The Chl a Carboxylic Biosynthetic Routes: (Photo) Conversion of Protochlorophyllides (Pchlides) a to Chlorophyllide (Chlide) a - Chlorophyll Biosynthesis and Technological Applications - page 239

9.4.1.2 Photoconversion of DV Pchlide a to DV Chlorophyllide

a in DDDV-LDV-LDDV Plants via Route 8 During

Photoperiodic Greening

In green DDV-LDV-LDDV plant species such as cucumber, DV Pchlide a is
continuously present during the light cycles of the photoperiod and only trace
amounts of MV Pchlide a are formed (Carey et al. 1985 ; Ioannides et al. 1994 ).
Interruption of the light cycle by a brief dark period (LD) indicated that such plant
species form most of their Chl via regenerated DV Pchlide a (Abd-El-Mageed
et al. 1977 ). These observation suggested very strongly that during the light cycles
of the photoperiod, green DDV-LDV-LDDV plant species formed most of their
MV Chl via DV Pchlide a , and DV Chlide a as depicted in route 8 .

9.4.2 Photoconversion of MV Pchlide a to MV
Chlorophyllide a in DDV-LDV-LDDV Plants
via Routes 2, 3 and 0

In DDV-LDV-LDDV etiolated tissues, or in greening DDV-LDV-LDDV tissues
during the first few dark-cycles of the photoperiod small amounts of MV Pchlide
a are formed fromMVMpe via route 2 (Tripathy and Rebeiz 1986 ), or via route 3 by
4-vinyl reduction of DV Pchlide a during prolonged dark-incubations (Tripathy and
Rebeiz 1988 ). It can also take place via route 0 as discussed below (Fig. 9.3 ).

9.4.2.1 Photoconversion of MV Pchlide a to MV Chlorophyllide

a in DDDV-LDV-LDDV Plants via Route 2

In DDV-LDV-LDDV etiolated tissues, or in greening DDV-LDV-LDDV tissues
during the first few dark-cycles of the photoperiod small amounts of MV Pchlide
a are formed from MV Mpe via route 2 (Tripathy and Rebeiz 1986 ). Such
t-LW-MV Pchlides a are readily photoconvertible to MV Chlide a by PORA
(Belanger and Rebeiz 1980 ). Biosynthesis of MV Chlide a via biosynthetic routes
2, also takes place in greening DDV-LDV-LDDV plants during the first few dark
phases of the photoperiod when t-LW-Pchlide a accumulation is substantial (Cohen
et al. 1977 ; Cohen and Rebeiz 1978 ).

9.4.2.2 Photoconversion of MV Pchlide a to MV Chlorophyllide

a in DDDV-LDV-LDDV Plants via Route 3

In route 3, MV Pchlide a is formed from DV Pchlide a by reduction of the vinyl side
chain at position 4 to ethyl then photoreduction of the MV Pchlide a thus formed to
MV Chlide a .