The  direct  role  of  chlorophyll  as  a  chelator  of solar  energy   and   a  catalyst  in   carbohydrate synthesis has been established. The Aurea mutant used in this study was discovered and des- Maksoud, M. A., A. A.  M. Omar, and M. Marwan Effect of the aurea gene on some chemical activities in leaves. cribed by A. Persson (1959), who selected it after X-ray treatment of soaked seeds with 10,000 R. A variegated XI plant appeared which had Aurea as a ground color with green and lighter patches occurring in it. The progeny of this plant segregated in the ratio of 1 green (++) : 2 Aurea (A+) : 1 Yellow   (AA)*.   The   yellow   seedlings   appeared   to   develop   no   chlorophyll   and   later   died.   The heterozygote was as vigorous as the normal, but could be recognized immediately by its pale green color. The  objective  of  the  presented  experiments  was  to  study,  mainly,  the  indirect  roles  of chlorophyll. Thus,  normal  green  plants,  Aurea  mutants,  graft  hybrid  combinations  between  them and  Aurea  mutants  sprayed  with  different  growth  regulators  (biweekly  throughout  their  life)  were used in a pot experiment. The leaves were used for the chemical analyses. Seedlings: In the Aurea and yellow mutants, gene A reduced the concentration of chlorophylls (a) and  (b)  in  the  same  3:1  ratio  of  their  presence  in  the  normal  green.  The  change  from  the  normal genotype (++) to the other mutant types (A+) and (AA), showed that the two A genes were unequal in their subtractive effect for each chlorophyll type. Mature  Plants:  Chlorophyll  content  was  higher  at  this  stage  than  in  the  seedlings.  However, relative  to  the  normal  green,  the  concentration  of  both  chlorophylls  was  reduced  in  the  Aurea mutant by the A gene in the same 3:1 ratio. After fruit setting Ungrafted:  Chlorophyll  content  was  the  lowest  of  all  developmental  stages.  Meanwhile,  the reduction in the concentration of chlorophylls in the Aurea, relative to the normal green, was still in  the  3:1  ratio.  Average  number  of  chloroplasts  per  guard  cell,  catalase  activity,  and  C/N  ratio were  lower  in  the  Aurea  than  in  the  normal  green,  however,  protein  content  was  lower  in  the latter  than  in  the  former.  The  persistence  of  the  3:1  ratio  between  chlorophyll  types during all the developmental stages, in both the normal green and the Aurea, implied that the mutation from gene + to A probably slowed down the conversion rate of the precursor to chlorophyll (b), rather than of chlorophyll (b) to (a). Graft hybrids: Chlorophyll content, chloroplast number, catalase activity, and C/N ratios were intermediate  between  the  respective  values  for  the  ungrafted  normal  green  and  Aurea.  Such  a result was attributed to the interaction between genotypically different vegetative tissues when grafted. Relative to the respective ungrafted types, graft or stock, the normal green accumulated more nitrogen, while the Aurea accumulated less nitrogen. The fluctuations in the nitrogen content were  significant,  while  those  in  sugar  were  non-significant.  Consequently,  the  two  genotypes unequally reciprocated influence, with nitrogen as the limiting factor for the differences in the C/N ratios amongst the graft hybrids.  That the ungrafted Aurea had more protein but less sugar than the  ungrafted  normal  green  indicated  that  sugar  concentration  seemed  to  be  the  limiting  factor for catalase activity. However, despite the apparent linear proportionality between the activity of that  enzyme  and  the  concentration  of  sugar,  the  probability  that  this  proportionality  might  have been  subject  to  nitrogen  toxicity  in  the  graft  hybrids,  as  in  the  ungrafted  Aurea,  should  not  be excluded. Sprayed   Aurea:   Chlorophyll   concentrations,   and   chlorophyll   numbers   were   intermediate between the corresponding values in the normal green and the Aurea. However, the ratio between chlorophylls (a) and (b) fitted 3:1. Noteworthy, was that although sterol, vitamin C, methionine, and  sucrose  effectively  increased  the  number  of  chloroplasts,  they  were  not  as  effective  in increasing  chlorophyll  concentration,  a  result  indicating  the  non-association  between chloroplast number of multiplication and chlorophyll concentration or synthesis. * Symbols do not refer to any standard mutant. In all respects, Persson's mutant mimics Xantha (Xa).

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