Berry Fresh Weight Research Articles

Mineral sinks within ripening grape berries ( Vitis vinifera L.)

Trends in the accumulation of mineral elements into the grape berry components give information about vascular flow into the berry. Shiraz berries were dissected into receptacle, skin, pulp, brush and seeds and the accumulation of 10 mineral elements into these components was followed through development. The elements were separated into two categories according to their accumulation pattern into the berry. The first group of elements continued to accumulate throughout berry growth and ripening, and was comprised of phloem-mobile potassium, phosphorus, sulphur, magnesium, boron, iron and copper. The second group of elements accumulated mostly prior to veraison, and included the xylem-mobile minerals calcium, manganese and zinc. These results indicate that the xylem contribution to berry growth diminished after veraison. Berry fresh weight, dry weight, as well as berry sugar content, were all highly correlated with berry potassium content. While the pulp and skin were the strongest sinks for potassium and boron, seeds were the strongest sinks for calcium, phosphorus, sulphur, manganese and zinc. With the exception of calcium and manganese, seeds ceased to accumulate most elements during late ripening. The berry receptacle and brush did not accumulate any of the elements to levels above those of the other berry components at any stage of development. Therefore, they did not act as sinks for xylem- or phloem-mobile elements as vascular flow to the pulp and skin slowed.

Combining Plant Growth with Nutrient Content Measurements as a Method to Compare Nutrient Use by Different Raspberry Cultivars

ABSTRACT Monthly above-ground destructive sampling and partitioning of the plant into distinct component parts for growth and nutrient element (N, P, K, Ca, Mg, Na, B, Cu, Zn, Fe and Mn) analyses were used to compare elemental compositions in two red raspberry (Rubus idaeus L.) cultivars (‘Willamette’ and ‘Haida’) grown in a uniformly managed field plot. Quantitative measurements showed that the two cultivars had different growth patterns. ‘Haida’ yielded greater fresh berry weight and dry matter content than ‘Willamette’ on a per floricane basis, but, because of fewer ‘Haida’ than ‘Willamette’ floricanes in the plot after standard commercial pruning practices, fresh berry yield was similar for both cultivars on a unit area basis. ‘Haida’ berries ripened slightly earlier than ‘Willamette’. Stem, lateral and leaf growth differed between the two cultivars. Although only whole above-ground accumulation (kg ha-1) of one (Ca) of the ten elements measured was different in the two cultivars, the amounts and patterns of all nutrients in the various plant components of floricanes and primocanes differed in significant ways. In some cases, element concentrations in a specific plant component differed between cultivars while dry matter accumulation differed in the opposite way resulting in the same total accumulation in the cane involved. In other cases, there was greater accumulation in one cane type (primocane vs. floricane) than the other such that there was similar accumulation of that element in the whole plant. For Ca, accumulation in primocanes was greater for ‘Willamette’ than ‘Haida’ whereas there was no difference of accumulation in floricanes which resulted in greater accumulation of Ca in the whole above-ground plant in ‘Willamette’. Maximum accumulation of the elements in floricanes occurred generally earlier in the growing season (July to September) than in primocanes (September to October), and these maxima were frequently at different times for the two cultivars, making comparisons of nutrient compositions in the two cultivars complex. Detailed sampling periodically over the growing season in combination with element analysis of these raspberry plant components as done in this study provided a better basis for comparing nutrients in raspberry cultivars than examining element concentrations of a specific plant component (e.g., leaves) sampled once during the growing season because patterns of nutrients over time in the cultivars differed.

Determination of major anthocyanin pigments in Hellenic native grape varieties ( Vitis vinifera sp.): association with antiradical activity

In order to investigate the anthocyanin content and ascertain whether anthocyanins account for antioxidant activity in grape berry extracts, six prevalent anthocyanins were determined in 13 Hellenic native and four of the so-called “international” varieties widely cultivated in Greece. Anthocyanin content varied from 85.7 to 1914.0 mg kg −1 fresh berry weight, the mean being 731.7 mg kg −1. Assessment of the antiradical activity of extracts using the stable 2,2-diphenyl- β-picrylhydrazyl radical revealed a low and statistically insignificant correlation ( r 2=0.0724, P>0.05) with total anthocyanin content, suggesting that other constituents are likely to exert strong antioxidant effects in grapes.

Intrinsic change of physical and chemical properties of sea buckthorn (Hippophae rhamnoides) and implications for berry maturity and quality

SummaryBerries of seven elite sea buckthorn (Hippophae rhamnoides L.) genotypes of different origins were evaluated for changes in physical and chemical properties during two years with substantial climatic differences. All genotypes shared similar dynamic trends in characters such as berry fresh weight, colour, softness, vitamin C and titratable acidity. Colours changed from green to yellowish green and then to their appropriate fully ripe colours. The fully ripe colour generally signalled the cessation of rapid expansion of berry fresh weight which, in turn, signalled an increased rate of softening. The increase in berry fresh weight correlated strongly and significantly with decline in concentrations of vitamin C and titratable acidity. However, considerable differences existed for glucose and fructose in terms of origins. Genotype Chi (Chinese origin, subsp. sinensis) showed a steady and pronounced accumulation in concentrations of both glucose and fructose. Glucose was the major sugar component detected in genotypes of subsp. rhamnoides, but this sugar showed only limited accumulation up to late August and scarcely altered or even declined during the remaining time. A hybrid F×C (Finnish origin × Chinese origin) displayed similar concentrations of glucose to genotype Chi, but its fructose concentrations were similar to subsp. rhamnoides. This may suggest that the gene(s) for high glucose is/are dominant, whereas those for high fructose are recessive. Climatic conditions did not affect dynamic rhythm greatly, but influenced the magnitude of some traits. The strong ranking correlation for dates of full colours attained during the two years among genotypes indicated that colour is a stable indicator of berry maturity. The coincidence of berry colour, cessation of rapid berry growth, mass expansion, and sugar/acid ratio provides a reliable prediction of harvesting time.

An ethanol spray at veraison enhances colour in red wines

Aqueous ethanol (5% v/v) was sprayed onto bunches of Vitis vinifera L. cv. Cabernet Sauvignon 8–9 weeks following full flowering (controls were sprayed with water). Internal ethylene concentration in treated berries increased to a maximum within 6 hours, and berry colour subsequently increased substantially (maximum attained 2–3 weeks after spraying). Berry fresh weight at harvest was unaffected by ethanol treatment, but wine made from treated grapes showed greater colour intensity compared with control grapes.

Accumulation of potassium and calcium by ripening berries on field vines of Vitis vinifera (L) cv. Shiraz

Ripening berries of Vitis vinifera (L) cv. Shiraz can show pre-harvest weight loss at sub-optimal sugar content (shrinkage). This later-age decline in berry weight implies that water loss from mature berries has begun to exceed water inflow from the parent grapevine. Such decrease in net inflow has been attributed to a cessation of xylem flow subsequent to veraison, followed by a cessation of phloem flow into berries during later stages of ripening. We address this issue in this present paper, and show a continuing increase in berry content of both potassium and calcium throughout ripening. We measured changes in berry fresh weight and berry content of potassium (phloem mobile) and calcium (phloem immobile) in fruit on field vines sampled from set to harvest. Berry fresh weight reached a plateau between 81 and 95 days after flowering, then declined to 75% of maximum fresh weight by 115 days. Dry weight maximum occurred 14 days after the onset of the fresh weight plateau. Potassium accumulation was slow pre-veraison, increased 3.5-fold post-veraison, and continued during berry shrinkage. Calcium content per berry also showed a linear increase throughout fruit enlargement and ripening phases. Assuming both potassium and calcium were entering berries via vascular conduits, our results imply a continuing connection between parent grapevine and ripening berries. Moreover, an abrupt change (increase) in the ratio of potassium/calcium content per berry subsequent to veraison implies that phloem inflow has increased relative to xylem inflow during post-veraison enlargement.

Genetic parameters of several biochemical compounds from green coffee, Coffea canephora

AbstractA factorial crossing scheme of Cofflea canephora (two parents from the Congolese group crossed to 14 parents of the Guinean group) was used to evaluate genetic parameters of several biochemical compounds, bean weight and crop outturn (ration of dry bean weight 10 fresh berry weight). For most characters studied, additive genetic effects were preponderant. Narrow‐sense heritability was high for caffeine content (h2ns= 0.80), fat matter content (h2ns, = 0.74), bean weight (h2ns= 0.73) and crop outturn (h2ns= 1). It was intermediate for trigonelline (h2ns= 0.38) and chlorogenic acid (h2ns= 0.36) content. Only sucrose content had a low narrow‐sense heritability (h2ns=0.11). There were few genetic and enviromnental correlations, Consequences for breeding, in relation to coffee drinking quality, are discussed.

The Effect of Limiting Leaf Area During Stage I of Berry Growth on Development and Composition of Berries ofVitis viniferaL. cv. Cabernet Sauvignon

The effects of limiting leaf area during the early stages of berry development on further berry growth and composition were investigated. Leaves were removed from fruiting grapevine cuttings (<i>Vitis vinifera</i> L., cv. Cabernet Sauvignon) just after fruit set giving a leaf area per berry of 1 cm² and 3.3 cm² for the treated and the control plants, respectively. Photosynthetic compensation did not occur at this stage. During the period of slow berry growth, the source capacities were restored by the development of new leaves. Consequently, at veraison, the leaf area per plant was similar for both groups of plants. Leaf removal just after fruit set strongly reduced berry growth. At the end of the first growth period, the berry fresh weight of the treated plants was half that of the control plants. The pericarp cell size was very much affected. Leaf area restoration allowed the treated berries to grow at the same relative growth rate as control berries during stage III. However growth rate compensation did not occur, and berry size at maturity was proportional to the size before veraison. Limiting leaf area shortened the first active growth period of the berries and delayed the onset of ripening. Berry composition was also affected by leaf removal. Osmolarity, titratable acidity, malic acid and soluble sugar concentration in the juice were significantly reduced on the treated plants at the end of the first growth period. Tartaric acid concentration was unaffected. At maturity, the organic acids and fructose concentrations were higher for the LS berries. Osmolarity, titratable acidity, and hexose accumulation rate were unaffected. We conclude that an early assimilate limitation affects the final berry size, but does not reduce the potential growth and accumulation capacities of small berries during ripening.

Flower Bud Load Influences Blueberry Vegetative and Fruit Development

A field experiment was conducted in Gainesville, Fla., with two southern highbush blueberry cultivars, `Misty' and `Sharpblue', to investigate the influence of varying flower bud load on the timing and extent of vegetative and reproductive development. Flower bud load was adjusted on three different canes on ten plants by removing none, one-third, or two-thirds of the flower buds. Vegetative budbreak, leaf area, fruit number, and fruit fresh weight and dry weight were measured. Vegetative budbreak was delayed with increasing flower bud load. Vegetative budbreak, leaf area, and leaf area: fruit ratio decreased with increasing flower bud load. Fruit maturity was delayed and average berry fresh weight and dry weight declined with decreasing leaf area:fruit ratio. Responses were similar for both cultivars although `Misty' was more adversely affected by high flower bud load and low leaf area: fruit ratio.

Chemical Composition of Lowbush Blueberry Cultivars

The chemical composition of the lowbush blueberry (Vaccinium angustifolium Aiton) cultivars Blomidon, Cumberland, and Fundy were examined at three stages of fruit maturity, before and after refrigerated storage, in a 2-year study. There were differences (P&lt; 0.001) related to maturity and cultivar in berry fresh weight, percentage dry matter, fruit firmness, percentage soluble solids, titratable acidity, and the concentration of sugar, acids, and anthocyanins. Among the nine organic and phenolic acids measured, seven acids varied among the maturity groups and eight varied among the cultivars. Between the 2 years of study there was a 60% difference in total fruit acid content as well as in the relative amounts of each acid. The 2-year mean profile of lowbush blueberry acids was distinctly different from that recently reported for highbush (Vaccinium corymbosum L.) and rabbiteye blueberries (Vaccinium ashei Reade). The level of certain acids as well as the concentration of anthocyanins increased during cold storage. Estimation of sugar concentration by percentage soluble solids overestimated sugar concentration by 3070. Acid measurement by titration underestimated acid content as measured by HPLC by 61%. Results of this study illustrate the variation in the chemical composition of lowbush blueberry fruit among cultivars, maturities, and seasons, and can be used to compare lowbush blueberries with other Vaccinium species.

EFFECTS OF POLLEN SOURCES ON OVULE AND BERRY DEVELOPMENT OF SOUTHERN HIGHBUSH BLUEBERRIES

To study the effects of pollen sources on ovule and berry development in southern highbush blueberries (Vaccinium corymbosum hybrids), 5-year-old `Sharpblue' plants were moved into a greenhouse for self- and cross-pollination experiments. Cross-pollination with `Gulfcoast' and `O'Neal' as pollen sources increased fruit weight by 58.2% and 54.9%, respectively, compared to self-pollination. Cross-pollination did not affect the number of total and small ovules significantly but did double the number of fully developed ovules and increase the average ovule size by 14%. The increase in number and size of fully developed ovules correlated with the significant difference in berry fresh weight between self- and cross-pollination. Cross- and self-pollination showed good correlations between fruit fresh weight and number or cross-sectional area of fully developed ovules. There was a poor correlation between fruit fresh weight and the number or cross-sectional area of partially developed ovules. This study provides further evidence that berry size in southern highbush is influenced strongly by the development of fully developed ovules.

The Influence of Cluster Thinning at Various Stages of Fruit Development on Flame Seedless Table Grapes

A study was conducted in 1991 and 1992 to determine the influence of cluster thinning at various stages of fruit development on Flame Seedless table grapes grown in the San Joaquin Valley of California. Grapevines adjusted to 45 clusters prior to bloom had one-third of their clusters removed at one of the following stages of fruit development: prebloom (PB), berry set (BS), berry set + 2 weeks (BS + 2), berry set + 4 weeks (BS + 4), and berry set + 6 weeks (BS + 6). A group of unthinned vines, carrying 45 clusters throughout the season, were included in the study. The leaf area:fruit weight ratios for vines thinned at BS and unthinned vines, respectively, were 11.9 and 10.2 cm² g^-1 in 1991 and 15.5 and 11.4 cm² g^-1 in 1992. Little difference in berry fresh or dry weight was observed among the treatments prior to fruit softening. After fruit softening, vines thinned between PB and BS + 4 generally exhibited greater berry fresh and dry weights than vines thinned at BS + 6 and unthinned vines. Berry diameter did not differ among the treatments at harvest in either season. Berry color was the compositional parameter most sensitive to date of cluster thinning. Vines thinned between PB and BS + 4 accumulated color more rapidly than vines thinned at BS + 6 and unthinned vines. Fruit soluble solids at harvest were greater for cluster thinned vines compared to unthinned vines. Total and cull yield were greatest for unthinned vines in both seasons. In 1991, vines thinned at BS + 6 had the lowest packable yields in the experiment. In 1992, the packable yields of vines thinned at BS + 6 and unthinned vines were similar and significantly lower than those of the remaining treatments. The results indicate that mid-season ripening Flame Seedless table grapes may be cluster-thinned between PB and BS + 4 with similar effects on fruit growth, fruit composition, and packable yield. Due to reduced packable yields, as well as variable effects on fruit composition, cluster thinning after berry softening (BS + 6) is not recommended.

Early Season Leaf Removal Reduces Fruit Set and Size in Cranberry (Vaccinium macrocarpon Ait.)

Fruit set is a major limiting factor in cranberry production. Many more flowers are produced than fruit. Intraplant competition for resources has been implicated as a possible limitation to fruit set (Baumann and Eaton, 1986; Birrenkott and Stang, 1989, 1990). Photosynthate for growth of individual fruit in cranberry may come from one or more sources, including carbohydrates stored in perennial tissues, photosynthesis by l-yearold or newly formed leaves on the upright bearing the fruit, or from reserves or photosynthesis of adjacent connected uprights. This research was undertaken to determine the relative importance of newly formed leaves on cranberry fruit set and growth. A 2-year-old bed of ‘Crowley’ cranberry growing near Babcock, Wis., was studied. At 2-week intervals, from 16 June to 21 Sept. 1982, new vegetative growth (apical bud and leaves) was removed from 14 fruiting uprights. These uprights were examined periodically during the season and any regrowth was removed as needed. On 12 Oct. the uprights from the eight leaf removal dates were harvested along with 28 untreated control uprights. For each upright, the number of flowers and fruits was counted and percent fruit set calculated. The berries were removed from the uprights and the berry fresh weight and length were measured. Transformed data were tested by analysis of variance with mean separation by LSD following a significant F value. Early removal of the newly produced leaves resulted in a reduced fruit count and fruit set (Table 1). The effect was most severe when leaves were removed on 14 July. Fruit set on uprights from which leaves were removed in August or September was higher than that typically reported in the literature for undisturbed plants (25% to 40%) in older beds (Birrenkott and Stang, 1989). The unusually high fruit set likely is related to the age of the planting. Upright density in a 2-year-old bed, as used by us, is normally substantially lower than in an older bed. Uprights thus were in full sun with little shading and competition. Visible bud growth in cranberry occurs in mid to late May with flowering beginning in late June and continuing for 3 to 4 weeks, into July. Fruit set was reduced most when leaves were removed near the end of the blossoming period, when the earliest set and newly expanding fruit would likely have the greatest demand for photosynthate. Removing the lowest two flowers or fruit early in their development increased fruit set on upper flowers more than removing fruit late during their development (Birrenkott and Stang, 1990). In addition, total nonstructural carbohydrates are at their lowest levels of the season during the fruit set period (Hagidimitriou and Roper, 1991). Leaf removal on 28 July or later had essentially no effect on fruit count or fruit set (Table 1). This result suggests that, later in the season, leaves further away from the fruit became more important in supporting fruit growth. This phenomenon has also been shown for apple (Rom and Ferree, 1986). Fruit size, measured as mean berry fresh weight and mean berry length, was reduced significantly when the newly formed leaves were removed on 30 June or 14 July (Table 1). However, when leaves were removed earlier (June 16) or later in the season (28 July or later), berry size was similar to that of the control. Removing the apical bud and new leaves on individual cranberry uprights during the blossoming period reduced fruit set and fruit size. The effect was greatest at the end of flowering when fruit are growing most rapidly and the potential demand for photosynthate is highest. This work suggests that competition for photosynthate may be a major limiting factor for fruit set in cranberry. New leaves on uprights appear to be an important source of carbohydrates; as the season progresses, other photosynthate sources may contribute needed resources.

Ethylene-induced fruit ripening in arabica coffee (Coffea arabica L.)

The effects of ethephon on arabica coffee (Coffea arabica L.) were tested in experiments conducted over 2 years in North Queensland. Rates tested were 0, 125, 250, 500, 750, 1000, 1500, and 2000 mgkg, applied when 15-20% (early treatment) or 45-50% (late treatment) of fruit were coloured. Measurements were made on the degree of leaf and fruit abscission, berry ripening, and berry weight. Ethephon did not cause significant fruit abscission, but rates &gt;500 mg/kg caused unacceptable leaf abscission. Rates of 250 mg/kg were marginally acceptable in terms of leaf abscission. Excessive defoliation led to dieback, which resulted in a reduced crop the following season. Ethephon concentrated berry ripening, significantly increased the number of red (mature) berries, and decreased the number of green (immature) berries. Rates of &gt;500 mg/kg were effective in accelerating berry ripening, while 125 mg/kg had a limited effect. Maturity stage of the bean at time of application helped to determine the ethephon response; early application of ethephon had a more pronounced effect on berry ripening than late application. Ethephon applied early at rates of 1500 and 2000 mg/kg decreased fresh berry weight compared with all other treatments but parchment weight was unaffected. Selection of a suitable rate of ethephon from these data is difficult because berry ripening is offset by leaf drop. Variability of response was also observed.

Cross-incompatibility of Two Related Rabbiteye Blueberry Cultivars

Abstract Two rabbiteye blueberry (Vaccinium ashei Reade) cultivars Beckyblue and its open-pollinated progeny Aliceblue, both of which are known to be highly male- and female-fertile, were self-pollinated, reciprocally cross-pollinated, and pollinated with pollen from a third cultivar, Climax, which is not closely related to the other two. Fruit set percentage on ‘Aliceblue’ and ‘Beckyblue’ averaged 65% when ‘Climax’ was the pollen parent and &lt; 1% when the cultivars were self-pollinated. Reciprocal crosses of ‘Beckyblue’ and ‘Aliceblue’ averaged 24% set, indicating a high degree of cross-incompatibility. There was no effect of pollen parent on berry fresh weight, although seed weight and seed number were reduced by self-pollination or pollination by the related cultivar.

Relationship Between Achene Number, Achene Density, and Berry Fresh Weight in Strawberry

Abstract Field-grown genotypes (Fragaria × ananassa Duchesne) were studied in two seasons to determine the relationship of primary berry fresh weight to the total number of achenes per berry and the number of achenes/cm2 of receptacle tissue. Within genotypes grown in matted rows (1985), berry fresh weight was correlated with the total number of achenes per berry. In the hill system (1986), berry weight was correlated with the number of achenes and the number of achenes/cm2. Genotypic variation in berry weight in the matted row was related to the total number of achenes. In the hill system, there were no differences in the total number of achenes per berry between high- and low-yielding genotypes, but the highest-yielding genotype had fewer achenes/cm2.

Effect of Fertilizer, Paclobutrazol, and Chlormequat on Strawberry

Abstract In a greenhouse study with strawberry (Fragaria × ananassa Duchesne), foliar sprays of paclobutrazol (PP333) at 10, 46, 215, or 1000 ppm and chlormequat chloride (CCC) at 215 or 1000 ppm decreased runnering, but PP333 was most effective. PP333 inhibited runnering more for ‘Totem’ than ‘Shuksan’, with the reverse true for CCC. Biweekly fertilization with 20N-4.3P-8.3K at 180 mg/pot increased leaf area and runnering relative to 45 mg/pot. PP333 at equal rates produced larger decreases in leaf area than CCC. Both high fertilizer and PP333 in a rate-dependent manner delayed leaf senescence and berry ripening. CCC increased yield in ‘Shuksan’ only, and while berry fresh weight was increased by PP333, no increase in yield occurred, as it was offset with a decreased number of berries that ripened over the period of our study. PP333 decreased pollen germination. Soil residues of PP333 were evident 11 weeks after application. Chemical names used: β-[(4-chlorophenyl)methyl]-α-(1,1-dimethylethyl)-1H- - 1,2,4-triazole-1-ethanol (paclobutrazol); 2-chloro-N, N, N-trimethylethanaminium chloride (chlormequat chloride).

Effect of harvest date on yield and quality of black currant fruit

Abstract The effect of time of harvesting was investigated in a black currant (Ribes nigrum cv. Magnus) trial in which 2-year-old border strip irrigated hedgerows were sequentially harvested on 11 occasions during a 7-week period in December and January. Highest machine and total yields were attained approximately 1 week before the crop was ready to harvest. By the time the fruit was ripe for machine harvest, a yield loss of l0% had occurred. After 17 days half the potential yield was lost. Changes in fresh berry weight, fruit colour, and sugar content during the harvest period are also described, and the implications of these findings to the commercial black currant grower are explained.

Size factors in strawberry fruit

Analysis of data relating to berries of 9 cultivars grown under different conditions indicates that the weight of ripe berries can be accounted for by the general equation Berry fresh weight (g) = ( Total no. of achenes − C)F ( No. of achenes/cm 2 of surface) where C is a numerical adjustment probably due to the non-spherical shape of berries, and F is the weight in g per unit area of tissue which forms the berry, and both may be characteristic of each cultivar under normal conditions. The number of achenes on perfect berries, equal to the number of ovules initiated on the flowers, is closely related to the position of the flower on the inflorescence. Expressing Rank value on the scale 1 : 1 2 : 1 4 : 1 8 for Rank 1 : Rank 2 : Rank 3 : Rank 4, a general equation Achene no. = (K × Rank value) + D can be applied to all cultivars, although K and D may vary between cultivars and to a less extent within a cultivar. If these size factors are in fact basically genetic, a grower may have little scope for influencing berry size except during berry development in the fruiting-season.

Effects of Bloom-Applied Gibberellic Acid on Soluble Solids and Berry Weight of Thompson Seedless Grapes and on Raisin Grades

The distributions of Thompson Seedless berries for weight and soluble solids weight were normal whether or not the vines were sprayed during bloom with gibberellic acid (GA₃) at concentrations of 5 or 10 ppm. The distributions for soluble solids content, however, mostly departed significantly from normality. Airstream grades of raisins, either as percent B or better, or percent substandard, correlated significantly with fruit maturity (°Brix) and fresh berry weight, similarly to raisins from nongibberellic acid-treated vines. Bloom-applied GA₃ at 10 ppm significantly increased fresh berry weight, but not maturity, vine yield, or percent water berries. Neither were raisin berry weight, airstream grades, or scoreable mold levels significantly affected by GA₃ at either 5 or 10 ppm.