Observations with the scanning electron microscope revealed that Al induced various morphological changes in the root surface, i.e. decrease in the turgescence of epidermal cel\s of the tip and elongating regions (barley), occurrence of a large number of small depressions mainly in the elongating region (oats and rice), destruction of epidermal and outer cortex cells in the tip and the elongating regions (maize), and cross-sectional deep cracks in the inner cortex cel\s mainly in the elongating region (pea); whereas few morphological changes occurred in the proximal portion of the root. Vital staining test for the elongating region after AI treatment showed that cel\ damage occurred only in the epidermis in the AI-tolerant oat plants, epidermis and outer cortex in the AI-sensitive maize plants, and epidermis and almost all of the cortex in barley plants highly sensitive to AI. AI content was higher in the root tip; K content was lower in the tip of hardly growing root, but was lowest in the middle portion, i.e., elongating region, of the growing root. By the AI treatment, the number of protoplasts of maize roots decreased and the plasmalemma of the protoplasts was abnormal, shrank or was thickened. These results indicate that: (1) in AI-sensitive plants the destruction of the root cells involves the more proximal and the more inner cel\s, and (2) that the destruction of cells associated with Al toxicity is not restricted to the meristematic region of the root. The fol\owing mechanisms are postulated: Al may bind to various kinds of binding sites in the plasmalemma of root cells, and consequently leakage of K out of the plasmalemma and passive Al permeation through the plasmalemma may be induced.

We demonstrate two-dimensional detection optical coherence tomography (OCT) using achromatic phase shifting with a rotating polarizer. This phase shifting, which experiences a light beam with a cyclic change in its polarization state, is, in principle, independent of wavelength. We simulated the wavelength dependence of an achromatic phase shifter using Jones calculus and found that the achromatic region exceeded 145 nm when the deviation of the phase retardation was less than +/- 0.5 degrees. Using the achromatic phase shifter and a conventional phase-shift calculation method, we obtained en face OCT images of an onion at different depths. This method is effective to enhance the quality of OCT with an ultrabroad-spectrum light source.

Temporal phase structure of a 10 fs optical pulse has been regenerated by a two-photon gated photosensitive Bragg grating. The refractive index modulation of n=0.03 has been achieved with 6 nano-joule IR laser pulses.The frequency domain phase conjugator (FDPC) generates time-reversed replica of a phase modulated (frequency chirped) pulse [1]. The time-reversed replica regenerates initial pulse shape after passing though again the same GDD element. We have demonstrated FD phase conjugation by the Time Ordered Pulse Recording/Readout in a Periodic Diffractive Optics (TOPEDO) where the temporal phase structure of optical pulse is recorded as a second-order cross correlation function in space as shown in Fig.1. The TOPEDO requires two-photon sensitive recording medium that effectively changes its index of refraction by low intensity irradiation. One of the advantages of the two-photon interference is that the two pulses can be interacted each other with a long time delay exceeding their coherent length. Moreover, the interference efficiently produces deep amplitude modulation even with small gate pulse energy.The first FDPC experiment has been demonstrated in semiconductor doped colored-glasses having index modulation n=10 -5 with sub-mJ and 100 fs laser pulses [2]. For the 10 fs pulses, however, these media are inefficient. Because diffraction efficiency proportion to square of coherent length, much higher index modulation is required for the a few cycle gratingsIn this paper, we have demonstrated deep modulation in refractive index with a few nano-joule laser pulses directly from a mode-locked oscillator without cavity extension. We have developed photosensitive dye-doped thermo plastic film for this purpose. Pulses coming from a 10 fs mode-locked laser was splitted into two-beams and interacts at the focal plane of a microscope objective as shown in Fig.2. The laser pulse bound 22 times between a pair of chirped mirror to compensate a GDD of 1260 fs 2 produced by the microscope objective. The pulse duration and Fourier phase were monitored by frequency shearing interferometory technique (SPIDER). An interference fringes at the focal plane is 13 micron wide and 207 micron thick. The average laser intensity at the plane was 3.7 GW/cm 2 . C307 laser dye solved in vinyl acetate having an absorption cross section of nonlinear medium Recorded chirpedgrating Frequency chirped pulse Readout pulse Reference pulse Time reversed replica nonlinear medium nonlinear medium Recorded chirpedgrating Frequency chirped pulse Readout pulse Reference pulse Time reversed replicaFig.1 Schematics illustration of two-photon-gated pulse recording and time-reversed readout in a periodic diffractive optics. 697 0-7803-9217-5/05/$20.00©2005 IEEE WDD4 16:30 -16:45

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