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Query: UMLS:C0008272 (chlorosis)
 2,195 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Leaves of rye seedlings (Secale cereale L.) grown in the presence of four chlorosis-inducing herbicides under a low light intensity of 10 lux formed chlorophyll. When segments of such dim-light-grown leaves were exposed to 30,000 lux at either 0 degrees C or 30 degrees C, treatments with aminotriazole or haloxidine (group 1) showed no or only minor changes of their chlorophyll contents. In treatments with San 6706 or difunon (group 2), however, rapid photodestruction of chlorophyll occurred both at 0 degrees C and at 30 degrees C and was accompanied by an increase of malondialdehyde that was not seen in the presence of group 1 herbicides. Unlike the in vivo behavior, virtually equal rates of chlorophyll breakdown were observed for aminotriazole and San 6706 treatments in suspensions of isolated chloroplasts from 10 lux-grown leaves after exposure to strong light. The free radical scavengers p-benzoquinone and hydroquinone and the d-penicillamine copper complex exerting superoxide dismutating activity effectively prevented photooxidation of chlorophyll in 10 lux-grown herbicide-treated leaf segments or even restored an accumulation of chlorophyll at 30,000 lux. Ascorbate and several singlet oxygen or hydroxyl radical scavengers had no protective effects. Deuterium oxide and H(2)O(2) did not enhance the degradation of chlorophyll. Superoxide dismutase activity was decreased in leaves bleached in the presence of group 2 herbicides.
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PMID:Nature of photooxidative events in leaves treated with chlorosis-inducing herbicides. 1666 67

We analysed Pyrus communis cv. Conference and Cydonia oblonga BA29, differently tolerant to lime-induced chlorosis, to identify the key mechanisms involved in their different performance under Fe deficiency induced by the absence of Fe (-Fe) or by the presence of bicarbonate (+FeBic). Under our experimental conditions, a decrease in root elongation was observed in BA29 under bicarbonate supply. Superoxide dismutase (SOD) and peroxidase (POD) activities were analysed and the relative isoforms were detected by native electrophoresis. The data obtained for both genotypes under -Fe and for BA29 +FeBic suggest the occurrence of overproduction of reactive oxygen species (ROS) and, at the same time, of a scarce capacity to detoxify them. The detection of ROS (O(2)(-) and H(2)O(2)) through histochemical localization supports these results and suggests that they could account for the modifications of mechanical properties of the cell wall during stress adaptation. On the other hand, in the cv. Conference +FeBic, an increase in non-specific POD activity was detected, confirming its higher level of protection in particular against H(2)O(2) accumulation. Peroxidases involved in lignification were assayed and histochemical analysis was performed. The results suggest that only in BA29 under bicarbonate supply can the presence of ROS in root apoplast be correlated with lignin deposits in external layers and in endodermis as a consequence of the shift of PODs towards a lignification role. We suggest that in BA29 the decrease in root growth could impair mineral nutrition, generating susceptibility to calcareous soils. In the cv. Conference, the allocation of new biomass to the root system could improve soil exploration and consequently Fe uptake.
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PMID:Oxidative stress responses and root lignification induced by Fe deficiency conditions in pear and quince genotypes. 2138 6

Iron deficiency chlorosis (IDC) is an abiotic stress often experienced by soybean, owing to the low solubility of iron in alkaline soils. Here, soybean lines with contrasting Fe efficiencies were analyzed to test the hypothesis that the Fe efficiency trait is linked to antioxidative stress signaling via proper management of tissue Fe accumulation and transport, which in turn influences the regulation of heme and non heme containing enzymes involved in Fe uptake and ROS scavenging. Inefficient plants displayed higher oxidative stress and lower ferric reductase activity, whereas root and leaf catalase activity were nine-fold and three-fold higher, respectively. Efficient plants do not activate their antioxidant system because there is no formation of ROS under iron deficiency; while inefficient plants are not able to deal with ROS produced under iron deficiency because ascorbate peroxidase and superoxide dismutase are not activated because of the lack of iron as a cofactor, and of heme as a constituent of those enzymes. Superoxide dismutase and peroxidase isoenzymatic regulation may play a determinant role: 10 superoxide dismutase isoenzymes were observed in both cultivars, but iron superoxide dismutase activity was only detected in efficient plants; 15 peroxidase isoenzymes were observed in the roots and trifoliate leaves of efficient and inefficient cultivars and peroxidase activity levels were only increased in roots of efficient plants.
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PMID:Understanding the Role of the Antioxidant System and the Tetrapyrrole Cycle in Iron Deficiency Chlorosis. 3154 Feb 66