Leaf-root interaction is a critical factor for plant growth during maturation and activity of roots is maintained by a sufficient supply of photosynthates. To explain photosynthate distribution among organs in field crops, the node unit hypothesis is proposed. One node unit consists of a leaf and an upper adventitous root, as well as the axillary organs and the lower adventitious root, which is adjacent to one node. Using 14C as tracer, the carbon distribution system has been clarified using spring wheat, soybean, tomato, and potato. The interrelationship among organs from the strongest to the weakest is in the following order: (1) within the node unit > (2) between the node unit in the same or adjacent phyllotaxy > (3) in the main root or apical organs, which are adjacent to the node unit. Within the node unit, 14C assimilated in the leaf on the main stem tended to distribute to axillary organs in the same node unit. The 14C assimilated in the leaf of axillary organs tended to distribute within the axillary organs, including adventitious roots in the axillary organ and then translocated to the leaf on the main leaf of the same node unit. In different organs of the node unit in the same or adjacent phyllotaxy, 14C assimilated in the leaf on the main stem was also distributed to the organs (node unit) belonging to the same phyllotaxy in dicotyledons, while in monocotyledons, the effect of phyllotaxy on 14C distribution was not clear. Among roots/apical organs and node unit, 14C assimilated in the upper node unit was distributed to apical organs and 14C assimilated in the lower node unit was distributed to roots. Thus the node unit hypothesis of photosynthate distribution among organs is very important for understanding the high productivity of field crops. and M. Osaki ... [et al.].
IsiA is a membrane-bound Chl a-antenna protein synthesized in cyanobacteria under iron deficiency. Since iron deficiency is a common nutrient stress in significant fractions of cyanobacterial habitats, IsiA is likely to be essential for some cyanobacteria. However, the role it plays in cyanobacteria is not fully understood. In this review paper, we summarize the research efforts directed towards characterizing IsiA over the past three decades and attempt to bring all the pieces of the puzzle together to get a more comprehensive understanding of the function of this protein. Moreover, we analyzed the genomes of over 390 cyanobacterial strains available in the JGI/IMG database to assess the distribution of IsiA across the cyanobacterial kingdom. Our study revealed that only 125 such strains have an IsiA homolog, suggesting that the presence of this protein is a niche specific requirement, and cyanobacterial strains that lack IsiA might have developed other mechanisms to survive iron deficiency., H.-Y. S. Chen, A. Bandyopadhyay, H. B. Pakrasi., and Obsahuje bibliografické odkazy
Properties and functional activity of the photosynthetic apparatus in Vida faba L. plants grown at 10, 50, 100 and 150 W PAR were studied. Responses of the photosynthetic apparatus in high, HI (125 W m-^) and low irradiance, LI (10 W m-2) plants to a change in irradiance (/) depended on the leaf age. The chlorophyll (a + b) content per unit of the leaf area remained relatively constant during the first 3 d after a shift in /. Acclimation of the photosynthetic electron transport activity to I depended on / in the preceding period and on the phase of leaf development.
Fusilade (fluazifop-p-butyl) is one of the herbicides that inhibit acetyl-CoA carboxylase. The exogenous effect of 30, 60, and 90 ppm fusilade on peanut (Arachis hypogaea L. cv. Giza 5) leaves was studied. With increasing fusilade concentration, the peanut leaf chlorosis appeared after 7-10 d. Declined leaf pigment contents confirmed the leaf chlorosis. Electron microscopic observation of the fusilade-treated (FT) leaves revealed disorganization in the ultrastructure of mesophyll cell chloroplasts. An increase of plastoglobuli occurrence within chloroplasts and degenerated grana thylakoids were observed in FT leaves. Fusilade treatments induced mainly the enhancement of malondialdehyde content and the activities of peroxidases (guaiacol and ascorbate). On contrary, a decrease in H2O2 content, catalase and superoxide dismutase activities was recorded. Enhancements of the guaiacol and ascorbate peroxidase activities were associated with the decreasing H2O2 content in the FT leaves. Hydrogen peroxide seems not to be involved in the oxidative stress of FT leaves. In the FT leaves, the oxidative stress confirmed by chlorophyll degradation and lipid peroxidation might be caused by the other reactive oxygen species probably due to the decrease of superoxide dismutase activity., K. A. Fayez, D. E. M. Radwan, A. K. Mohamed, A. M. Abdelrahman., and Obsahuje bibliografii
We have examined the effect of gabaculine (3-amino-2,3-dihydrobenzoic acid) on chlorophyll (Chl) binding photosystem (PS) apoproteins in thylakoid ineinbranes relative to the effect on pigment accumulations and grana thylakoid stacking in wheat {Triticum aesíivum L.) seedling leaves. The accumulations of critical PSI, PS2, light- harvesting complex (LHCl and LHC2) apoproteins differed in response to gabaculine treatment. The reaction center proteins. Dl of PS2 and the 68 kDa PSI, were not detected in either primary or secondary leaf chloroplasts of treated etiolated seedlings after greening or secondaiy leaf chloroplasts of treated green seedlings. However, the LHC apoproteins accumulated at reduced levels relative to the Controls and LHCl was more sensitive to treatment than LHC2. Gabaculine decreased plastid pigment levels in primary leaf chloroplasts of treated etiolated seedlings by only 50 % and in secondaiy leaf chloroplasts by more than 85 % of that in the Controls. The accumulations of Chl o, Chl h, and the carotenoids, neoxanthin and í3-carotene, were most sensitive to treatment and were decreased in a similar manner. Granal thylakoid development was more sensitive to treatment than stroma thylakoid development and LHC2 apoprotein accumulations enriched stroma thylakoids in some treatments. The lack of starch and critical reaction center apoproteins in these chloroplasts suggest a loss of photosynthetic competency.