Biomedical Engineering Reference
In-Depth Information
depended on the types of wheat. Wheats different in disease resistance all have
the PALactivity peak after the inoculation of powdery mildew 12 hours later. The
activity peaks of enzymes related to disease resistance are high and have a long
duration. The activity peak of susceptible cultivars would decline quickly and
become close to the normal level after 24 h. PAL and POD activity increased
sharply after bacterial infection in the leaves of mung bean. After inoculating
Verticillium dahliae toresistant varieties of cotton in SBSI (Seabrook Sea Island)
and susceptible varieties in Rowden, the expression of mRNA, encoding PAL and
COMT, was higher than that of the reference substance. After the cotyledon, leaf,
and stem of
Arabidopsis thaliana
,
Piplotaxis muralis
,
Piplotaxis tenuifolia
, and
Raphanus raphanistrum
and the cotyledon of
Sisymbrium loeselii
were inoculated
with
Leptosphaeria maculans
, they all had strong resistance characteristics to tissue
browning and lignin deposition.
In recent years, research on the metabolism of lignin and plant resistance
has been plentiful. Pot-planting experiments of three poplar clones from
Aigeiros
sp. under waterlogging conditions showed that, in comparison to their respective
controls, the activities of PAL and the contents of organic components in the basal
stem phloem of all clones tested had obvious changes. When the waterlogging time
was prolonged to 40 days, the metabolism within the plant was confused resulting
in the abnormal contents of organic components, the PAL activity increased, and the
plant growth decreased significantly. Through research on the overwintering shoots,
as the temperature decreased, the PAL activities of the terminal bud, cortex, and
xylem steadily increased until December, when it reached peak activity. The PAL
activity of different strains in the coldest month was different [
45
].
In the interaction with phytopathogenic organisms, the lignification of the
secondary cell wall is one of the characteristics of the disease resistance response.
The lignin, as an important physical antibacterial substance in plants, can be
deposited in the HRGP of cell wall as structural barriers, reinforcing the cell wall
and protecting cells from infection by phytopathogenic organisms. The infection of
ulcer germs can induce accumulation of HRGP and lignin deposition in the cell wall
of poplar. The accumulation of different varieties of HRGP and lignin in the poplar
cell wall is different and has a positive correlation with disease resistance. Treating
tobacco seedlings with jasmonate acid not only can improve the ability of seedlings
to be resistant to anthracnose but also can significantly increase seedling POD
activity and lignin content. POD does not play a critical role in the disease resistance
induced by methyl jasmonate, but lignin is closely related to the disease resistance.
In addition, the lignin content in leaves of grape and cucumber has a relationship
to disease resistance. Xu et al. reported that, when watermelon was infected by
Fusarium oxysporum
, lignin in seedling leaves and stems/roots, HRGP content,
and POP and PAL activity would increase in different degrees with the infection
in resistant varieties, and the increase of resistant varieties was significantly higher
than for the susceptible varieties.
The biosynthetic pathway of lignin is a branch of the phenylpropanoid material
synthesis pathway of a plant. There are reciprocal chiasmata on enzymes involved in
these synthesis pathways. Therefore, in those susceptible and under waterlogging,
