown in plots with and without mulch showed the same pattern. However, the enzyme activity was higher in roots grown in mulched plots. The acid invertase activity in SF gradually increased during growth and development while no specific inclining or declining pattern was found in CWBF. Mulching did not significantly affect the amount of fructose (Fru) and glucose (Glc) contents during growth and development. However, sucrose (Suc) content in roots grown in plots with mulch was higher than those grown without mulch throughout the experimental period. Fru and Glc contents in the bottom portion of the root were also found to have same pattern as the top portion. Present results suggest that mulching could increase crop yield by producing heavier root weight and improve product quality such as sweetness due to higher Suc content of the roots.
  Wanraya Suthumchai , Toshiyuki Matsui , Kazuhide Kawada and Yusuke Kosugi
  This study investigated the changes in activities of sugar metabolizing enzymes (acid invertase, sucrose synthase (SS) and sucrose phosphate synthase (SPS)) and sugar contents during storage at low temperature in lettuce head (cvs. ‘Shizuka’ and ‘Shisuko’). The acid invertase activity decreased while the SS activity showed a continuous increase during storage. In both cultivars and portions, sugar contents declined after 2 days of storage especially sucrose content. The SS activity and sugar contents had a significant negative correlation in both portions of ‘Shisuko’. However, a significant positive correlation was observed between acid invertase activity (soluble fraction) and sugar contents in the leaf portion of both cultivars. SPS activity did not show specific inclining or declining pattern throughout the storage time. Among the two cultivars, ‘Shizuka’ showed lower percentage of weight loss, degree of yellowing and respiration rate than ‘Shisuko’ which might be the reason for longer storage life of the latter.
  Dulal Chandra , Toshiyuki Matsui , Haruo Suzuki and Yusuke Kosugi
  This study investigated the physiological and biochemical changes during postharvest storage of two crisphead lettuce (Lactuca sativa L.) cultivars, `Shizuka` and `Cisco`. Lettuce heads were stored for up to 10 days at 20°C. Both cultivars showed remarkable changes in weight loss and respiration rate along with hue angle value. The glutamine synthetase (GS, EC 6.3.1.2) activity decreased gradually in the leaf portion of both cultivars. However, in the midrib portion, these changes were not so prominent. Increased activities of glutamate dehydrogenase (GDH, EC 1.4.1.2) were found in both portions and cultivars with little fluctuation on 2 and 4 days. The aminating activity of GDH was substantially higher than deaminating activity. Though ammonia content was increasing throughout the storage period, significantly higher accumulation was started after 4 days. However, the initial content and accumulation of ammonia were noticeably higher in the cultivar `Cisco` for both portions. There was a highly significant negative correlation observed between GS activity and ammonia content whereas a significantly positive (highly in `Cisco`) relationship was found between GDH activity and ammonia content in the leaf portion of both cultivars. An inverse relationship between GS and GDH indicated that these two enzymes are subject to concurrent regulation by a common metabolite. Based on the parameters determined in this study, the cultivar `Shizuka` showed longer shelf-life than `Cisco`.
  Kassinee Sitthiwong , Toshiyuki Matsui , Nobuyuki Okuda and Haruo Suzuki
  This study investigated the changes in carbohydrate content and activities of acid invertase, sucrose synthase (SS) and sucrose phosphate synthase (SPS) in two vegetable soybean cultivars (Glycine max (L.) Merr. vars. Ajigen and Fuuki) during fruit development ranging from 28 to 63 days after anthesis. In both cultivars, sucrose was the predominant sugar while fructose and glucose were found in trace amounts. Sucrose accumulation was highest at 35 and 42 days after anthesis in Fuuki and Ajigen, respectively. On the other hand, fructose and glucose were almost maintained throughout the experimental period. The activity of soluble acid invertase was highest at the 42 days but was not maintained until the 63 days after anthesis. The acid invertase activity in cell wall-bound fraction was highest in young fruit (28 days after anthesis) and gradually decreased throughout development. Ajigen had higher activity than Fuuki. SS activity showed a continuous increase with time while SPS activity did not show specific inclining or declining pattern. SS and SPS activities in Fuuki were higher than Ajigen. There was a highly significant negative correlation observed between the acid invertase activity in cell wall-bound fraction and sucrose content in Ajigen. A significant positive correlation was also found between the SS and SPS activities and sucrose content in Fuuki. However, a highly significant negative correlation was observed between SS activity and other soluble sugars (glucose and fructose) in both cultivars except glucose content in Fuuki. No significant correlation was found between the SPS activity and other soluble sugars (glucose and fructose) in both cultivars.
  Bimal Kumar Pramanik , Toshiyuki Matsui , Haruo Suzuki and Yusuke kosugi
  The rapid senescence of broccoli head after harvest at ambient temperatures is accompanied by rapid drop of sucrose from florets. To understand such biochemical changes, we isolated a cDNA for Sucrose Synthase (SS) from broccoli branchlets. The cDNA clone, BoSS (B. oleracea sucrose synthase) (AB212623) encodes an mRNA of 608 bp. The deduced amino acid sequence is highly homologous to SS from Arabidopsis, cotton, mungbean and pea. Transcripts of BoSS were present in both branchlets and florets throughout the storage period. The SS enzyme activity of both portions gradually increased throughout the storage duration except for a transient decrease on the 48 h of storage. However, transcripts were only consistent with enzyme activity up to 24 h of storage. The initial increase in enzyme activity and transcripts level after 24 h of storage caused about 50% decline of sucrose content.
  Kassinee Sitthiwong , Toshiyuki Matsui and Sutevee Sukprakarn
  Ten pepper (Capsicum annuum L.) germplasm accessions from Thailand were screened using random amplified polymorphic DNA (RAPD) markers. Twelve dodecamer oligonucleotide primers, singly and in combination were used. The similarity values among the studied genotypes range from 0.209 to 0.891. The resulting dendrogram divided the accessions into two major groups. The first group which include 8 accessions with white corolla was further divided into two subgroups. The first subgroup included 4 long-fruited (CA849, CA958, CA1107 and CA1118) and 1 medium-fruited (CA365). The second subgroup included 1 medium-fruited (CA367) and 1 short-fruited (CA398). However, the medium-fruited CA020 could not be clustered into any subgroup. The second group included a short-fruited with 1 white having green margin corolla (CA024) and a yellow green with green-yellow spots corolla (CA034). The obtained clustering based on RAPD markers was consistent with morphological characteristics of the different pepper accessions.
  Kassinee Sitthiwong , Toshiyuki Matsui , Nobuyuki Okuda and Yusuke Kosugi
  Changes in carbohydrate content and the activity and gene expression of sucrose synthase (SS; EC 2.4.1.13) were studied in vegetable soybean (Glycine max (L.) Merr. cvs. ‘Ajigen’ and ‘Fuuki’) stored at 20°C for 10 days. After vegetable soybean is harvested, there was a progressive deterioration as shown in the reduction of sugars in both cultivars throughout the experimental period. In addition, SS activity decreased after 2 days of storage and increased with some fluctuations thereafter in both cultivars throughout the storage period. SS activity was higher in ‘Fuuki’ than ‘Ajigen’. To understand the molecular basis of induction of SS during posharvest senescence, the partial clone cDNA, GmSS (Glycine max sucrose synthase; AB213027) consisted of 607 nucleotides was isolated from vegetable soybean seeds. The GmSS gene showed highest identity at nucleotide and amino acid levels with mung bean at 94 and 98%, respectively. A radial phylogenetic tree of the amino acid sequence of GmSS (AB213027) and SS from mung bean (D10266) are strongly clustered in a subgroup, belonging to Fabaceae family. Although the level of transcripts was not consistent with enzyme activity, the expression was found in both cultivars throughout the experimental period. The inconsistency between the SS activity and gene expression may be due to post-transcriptional regulatory and/or encoded with another distinct isoforms of SS genes. Another result for this inconsistency between SS activity and gene expression could be due to the regulation of sugars by other harvest related genes.
  Dewoowoogen Porras Baclayon , Toshiyuki Matsui , Haruo Suzuki and Yusuke Kosugi
  Quality of broccoli deteriorates rapidly after harvest due to major physio-biochemical changes. In this study, the changes in ammonia content and activity and gene expression of glutamate dehydrogenase (GDH; EC 1.4.1.2) during storage at 20°C for five days were investigated. The branchlets were separated from the florets at the end of each storage period. Ammonia assay showed that the level in the branchlet portion was almost constant while in the floret portion increased rapidly after three days of storage to about seven times the content at harvest. Enzymatic analysis, on the other hand, revealed that GDH, in both amination and deamination activities, decreased in the branchlets while a gradual increase was observed in the floret portion as storage progressed. To better understand these biochemical changes, a cDNA encoding GDH in broccoli was isolated, cloned and sequenced. The partial cDNA clone referred to as BoGDH (Brassica oleracea glutamate dehydrogenase gene; AB212934) encodes an mRNA of 781 bp. The deduced amino acid sequence showed highest similarity with the GDH gene from Arabidopsis associated with stress. Although the transcript was not consistent with enzyme activity, RNA gel blot analysis revealed that BoGDH was present in both branchlet and floret portions throughout the storage duration. The results suggest that GDH plays an essential role during postharvest senescence. Furthermore, it is likely that its expression is controlled by multigenes and regulated either transcriptionally or posttranscriptionally.
  Dewoowoogen Porras Baclayon , Toshiyuki Matsui , Haruo Suzuki and Yusuke Kosugi
  Tissue toughness or textural changes which are closely associated with lignifications in vegetables often provide problem to consumer acceptability particularly those which are consumed raw or half-cooked. To obtain fundamental knowledge underlying this change, enzymatic and molecular analyses of phenylalanine ammonia-lyase (PAL; EC 4.3.1.5), enzyme catalyzing the conversion of L-phenylalanine to trans-cinnamic acid in the first step of phenylpropanoid pathway were conducted in the edible branchlets of broccoli during early postharvest senescence. While toughness of the tissue or breaking force as estimated by resistance to pressure on shearing continuously increased, PAL activity decreased after few hours from harvest. The expression of BoPAL was at maximum level on the 12 h from harvest in the upper branchlets. In the lower branchlets, the expression was initially high but declined 6 h from harvest and slightly increased until 24 h of storage. The results imply that, in addition to PAL, other lignin-specific enzymes and/or tissue structural changes may have more significant roles in tissue toughening of broccoli branchlets.
  Wanraya Suthumchai , Toshiyuki Matsui , Kazuhide Kawada , Yusuke Kosugi and Koichi Fujimura
  The objective of this study was to understand the effect of environmental changes during growth and after harvest on the quality of lettuce. In both cultivars and portions, acid invertase activities (soluble and cell wall-bound fractions) increased throughout the harvest month, except in April in the leaf portion. SS and SPS activities declined with few fluctuations in any portions of both cultivars. The activities of three sucrose metabolizing enzymes were higher in the midrib than in the leaf portions. Sucrose concentration increased from December to a maximum in January and again decreased up to April. On the other hand, glucose and fructose concentrations declined up to March and increased in April. There was a highly significant negative correlation between the activity of acid invertase in cell wall-bound fraction and sucrose content. A higher concentration of reducing sugars was found in `Bittsu` than `Shisuko`. Fructose was higher than glucose and sucrose contents in the both portions of two cultivars.
  Fabio Gimena Enriquez , Toshiyuki Matsui , Pankaj Kumar Bhowmik Haruo Suzuki and Kazuhide Kawada
  Asparagus (Asparagus officinalis L. cv. Welcome) spears deteriorates rapidly after harvest and is associated with an increase in the ammonia content of the spear tip. In other plant systems it is thought that ammonia buildup is toxic and causes tissue deterioration. To further investigate these phenomena the authors held the spears at 20°C after harvest and examined the glutamine synthetase (GS, EC 6.3.1.2) and glutamate dehydrogenase (GDH, EC 1.4.1.2) activities and ammonium content in the spears. GS is the key enzyme responsible for assimilating ammonium while GDH catalyses the amination of oxoglutarate to glutamate (NADH-GDH) and the deamination of glutamate to oxoglutarate (NAD+-GDH). Spears were stored for up to 5 days at 20°C. Accumulation of ammonium increased as the days of storage progressed. The GS activity declined whereas the GDH activities almost doubled after 5 days of storage at 20°C. The increased GDH activities could be caused by a higher ammonium levels in the spears. The rise in GDH activities is linked with a corresponding decline in GS activity. Glutamine and glutamic acid content decreased with days of storage. It may be concluded that the rapid changes in the physiology of asparagus spears are induced in response to harvest, storage and the amino acid loss content are commonly associated with senescence in plant tissue.
  Bimal Kumar Pramanik , Toshiyuki Matsui , Haruo Suzuki and Yusuke Kosugi
  Changes in acid invertase activity and sugar distribution were studied during postharvest senescence of broccoli (Brassica oleracea L. cvs. ‘Hartland’ and ‘Sairin’) stored at 20°C. Broccoli head began to degreen after 3 days of storage and the degree of yellowing gradually increased at the end of the storage period. Respiration rate decreased markedly during the first 24 h of postharvest storage and increased slightly thereafter. In both cultivars and portions, the invertase activity increased gradually at the end of the storage time. The acid invertase in cell wall-bound fraction (CWBF) showed a higher activity than that in soluble fraction (SF). Again, the branchlets showed a significantly higher invertase activity than that of florets. Of the two cultivars, ‘Sairin’ showed a higher invertase activity in both portions. Sucrose content gradually decreased in both portions of the two cultivars with time. It was negatively correlated with the acid invertase activity in both portions accounting well for the relation between the substrate and the activity. Fructose content was higher than glucose and sucrose in the florets as well as branchlets in both cultivars. Comparing the two cultivars, ‘Sairin’ showed higher enzyme activities, sugar content and respiration rate than ‘Hartland’.
 
 
 
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