**6. References**


activity in transgenic rice than in the wild type. The same was true in transgenic tobacco and *Arabidopsis* (Wang et al., unpublished). Thus, enhancement of SOD activity was accompanied with increase of endogenous or exogenous ALA levels. However, the

That ALA induced the increase of enzymes eliminating H2O2, such as APX, CAT and POD, has been suggested (Nishihara et al., 2003; Liu et al., 2006). Since ALA is the essential biosynthetic precursor of tetrapyrrole compounds including heme, and the latter is a necessary component for the activity of all three enzymes (Tsiftsoglou et al., 2006), it is reasonable to deduce that ALA induces heme accumulation, which is beneficial for H2O2 eliminating enzyme activity. In this work, it was also observed that ALA induced increase of activities of APX and CAT in pear leaves (Fig. 9). However, ALA treatment also increased the content of H2O2 in pear leaves, which might be at a safe level, because MDA content with ALA treatment was significantly lower than the control (Fig. 8). In Table 1, H2O2 level was correlated with *PET, Ψ0*, *φE0*, the activities of SOD, APX, CAT and Rubisco initial activity, as well as transcript of gene coding *Rubisco small unit*. This means that H2O2 might be an active signal molecule rather than an adverse ROS, involved in regulation of antioxidant enzyme activity and physiological or molecular processes. H2O2 has been suggested as a cellular signal, and has wide-ranging effects in many biological processes (Finkel and Holbrook, 2000). It can also regulate gene expression in plants (Neill et al., 2002; Apel and Hirt, 2004). However, whether ALA promotion on plant photosynthesis is

The work was financially supported by the Priority Academic Program Development of

Agarwal S, Sairam RK, Srivastava GC, Tyagi A, Meena RC. Role of ABA, salicylic acid,

Apel K, Hirt H. Reactive oxygen species: metabolism, oxidative stress, and signal

Appenroth KJ, Stockel J, Srivastava A, Strasser RJ. Multiple effects of chromate on the

Beauchamp CO, Fridovich I. Superoxide dismutase: Improved assays and an assay

Chakrabory N, Tripathy BC. Involvement of singlet oxygen in 5-aminolevulinic acid induced photodynamic damage of cucumber chloroplast. Plant Physiol, 1992, 98: 7-11 Farquhar GD, Sharkey TD. Stomatal conductance and photosynthesis. Ann Rev Plant

Finkel T, Holbrook NJ. Oxidants, oxidative stress and biology of ageing. Nature, 2000,

Heath RL, Packer L. Photoperoxidation in isolated chloroplasts: I. Kinetics and stoichiometry of fatty acid peroxidation. Arch Biochem Biophys 1968, 125: 189-198

calcium and hydrogen peroxide on antioxidant enzymes induction in wheat

photosynthetic apparatus of *Sprirodela polyrhiza* as probed by OJIP chlorophyll a

mechanism of SOD activity induced by ALA has no been known.

dependent on H2O2 signal need further study.

Jiangsu Higher Education Institutions (PAPD).

Physiol, 1982, 33: 317- 345

408:239-247

seedlings. Plant Sci, 2005, 169:559-570

transduction. Ann Rev Plant Biol, 2004, 55: 373-399

fluorescence measurements. Environ Pollu, 2001, 115:49-64

applicable to acrylamide gels. Anal Biochem, 1971, 44:276-287

**5. Acknowledgement** 

**6. References** 


**12** 

*Bar-Ilan University,* 

*Ramat-Gan, Israel* 

**Photoacoustics: A Potent Tool for the Study of** 

Phytoplankton cells are ideal organisms for the study of various aspects of photosynthesis, since most of their cells are devoted to components related to the harvesting of light energy and its storage as high energy compounds. They lack flowers, roots and all of the many structures and mechanism evolved in the course of the emergence of plants from the primordial oceans and conquering land. The products of photosynthesis are synthesized while carbon from assimilated CO2 is being reduced and oxygen from photolytically split water is evolved. In most open water bodies – freshwater and marine – the energy input of the entire ecosystem depends on microscopic free-floating photosynthetic organisms- the phytoplankton. The determination of phytoplankton biomass and its photosynthesis activity

The photoacoustic method allows the direct determination of the biomass of different taxa of phytoplankton and the efficiency of their photosynthesis. The latter is accomplished by relating the energy stored photochemically by photosynthesis to the total light energy

The method yields rapid, direct results of the efficiency of photosynthesis, compared to standard measurements based on 14 C fixation and oxygen evolution, or compared to

We review the history of the application of photoacoustics to photosynthesis research. Our results show that the pulsed photoacoustic technique provides direct information on the biomass and phytoplankton photosynthesis and demonstrate its application in the study of

The photoacoustics has a high potential for following the effects of environmental parameters such as irradiance, nutrient status and pollution on phytoplankton communities

The photoacoustic effect was first investigated in the 1880 by Alexander Graham Bell. During his experiments with the "photophone", which carried an acoustic signal with a beam of sunlight that was reflected by an acoustic modulated mirror, he noticed that a

phytoplankton ecology and physiology and in basic research of their photobiology.

**1. Introduction** 

is a great interest to ecologists.

absorbed by the plant material.

and their photosynthetic activity.

indirect results from measurements of variable fluorescence.

**2. The history of photoacoustic effect definition** 

**Energy Fluxes in Photosynthesis Research** 

Yulia Pinchasov-Grinblat and Zvy Dubinsky *The Mina & Everard Goodman Faculty of Life Sciences,* 

