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Start Over Coverage 259-265

2. Great promoting effect of high irradiance from germination on flowering in Arabidopsis thaliana - a process of photo-acclimation

Creator:
Moharekar, S., Tanaka, R., Ogawa, K. I., Tanaka, A., and Hara, T.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
chlorophyll, flowering time, leaf number, rosette, and xanthophyll de-epoxidation
Language:
Multiple languages
Description:
Arabidopsis thaliana L., ch1-1 (chlorophyll b-less mutant), gi-1 (GI deficient mutant), cry2-1 (blue-light-photoreceptor CRY2 deficient mutant), and Columbia (Col; wild ecotype) were grown under broad range of irradiances (I) from the beginning of germination and the effect of I on the survival, development, and flowering was studied. Under low and moderate I (<300 µmol m-2 s-1), flowering time and plant size at flowering showed great variations among ch1-1, gi-1, cry2-1, and Col, whereas under higher I (>500 µmol m-2 s-1), these characteristics were almost the same. Hence under high I, development and flowering of ch1-1, gi-1, cry2-1, and Col converged to almost the same state. Flowering time was negatively correlated with I, and under high I acclimation in A. thaliana was associated with a decrease in chlorophyll (Chl) content and increases in xanthophyll cycle pool and membrane-bound APX activity (EC 1.11.1.11) suggesting that an increase in oxidative stress induces earlier flowering. The plants of gi-1 and cry2-1 survived but Col and ch1-1 died under 1 000 µmol m-2 s-1, showing that mutants deficient in GI or CRY2 are more photo-stress-tolerant than Col and the Chl b-less mutant. Hence high I promotes in plants of Arabidopsis raised from germination till flowering the development and flowering time involving modulation of the photosynthetic apparatus, and this promoting effect is independent of the functions of flower-inducing GI or CRY2 gene. This can be regarded as photo-acclimation of A. thaliana for survival and reproduction under high I. and S. Moharekar ... [et al.].
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

5. The susceptibility of cucumber and sweet pepper to chilling under low irradiance is related to energy dissipation and water-water cycle

Creator:
Li, X.-G., Meng, Q.-W., Jiang, G.-Q., and Zou, Q.
Format:
bez média and svazek
Type:
model:article and TEXT
Language:
Multiple languages
Description:
The photoprotection of energy dissipation and water-water cycle were investigated by comparing chilling sensitivity of photosystems 2 (PS2) and 1 (PS1) in two chilling-sensitive plants, cucumber and sweet pepper, upon exposure to 4 °C under low irradiance (100 μmol m-2 s-1) for 6 h. During chilling stress, the maximum photochemical efficiency of PS2 (Fv/Fm) decreased only slightly in both plants, but the oxidisable P700 decreased markedly, which indicated that PS1 was more sensitive to chilling treatment under low irradiance than PS2. Sweet pepper leaves had lower Fv/Fm, higher non-photochemical quenching (NPQ), and higher oxidisable P700 during chilling stress. Activity of superoxide dismutase (SOD) and ascorbate peroxidase (APX) in cucumber leaves was higher, but APX activity decreased apparently compared to that at room temperature. The productions of active oxygen species (H2O2, O2 -) increased in both plants, faster in cucumber leaves than in sweet pepper leaves. In sweet pepper leaves, a stronger de-epoxidation of the xanthophyll cycle pigments, a higher NPQ could act as a major protective mechanism to reduce the formation of active oxygen species during stress. Thus sensitivity of both plants to chilling under low irradiance was dominated by the protective mechanisms between PS1 and PS2, especially the energy dissipation and the water-water cycle. and X.-G. Li ... [et al.].
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public