The detection of a 20 Hz bioelectric potential enables the determination of the nutritional status of the plant without breaking. In addition, low-intensity light emitted at 20 Hz improves plant growth. Excessive irradiation, however, decreases plant growth, thereby showing the importance of an appropriate amount of irradiation for improving plant growth. We recently combined nutrient diagnosis and irradiation methods into a complete method to determine whether plant growth could be improved. This study was conducted to clarify the effect on growth recovery using this method. The total system was applied to barley cultivated in soil, where the plants were irradiated based on bioelectric potential measurements. At the time of harvest, based on yield components (grain weight, number of ears), we developed the following conclusions and recommendations for barley in low-nutrient conditions. Barley in low-nutrient conditions displayed a 20 Hz bioelectric potential.
1. The amount and timing of the 20 Hz irradiation were determined based on diagnosis of the 20 Hz bioelectric potential signal from the barley plants. Irradiation was carried out during the daytime, according to the strength of the 20 Hz bioelectric potential signal.
2. Barley irradiated at 20 Hz in conjunction with the automatic detection of a bioelectric signal demonstrated better growth than nonirradiated plants.
3. Nitrate uptake in barley grown in low-nutrient conditions was increased by exposing it to weak red light at 20 Hz, in conjunction with the automatic detection of bioelectric signal from the plants (Table 4).
This study revealed that barley cultivated at a low nutrient level by a system of irradiation with automatic bioelectric detection could achieve higher yield than barley grown by the more common method using a large amount of fertilizer.

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Increase in sea surface temperature and excessive input of nutrient in reef waters, due to anthropogenic activities have been among the various factors responsible for bleaching and mortality of corals around the world. So, this study investigated the effects of elevated nitrate (NO₃) concentration and temperature on the coral, Pocillopora damicornis. Coral fragments were incubated for two days at different temperatures (27°C and 32°C) and NO₃ concentrations (∼0.4 μM and 10 μM). Following 48 hours of stress under 32°C and 10 μM NO₃, the nubbins were moved to 27°C and ambient (∼0.4 μM) NO₃ levels for 48 hours of recovery period. Maximum quantum yield (F_v /F_m) and maximum excitation pressure (Qm) at photosystem II indicated that combined effect of high temperature and high NO₃ were more severe and only corals under these conditions exhibited an incomplete recovery. Furthermore, zooxanthellae density and pigment data showed that the response mechanism of these coral nubbins were different from high temperature or high NO₃ stress only. Aftre the recovery phase, zooxanthellae density was higher (∼1.5 fold) whereas chlorophyll a per cell was lower (∼1.5 fold) than the control (27°C and ∼0.4 μM NO₃) for combined stress of high nitrate and temperature. On the other hand, xanthophyll ratio for these nubbins was still significantly higher than the control, thus showing a possible mechanism of recovery by dissipating excess loght energy as heat. Hence, this study showed that under thermal stress, high nitrate amplifies damage to the in hospite zooxanthellae of the coral Pocillopora damicornis and recovery of the holobiont is more diffi cult after the stress.

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