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Takaya Moriguchi and Roger J. Romani

A strong association is implicit between mitochondrial function and the energy demands of cells responding to stress. Yet, the dynamics of this organelle-cellular dependency have been difficult to resolve. This study examines a new diagnostic parameter namely, mitochondrial maintenance and self-restoration as exhibited by the course of respiratory functions (states 3 and 4 respiratory rates, respiratory control) of mitochoudria extracted during and after exposure of intact `Hass' avocado (Persea americana) fruit to different stress atmospheres: anoxia (100% N2) or high (25% and 75%) CO2 for varying durations. Comparisons are made with direct exposure of the mitochondria themselves to similar atmospheres. In general, exposure of the fruit to CO2 rich atmospheres enhanced the capacity of their mitochondria to restore energy-linked functions whereas anoxia caused irreparable damage. The physiological (climacteric) state of the fruit also affected the stress capacity of the mitochondria contained therein, anaerobiosis being more harmful to mitochondria in riper fruit. In contrast to their effects in vivo, in vitro anoxia appeared to sustain mitochondrial energy-linked functions, whereas high CO2 was clearly harmful. These and other observations are discussed in the context of mitochondrial self-restoration or homeostasis and its relevance to postharvest stress-atmosphere storage for purposes such as pathogen suppression or insect control.

Open access

Chi M. Do, Kate L. Delaporte, Vinay Pagay and Carolyn J. Schultz

potassium homeostasis in the cytoplasm is vital to avoid sodium toxicity and maintain cells with normal metabolism and functioning ( Shabala and Pottosin, 2014 ). In this study, the higher K + content in leaves compared with roots could be due to a

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Joseph J. King and Dennis P. Stimart

In an attempt to analyze genetically the interaction of endogenous auxin concentration and adventitious root formation, an EMS mutagenized M2 population of Arabidopsis thaliana was screened for mutants with altered abilities to form adventitious roots. A selected recessive nuclear mutant, rooty (rty), is characterized by extreme proliferation of roots, inhibition of shoot development and other morphological alterations suggestive of auxin or ethylene effects. The rty phenotype occurs in wild type seedlings grown on auxin containing medium and relatively normal growth is stimulated in rty seedlings growing on cytokinin containing medium. Analysis by GC-MS found that endogenous IAA concentrations in rty are 2 to 17 times higher than in wild type depending on tissue type and IAA form. Dose response experiments with IAA and NAA indicated that rty does not express increased sensitivity to auxin. These data suggest that the rty phenotype is due to elevated endogenous auxin. A genetic map location for rty and possible roles for the wild type RTY gene product in regulating auxin concentration will be presented.

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Bruce W. Wood

micronutrient homeostasis (i.e., processes ensuring that the various endogenous environments of cells is such that these metals are maintained within a non-toxic physiological range) during the post-budbreak canopy expansion growth phase of pecan. Either

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Ying Qu, Xue Bai, Yajun Zhu, Rui Qi, Geng Tian, Yang Wang, Yonghua Li and Kaiming Zhang

, enzyme activities, and AsA-GSH-controlled redox homeostasis In B. semperflorens , the activities of antioxidant enzymes, including SOD, CAT, APX, MDHAR, DHAR, and GR, were unaffected by DMTU treatment, while they were increased under LT conditions ( Fig

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Misael O. Vega-García, Greici López-Espinoza, Jeanett Chávez Ontiveros, José J. Caro-Corrales, Francisco Delgado Vargas and José A. López-Valenzuela

a new redox homeostasis under the stress condition ( Foyer and Noctor, 2005 ). Proteomic studies have identified several proteins associated with plant tissue responses at low temperature; they are involved in several processes, including signal

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Longxing Hu, Tao Hu, Xunzhong Zhang, Huancheng Pang and Jinmin Fu

of plant salt tolerance through its role in ion homeostasis and Na + /K + discrimination under salinity conditions ( Hamdia and Shaddad, 2010 ). It has been shown that a low concentration of exogenous GB is very efficient in reducing the K + loss in

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Juan O. Quijia Pillajo, Laura J. Chapin and Michelle L. Jones

real-time PCR during leaf and flower development in Petunia hybrida BMC Plant Biol. 10 1 11 Miller, G. Suzuki, N. Ciftci-Yilmaz, S. Mittler, R. 2010 Reactive oxygen species homeostasis and signalling during drought and salinity stresses Plant Cell

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Ao Liu, Jibiao Fan, Margaret Mukami Gitau, Liang Chen and Jinmin Fu

stress. Overall, NO has the positive effect of maintaining ion homeostasis in bermudagrass subjected to high salinity. However, why K and Ca content showed same changing trends when treated with SNP or PTIO plus L-NAME under normal situation remains

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Thomas E. Marler and Nirmala Dongol

The profile of nonstructural carbohydrates (NSC) was quantified to determine sugar and starch relationships of megagametophyte tissue during Cycas micronesica K.D. Hill seed ontogeny. Field work occurred in northern Guam where megastrobili were marked and dated as they emerged from stem apices of plants in a natural population. Seeds were harvested beginning 6 months after megastrobili emergence and continuing until 28 months, and gametophyte tissue was separated from the remainder of each seed. Carbohydrates within lyophilized gametophyte tissue were quantified by high-pressure liquid chromatography. The levels of glucose and fructose declined from a high at 6 months to a homeostasis at 11 months, and the levels of sucrose similarly declined from 6 months to a homeostasis at ≈14 months. Starch content exceeded sugar content and increased from 6 months to reach a homeostasis at ≈18 months. Maltose was not detected in any sample. Stoichiometric quotients changed dramatically until ≈14 months, when they became fairly stable until 28 months. Starch concentration was ≈5-fold greater than sugar concentration at 6 months, and increased to ≈15-fold greater than sugar concentration by 28 months. Total NSC in mature megagametophytes was almost 70% on a dry weight basis. Our results are in agreement with the biological function of this haploid tissue, as copious carbohydrate resources are readily available to support embryo and seedling growth.