Increased Starch Concentrations Research Articles

Effect of Zeolite Concentration on Hydrogel Characteristics of Arrowroot-Based Starch-G-Poly(Acrylic Acid)/Zeolite Composite

This study aims to synthesize a hydrogel zeolite composite of arrowroot starch graft copolymerized with acrylic acid through a radical polymerization reaction in a water. Various scenarios were tested using different natural zeolite concentration to determine the impact on swelling/water absorption of the composite. The resulting product was a solid gel-the test results showed that the swelling increased as the ratio of starch to acrylic acid decreased. Increased starch concentrations generally lead to decreased water absorption (swelling capacity). Adding a zeolite improved swelling to some extent and the optimum zeolite concentration was 60%. The increased concentration of zeolite also hardened the hydrogel composite. The highest swelling in the hydrogel composite of starch-g-poly(acrylic acid)/zeolite 60% is 1056.25 g.g-1. FTIR analysis of functional groups was conducted to determine differences in the IR spectra of arrowroot starch, acrylic acid, hydrogels, zeolites, and composite hydrogel. Si-O signal appearing on the IR spectra of hydrogel composite with wave number 1030 cm-1 indicates that composite hydrogel with zeolite was synthesized

Simulated nitrogen deposition promotes the carbon assimilation of shrubs rather than tree species in an evergreen broad-leaved forest

Although understory addition of nitrogen (UAN) is commonly used to simulate nitrogen deposition in field studies in forest ecosystems, it ignores the effects of atmospheric nitrogen deposition on the canopy. We studied the effects of nitrogen deposition simulated by UAN and by canopy addition of nitrogen (CAN) on leaf structure, chemical properties, Calvin cycle, and photosynthate distribution strategy of representative woody plant species in a subtropical evergreen broadleaved forest in South China. The results showed that maximum photosynthetic rate (Amax) of shrub species Blastus cochinchinensis and Ardisia quinquegona under CAN treatments was significantly higher than that of UAN treatments at the same N addition concentration. The concentrations of intermediates (PGK, DPGA and G3P) in Calvin cycle of B. cochinchinensis and A. quinquegona, and Castanea henryi were significantly increased with CAN treatments, but the opposite was true with UAN treatments. CAN25 significantly increased starch concentrations of shrub species Lasianthus chinensis and B. cochinchinensis, and significantly decreased sucrose concentrations of shrub species A. quinquegona and tree species C. henryi. Correlation analyses showed that nitrogen application amount under different modes helped explain the changes in Amax and Calvin cycle intermediates. In summary, nitrogen deposition may promote the Amax and Calvin cycle of shrub species, and the adaptability of shrub species to nitrogen deposition is higher than that of tree species, which may help to explain the degradation of subtropical evergreen broad-leaved forest.

Enzymatically modified quinoa starch-based Pickering emulsion: Effect of enzymolysis and emulsifying conditions

Both the effects of enzymolysis condition on the microstructures and emulsifying property of enzymatic modified quinoa starch (EMQS) and the effects of emulsion formulation on the EMQS based emulsions were investigated. The emulsifying capacity (EC) and stability (ES) of EMQS were positive correlated with enzyme amount (0–2.4 % w/wstarch). The particle sizes of EMQS decreased and its hydrophobicity increased with increasing enzyme amount (0–2.4 % w/wstarch), which were the main reasons for the increasing emulsifying performance of EMQS. With the increasing starch concentration, the EC of the EMQS increased, the oil droplet size of the emulsion decreased. With the oil/water ratios ranging from 1:9 to 6:4, the emulsification index (EI) and oil droplet size of the emulsion increased. EMQS based emulsion had a relatively good stability in the pH range of 2–10. This study lays the foundation for the application of EMQS as a stable clean-label Pickering emulsifier.

Here comes the flood! Stress effects of continuous and interval waterlogging periods during the growing season on Scots pine saplings

Future climate scenarios for the boreal zone project increasing temperatures and precipitation, as well as extreme weather events such as heavy rain during the growing season. This can result in more frequent short-term waterlogging (WL) leading to unfavorable conditions for tree roots. In addition, it is decisive whether short-term WL periods during the growing season occur continuously or periodically. We assessed the effects of short-termed WL on 4-year-old Scots pine (Pinus sylvestris L.) saplings after shoot elongation started. Waterlogging (WL) lasted either continuously for 2.5weeks (ContWL) or noncontinuously for 5 weeks, consisting of three repeated 1-week-interval WL periods (IntWL). Both treatments resulted in the same duration of soil anoxia. We studied soil gases, root and shoot growth and physiology, and root survival probability and longevity during the experiment. In the final harvest, we determined shoot and root biomass and hydraulic conductance and electrical impedance spectra of the root systems. Soil CO2 and CH4 concentrations increased immediately after WL onset and O2 decreased until anoxia. Waterlogging decreased fine root survival probability, but there was no difference between WL treatments. Shoot growth suffered more from ContWL and root growth more from IntWL. Needle concentrations of pinitol increased in the WL saplings, indicating stress. No WL effects were observed in photosynthesis and chlorophyll fluorescence. Increased starch concentration in needles by WL may be due to damaged roots and thus a missing belowground sink. Electrical impedance indicated suffering of WL saplings, although root hydraulic conductance did not differ between the treatments. Oxidative stress of short-term and interval WL can have long-lasting effects on shoot and root growth and the physiology of Scots pine. We conclude that even short-term WL during the growing season is a stress factor, which will probably increase in the future and can affect carbon allocation and dynamics in boreal forests.

Gelatin/starch orally disintegrating films as a promising system for vitamin C delivery

Orally disintegrating films (ODFs) may disintegrate rapidly or slowly when in contact with saliva, acting as carriers of different compounds. The objective of this work was the production of gelatin and starch ODFs as vehicles of vitamin C obtained via a spray-drying method from camu-camu powder. ODFs were produced by mixing gelatin and/or starch as main components, sorbitol as plasticizer, and the powder from camu-camu as an active compound. The ODFs were characterized regarding their visual qualities, mechanical properties, contact angle, surface pH, disintegration time (in vitro and in vivo), ascorbic acid degradation, antioxidant activity stability and sensory attributes. The ODFs were homogeneous and easy to handle. An increased starch concentration in the ODF promoted a significant increase of hydrophilicity and thus, the decrease of in vitro disintegration time. The ODFs also showed a fast in vivo disintegration time. Moreover, the evaluation of the sensory attributes demonstrated that ODF consumption was palatable to the panelists. Therefore, ODFs with camu-camu extract can be used as an efficient and natural supplementary source of vitamin C and as a potential carrier of antioxidant compounds.

Effects of starch concentration on calcium-enhanced black bullhead catfish protein gels.

Calcium‐enhanced protein recovered from black bullhead catfish was used to develop gels containing increasing amounts of potato starch (0–20 g/kg protein paste) and the effects of starch on functional, textural, and color properties were tested. Energy required to unfold protein groups was greater with the addition of 5 g starch/kg protein paste. Gels containing starch were harder, chewier, and less springy (p < .05) than gels without starch. For most measurements, regression analysis showed that increasing the starch concentration beyond 5 g/kg did not contribute to further significant textural changes. Torsional shear stress and strain along with Kramer shear force increased as the concentration of starch increased (R 2 = .79, .79, and .53, respectively). The addition of ≥10 g starch/kg protein paste resulted in darker gels and gels got darker as more starch was added (R 2 = .71). Results showed no benefit to increasing starch concentration in gels beyond 5 g starch/kg protein paste.

Consecutive applications of brassica green manures and seed meal enhances suppression of Meloidogyne javanica and increases yield of Vitis vinifera cv Semillon

This study examined the result of 1–3 year application sequences of two brassica green manures (Indian mustard cv Nemfix and BQ mulch™), Nemfix seed meal and Nemacur ® on the suppression of root knot nematode Meloidogyne javanica in soil and roots, and the consequent improvement on vigour and productivity of Vitis vinifera cv Semillon. Soil examination revealed ca. 37–78% suppression of M. javanica populations when soil was amended with brassica green manures, Nemfix seed meal and Nemacur ® for 1–3 consecutive years compared to unamended soil. In all cases, M. javanica populations were significantly reduced after 1 year of treatment with a further reduction in the second year of treatment. The third year application did not have any significant reduction over the second year treatment. A suppression of M. javanica populations in soil after 3 consecutive years of application of brassica green manures, Nemfix seed meal and Nemacur ® significantly increased yield by 69–101% compared to the inoculated control (unamended) treatment. Three consecutive years of application of green manures and Nemfix seed meal significantly increased starch concentration in the roots to between 23 and 25% compared to the inoculated control treatment (concentration 14%). Fresh pruning weights were significantly increased by 35% in 2–3 consecutive years of application of Nemfix green manure treatment only compared to the inoculated control treatment. Applications of the green manures, Nemfix seed meal and Nemacur ® for 1–3 consecutive years did not have any significant effect on berry juice characteristics.

REVIEW: Molecular Interactions in Starch‐Water Systems: Effect of Increasing Starch Concentration

ABSTRACTStarch is a major part of our diet. Food processing determines the physicochemical properties of starch in processed foods. An understanding of such properties is important in the development of strategies to modulate desirable textural attributes as well as the digestibility of starch in foods such as baked and extruded products. This review summarises the molecular interactions that occur during gelatinization and retrogradation of starch molecules studied using starch‐water systems focusing on those with starch concentrations of 60–150% db relevant to baked and extruded foods. Little information exists on effects of starch concentration on digestibility and polymer conformations and structures of processed starch in concentrated systems.

Kinetic characteristics of β-cyclodextrin production by cyclodextrin glycosyltransferase from newly isolated Bacillus sp. C26

The kinetic characteristics of β-cyclodextrin production by a cyclodextrin glycosyltransferase (CGTase) produced by Bacillus sp. C26, a new isolate from a soil sample was investigated. Considering highest yield and initial production rate of β-cyclodextrin, among the starches examined, soluble starch, tapioca starch, sago starch, corn starch and rice starch, tapioca starch was the best substrate for this CGTase. The optimum temperature for tapioca starch gelatinization prior to its use as a substrate for β-cyclodextrin production was 65oC. The yield and initial production rate of β-cyclodextrin increased with increasing starch concentration up to 6% and an enzyme concentration up to 48 U/g-starch. The kinetic parameters of V max and K m of β-cyclodextrin production from tapioca starch by CGTase were 1.59 mg/mL/h and 22.3 mg/mL, respectively. Considering high initial production rate and high yield of β-cyclodextrin, the optimum reaction temperature was at 50oC. This study provided the necessary kinetic information that may be useful to define the most suitable condition for industrialized production ofβ-cyclodextrin with the high yield and productivity.

Yield and nutritive value of timothy as affected by temperature, photoperiod and time of harvest

AbstractScenarios of global climate change forecast an increase in air temperature of 3°C over the next 100 years in eastern Canada. Growth and nutritive value of cool‐season grasses are known to be affected by air temperature. It is also believed that grasses grown at high latitude have a greater nutritive value. The objectives of this study were to assess the effect of four combinations of day/night temperature and photoperiod (15 h–17/5°C; 15 h–22/10°C; 15 h–28/15°C; and 17 h‐17/5°C) on dry‐matter (DM) yield, in vitro true DM digestibility (IVTD), in vitro digestibility of neutral‐detergent fibre (NDF), and concentrations of NDF, acid‐detergent fibre (ADF), lignin, minerals and non‐structural carbohydrates (NSC) in timothy grown under controlled conditions. Furthermore, herbage was harvested in the morning and in the afternoon to assess the impact of the time of harvest. The dietary cation–anion difference [DCAD = (K+ + Na+) − (Cl− + 0·6 S2−)] and the grass tetany index [GT index = K+/(Ca2+ + Mg2+)] were also calculated. Higher temperature regimes significantly decreased IVTD and digestibility of NDF but had a limited effect on concentrations of NDF, ADF and lignin. DM yield of herbage was less and the concentration of NSC was greater in timothy grown under a temperature regime of 28/15°C than the 17/5°C and 22/10°C regimes; this effect is mainly explained by a response to temperature stress. Values of DCAD and the GT index of herbage were also lower under the 28/15°C than the 17/5°C and 22/10°C regimes as a result of a decreased plant K concentration. Under the 17/5°C regime, an increase in 2 h of photoperiod resulted in increased DM yield, decreased concentrations of K, Ca, Mg, Cl and N, and an increased starch concentration; IVTD or digestibility of NDF were not affected, although lignin concentration was reduced. Harvesting timothy in the afternoon rather than in the morning resulted in higher NSC, mainly sucrose, concentrations, and decreased ADF and NDF concentrations. The forecasted increase in air temperature in eastern Canada over the next 100 years will result in lower yields and nutritive value of timothy.

Interactions between flavour release and rheological properties in model custard desserts: Effect of starch concentration and milk fat

The influence of the concentration of various reagents and of the storage time on the flavour release of custard desserts was evaluated by headspace solid-phase microextraction and supported by rheological measurements. The presence of milk fat induced a significant decrease of the headspace concentration of flavour compounds, mainly due to hydrophobic matrix–flavour interactions. An elevated starch concentration enhanced the strength of the custard gels considerably. However, the increasing starch concentration resulted in an increased flavour release at low flavour concentrations, while a tendency to flavour retention was noted at higher flavour concentrations. During storage time, a denser network was formed as shown by rheological measurements, but no significant difference in flavour release was noted upon storage (three days). These results show that the complex interactions between flavour compounds and the food matrix in a model custard are difficult to predict and have to be carefully evaluated by a combination of rheological parameters and physicochemical interactions.

Effect of resistant starch on the water binding properties of imitation cheese

The effect of moisture and resistant starch concentration on the water activity ( a w) and water sorption of imitation cheese was investigated. The Guggenheim–Anderson–deBoer (GAB) equation was found to be a good description of the experimental moisture sorption isotherms. Inclusion of starch in cheese increased moisture sorption over the a w range studied. The GAB monolayer value indicated starch-containing cheese bound an additional 1.4 g water/100 g dry matter when compared to a starch-free cheese. Increasing cheese moisture content had an insignificant effect on moisture sorption but increased a w. Increasing starch concentration had little influence on the GAB parameters but nonetheless decreased a w. It is believed that starch, while relatively inert in terms of water binding, may organise water molecules causing them to be physically entrapped within the cheese matrix. By not competing with protein for water molecules, the starch allowed the water to remain available for plasticization to maintain good functionality of the cheese.

Nonthermal starch hydrolysis using ultra high pressure: I. Effects of acids and starch concentrations

Corn starches with 2 mol/l hydrochloric acid (HCl), 2 mol/l sulfuric acid (H 2SO 4) and 2 mol/l oxalic acid (C 2H 2O 4) were pressurized at 600 MPa for 30 min. Corn starch with C 2H 2O 4 formed a gel after ultra-high-pressure (UHP) treatment. Corn starch with HCl showed partial disintegration but starch with H 2SO 4 maintained its shape. Corn starch with HCl showed higher (0.42–0.47) degree of hydrolysis compared to starch with C 2H 2O 4 (about 0.14) and H 2SO 4 (0.13–0.14) regardless of increasing starch concentration up to 20 g/100 g sample. Main component of starch hydrolysate was maltose for HCl and oligosaccharides for H 2SO 4 and C 2H 2O 4. Crystallinity of starch with HCl decreased with decreasing starch concentration as observed by both differential scanning calorimetry (DSC) and X-ray diffraction. Therefore, UHP can be used for nonthermal starch hydrolysis and HCl would be a good catalyst for UHP starch hydrolysis compared to H 2SO 4 and C 2H 2O 4. This work provides a potential of nonthermal UHP processing for new starch hydrolysis method.

Effects of simultaneous ozone exposure and nitrogen loads on carbohydrate concentrations, biomass, and growth of young spruce trees (Picea abies)

Spruce saplings were grown under different nitrogen fertilization regimes in eight chamberless fumigation systems, which were fumigated with either charcoal-filtered (F) or ambient air (O3). After the third growing season trees were harvested for biomass and non-structural carbohydrate analysis. Nitrogen had an overall positive effect on the investigated plant parameters, resulting in increased shoot elongation, biomass production, fine root soluble carbohydrate concentrations, and also slightly increased starch concentrations of stems and roots. Only needle starch concentrations and fine root sugar alcohol concentrations were decreased. Ozone fumigation resulted in needle discolorations and affected most parameters negatively, including decreased shoot elongation and decreased starch concentrations in roots, stems, and needles. In fine roots, however, soluble carbohydrate concentrations remained unaffected or increased by ozone fumigation. The only significant interaction was an antagonistic effect on root starch concentrations, where higher nitrogen levels alleviated the negative impact of ozone.

The effect of crop maturity on the nutritional value of maize silage for lactating dairy cows. 2. Ruminal and post-ruminal digestion

AbstractTo evaluate the effect of crop maturity on digestion of maize silage in the rumen and post-ruminal digestive tract, four multiparous Holstein-Friesian cows fitted with a simple cannula in the proximal duodenum and a rumen cannula were offered four diets in a 4 ✕ 4 Latin-square design. Forage maize (cv. Hudson) was harvested and ensiled at target dry matter (DM) contents of 230, 280, 330 and 380 g per kg fresh weight (FW) to provide a range of starch contents. The mean values for volatile-corrected DM (VCDM) and starch content of the four maize silages as given were 221, 277, 308 and 372 g/kg FW and 173, 257, 328 and 382 g/kg VCDM respectively. Grass silage (GS) containing 250 g VCDM per kg FW was produced from the primary growth of a perennial ryegrass sward. The diets were 8·7 kg DM per day of a dairy concentrate supplement with one of four forage treatments offered ad libitum. The forage treatments were a 3 : 1 DM ratio of maize silage with GS, designated as T23, T28, T33 and T38. Each period lasted 6 weeks with rumen and duodenal samples being taken over 3 days in week 4 and faeces being collected in respiration chambers over 6 days in either week 5 or 6. Milk yield tended to increase with advancing maturity (30·5, 31·8, 32·5 and 32·3 kg/day) but individual treatment differences were not significant. DM intake increased from 19·62 to 21·30 kg/day (P &lt; 0·05) but there were no significant effects on digestibility in the rumen, post-ruminal tract or total tract. Digestibility of neutral detergent fibre in the rumen declined with increasing starch content in the maize silage (P &lt; 0·05) but total digestibility was not significantly affected. Starch intake increased from 3·11 to 5·04 kg/day (P &lt; 0·001), duodenal flow from 0·40 to 0·89 kg/day (P &lt; 0·01) and the amounts digested in the rumen and post-ruminal tract respectively from 2·72 and 0·34 kg/day to 4·16 and 0·71 kg/ day (P &lt; 0·01). However the only significant effect on starch digestibility was a small fall in total digestibility from a mean of 0·981 for T23, T28 and T33 to 0·966 for T38. There were no treatment effects on nitrogen digestion. The molar proportions of acetic acid and n-caproic acid decreased and that of n-butyric acid increased with advancing maturity. It is concluded that the changes in composition of maize silage with increasing maturity result in large increases in the contribution of starch to DM digested in the rumen but only small differences in rumen fermentation. Post-ruminal starch digestion doubles but this is due to the increased starch concentration of the silage rather than major changes in digestion and the amount is small compared with that likely to result from feeding maize grain.

Phosphorus‐deficiency effects on response of symbiotic N2 fixation and carbohydrate status in soybean to atmospheric CO2 enrichment

The impact of phosphorus (P) deficiency on response of symbiotic N2 fixation and carbohydrate accumulation in soybean (Glycine max [L.] Merr.) to atmospheric CO2 enrichment was examined. Plants inoculated with Bradyrhizobium japonicum MN 110 were grown in growth chambers with controlled atmospheres of 400 and 800 μL CO2 L‐1 and supplied either 1.0 mM‐P (P‐sufficient) or 0.05 mM‐P (P‐deficient) nitrogen (N)‐free nutrient solution. When plants were supplied with sufficient P, CO2 enrichment significantly increased whole plant dry mass (83%), nodule mass (67%), total nitrogenase activity (58%), and N (35%) and P (47%) accumulation at 35 days after transplanting (DAT). Under sufficient P supply, CO2 enrichment significantly increased starch concentrations in nodules compared to the normal atmospheric CO2 treatment. Under normal CO2 levels (400 μL L‐1) nonstructural carbohydrate concentration (starch plus soluble sugar) was significantly higher in leaves of P‐deficient plants than in leaves of P‐sufficient plants in which nonstructural carbohydrate concentration exhibited a strong diurnal pattern. Under deficient P supply whole plant dry mass, symbiotic N2‐fixation parameters, and N and P accumulation were not enhanced by atmospheric CO2 enrichment. Phosphorus deficiency decreased nonstructural carbohydrate accumulation in nodules at the end of a 10‐day period in which functional activity was developing by 86% relative to P‐sufficient controls. While P deficiency elicited significant increases in the nonstructural carbohydrate concentration in leaves, it caused significant decreases in the nonstructural carbohydrate concentration in nodules over the diurnal cycle from 30 to 31 DAT. Collectively, these results indicate that the lack of a symbiotic N2‐fixation response to atmospheric CO2 enrichment by P‐deficient plants may be related to the decreased carbohydrate status of nodules.

Micropropagation of oca on a high sucrose medium promotes starch accumulation and plant establishment in soil

Abstract The in vitro micropropagation of oca (Oxalis tuberosa Mol., Oxalidaceae) on a medium with 30 g/litre versus 60 g/litre sucrose had no effect on multiplication rates and general plant phenotype. The only differences noted at the higher sucrose concentration were shortened internodes and more robust stem tissue, which provided a plant growth form more appropriate for micropropagation and transplantation out of culture. Substantially increased starch concentrations were measured in leaves, stems, and roots of the oca plants cultured on the high‐sucrose medium. Oca plants cultured in vitro on a medium with 60 g/litre sucrose showed markedly improved growth in soil following transfer out of culture. This was attributed to the in vitro plants accumulating and storing more reserves when grown on the high‐sucrose medium.

Changes in rheological properties of hydroxypropyl potato starch pastes during freeze—thaw treatments. III. Effect of cooking conditions and concentration of the starch paste

AbstractThe effects of different cooking conditions and concentrations on the freeze‐thaw stability of hydroxypropyl potato starch (molar substitution 0·125) paste were investigated by dynamic rheological measurements and syneresis determination. The cooking conditions of the starch were chosen by taking the starch pastes at peak consistency (SP/Peak), at half breakdown consistency (SP/HB), after being held at 95°C for 15 min (SP/95°C) and after the whole pasting cycle (SP/25°C) in the Brabender Amylograph. The concentration effect was studied with the starch pastes after a whole pasting cycle at 35, 50 and 65 g kg−1. Depending on cooking conditions and concentration, the rheological responses in changes of complex modulus (G*) and phase angle () of the starch pastes, with regard to the number of freeze‐thaw cycles, differed considerably. This indicated that the starch pastes had undergone various structural changes during freeze‐thaw treatments. With an increased extent of pasting, and with an increased starch concentration, the rheological responses indicative of the destabilisation process of the starch pastes were, in general, delayed. The number of freeze‐thaw cycles required for the appearance of a peak in G*, related to the first syneresis, was one, two, five and six for SP/Peak, SP/HB, SP/95°C and SP/25°C, respectively. For the starch pastes at 35, 50 and 65 g kg−1, it was four, six and seven cycles, respectively. Based on these rheological data, it was suggested that the amount of inter‐mingled amylose and amylopectin in the dispersion of hydroxypropyl starch paste is the main controlling factor, which plays a critical role in the rheological response as well as in the syneresis.

Effects of root hypoxia and a low P supply on relative growth, carbon dioxide exchange rates and carbon partitioning in Pinus serotina seedlings

The present study was conducted to determine how 10 weeks of root hypoxia and a low P supply altered relative growth, and carbon acquisition and partitioning in a moderately flood tolerant pine. Pond pine (Pinus serotina Michx.) seedlings were grown in continuously flowing solution culture at 5 or 100 μM P, under aerobic or hypoxic solution conditions. Staggered harvests were used to ascertain changes in biomass allocation and relative growth over time. Carbon dioxide exchange rates (CER) were determined by infrared gas analysis, and needles were analyzed for inorganic P (Pi), sucrose, reducing sugars and starch. Although aeration treatment had no significant effect on shoot dry weight or shoot ontogeny, root dry weight of hypoxic seedlings was significantly lower than that of aerobic seedliings after 8 weeks, regardless of the P treatment. Mean relative growth rates (RGR) of roots in the high P treatment initially decreased under hypoxia, but recovered by the sixth week with the production of adventitious roots. Two weeks of hypoxic growth conditions decreased CER and stomatal conductances of seedlings in the high P treatment by more than 30% relative to their aerobic counterparts. Stomatal closure was not accompanied by a decrease in intracellular CO2, but was accompanied by an increase in starch accumulation. Recoveries of CER, stomatal conductance and carbohydrate metabolism coincided with the recovery of root growth. Low P growth conditions did not significantly affect shoot or root dry weight until the sixth week of treatment. However, differences in seedling RGR, particularly needle RGR, were discernable during the first 2 weeks. Low P treatment effects on CER paralleled changes in needle RGR, with needle RGR more affected than CER. After 6 weeks, CER of aerobically grown seedlings in the low P treatment were only 15% lower than CER of seedlings in the high P treatment, despite a 31% and 75% reduction in needle RGR and Pi concentrations, respectively. Increased starch concentrations of recently expanded needles at this time were probably a result of diminished growth. The inhibitory effect of a low P supply on shoot growth, more specifically on needle expansion and emergence of new fascicular needles, probably limited net carbon fixed per plant more than any direct effect of low P on CER per se.

Carbohydrates and their effects on growth and establishment ofTiliaandBetula: I. Seasonal changes in soluble and insoluble carbohydrates

SummaryChanges in starch, sugar and total carbohydrate concentrations were monitored in roots, stems and leaves of newly transplanted Tilia and Betula plants throughout one growing season. Sucrose, glucose and fructose were present with small amounts of sorbitol. Concentrations of starch and sugar and the total carbohydrate content of the roots of both species declined between planting and early June, the result of reduced concentrations within primary roots, and the death of fine roots. It is suggested that this decline in root carbohydrate is partly explained by translocation to the above-ground organs to support budburst and early leaf growth. New roots and increases in the total root carbohydrate were measured much sooner after transplanting Betula than Tilia. By early July total carbohydrate in the roots of both species had increased considerably, a change attributable to increased starch concentrations in primary roots; fine roots, in contrast, contained least carbohydrate at this time. Most rapid g...