Sugarbeet Biochemical Quality Changes During Factory Pile Storage. Part II. Non-sugars.

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1 April - June 200 I Biochemical Changes During Pile Storage 173 Sugarbeet Biochemical Quality Changes During Factory Pile Storage. Part II. Non-sugars. Susan S. Martin', Judy A. Narum 2, and Ken H. Chambers 3 I USDA, A RS, Crops Research Laboratory, J701 Center Avenue, Fort Collins CO 80526; 2((ormerly) Beet Sugar Development Foundation, 800 Grant St., Suite 300, Denver CO 80203; and 3Holly Sugar Corporation, Po. Box 9, Sugar Land, Texas ABSTRACT Processing sugarbeet for sucrose production begins with an aqueous extraction. Besides sucrose, the extract also contains other water soluble root chemicals, which are viewed as undesirable " impurities" by the processor. Many impurities are removed or greatly diminished during processing, but some of those that remain reduce sucrose recovery, resulting in a loss ofsugar to molasses. We investigated sugarbeet varietal differences in accumulation ofseveral important impurities at harvest and after pile storage at three locations: Sidney MT, Worland WY, and Hereford TX. At each location a group of locally adapted varieties was used. Paired root samples were prepared at harvest. One of each pair immediately was analyzed for sucrose by polarimetry, and a portion of each sucrose filtrate was frozen for subsequent anal)'sis by HPLC for sugars and quality components (Na, K, amino N, betaine). The second sample ofeach pair, in an air-permeable bag, was placed into the factory storage pile for 110 d at Sidney, 90 d at Worland, or 56 d at Hereford, then recovered and analyzed similarly to unstored samples. Data were anal)'zed separately for each location. Analyses of the sugar components (sucrose, glucose, fructose, and raffinose) have been reported previously. Component concentrations were expressed in g per 100 g sucrose (g/loos) as a relevant way to evaluate processing

2 174 Journal of Sugar Beet Research Vol 38 No 2 characteristics. Small but significant differences among cultivars for Na and K occurred at all three locations at harvest and at Sidney and Worland after storage. Sodium at harvest ranged from 0.49 to 0.65 g/ioos at Sidney, 0.16 to 0.40 at Worland, and 0.34 to 0.59 at Hereford. Ranges for potassium at harvest were 0.87 to 0.99 g/ IOOS at Sidney, 0.54 to 0.79 at Worland, and l.51 to 1.79 at Hereford. Across cultivars, increases in atharvest and post-storage concentrations (giloos) occurred at all locations for K and at Sidney and Hereford for Na. Cultivars differed in amino Nand betaine (gi100s) at harvest at Sidney and Worland, in amino N post-storage at Sidney, and in betaine poststorage at all three locations. Across cultivars, amino N concentration as g/ioos increased with storage at all locations. Across cultivars, total impurity values incorporating all determined quality components (2.5Na + 3.5K + 9amino N + glucose + fructose + raffinose + betaine) were greatest at Hereford (16.6 and 24.2 g/ioo S at harvest and after storage, respectively), least at Worland (6.0 and 9.9), and intermediate at Sidney (9.1 and 14.5) Add itional Key Words: Bela vulgaris L. ssp. vulgaris, sodium, potassium, amino N, betaine, glycinebetaine, quality, impurity value. Losses in sucrose and quality during storage of sugarbeet (Bela vulgaris L. ssp. vulgaris, Sugar Beet Group) (Lange et ai., 1999) are continui.ng concerns of sugarbeet growers and processors. Many factors contribute to such losses, but under storage conditions that minimize the effects of injury and disease, respiration and sugar transformations are important factors. Bugbee (1993) and Tungland et al. (1998) provide recent reviews of the literature on sucrose loss in storage, its causes, and methods for reducing losses. Vukov and Hangyal (1985) and Harvey and Dutton (1993) have reviewed root chemical quality and its relationship to storage and processing quality. Sugarbeet cultivars differ in the rate and degree to which they lose sucrose and recoverable sugar during storage (e.g., Wyse and Dexter, 1971). Several workers have pointed out the importance of respiration in storage losses, the variation in respiration found among cu ltivars (Wyse, 1973 ; Wyse et al., 1979; Akeson and Widner, 1981), and the pre-harvest and harvest factors that affect sugarbeet quality and subsequent storage

3 April - June 2001 Biochemical Changes During Pile Storage 175 and processing quality (e.g., Cole, 1977). Such studies often were limited in the number or types of cultivars included, frequently depending on breeding lines and employing special, limited or controlled storage conditions. Our objective was to evaluate, through use of sensitive and specific techniques for analysis of sugarbeet quality components and sugars, the biochemical changes that occurred during factory pile storage of commercial cultivars, grown and harvested by standard commercial practice. Only the nonsugars data are reported here; the sugar component data were reported in Part I of this paper (Martin et ai., 200 J). MATERIALS AND METHODS This experiment was conducted during the J campaign at Holly Sugar Corporation factories in Sidney, Montana; Worland, Wyom ing; and Hereford, Texas. At each location adifferent set of locally adapted commercial hybrids was grown (Table I); thus, data for each location were analyzed separately. The experimental procedures for growing, harvesting, pile storage, and analytical sampling were described in detail in Part I of this report (Martin et ai., 200 I). Five replicate sample pairs were analyzed for each cultivar. For analysis of qualityrelated chemical components at harvest or from pile-stored samples at the time of recovery, sucrose filtrate samples prepared as described in Part I were transported on dry ice to the USDA-ARS sugar beet laboratory in Fort Coilins, Colorado, where they were held at -20 C until further processing as described below. Samples were placed in the pile and removed from the pile, respectively, on October IllJanuary 29 at Sidney; October 12/ January 10 at Worland; and November 21 /January 16 at Hereford. Thus, pile storage time was 110 d at Sidney, 90 d at Worland, and 56 d at Hereford. Betaine was determined in the same HPLC runs used to analyze sugar components. These sample preparation and analytical methods have been described in detail elsewhere (Martin et ai., 2001). Sodium and potassium were determined by emission spectroscopy with a lithium internal standard and a.-amino nitrogen ("amino N") was measured by spectrophotometry after reaction with ninhydrin. Amino N is expressed as N in glutamic acid. For a comparative estimate of quality among locations, a "Total Impurity" (TI) value for each location at harvest and after storage was calculated by the following equation (after Hobbis and Batterman, 1975): TI = 2.5Na + 3.5K + 9AminoN + Glucose + Fructose + Raffinose + Betaine where all quantities were in gil 00 g sucrose. The coefficients applied to Na, K, and amino N account for the molecular mass of their salts; the

4 176 Journal of Sugar Beet Research Vol 38 No 2 Table 1. Experimental locations (1989), sugarbeet cultivars studied at each location, and length of factory pile storage. Pile Location Cultivar Company Storage -days- Sidney, Montana Beta 1996 Betaseed 110 KW 1745 KWS M 865 MaribolAmerican Crystal Monohikari Seedex MonoHyllOI Hilleshog (Novartis) MonoHy 1105 " Worland, Wyoming HH44 Holly 90 HH 50 MonoHyR2 Hilleshog ACH 164 American Crystal ACH 191 Hereford, Texas HH42 Holly 56 TX 18 Hilleshog other components were detennined and expressed directly in tenns of their molecular mass. Sugars concentrations used in these calculations were taken from Part I of this report (Martin et ai., 200 I). Data summary statistics and analyses of variance (anova) for each component at each location were calculated with SAS (SAS Institute, Inc., Cary NC). When the anova F-test was significant, means were separated by Duncan's multiple range test. RESllLTS AND DISCllSSION Sodium and Potassium. Sugarbeets at the three locations studied contained varied amounts of sodium (Na) and potassium (K) relative to the amounts of sucrose present (Table 2). Different cultivars were grown at each location; thus, direct statistical comparisons cannot be made. Nevertheless, it is clear that the group of cultivars as a whole at Sidney and Hereford accumulated more Na per unit of sucrose than did those at Worland, and the Hereford sugarbeets accumulated about twice as much K per unit of

5 April - June 2001 Biochemical Changes During Pile Storage 177 Table 2. Sodium and potassi um contents of sugarbeets at harvest and after storage in a factory pi Ie at Sidney MT (ll 0 d storage), Worland WY (90 d), or Hereford TX (56 d). A different group of locally adapted cultivars was grown at each location. --Sodium - --Potassium - At Post- At Post- Location Cultivar Harvest storage harvest storage gl loo g sucrose Sidney MT B at 0.47b 0.87 c 0.99 b KW a 0.52 b 0.99 b 1.01 ab M a 0.65 a 0.97 b 1.08 a Monohikari 0.49b 0.35 c 0.98 b 1.04 ab MH a 0.47 b 0.92 be 0.96 b MH a 0.39 c 1.10 a 1.11 a Mean ** * Worland WY ACH b 0.29 be 0.79 a 0.85 a ACH b 0.36 b 0.54 c 0.56 c HM-R c 0.26 c 0.70 b b HH c 0.16 d 0.67 b 0.65 b HH a 0.46 a 0.65 b 0.71 b Mean * Hereford TX HH a a 2.10 a TX b b 1.96 b Mean * ** *,** Statistically significant difference at P = 0.05 or 0.01, respectively, between at harvest values and post-storage values. twithin columns and within each location, means followed by a different letter are significantly different at the 0.05 level ofprobability (significant F-test; mean separation by Duncan's multiple range test). Where no letters appear, values did not differ signi ficantly according to the analysis of variance. sucrose as the Sidney or Worland beets. Potassium is an essential element for plants, involved in many aspects ofgrowth and metabolism, but sodium is nonessential for most plants and at high concentrations can be toxic (Schachtman and Liu, 1999). Draycott (1993) pointed out, however, that for best performance sugarbeet requires an adequate supply of both Na and K. Recognized as a highly salt tolerant crop (Maas and Hoffman, 1977), sugarbeet is known for its ability to accumulate elevated quantities

6 178 Journal of Sugar Beet Research Vol 38 No 2 ofna and K when high levels of these cations are present in soil (whether naturally or through fertilization) or in irrigation water. Sodium and potassium are highly soluble and are extracted in the diffusion process along with sucrose. Their presence in the diffusion juice is undesirable because they are highly melassigenic, preventing complete recovery of the sucrose present (Rorabaugh and NOIman, 1956; Carruthers et ai., 1962; Harvey and Dutton, 1993; Schiweck, 1998). Cultivars differed significantly for Na and K concentration at harvest at all locations, and post-storage at Sidney and Worland (Table 2). Significant difference between at harvest and post-storage values occurred for Na at Sidney and Hereford, and for K at all three locations (Table 2). In the analysis ofvariance the Entry X Storage interaction was not significant for Na or K at any location. Actual Na and K contents within the sugarbeet root are stable and do not change during storage (Tungland et ai., (998). However, the fact that the sucrose content decreases with storage inevitably means that Na or K concentration per unit sucrose will increase with storage, assum ing all other factors are unchanged. Changing beet hydration or altered Na or K extractability as a result of cell wall changes during storage also can affect sodium and potassium values. From a processing standpoint, however, expressing Na and K values per unit sucrose present is most useful because this reflects the composition ofthe diffusion juice and all subsequent processing chemistry requirements. Monohikari at harvest contained significantly less Na per unit ofsucrose than did any other cultivar at Sidney (Table 2), and after storage Na remained lowest in Monohikari. Potassium content of the Sidney cultivars averaged about twice their Na level, with Beta 1996 significantly lower than all others at harvest and remaining among a larger low K group after storage. After storage, Na per unit sucrose decreased significantly, contrary to K which increased, and contrary to results for Na at the other two locations (Table 2). At Worland Na levels did not change significantly during storage, whereas K levels increased slightly but significantly with storage (Table 2). HH 44 contained the least Na per unit sucrose, and ACH 191 the least potassium. Both Na and K differed between at harvest and post-storage samples at Hereford, with TX 18 consistently lower in both elements. The high levels ofna and K per unit sucrose at Hereford could be expected to contribute to low juice purity and to problems in sucrose recovery. Both sodium and potassium are abundant in soils and irrigation water of the western U.S. and sugarbeet seldom requires additional for maximal sucrose production (Carter, 1986a, 1986b). Carter (1986a) reported that uptake ofboth elements by sugarbeet is affected by nitrogen

7 April - June 2001 Biochemical Changes During Pile Storage 179 uptake, plant growth rate, Na and K availability, genotype, and year. Our study gave no information on a possible Genotype X Year interaction; thus, the data can be interpreted only with respect to the other factors. The Na and K concentrations of sugarbeet at Hereford likely are related to correspondingly high concentrations ofamino N. The significant and high correlation between potassium and amino N at harvest (r = 0.96, computed on cultivar means for each location at harvest) may support a relationship between N uptake and K uptake, but the low correlation between sodium and amino N concentrations (r = 0.26) does not. Smith and Martin (1989) found that two cycles of selection for low amino N significantly lowered K content ofthe resulting population in comparison with the original parental population, but significantly increased Na. Similarly, two cycles of selection for low K led to significantly lower amino N but no change in Na content ofthe selected population compared with the parental population. Thus, K uptake appe,!rs closely linked to nitrogen uptake and growth, in which K plays essential roles, whereas Na uptake appears less closely linked with N uptake and presumably depends largely on Na availability in the soil and applied water. The ability of plants to selectively accumulate potassium over sodium appears to be a genetically controlled process that is just beginning to be elucidated (Schachtman and Liu, 1999). Nitrogenous components: Amino N and Betaine. Amino N concentrations per unit sucrose were low at Worland, slightly greater at Sidney, and high at Hereford (Table 3). In all cases post-storage values were slightly but significantly greater, probably primarily because ofdecreased sucrose after storage. Cultivar differences were small, though significant in a few instances (Table 3). Betaine levels were highest at Hereford, mirroring the high amino N results. Together, the amount of nitrogen incorporated into both amino N and betaine in Hereford beets at harvest leads us to conclude that there was prolonged uptake of nitrogen through the growing season. Amino N at harvest differed among entries at Sidney and Worland, but not between the two cultivars studied at Hereford (Table 3). Cultivar differences after storage occurred only at Worland. Nitrogen is the nutrient having the greatest effect on sugarbeet yield and quality, and nitrogen-containing substances comprise the largest portion ofextract non-sugars. Amino acids and amides such as glutamine typically comprise 25 to 50% of total N in sugarbeet, second in quantity on Iy to proteins (Bohn, 1998). A Ithough proteins are largely denatured and removed in processing, amino acids are largely unaffected and pass through to molasses (Schiweck et ai., 1993). Amino acids are considered

8 180 Journal of Sugar Beet Research Vol 38 No 2 Table 3. Amino N and betaine contents ofsugarbeets at harvest and after storage in a factory pile at Sidney MT (110 d storage), Worland WY (90 d), or Hereford TX (56 d). A different group of locally adapted cultivars was grown at each location. - AminoN Betaine - At Post- At Post- Location Cultivar harvest storage harvest storage g! I 00 g sucrose Sidney MT BI b b 1.60 ab KW b b 1.39 b M ab c 1.68 a Monohikari 0.23 a a 1.85 a MH b c 1.25 c MH a a 1.55 b Mean ** Worland WY ACH a 0.14 b 1.35 ab 1.10 a ACH c 0.10 c 1.06 c 0.90 b HM-R b 0.16 b 1.41 a 1.07 a HH b 0.11 c 1.28 b 1.08 a HH a 0.20 a 1.37 ab 1.15 a Mean * ** Hereford TX HH b TX a Mean * *,** Statistically significant difference at P = 0.05 or 0.0 I, respectively, between at harvest values and post-storage values. twithin columns and within each location, means followed by a different letter are significantly different at the 0.05 level ofprobability (significant F-test; mean separation by Duncan 's multiple range test). Where no letters appear, values did not differ significantly according to the analysis of variance. moderately melassigenic (Schiweck, 1998). Numerous studies have shown that accumulation of excessive nitrogenous compounds in the root at

9 April - June 200 I Biochemical Changes During Pile Storage 181 harvest is associated with excessive nitrogen availability (Draycott, 1993; Harvey and Dutton, 1993). Draycott (1993) calculated that a sugarbeet root amino N level of 0.35 glloo g sugar would reduce net crop value approximately 14% relative to an optimum amino N level of about 0.15 giloos. Betaine concentration differed with time only at Worland, where it appeared to decrease with storage (Table 3). This is contrary to most observations, where betaine is considered to maintain its level or increase somewhat with storage (Schiweck et ai., 1993). Cultivars differed for betaine at harvest at Sidney and Worland, and after storage at all locations. The betaine content ofsugarbeet at Hereford (Table 3) was notably high, more than double that found in beets ofother cultivars grown at the other two locations. Glycinebetaine (N,N,N-trimethylglycine) in the U.S. usually is called simply " betaine." As in other plants that accumulate betaine, in sugarbeet it is involved in sttess tolerance, particularly to salt or drought (osmotic stress) (Storey and Wyn Jones, 1977; Leigh et ai., 1981; Hanson and Wyse, 1982) and probably also to cold (Kishitani et ai., 1994). For these reasons sugarbeet usually contains significant amounts of betaine at harvest; Beiss (1994) estimated betaine contained 14-20% of the total nitrogen in beet, or 25-32% ofthe soluble nitrogen. Betaine is synthesized in leaves and transported to roots (Hanson et ai., 1985; Beiss, 1994). A stable compound, betaine mostly passes unchanged through sugarbeet processing (Schiweck et ai., 1993; Bohn, 1998). Thus, aided by its concentration and stability during processing, betaine is an important melassigenic substance. Sugarbeet and other members of the Chenopodiaceae accumu late greater amounts ofbetaine than do most other plants, which use the amino acid proline, sugar alcohols, or other compounds for osmotic adjustment related to stress tolerance (Somero et ai., 1992). Betaine levels in beets at Sidney and Worland were in the expected range for beets at harvest (Beiss, 1994; Bohn, 1998), but levels at Hereford were high and would be expected to contribute to processing difficulties for these beets. The high betaine concentrations at Hereford might be a response to soil salinity or drought. We did not control or test salt, drought, or any other stress factor that might have been related to betaine accumulation. Our data and those of others (e.g., Hanson and Wyse, 1982) show genetic variability for betaine accumulation, and Smith and Martin (1989) found selection for low amino N also lowered betaine levels. However, evaluation of the feasibility of lowering betaine accumulation via plant breeding or molecular engineering (McCue and Hanson, 1992; Hanson et ai., 1994) would require determination of potentially negative effects on sugarbeet stress tolerance. Furthelmore,

10 182 Jouma! of Sugar Beet Research Vol 38 No 2 because sugarbeet is such an excellent accumulator of betaine, some sugarbeet processors recover it from molasses as an economically valuable byproduct. Purity. The purity of a sugarbeet juice is defined as the fraction of the soluble solids that is sucrose. Purity is a useful concept that allows estimation ofthe amount ofsucrose that can be recovered from the solution (e.g., Dexter et ai, 1967). The converse of the defmition of purity is that all the soluble extract components that are not sucrose are considered "impurities." Carruthers and Oldfield (1961) defined an "impurity value" and related it to factory purity measurements. Carruthers, Oldfield, and Teague (1962) related the purity ofa clari fied thin juice to determinations ofna, K, and amino N in a clarified sucrose filtrate, obtaining the equation: Purity = 97 - O.8(2.5K + 3.5Na +1OAmN) where K, Na, and amino N were expressed in glloo g sucrose. Subsequently, many others investigated purity prediction and the prediction of sugar loss to molasses, with numerous models being published, most based on Na, K, and amino N. Excellent recent summaries and discussion of quality prediction have been provided by Harvey and Dutton (1993) and Burba (1998). No single equation can predict a factory's actual purity as it varies throughout the campaign with the impurities in the sugarbeets entering the factory, which in tum are affected by genetic, agronomic, and environmental factors, as well as by conditions ofharvest and storage (Last and Draycott, 1977; Burba 1998). Nevertheless, calculations of impurity values, purity, recoverable sugar, or sugar loss to molasses provide useful estimates of the processing quality of sugarbeet (Burba, 1998). The various "impurities," i.e., all soluble extract components other than sucrose, have differing degrees of negative influence on the ability to recover the sucrose present in the solution (Rorabaugh and Norman, 1956; Carruthers et al., 1962; Harvey and Dutton, 1993 ; Schiweck, 1998). Sodium, potassium, amino N, and betaine are among the most me1assigenic compounds in aqueous sugarbeet extracts that are not removed appreciably in processing for sucrose recovery. Typically, sodium and potassium salts, amino N compounds, and betaine together represent about 80% of total non-sugars. Because they are relatively easy to measure and adaptable to automated analyses, measurements of Na, K, and amino N often have been used in mathematical models designed for purity prediction. Betaine is included in some determinations of "impurity values" (e.g., Carruthers and Oldfield, 1961), but because it is difficult to detelmine quantitatively and its analytical methods are not

11 April - June 200 I Biochemical Changes During Pile Storage 183 suited to rapid, routine analyses, it is omitted in most purity predictive equations (Burba, 1998). Other components are recommended for inclusion in impurity index calculations when beets have been stored for significant periods or are in poor condition for any reason. For a comparison of beet quality among locations, we calculated an " impurity value" (IV) based only on Na, K, and amino N, and "Total ImplU"ities" based on those components plus glucose, fructose, raffinose, and betaine (Table 3; see Materials and Methods). At harvest IVs were lowest at Worland, highest at Hereford, and intermediate at Sidney (Figure 1), with g/100 9 Sucrose o ~~-=~----~~-=~----~~~~ o 110d o god o 56d Sidney Worland Hereford :,:, Invert I11III Raffinose _Betaine, ;,~.. Imp. Val. I:l2lTotallmpurities Figure l. Impurities at harvest or after storage at Sidney MT (110 d storage), Worland WY (90 d), or Hereford TX (56 d). Different sets of locally adapted varieties were used at each location. Data (gil 00 g HPLCdetermined sucrose) are "invert sugar" (glucose + fructose), raffinose (including kestoses, if present), betaine, " Impurity Value" (calculated as 2.5Na + 3.5K +9AminoN), and "Total Impurities," the total of all the listed components. the same relative order after storage. Because each component of the total impurities (TI) followed essentially the same pattern, TI values also were lowest at Worland (6.0 and 9.9 gil OOS at harvest and after storage, respectively), highest at Hereford (J 6.6 and 24.2), and intermediate at Sidney (9.1 and 14.5; Figure I). Both IV and TI at Hereford at harvest were greater than comparable values at Sidney or Worland after 11 Od or 90d storage, respectively. Because of the many variables that affect

12 184 Journal of Sugar Beet Research Vol 38 No 2 determination of recoverable sugar or sugar loss to molasses (Burba, 1998), we have not extended these calculations. Nevertheless, one can conclude that processing quality after factory pile storage typically is diminished, sometimes substantially. Perhaps future sugarbeet genotypes wi II make use of the existing genetic variation to decrease at-harvest concentrations of several of these quality determining compounds (Smith and Martin, 1989), or of molecular engineering to inhibit or alter reactions that lead to their accumulation during pile storage. ACKNOWLEDGMENTS We thank agricultural and tare lab personnel of Holly Sugar Corporation at Sidney MT, Worland WY, and Hereford TX for their cooperation and assistance with this research, and Christina G. Andre for careful technical assistance with the analyses at Fort Collins. LITERATURE CITED Akeson, W. R., and J. N. Widner Di fferences among sugarbeet cultivars in sucrose Joss during storage. 1. Amer. Soc. Sugar Beet Techno!. 21 (I): Beiss, Zum Betainegehalt der Zuckerriibe. Betaine in sugar beets. Zuckerind. 119: Bohn, K Nitrogenous compounds. Section , pages In P. W. van der Poel, H. Schiweck, and T. K. Schwartz (eds.). Sugar Technology. Verlag Dr. Albert Bartens, Berlin pp. Bugbee, W. M Storage. p In D. A. Cooke and R. K. Scott (eds.). The Sugar Beet Crop. Chapman and Hall, London. 675 pp. Burba, M Formulas to calculate sugar i.n molasses, nonsugar content in thick juice and resulting ph value (alkalinity) ofthick juice from beet analysis. Section 3.2, pages In P. W. van der Poel, H. Schiweck, and T. K. Schwartz (eds.). Sugar Technology. Verlag Dr. Albert Bartens, Berlin pp. Carruthers, A., and 1. F. T. Oldfield Methods for the assessment of beet quality. Int. Sugar J. 63: 72-64, ,

13 April - June 200 I Biochemical Changes During Pile Storage 185 Carruthers, A., J. F. T. Oldfield, and H. 1. Teague Assessment of beet quality. 15 th Ann. Tech. Conf., British Sugar Corp. Carter, J. N. 1986a. Potassium and sodium uptake by sugarbeets as affected by nitrogen fertilization rate, location, and year. J. Am. Soc. Sugar Beet Techno!. 23: Carter, 1. N. 1986b. Potassium and sodium uptake effects on sucrose concentration and quality of sugar beet roots. 1. Am. Soc. Sugar Beet Techno!. 23: Cole, D. F Effect of cultivar and mechanical damage on respiration and storability of sugarbeet roots. J. Am. Soc. Sugar Beet Techno!. 19: Dexter, S. T., M. G. Frakes, and F. W. Snyder A rapid and practical method ofdetermining extractable white sugar as may be applied to the evaluation of agronomic practices and grower deliveries in the sugar beet industry. 1. Am. Soc. Sugar Beet Techno!. 14: Draycott, A. P Nutrition. p In D. A. Cooke and R. K. Scott (eds.). The Sugar Beet Crop. Chapman and Hall, London. 675 pp. Hanson, A. D., A. M. May, R. Grumet, J. Bode, G. C. Jamieson, and D. Rhodes Betaine synthesis in chenopods: localization in chloroplasts. Proc. Nat!. Acad. Sci. USA 82: Hanson, A. D., B. Rathinasabapathi, 1. Rivoal, M. Burnet, M. Dillon, and D. A. Gage Osmoprotective compounds in the Plumbaginaceae: a natural experiment in metabolic engineering of stress tolerance. Proc. Nat!. Acad. Sci. USA 91: Hanson, A. D., and R. E. Wyse Biosynthesis, translocation, and accumulation of betaine in sugar beet and its progenitors in relation to salinity. Plant Physio!. 70: Harvey, C. w., and J. V. Dutton Root quality and processing. p In D. A. Cooke and R. K. Scott (eds.). The Sugar Beet Crop. Chapman and Hall, London. 675 pp.

14 186 Journal of Sugar Beet Research Vol 38 No 2 Hobbis, 1., and L. Batterman Storageability characteristics of sugarbeet varieties. Sugar J. 37(12): Kishitani, S., K. Watanabe, S. Yasuda, K. Arakawa, and T. Takabe Accumulation of glycine betaine during cold acclimation and freezing tolerance in leaves of winter and spring barley plants. Plant Cell Environ. 17: Lange, w., W. A. Brandenburg, and T. S. M. De Bock Taxonomy and cultonomy of beet (Beta vulgaris L.). Bot. J. Linn. Soc. 130: Last, P. 1., and A. P. Draycott Relationships between clarified beet juice purity and easily- measured impurities. Int. Sugar J. 79: Leigh, R. A., N. Ahmad, and R. G. Wyn Jones Assessment of glycinebetaine and proline compartmentation by analysis of isolated beet vacuoles. Planta 153: Maas, E. Y., and G. J. Hoffman Crop salt tolerance-current assessment. J.!rrig. Drainage Div., ASCE 103: Martin, S. S., J. A. Narum, and K. H. Chambers Sugarbeet biochemical quality changes during factory pile storage. Part I. Sugars. J. Sugar Beet Res. 38( I): McCue, K. F, and A. D. Hanson Salt-inducible betaine aldehyde dehydrogenase from sugar beet: cdna cloning and expression. Plant Mol. BioI. 18: I-II. Rorabaugh, G., and L. W. Norman The effect ofvarious impurities on the crystallization ofsucrose. J. Am. Soc. Sugar Beet Technol. 9: Schachtman, D., and W. Liu Molecular pieces to the puzzle of the interaction between potassium and sodium uptake in plants. Trends PI. Sci. 4(7):

15 April - June 200 I Biochemical Changes During Pile Storage 187 Schiweck, H Influence of individual nonsugars on molasses fonnation. Section , pages In P. W. van der Poel, H. Schiweck, and T. K. Schwartz (eds.). Sugar Technology. Verlag Dr. Albert Bartens, Berlin. ILL8 pp. Schiweck, H., C. Jeanteur-DeBeukelaer, and M. Vogel Das Verhalten der stickstofthaltigen Nichtzuckerstoffe von RUben wahrend des Fabrikationsprozesses. The behavior of nitrogen containing nonsugar substances ofbeet during the sugar recovery process. Zuckerind. L18: Smith, G. A., and S. S. Martin Effect of selection for sugarbeet purity components on quality and sucrose extractions. Crop Sci. 29: Somero, G. N., C. B. Osmond, and C. L. Bolis. L992. Water and Life: Comparative Analysis of Water Relationships at the Organismic, Cellular, and Molecular Levels. Springer-Verlag, New York. 371 pp. Storey, R., and R. G. Wyn Jones Quaternary ammonium compounds in plants in relation to salt resistance. Phytochemistry 16: TungJand, B. c., R. E. Watkins, and P.-v. Schmidt Sugarbeet storage. Section 5.4, pages in P. W. van der Poel, H. Schiweck, and T. K. Schwartz (eds.). Sugar Technology. Verlag Dr. Albert Bartens, Berl in pp. Vukov, K., and K. Hangyal Sugar beet storage. Sugar Techno!' Rev. 12: Wyse, R. E General postharvest physiology ofthe sugarbeet root. in Postharvest Losses of Sucrose in Sugarbeet. Proceedings of BSDF Conference, Monterey, California. Beet Sugar Development Foundation, Denver.

16 188 Journal of Sugar Beet Research Vol 38 No 2 Wyse, R. E., and S. T. Dexter Source of recoverable sugar losses in several sugarbeet varieties during storage. J. Am. Soc. Sugar Beet Techno\. 16: Wyse, R. E., J. C. Theurer, and D. L. Doney Genetic variability in post-harvest respiration rates of sugarbeet roots. Crop Sci. 18: