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73 results on '"Coskun D"'

1. In defence of the selective transport and role of silicon in plants

Author

Coskun, D, Deshmukh, R, Sonah, H, Menzies, JG, Reynolds, O, Ma, JF, Kronzucker, HJ, Bélanger, RR, Coskun, D, Deshmukh, R, Sonah, H, Menzies, JG, Reynolds, O, Ma, JF, Kronzucker, HJ, and Bélanger, RR

Abstract

With interest, we read the Letter by Exley & Guerriero (2019; in this issue of New Phytologist, pp. 511–513) ‘A reappraisal of biological silicification in plants?’ in response to our recent Tansley review on the biological roles of silicon (Si) (Coskun et al., 2019).

Published
2019

2. Membrane fluxes, bypass flows, and sodium stress in rice: the influence of silicon

Author

Flam-Shepherd, R, Huynh, WQ, Coskun, D, Hamam, AM, Britto, DT, Kronzucker, HJ, Flam-Shepherd, R, Huynh, WQ, Coskun, D, Hamam, AM, Britto, DT, and Kronzucker, HJ

Abstract

Provision of silicon (Si) to roots of rice (Oryza sativa L.) can alleviate salt stress by blocking apoplastic, transpirational bypass flow of Na+ from root to shoot. However, little is known about how Si affects Na+ fluxes across cell membranes. Here, we measured radiotracer fluxes of 24Na+, plasma membrane depolarization, tissue ion accumulation, and transpirational bypass flow, to examine the influence of Si on Na+ transport patterns in hydroponically grown, salt-sensitive (cv. IR29) and salt-tolerant (cv. Pokkali) rice. Si increased growth and lowered [Na+] in shoots of both cultivars, with minor effects in roots; neither root nor shoot [K+] were affected. In IR29, Si lowered shoot [Na+] via a large reduction in bypass flow, while in Pokkali, where bypass flow was small and not affected by Si, this was achieved mainly via a growth dilution of shoot Na+. Si had no effect on unidirectional 24Na+ fluxes (influx and efflux), or on Na+-stimulated plasma-membrane depolarization, in either IR29 or Pokkali. We conclude that, while Si can reduce Na+ translocation via bypass flow in some (but not all) rice cultivars, it does not affect unidirectional Na+ transport or Na+ cycling in roots, either across root cell membranes or within the bulk root apoplast.

Published
2018

3. The nitrogen-potassium intersection: membranes, metabolism, and mechanism

Author

Coskun, D, Britto, DT, Kronzucker, HJ, Coskun, D, Britto, DT, and Kronzucker, HJ

Abstract

Nitrogen (N) and potassium (K) are the two most abundantly acquired mineral elements by plants, and their acquisition pathways interact in complex ways. Here, we review pivotal interactions with respect to root acquisition, storage, translocation and metabolism, between the K+ ion and the two major N sources, ammonium (NH4+ ) and nitrate (NO3- ). The intersections between N and K physiology are explored at a number of organizational levels, from molecular-genetic processes, to compartmentation, to whole plant physiology, and discussed in the context of both N-K cooperation and antagonism. Nutritional regulation and optimization of plant growth, yield, metabolism and water-use efficiency are also discussed.

Published
2017

4. The Role of Silicon in Higher Plants under Salinity and Drought Stress

Author

Coskun, D, Britto, DT, Huynh, WQ, Kronzucker, HJ, Coskun, D, Britto, DT, Huynh, WQ, and Kronzucker, HJ

Abstract

Although deemed a "non-essential" mineral nutrient, silicon (Si) is clearly beneficial to plant growth and development, particularly under stress conditions, including salinity and drought. Here, we review recent research on the physiological, biochemical, and molecular mechanisms underlying Si-induced alleviation of osmotic and ionic stresses associated with salinity and drought. We distinguish between changes observed in the apoplast (i.e., suberization, lignification, and silicification of the extracellular matrix; transpirational bypass flow of solutes and water), and those of the symplast (i.e., transmembrane transport of solutes and water; gene expression; oxidative stress; metabolism), and discuss these features in the context of Si biogeochemistry and bioavailability in agricultural soils, evaluating the prospect of using Si fertilization to increase crop yield and stress tolerance under salinity and drought conditions.

Published
2016

5. K+ Efflux and Retention in Response to NaCl Stress Do Not Predict Salt Tolerance in Contrasting Genotypes of Rice (Oryza sativa L.)

Author

Zhang, J, Coskun, D, Britto, DT, Jean, Y-K, Kabir, I, Tolay, I, Torun, AA, Kronzucker, HJ, Zhang, J, Coskun, D, Britto, DT, Jean, Y-K, Kabir, I, Tolay, I, Torun, AA, and Kronzucker, HJ

Abstract

Sudden elevations in external sodium chloride (NaCl) accelerate potassium (K(+)) efflux across the plasma membrane of plant root cells. It has been proposed that the extent of this acceleration can predict salt tolerance among contrasting cultivars. However, this proposal has not been considered in the context of plant nutritional history, nor has it been explored in rice (Oryza sativa L.), which stands among the world's most important and salt-sensitive crop species. Using efflux analysis with (42)K, coupled with growth and tissue K(+) analyses, we examined the short- and long-term effects of NaCl exposure to plant performance within a nutritional matrix that significantly altered tissue-K(+) set points in three rice cultivars that differ in salt tolerance: IR29 (sensitive), IR72 (moderate), and Pokkali (tolerant). We show that total short-term K(+) release from roots in response to NaCl stress is small (no more than 26% over 45 min) in rice. Despite strong varietal differences, the extent of efflux is shown to be a poor predictor of plant performance on long-term NaCl stress. In fact, no measure of K(+) status was found to correlate with plant performance among cultivars either in the presence or absence of NaCl stress. By contrast, shoot Na(+) accumulation showed the strongest correlation (a negative one) with biomass, under long-term salinity. Pharmacological evidence suggests that NaCl-induced K(+) efflux is a result of membrane disintegrity, possibly as result of osmotic shock, and not due to ion-channel mediation. Taken together, we conclude that, in rice, K(+) status (including efflux) is a poor predictor of salt tolerance and overall plant performance and, instead, shoot Na(+) accumulation is the key factor in performance decline on NaCl stress.

Published
2013

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