Environmental Engineering Reference
In-Depth Information
including reaction centers, donor side and acceptor side under environmental stress. More
recently, PEA Senior and M-PEA have been designed, and they can tell us not only the
information from JIP test but also the changes in PSI, since chlorophyll a fluorescence and
820 nm transmission can be simultaneously recorded (Figure 2). This technology will extend
our knowledge about PSI and the cooperation between PSI and PSII and give us a more
thorough and comprehensive picture about the operating mechanisms of plant photosynthetic
apparatus (Zhang et al. 2011; Yan et al. 2012). It is noticeable that CO
2
fixation process is
also a critical step for photosynthesis (Salvucci and Crafts-Brandner 2004). Rubisco enzyme
and its activation enzyme play a key role in this step, and their activities and contents can be
measured, but the procedure is relatively complex. However, carboxlation efficiency can be
measured by using portable open gas exchange systems, and this parameter can indirectly
reflect the performance of Rubisco enzyme (Voncaemmerer and Farquhar 1981).
Figure 2. Kinetics of prompt fluorescence and modulated 820 nm reflection detected by M-PEA in a
fully expanded leaf of Jerusalem artichoke. MR
0
is the value of modulated 820 nm reflection at the
onset of red light illumination (0.7 ms, the first reliable MR measurement). MR
1
is the value of
modulated 820 nm reflection after far-red light illumination. O, J, I and P indicate the specific steps in
chlorophyll a fluorescence transient.
In conclusion, photosynthesis and biomass should be taken as the criterion for judging
negative effects of salinity on plants. How salinity exerts harmful effects on plants and the
corresponding physiological regulation ways is elucidated in the following paragraphs.
