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application of phosphate (PO 4 ) was recently reported to increase leaf P concentrations and improve fruit yield of ‘Thompson Seedless’ grapevines ( Saleh et al., 2007 ). Spraying the foliage of grapevines with P may be an effective method to boost vine P

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not shown a relationship with shoot size. Because high NO 3 – fertilizers typically contain little or no phosphate, we hypothesized that it is a low phosphorus (P) stress brought on by using these fertilizers that accounts for suppression of shoot

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were custom blends of the following individual technical grade salts: calcium nitrate tetrahydrate [Ca(NO 3 ) 2 ·4H 2 O], potassium nitrate (KNO 3 ), monopotassium phosphate (KH 2 PO 4 ), potassium sulfate (K 2 SO 4 ), magnesium sulfate heptahydrate

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Abbreviations: NADP, nicotinamide adenine dinucleotide phosphate; ppp, pentose phosphate pathway; TU, thiouria. A contribution of the Georgia Agricultural Experiment Station, College Station, Athens. This research was supported by state and Hatch

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., 2006 ; Lingle and Dunlap, 1987 ; Schaffer et al., 1987 ; Winter and Huber, 2000 ). It was reported that both acid invertase (EC 3.2.1.26) and sucrose phosphate synthase (EC 2.4.1.14) are determinants of sucrose accumulation in melon fruit. However

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Abstract

Although premium wine grapes (Vitis vinifera L.) are planted in soils of low P availability, there is little knowledge of P requirements and of the appropriate methods of P analysis in grapevines. Therefore, acetic acid extractable P was investigated as a method for determining grapevine P status. Analysis of absorption spectra established that absorbance peaks at 710 or 882 nm of the phosphomolybdate complex formed in acetic acid extracts of grapevine tissues can be used for analysis of P status. Acetic acid-extractable P was independent of sample size and extraction time and was linearly related (r 2 = 0.96) to total P in four premium wine grape varieties. Lamina indicated whole plant P status better than petioles, since extractable P accumulated more in lamina than in petioles. Total and extractable P of basal lamina decreased significantly after anthesis, which diminished the differences between P-sufficient and P-deficient vines. Therefore, the best time to assess vine P status using leaves is at anthesis. When P fertilizer was applied, lamina-extractable P was positively correlated with berry weight, yield, and pruning weight in Chenin blanc vines growing under P-deficient conditions. The results indicate that acetic acid extractable P in lamina sampled at anthesis is a sensitive measure of grapevine P status.

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+ ), phosphate (PO 4 3− ), potassium (K), calcium (Ca), magnesium (Mg), and sulfate (SO 4 2− ). There were six replications per mulch depth arranged on a single bench in a completely randomized design. Samples were collected daily for nine days, excluding

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Phosphate deficiency is wide spread in the nature. The deficiency results in several morphological and biochemical changes in plants. Some of these changes have been shown to involve altered gene expression. We have isolated two full--length cDNAs (AtPT1 and AtPT2), showing significant amino acid sequence similarity with the high-affinity phosphate transporters of yeast, Neurospora and the mycorrhizal fungi Glomus versiforme, from a phosphate-starved Arabidopsis root library. The transcripts of both genes are highly induced under Pi starvation and they are expressed in roots. Using Arabidopsis cDNAs as probes, we have isolated several tomato root cDNA clones representing the two different genes. The expression characteristics of the tomato isoforms of the putative high affinity phosphate transporter genes will be discussed. The northern blots of RNA isolated from phosphate-deficient and phosphate-sufficient roots of tomato indicated that both genes are strongly induced in response to Pi starvation in roots. Furthermore, by the method of differential display of mRNA, we have cloned and characterized a full-length cDNA representing a Pi starvation induced gene (TPSI1) from tomato. The gene is expressed as a specific response to Pi starvation in roots and leaves. The TPSI1 is an intron-less gene represented by a single copy in the tomato genome. The structure, expression, and functional significance of these genes will be discussed. This research has been supported, in part, by USDA grant 94-37100-0834 to KGR.

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interactions on the growth and marketability of anthurium; thus, the present study had the objective of determining the response of container-grown plants to varying proportions of anions [nitrate (NO 3 − ), phosphate (H 2 PO 4 − ), and sulphate (SO 4 2− )] in

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as an absorbent. Although some commercial growers are using this material as a root medium component, it is not expected to sorb PO 4 -P because it lacks charged sorption sites. Phosphate retention properties of clays after calcining are generally

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