共查询到20条相似文献,搜索用时 46 毫秒
1.
Starch synthesis in potato tubers grown at varied K nutrition 0.1 (K 1), 0.25 (K 2) and 1.0 mmol K L - nutrient solution (K 3) was investigated with particular regard to the activity of selected enzymes (sucrose synthase, UDP-D-glucose pyrophosphatase, starch phosphorylase, amylases) in dependence on tuber K content. Allocation of K to the tubers was nearly the same in all treatments. The activity of enzymes related to tuber K content did not differ significantly. Starch and K content of tubers increased with progressing age, whereas a decrease was observed in growth rate, starch synthesis per day and K uptake per day. Positive correlations between the rates of K uptake, starch production and growth indicate that the dynamic phase of K supply to the tubers is of greater importance for starch synthesizing processes than the influence of total K content. 相似文献
2.
The aim of this work was to discover whether genetic manipulation of 6-phosphofructokinase [EC 2.7.1.11; PFK(ATP)] influenced the rate of respiration of tuber tissue of Solanum tuberosum L. Transgenic plants were produced that contained the coding sequence of the Escherichia coli pfkA gene linked to a patatin promoter. Expression of this chimaeric gene in tubers resulted in a 14to 21-fold increase in the maximum catalytic activity of PFK(ATP) without affecting the activities of the other glycolytic enzymes. Tubers, and aged disks of tuber tissue, from transformed plants showed no more than a 30% fall in the content of hexose 6-monophosphates; the other intermediates of glycolysis increased threeto eightfold. Fructose-2,6-bisphosphate was barely detectable in aged disks of transformed tubers. The relative rates of 14CO 2 production from [1- 14C]-and [6- 14C]-glucose supplied to disks of transformed and control tubers were similar. Oxygen uptake and CO 2 production by aged disks of transformed tubers did not differ significantly from those from control tubers. The same was true of CO 2 production, in air, and in nitrogen, for tuber tissue. It is concluded that PFK(ATP) does not dominate the control of respiration in potato tubers.Abbreviations Fru2,6bisP
fructose-2,6-bisphosphate
- FW
freshweight
- GUS
-glucuronidase
- PFK(ATP)
6-phosphofructokinase
- PFK(PPi)
pyrophosphate: fructose-6-phosphate 1-phosphotransferase 相似文献
3.
Changes in 14C 2H 4 metabolism in the abscission zone were monitored during cotton (cv. Deltapine 16) leaf abscission. Rates of 14C 2H 4 oxidation to 14CO 2 and tissue incorporation in abscission zone segments cut from the second true leaf of nonabscising leaves of intact plants were similar (about 200 disintegrations per minute per 0.1 gram dry weight per 5.5 hours) and relatively constant over a 5-day period. Deblading to induce abscission caused a dramatic rise in 14C 2H 4 oxidation, but tissue incorporation was not markedly affected. This rise occurred well before abscission, reaching a peak of 1,375 disintegrations per minute per 0.1 gram dry weight per 5.5 hours 2 days after deblading when abscission was 40%. The rate then gradually declined, but on day 5 when abscission reached completion, it was still nearly three times higher than in segments from nonabscising leaves. Application of 0.1 millimolar abscisic acid in lanolin to the debladed petiole ends increased the per cent abscission slightly and initially stimulated 14C 2H 4 oxidation. In contrast, naphthaleneacetic acid applied in a similar manner delayed and markedly inhibited both abscission and 14C 2H 4 oxidation. 相似文献
4.
The role of K + in potato ( Solanum tuberosum L.) tuberization, based on the effects of K fertilizer and soil exchangeable K +, appears to be mostly contradictory. Here, we provide evidence that K + at high concentrations is detrimental to tuber development in vitro once induction has taken place. An experimental system using in vitro-cultured single-node cuttings showed that K + at ≥30.0 mM significantly reduced tuber fresh mass concomitant with a corresponding decline in starch content. However, high
K + did not affect tuber induction in terms of number of tubers developed per cutting. High K +-induced inhibitory effect on tuber development was attributed to a reduced rate of assimilate partitioning. 86Rb(K) transport to stolons, and tubers that acted as strong sinks in vitro were proportional to exogenous K + levels; however, 86Rb accumulation and K + deposition were markedly reduced in tubers as compared with that in stolons, especially at higher K + levels. The results indicated a diminishing sink strength developed by tubers with increasing K nutrition. Highly significant
negative correlations between 86Rb accumulation/K + deposition in both the sink organs and tuber fresh mass reinforced the inhibitory effect of high K + on tuber development. The rate of tuber K removal in vitro was similar to that of crop K removal reported in vivo, suggesting highly conserved K uptake and transport mechanisms during tuberization process. The results have been discussed
in the context of possible effects of high K + on impairing sucrose uptake and metabolism. 相似文献
5.
In leaf pieces from nodulated soybean ( Glycine max [L] Merr cv Maple Arrow) plants, [ 14C]urea-dependent NH 3 and 14CO 2 production in the dark showed an approximately 2:1 stoichiometry and was decreased to less than 11% of the control (12-19 micromoles NH 3 per gram fresh weight per hour) in the presence of 50 millimolar acetohydroxamate, a urease inhibitor. NH 3 and CO 2 production from the utilization of [2- 14C] allantoin also exhibited a 2:1 stoichiometry and was reduced to a similar extent by the presence of acetohydroxamate with a concomitant accumulation of urea which entirely accounted for the loss in NH 3 production. The almost complete sensitivity of NH 3 and CO 2 production from allantoin and urea metabolism to acetohydroxamate, together with the observed stoichiometry, indicated a path of ureide assimilation (2.0 micromoles per gram leaf fresh weight per hour) via allantoate, ureidoglycolate, and glyoxylate with the production of two urea molecules yielding, in turn, four molecules of NH 3 and two molecules of CO 2. 相似文献
6.
In pot experiments with Solanum tuberosum L. (cv Saturna) the application of KCl as compared to K 2SO 4 delayed tuber development. The solute composition of leaves of the KCl treated plants was significantly lower in K + and NO 3
-, but higher in Mg 2+, Ca 2+ and Cl -. Since the solute potential in the KCl treated plants was more negative and associated with a higher water content, a higher turgor pressure can be assumed. This could explain the enhanced shoot growth observed with KCl. Application of K 2SO 4, on the other hand, accelerated the development of tubers. This might result from a less competitive shoot sink in K 2SO 4 treated plants and a stimulated phloem loading and translocation of assimilates by higher concentrations of leaf-K. 相似文献
7.
The effect of short- and long-term changes in shoot carbon-exchange rate (CER) on soybean ( Glycine max [L.] Merr.) root nodule activity was assessed to determine whether increases in photosynthate production produce a direct enhancement of symbiotic N 2 fixation. Shoot CER, root + nodule respiration, and apparent N 2 fixation (acetylene reduction) were measured on intact soybean plants grown at 700 microeinsteins per meter per second, with constant root temperature and a 14/10-hour light/dark cycle. There was no diurnal variation of root + nodule respiration or apparent N 2 fixation in plants assayed weekly from 14 to 43 days after planting. However, if plants remained in darkness following their normal dark period, a significant decline in apparent N 2 fixation was measured within 4 hours, and decreasing CO 2 concentration from 320 to 90 microliters CO 2 per liter produced diurnal changes in root nodule activity. Increasing shoot CER by 87, 84, and 76% in 2-, 3-, and 4-week-old plants, respectively, by raising the CO 2 concentration around the shoot from 320 to 1,000 microliters CO 2 per liter, had no effect on root + nodule respiration or acetylene-reduction rates during the first 10 hours of the increased CER treatment. When the CO 2-enrichment treatment was extended in 3-week-old plants, the only measured parameter that differed significantly after 3 days was shoot CER. After 5 days of continuous CO 2 enrichment, root + nodule respiration and acetylene reduction increased, but such changes reflected an increase in root nodule mass rather than greater specific root nodule activity. The results show that on a 24-hour basis the process of symbiotic N 2 fixation in soybean plants grown under controlled environmental conditions functioned at maximum capacity and was not limited by shoot CER. Whether N 2-fixation capacity was limited by photosynthate movement to root nodules or by saturation of metabolic processes in root nodules is not known. 相似文献
8.
In the dark, leaf tissue of crisphead lettuce ( Lactuca sativa L.) metabolized 14CO to 14CO 2 and acid-stable products. Tissue incubated at 2.5°C for 3.5 hours and 48 hours converted about 1% and 17%, respectively, of the applied 14CO to 14CO 2, and incorporated about 0.04% and 0.6% of the 14C in acid-stable products. Examination of soluble acid-stable products from 14CO and 14CO 2-treated leaf tissue revealed that the labeling patterns of both treatments were identical during the 3.5-hour and the 48-hour incubation periods. Malate, citrate, and aspartate together comprised 70% or more of the soluble radioactivity from both treatments. Incorporation of radioactivity from CO into soluble acid-stable products during a 3-hour incubation period at 2.5°C was inhibited 90% by adding 3% nonradioactive CO 2. These results indicate that in head lettuce in the dark 14CO is metabolized primarily to 14CO 2 which is the precursor of acid-stable products. In leaf discs at 2.5°C, the apparent Km for CO oxidation to CO 2 was 5.3 microliters per liter and the Vmax was 9.7 nanoliters per gram per hour. The mitochondrial fraction of the leaf homogenate was the most active fraction to oxidize CO to CO 2, and this activity was heat-labile and cyanide-sensitive. 相似文献
9.
Portulacaria afra (L.) Jacq., a perennial facultative Crassulacean acid metabolism (CAM) species, was studied under natural photoperiods and temperatures in San Diego, California. The plants were irrigated every fourth day throughout the study period. Measurements of 14CO 2 uptake, stomatal resistance, and titratable acidity were made periodically from July 1981 through May 1982. P. afra maintained C 3 photosynthesis during the winter and the spring. Diurnal acid fluctuations were low and maximal 14CO 2 uptake occurred during the day. The day/night ratio of carbon uptake varied from 5 to 10 and indicated little nocturnal CO 2 uptake. CAM photosynthesis occurred during the summer and a mixture of both C 3 and CAM during the fall. Large acid fluctuations of 100 to 200 microequivalents per gram fresh weight were observed and maximal 14CO 2 uptake shifted to the late night and early morning hours. Daytime stomatal closure was evident. A reduction in the day/night ratio of carbon uptake to 2 indicated a significant contribution of nocturnal CO 2 uptake to the overall carbon gain of the plant. The seasonal shift from C 3 to CAM was facilitated by increasing daytime temperature and accompanied by reduced daytime CO 2 uptake despite irrigation. 相似文献
10.
Dry-matter accumulation was greater in staked than in unstaked plants of the lesser yam ( Dioscorea esculenta). Staking, N and K application tended to increase the proportion of dry matter diverted into the tubers. Staking was the most important factor in increasing total tuber production, which was one and a half times greater in staked than in unstaked plants. Leaf-area development was closely and positively related to vine growth, and since staking and N application encouraged vine growth these treatments therefore led to the production of plants with greater leaf area. Leaf-area duration was increased by staking and N application and was closely and positively related to tuber yield. Staking and N application increased tuber number per plant while K application increased the size of individual tubers. Staking and K application increased bulking rate and both treatments increased the period of bulking by causing earlier tuber initiation. 相似文献
11.
Nitrate uptake by roots of cowpea ( Vigna unguiculata) was measured using 15NO 3−, and the energy cost to the root was estimated by respirometry. Roots of 8-day-old cowpea seedlings respired 0.6 to 0.8 milligram CO 2 per plant per hour for growth and maintenance. Adding 10 millimolar NO 3− to the root medium increased respiration by 20 to 30% during the following 6 hours. This increase was not observed if the shoots were in the dark. Removal of NO 3− from the root medium slowed the increase of root respiration. The ratios of additional respiration to the total nitrogen uptake and reduced nitrogen content in roots were 0.4 gram C per gram N and 2.3 grams C per gram N, respectively. The latter value is close to theoretical estimates of nitrate assimilation, and is similar to estimates of 1 to 4 grams C per gram N for the respiratory cost of symbiotic N 2 fixation. 相似文献
12.
The addition of glyoxylate to tobacco ( Nicotiana tabacum) leaf discs inhibited glycolate synthesis and photorespiration and increased net photosynthetic 14CO 2 fixation. This inhibition of photorespiration was investigated further by studying the effect of glyoxylate on the stimulation of photosynthesis that occurs when the atmospheric O 2 level was decreased from 21 to 3% (the Warburg effect). The Warburg effect is usually ascribed to the increased glycolate synthesis and metabolism that occurs at higher O 2 concentrations. Photosynthesis in control discs increased from 59.1 to 94.7 micromoles of CO 2 per gram fresh weight per hour (a 60% increase) when the O 2 level was lowered from 21 to 3%, while the rate for discs floated on 15 millimolar glyoxylate increased only from 82.0 to 99.7 micromoles of CO 2 per gram fresh weight per hour (a 22% increase). The decrease in the O 2 sensitivity of photosynthesis in the presence of glyoxylate was explained by changes in the rate of glycolate synthesis under the same conditions. The rate of metabolism of the added glyoxylate by tobacco leaf discs was about 1.35 micromoles per gram fresh weight per hour and was not dependent on the O2 concentration in the atmosphere. This rate of metabolism is about 10% the amount of stimulation in the rate of CO2 fixation caused by the glyoxylate treatment on a molar carbon basis. Glyoxylate (10 millimolar) had no effect on the carboxylase/oxygenase activity of isolated ribulose diphosphate carboxylase. Although the biochemical mechanism by which glyoxylate inhibits glycolate synthesis and photorespiration and thereby decreases the Warburg effect is still uncertain, these results show that cellular metabolites can regulate the extent of the Warburg effect. 相似文献
13.
This study examined the effect of K (as K 2SO 4) supply on acid production under N 2-fixing plants of lupin (Lupinus angustifolius L. cv. Gungurru) and clover (Trifolium subterraneum L. cv. Dalkeith) grown in a K-deficient soil with a low pH buffer capacity for 55 days in the glasshouse at 20/12 °C (day/night). Increasing K supply up to 240 mg K kg -1 soil markedly increased plant growth of both species but clover growth was more responsive than lupin. Growing plants for 55 days decreased soil pH by 0.65–0.85 units under lupin and 0.45–0.83 units under clover. The amounts of H + produced per kg biomass (specific acid production) were the highest at the nil K supply, generally decreased with increasing K level up to 30 mg K kg -1 under lupin and up to 120 mg K kg -1 soil under clover and only slightly increased with further increasing K under lupin. Increasing K 2SO 4 supply proportionally increased plant uptake of K and SO
4
2-
but generally decreased concentrations of Ca, Mg, Na, P and Cl. Specific acid production correlated well with concentrations of excess cations and ash alkalinity, and total acid production was strongly correlated with total excess cations and total ash alkalinity in plants. These relationships were not affected by K treatment and species. Specific acid production also correlated with plant Ca concentration but not with K concentration. In addition, lupin and clover extruded similar amounts of H + per kg biomass produced. It is suggested that application of K 2SO 4 does not have a significant impact on acid production by lupin and clover. 相似文献
14.
A FACE (Free Air CO 2 Enrichment) experiment was carried out on Potato ( Solanum tuberosum L., cv. Primura) in 1995 in Italy. Three FACE rings were used to fumigate circular field plots of 8 m diameter while two rings were used as controls at ambient CO 2 concentrations. Four CO 2 exposure levels were used in the rings (ambient, 460, 560 and 660 μmol mol –1). Phenology and crop development, canopy surface temperature, above- and below-ground biomass were monitored during the growing season. Crop phenology was affected by elevated CO 2, as the date of flowering was progressively anticipated in the 660, 560, 460 μmol mol –1 treatments. Crop development was not affected significantly as plant height, leaf area and the number of leaves per plant were the same in the four treatments. Elevated atmospheric CO 2 levels had, instead, a significant effect on the accumulation of total nonstructural carbohydrates (TNC = soluble sugars + starch) in the leaves during a sunny day. Specific leaf area was decreased under elevated CO 2 with a response that paralleled that of TNC concentrations. This reflected the occurrence of a progressive increase of photosynthetic rates and carbon assimilation in plants exposed to increasingly higher levels of atmospheric CO 2. Tuber growth and final tuber yield were also stimulated by rising CO 2 levels. When calculated by regression of tuber yield vs. the imposed levels of CO 2concentration, yield stimulation was as large as 10% every 100 μmol mol –1 increase, which translated into over 40% enhancement in yield under 660 μmol mol –1. This was related to a higher number of tubers rather than greater mean tuber mass or size. Leaf senescence was accelerated under elevated CO 2 and a linear relationship was found between atmospheric CO 2 levels and leaf reflectance measured at 0.55 μm wavelength. We conclude that significant CO 2 stimulation of yield has to be expected for potato under future climate scenarios, and that crop phenology will be affected as well. 相似文献
15.
The effects of CO 2 concentration and illumination on net gas exchange and the pathway of 14CO 2 fixation in detached seeds from developing fruits of Lupinus albus (L.) have been studied. Increasing the CO2 concentration in the surrounding atmosphere (from 0.03 to 3.0% [v/v] in air) decreased CO2 efflux by detached seeds either exposed to the light flux equivalent to that transmitted by the pod wall (500 to 600 micro-Einsteins per square meter per second) in full sunlight or held in darkness. Above 1% CO2 detached seeds made a net gain of CO2 in the light (up to 0.4 milligrams of CO2 fixed per gram fresh weight per hour) but 14CO2 injected into the gas space of intact fruits (containing around 1.5% CO2 naturally) was fixed mainly by the pod and little by the seeds. Throughout development seeds contained ribulose-1,5-bisphosphate carboxylase activity (EC 4.1.1.39), especially in the embryo (up to 99 micromoles of CO2 fixed per gram fresh weight per hour) and phosphoenolpyruvate carboxylase (EC 4.1.1.31) in both testa (up to 280 micromoles of CO2 fixed per gram fresh weight per hour) and embryo (up to 355 micromoles of CO2 fixed per gram fresh weight per hour). In kinetic experiments the most significant early formed product of 14CO2 fixation in both light and dark was malate but in the light phosphoglyceric acid and sugar phosphates were also rapidly labeled. 14CO2 fixation in the light was linked to the synthesis of sugars and amino acids but in the dark labeled sugars were not formed. 相似文献
16.
Respiration of 18-month-old Solarium tuberosum L. tubers was about 53% greater than that of 6-month-old tubers during sprouting at 23°C; yet, a significant loss of sprout vigor in the older tubers was apparent. Involvement of alternative oxidase (AO) in the age-induced difference in tuber respiration was assessed. AO was only detected in immunoblots if tissue disks from tubers were pre-incubated for 24 h prior to isolation of submitochondrial membrane particles (SMPs). No AO 1 was detected in SMPs from nonincubated tuber tissue of either age, indicating that it was not contributing to tuber respiration during sprouting as previously thought. Respiratory control and ADP/O ratios indicated that oxidative phosphorylation was fully coupled to electron transport in mitochondria isolated from 6- and 18-month-old tubers. Cytochrome c oxidase (EC 1.9.3.1) activities of intact mitochondria were also not affected by tuber age. The difference in respiration during sprouting was unique to whole tubers, as oxygen consumption by mitochondria from young and oid tubers was equal on a milligram protein basis. Sprouting 18-month-old tubers had 15% more mitochondrial protein per gram fresh weight than did 6-month-old tubers. Older tubers also produced more ATP than younger tubers prior to and during sprouting, through a fully coupled, Cyt-mediated respiratory pathway, reduced sprout vigor notwithstanding. From 5 to 10 days of sprouting, coinciding with development of the age-induced difference in whole-tuber respiration, ATP concentration in 18-month-old tubers increased to become 52% higher than that in 6-month-old tubers. ATP synthase (EC 3.6.1.34), assessed by SDS-PAGE and immunoblots of β- and oligomycin-sensitivity conferring protein-subunits, also increased as a proportion of SMP protein in older tubers during this period. Relative to 6-month-old tubers, the increased respiration and associated oxidative phosphorylation of 18-rnonth-old tubers during sprouting were probably in response to a lower adenylate energy charge (AEC) prior to sprouting (from 0 fo 5 days). From 5 to 10 days of sprouting, AEC of 18-rnonth-old tubers increased to equal that of 6-month-old tubers and the two tuber ages maintained the same AEC for the remainder of the 20-day sprouting interval. Higher respiration and lower AEC of older tubers in storage at 4°C, along with the fact that older tubers respired at a higher rate to achieve the same AEC as younger tubers during sprouting, indicate greater utilization of ATP by older tubers. 相似文献
17.
Potassium (K +) plays important roles in the development of plants and the response to various environmental stresses. However, the involvement of potassium in alleviating heavy metal stress in tobacco remains elusive. Greenhouse hydroponic experiments were conducted to evaluate the alleviating effects of K + on tobacco subjected to cadmium (Cd) toxicity using four different K + levels. Dose-dependent increases of plant biomass were found in both 0-μM Cd and 5-μM Cd treatments under different K + levels, with the exception of the 1-mM KHCO 3 (K3) treatment. The best mitigation effect was recorded with the 0.5-mM K + (K2) treatment, which greatly alleviated Cd-induced growth inhibition, photosynthesis reduction, and oxidative stress. Compared with K0 treatment (no KHCO 3 addition), K2 treatment significantly reduced Cd uptake and translocation after 5 and 10 days of Cd treatment. Moreover, the net photosynthetic rate, intracellular CO 2 concentration, stomatal conductance, and transpiration rate as well as K +, zinc, manganese, copper, and iron concentrations in both shoots and roots after 10 days of Cd treatment significantly improved under the K2 treatment, and malondialdehyde accumulation in both shoots and roots was repressed, compared with K0 + Cd. Superoxide dismutase was found to play key roles in alleviating Cd-induced oxidative pressure in shoots of plants in K2 treatment under Cd treatment. Our findings advocate a positive role for K + in reducing pollutant residues for safe production, especially in soils slightly or moderately polluted with Cd. 相似文献
18.
Mesophyll cells and bundle sheath strands were isolated rapidly from leaves of the C 4 species Digitaria pentzii Stent. (slenderstem digitgrass) by a chopping and differential filtration technique. Rates of CO 2 fixation in the light by mesophyll and bundle sheath cells without added exogenous substrates were 6.3 and 54.2 micromoles of CO 2 per milligram of chlorophyll per hour, respectively. The addition of pyruvate or phosphoenolpyruvate to the mesophyll cells increased the rates to 15.2 and 824.6 micromoles of CO 2 per milligram of chlorophyll per hour, respectively. The addition of ribose 5-phosphate increased the rate for bundle sheath cells to 106.8 micromoles of CO 2 per milligram of chlorophyll per hour. These rates are comparable to those reported for cells isolated by other methods. The Km(HCO 3−) for mesophyll cells was 0.9 m m; for bundle sheath cells it was 1.3 m m at low, and 40 m m at higher HCO 3− concentrations. After 2 hours of photosynthesis by mesophyll cells in 14CO 2 and phosphoenolpyruvate, 88% of the incorporated 14C was found in organic acids and 0.8% in carbohydrates; for bundle sheath cells incubated in ribose 5-phosphate and ATP, more than 58% of incorporated 14C was found in carbohydrates, mainly starch, and 32% in organic acids. These findings, together with the stimulation of CO 2 fixation by phosphoenolpyruvate for mesophyll cells and by ribose 5-phosphate plus ATP for bundle sheath cells, and the location of phosphoenolpyruvate and ribulose bisphosphate carboxylases in mesophyll and bundle sheath cells, respectively, are in accord with the scheme of C 4 photosynthesis which places the Calvin cycle in the bundle sheath and C 4 acid formation in mesophyll cells. 相似文献
19.
Meta‐analysis techniques were used to examine the effect of elevated atmospheric carbon dioxide [CO 2] on the protein concentrations of major food crops, incorporating 228 experimental observations on barley, rice, wheat, soybean and potato. Each crop had lower protein concentrations when grown at elevated (540–958 μmol mol ?1) compared with ambient (315–400 μmol mol ?1) CO 2. For wheat, barley and rice, the reduction in grain protein concentration was ~10–15% of the value at ambient CO 2. For potato, the reduction in tuber protein concentration was 14%. For soybean, there was a much smaller, although statistically significant reduction of protein concentration of 1.4%. The magnitude of the CO 2 effect on wheat grains was smaller under high soil N conditions than under low soil N. Protein concentrations in potato tubers were reduced more for plants grown at high than at low concentrations of ozone. For soybean, the ozone effect was the reverse, as elevated CO 2 increased the protein concentration of soybean grown at high ozone concentrations. The magnitude of the CO 2 effect also varied depending on experimental methodology. For both wheat and soybean, studies performed in open‐top chambers produced a larger CO 2 effect than those performed using other types of experimental facilities. There was also indication of a possible pot artifact as, for both wheat and soybean, studies performed in open‐top chambers showed a significantly greater CO 2 effect when plants were rooted in pots rather than in the ground. Studies on wheat also showed a greater CO 2 effect when protein concentration was measured in whole grains rather than flour. While the magnitude of the effect of elevated CO 2 varied depending on the experimental procedures, a reduction in protein concentration was consistently found for most crops. These findings suggest that the increasing CO 2 concentrations of the 21st century are likely to decrease the protein concentration of many human plant foods. 相似文献
20.
Potato plants ( Solanum tuberosum L.) were grown in water culture.About 14 d after tuber initiation no significant differenceswere found between apical and basal tuber parts in 14C-uptakeand partitioning into various fractions from 14C-labelled photosynthate.Thus, the fresh weight of these tubers could be used as a parameterfor the sink size. The 14C-content per tuber (sink strength)20 h after 14CO 2-supply to the foliage was significantly correlatedwith the tuber fresh weight. No correlation was found betweenthe 14C-concentration of the tuber (sink activity; ct. min g fr. wt.) and tuber fresh weight. Consequently, tuberfresh weight (sink size) per se must have been a factor whichinfluenced sink strength. Stolon parameters characterizing theirgrowth prior to tuber initiation (e.g. stolon volume) and theircapacity for photosynthate transport (diameter, length) weremeasured at the time of tuber initiation. Significant correlationswere found between these stolon parameters and subsequent growthof individual tubers. Anatomical studies on the proportion ofvarious tissues in the cross sectional area of stolons supportthe idea of a negative relation between growth of individualtubers and transport resistance in the phloem of the stolons.It is concluded that in the initial phase of tuber growth, mainlyfactors outside of the tuber determine its growth rate. In laterstages of tuber growth, when the sink strength increases, thecompeting strength of individual tubers for photosynthate isdominated mainly by factors within the tuber itself, such astheir sink size and sink activity. Key words: Potato tuber, sink size, tuber initiation, transport resistance 相似文献
|