Abstract:
A rapid and sensitive HPLC method for quantifying both the
reduced and oxidized forms of glutathione simultaneously in woody
plant tissues was developed. This method was applicable to a variety
of woody plant species and different tissues. Total glutathione
content in the bark tissue of seven of the woody plant species tested
were lower during active plant growth, and higher in the dormant
stage. All tested tissues of peach plants contained glutathione. The
highest and lowest content was found in the leaves and roots,
respectively.
'Redhaven' peach trees acquired the onset of rest on 1 Oct,
before any chilling had been experienced. Maximum rest was reached on
1 Nov after the plants were exposed to 320 CU, and 50% of the buds
were broken at 860 CU on 1 Dec. Total budbreak and phytotoxicity
induced by hydrogen cyanamide applied to 'Redhaven' peach trees was
dependent on concentration and time of application. Phytotoxicity was
evident at all application dates, but greatest at the highest
concentrations. Plants were more resistant to hydrogen cyanamide at
maximum rest. Hydrogen cyanamide induced budbreak was best during the
post-rest period. Budbreak and phytotoxicity induced by hydrogen
cyanamide applied during the quiescent stage were dependent on posttreatment
temperature and concentration. All cyanamide treatments
inhibited budbreak at all tested temperatures. The inhibition was
greatest at the the lowest temperature and at the highest
concentrations. Phytotoxicity was greater at 15C and 35C than at 25C,
and increased with increased concentrations.
The content of GSH and GSSG in the buds changed with the
development of rest. During the early phases of rest, when rest
intensity increased, the content of GSH and GSSG decreased (15 Oct)
and then increased at maximum rest (1 Nov). Content of GSH continued
to increase and peaked on 1 Dec at 860 CU. On 15 Dec when the buds
were qxiiescent GSH content decreased. In contrast, contents of GSSG
did not drop during cjuiescence and were highest on 15 Dec. GSH content
induced by chilling was closely associated with the end of rest.
Hydrogen cyanamide treatments caused a rapid decrease of GSH
content within 12 hr followed by a large increase 24 hr after
application. The changes of GSH induced were inversely proportional to
cyanamide concentration. Non-treated plants showed at relatively
constant GSH and GSSG content during this period of time. Hydrogen
cyanamide treatments increased GSH contents at all application dates.
The extent of GSH changes was dependent on the physiological status of
the bud and cyanamide concentration. At maximum rest the plants were
more resistant to cyanamide and this coincided with the highest
induced GSH content as compared to all application dates.
