Myeong Ja Kwak

Physiological and biochemical traits of different water and light intensities on cork oak (Quercus suber L.) seedlings

The present study was conducted to assess the impacts of different water and light intensities on the physiological and the biochemical aspects of cork oak (Quercus suber L.) seedlings from acorns collected from Tabarka (Northern Tunisia). The experiments were divided into two treatments: Water stress (well-watered: 25 to 35%, moderate drought stress: 15 to 20%, and severe drought stress: 7 to 10%) and light intensity stress (full sunlight: 100% of full sunlight, 1,200 μmol m -2 s -1 , moderate sunlight: 65 to 70% of full sunlight, 800 μmol m -2 s -1 , low sunlight: 20 to 25% of full sunlight, 300 μmol m -2 s -1 , and extremely low sunlight: 3 to 4% of full sunlight, 40 μmol m -2 s -1 ). Proline accumulation was higher in the severe drought stress and extremely low sunlight compared with other water and light intensity levels. Total nitrogen concentration (T-N) on a dry mass basis was significantly higher in seedlings grown in the low sunlight and the extremely low sunlight than in the full sunlight and the moderate sunlight. The photosynthetic rate (PN), the stomatal conductance (Gs), and the transpiration rate (Tr) of the seedlings of Q. suber showed similar tendencies both in the three drought water levels and in the four light intensity levels during treatment periods, while the water use efficiency (WUE) was not significantly different among each treatment. PN for the full sunlight was lower at a maximum value (≈ 8.2 μmol m -2 s 1 ) compared with the moderate sunlight. On the other hand, the maximum photosynthesis was higher for the moderate sunlight seedlings when compared to the full sunlight seedlings, although the leaf from the full sunlight was light saturated at near 1000 μmol m -2 s -1 compared with the moderate sunlight. In all treatments, both maximum Rubisco activity and electron transport capacity expressed from the A/Ci response curves (Vcmax and Jmax) increased with well-watered (WW) and the full sunlight (FL). Under water treatments, the slopes and explained variances for severe drought stress were considerably lower than those under WW and moderate drought stress (MDS) at 60 and 90 days of treatment. In conclusion, the different water and light intensity levels affected the physiological and the biochemical parameters of Q. suber. The lower assimilation rate was associated with lower stomatal conductance, the nitrogen allocation to photosynthetic functions, maximal Rubisco activity (Vcmax) and electron transport rate (Jmax).

Photosynthesis and chlorophyll fluorescence responses of Populus sibirica to water deficit in a desertification area in Mongolia

In the present study, photosynthetic traits and chlorophyll (Chl) fluorescence parameters of Populus sibirica grown under different irrigation regimes were investigated to estimate seedling growth and vitality for reforestation of a desertification area. According to our results, photosynthesis and Chl fluorescence were significantly affected by water deficit only under severe drought conditions.

Physiological changes and growth promotion induced in poplar seedlings by the plant growth-promoting rhizobacteria Bacillus subtilis JS

This study aimed to determine the effects of plant growth-promoting rhizobacteria Bacillus subtilis JS on the growth and physiological changes of Populus euramericana and Populus deltoides × P. nigra. Poplar seedlings were treated with B. subtilis JS and their growth was monitored for up to 120 d. Three different types of treatments [control, B1 (B. subtilis:double-distilled water, 1:100, v/v), and B2 (1:50)] were established. B. subtilis JS enhanced seedling height by 62% and total biomass by 37% after 120 d. Physiologically, the photosynthetic rate increased by 54%, and the total chlorophyll (Chl) content, foliage nitrogen and phosphate content were significantly higher after treatment with B2 than that of the control. These results suggest that the total Chl content is directly related to not only the photosynthetic capacity of the foliage but also to the nitrogen content, indicating that the strain JS may promote the growth of poplar.

Physiological and biochemical responses of elevated ozone on Pterocarpus indicus under well-watered and drought conditions

Abstract Seedlings of Pterocarpus indicus were grown in both well-watered and drought stress conditions in phytotron. Seedlings grown under well-watered and drought stress conditions were exposed to either combined or without ozone of 200 ppb for one month. First, the physiological responses to elevated ozone levels indicated a decreased biomass. The seedlings grown in arid soil and exposed to ozone showed less biomass than those grown in arid soil but not exposed to ozone. Moreover, all the seedlings except the well-watered and unexposed ones showed a significantly lower photosynthetic rate (PN) over time. However, with the accumulation of ozone injuries, the antioxidant enzyme activities increased overall. In the study results, when exposed to ozone, the well-watered seedlings exhibited more antioxidative enzyme activity than did the seedlings grown in arid soil. Generally, P. indicus in arid soil suffered less damage from elevated ozone than did the well-watered plants.

The relationship between SO2 exposure and plant physiology: A mini review

Air pollutants are emitted from various sources into the atmosphere. During winter, greenhouses are heated by the burning of fuel in heating systems, which creates sulfur dioxide (SO2) that can be detrimental to plant growth and human health. However, there is a poor understanding of the comprehensive effects of SO2 on crops in a greenhouse environment. Therefore, this review aimed to summarize the impacts of greenhouse heating system-derived SO2 on the physiological, morphological, and biochemical responses of plants. In general, plant SO2 exposure has a negative effect on these processes. An initial decline in physiological activities appears several days following SO2 exposure. Morphological and biochemical activities are also negatively affected by extensive SO2 exposure. However, since sulfur is an essential nutrient for plant growth, low-level SO2 exposure has a positive impact on plants. Atmospheric SO2 is taken up by the plant via the stomata, after which it is assimilated and used to synthesize sulfur-containing amino acids, such as methionine and cysteine. Sulfur-containing compounds are crucial for plant growth, and various physiological and biochemical processes. It was concluded that SO2 is a significant greenhouse pollutant, especially for crops.