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1.
Nitrogen nutrition and Al toxicity with young beech plants. II: Mineral contents of young beech plants in relation to the source of nitrogen and the Al content of the nutrient solution Young beech plants were grown in aerated nutrient solutions with different Al concentrations over a period of 14 weeks. Nitrogen was supplied in either NO3 or NH4-form. pH-changes of the solutions were either corrected to the initial pH of 4,0 after two days, or not corrected over a period of two weeks. The cation contents of the roots and shoots were greater if the nitrogen was supplied in NO3-form. Increasing Al concentrations in the nutrient solutions led to an increase in Al contents and a decrease in Ca- and Mg-contents in roots and shoots.  相似文献   

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15N uptake and distribution by spring barley in relation to K nutrition and mildew attack Barley cv. Aramir was grown in complete nutrient solution containing 0,5 (K1), 1,5 (K2) and 4,5 mM K (K3) respectively till maturity. Part of the plants was infected by mildew (Erysiphe graminis), whereas control treatments were kept mildew-free by fungicide sprays. Symptoms of mildew attack were less at K2 and K3 and grain yields of infected plants were raised from 98 (K1) to 160 (K2) and 165 g/pot (K3). In control treatments grain yields were 130 (K1), 164 (K2) and 163 (K3) g/pot. During anthesis nitrogen in the nutrient solution was labelled with 15N for two days and 15N metablism was studied within 7 consecutive days. The aim of this pulse-chase experiment was to find out, how mildew attack and K nutrition influence N metabolism. The following results were obtained: a) 15N uptake increased from K1 to K2 in infected and healthy plants, though at slightly lower levels in the infected treatments. b) During 7 days after the 15N pulse up to 17,1% of the 15N absorbed were translocated into the grains. Better K status as well as spray treatments stimulated nitrogen translocation. c) Mildew attack of leaves does not seem to influence the conversion of grain-15N into grain proteins. Better K supply stimulates the rate of protein synthesis in the grain. d) In mildew infected leaves relatively more of the 15N absorbed is incorporated into leaf proteins. But this may be a consequence of slower grain growth, because already 7 days after anthesis infected plants in all K treatments had significantly lower grain yield. In spite of the short duration of the experiment the 15N data do not indicate that the visible depression of mildew attack by better K nutrition of the crop might inter alia be due to K stimulated defense reactions within N metabolism. This is in agreement with a previous experiment.  相似文献   

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Interaction between mechanically and hydraulically affected soil strength depending on time of loading Soil‐deformation analysis often only considers the direct effects of mechanical stress on changes in void ratio or pore functions while the interaction between hydraulic and mechanical processes is seldomly mentioned. Thus, we analyzed the effect of mechanical stress and time of soil settlement on changes in soil strength and the corresponding interactions between stress‐dependent changes in pore water pressure on precompression stress for a clayey silt. Disturbed samples with a bulk density of 1.4 g cm–3 and a water content of 25 g (100 g)–1 were compressed for four time steps (10–240 min) at eight stresses (20–400 kPa) with four replications. During the experiments, the changes of pore water pressure and void ratio were registered. With increasing time of stress application, we determined an increased soil strain. The higher the stress‐application time, the smaller gets the void ratio and the precompression stress value. Parallel to these variations in settlement, we also found changes in the pore‐water‐pressure values. This is a consequence of decreasing pore diameter while the water saturation increases. Thus, the proportion of neutral stresses on total stress increases which coincides with a change of water suction (= unsaturated) conditions up to even positive pore‐water‐pressure values (from less negative to positive pore water pressure values). From our experiments, we can conclude that the changes in pore‐water‐pressure values already occur at normal stress values smaller than the precompression stress. This underlines the increasing sensitivity of soil deformation processes close to the internal soil strength. The results support the idea, that in order to quantify the mechanical strength of structured unsaturated soils, we always have to determine the changes in pore‐water‐pressure values, too.  相似文献   

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Starch content of potato tubers in relation to K nutrition and tuber growth In a pot experiment with potato (cv Saturna) K content in tubers increased from 1.0 to 2.6 % of tuber-DM due to increasing rates of K fertilizer. Simultaneously starch in tuber fresh matter decreased from 21 to 15 %. Highest starch content in tuber dry matter was obtained in that K treatment which gave the highest yield in dry tubers. Measuring starch accumulation during tuber growth revealed that already in the flowering stage differences exist in the starch contents of the tuber dry matter between the lowest and highest K treatments, namely 69 % for K1 as compared with 64 % for K5. The rate of starch accumulation between flowering and final harvest, however, was similar in all K treatments. This suggests that K supply affects the storage tissue at an early stage of tuber development probably via different water relations of tubers.  相似文献   

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Nitrogen Assimilation in Roots and the Transport of Nitrogen Compounds in the Bleeding Sap of Roots in relation to Manganese Nutrition. The assimilation of nitrogen in the roots of 27 days old pumpkin plants was examined in relation to manganese nutrition. The transport of nitrogen compounds in the xylem was determined in roots and in the bleeding sap of roots using nitrate as the N-source. The maximum NO3 content in the roots was observed in the Mn treatment which resulted in the highest shoot yields (0.05 ppm Mn). The bleeding sap of this treatment was lowest in nitrate concentration, but showed the highest rate of transport of organic nitrogen compounds. In experiments with 15N in the nutrient solution the isotope was found in the roots in organic and in inorganic compounds. The composition of the fraction of free amino acids differed between roots and xylem sap. In the bleeding sap glutamine was especially dominant. In the roots the amino acid composition depended on the extent of Mn-supply. Lowest glutamine concentrations were found in the xylem sap from the treatment with maximum shoot yields. A numerical difference was found in the xylem sap between organic N (N(org)) and the amino acid nitrogen. This difference which account for more than 50 % of the organically bound nitrogen is suggested to be made up in part by low molecular weight peptides, amino sugars and other compounds. In Mn deficiency a general reduction in the intensity of nitrogen metabolism was found. With Mn toxicity the N assimilation activity was more intensive than for the low Mn supply. Simultaneously, however, the transport of organic N compounds from the root was lower.  相似文献   

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Influence of nitrogen nutrition and application of growth regulators on tuber initiation in potato plants In water culture the effect of continuous and discontinuous N-nutrition on tuber initiation was investigated. Additional applications of growth regulators on growing stolon tips were carried out. Continuous supply of nitrate or ammonium inhibited completely the tuber initiation in S. tuberosum varieties ?Ostara”? and ?Clivia”?, The inhibition was compensated by application of CCC and ABA on the stolon tip. In contrast to this stolon application of kinetin and root application of CCC were ineffective. Temporarily damaging of the root system led to tuber initiation even when nitrogen was supplied continuously. In S. andigena grown under short day continuous N supply only delayed the tuber initiation but could not prevent it. Discontinuous N supply promotes tuber initiation in S. tuberosum. A sudden increase in N supply caused ?re-growth”? of the tuber, i.e. a stolon was formed on the tuber apex. GA3 application on the growing tuber had the same effect. The effect of N nutrition on tuber initiation can be explained via changing the balance of endogenous growth regulators in general and the physiological aging of the leaves in particular. Discontinuous N supply seems to reduce cytokinin production in roots and therefore accelerates the aging of the leaves. This in turn favours the formation of inhibitors and/or presumably reduces the GA production in the shoot, which will change the balance of the growth regulators in the stolon tip in favour to tuber initiation.  相似文献   

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The influence of the relation between NO3 and NH4 in the nutrient solution on yield and organic and inorganic ion contents of tomato plants. . Tomato plants were grown in aerated media of oppositly varying supply of (NH4)2SO4-and NaNO3 with a constant N-quantity of 15 meq/1 or a quantity of NH4-, NO3 or (NO3 + NH4) increasing from 3 to 30 meq.N/1. Yield and ion content were determined. A maximum yield was achieved by a mixed N-supply i.e. 4 to 5 parts NO3, 1 part NH4-N and 7, 5 meq N/l. The “(C-A) value” was calculated by the content of the cationions “C” (=K+ + Na+ + Ca++ + Mg++ + NH4+) and the inorganic anions “A” (= NO3? + Cl? + H2PO4? + SO4). The “(C-A)” value is equivalent to the content of the organic anions. Furthermore we determined the citrate, malate, oxalate, and pektinate content. These make up 60–80% of the (C-A) value. The NO3- and K content increase considerably, the Ca-, Mg-, Na-, Citrate, Malate and Oxalate content increase less pronounced, the Cl-, H2PO4- and SO4- content decrease as the NO3 content increases from 0–80%. If the medium contains 80–100% NO3 - N, the NO3 and K content remain almost constant, while the Ca-, Mg-, citrate, malate and oxalate content especially increase in this case. The K content decreases in the presence of a high (NH4)2SO4 supply. Parallel to this the value (C-A) decreases greatly, so that it is less than the sum of the determined organic anions. In this case the content of organic anions obviously does not correlate with the (C-A) value. The yield correlates with the carboxylate contents. (C-A) values of 150–170 mval/100 gm. d. m. cause a lowering of the yield. The plants contain an almost equal amount of citrate, malate and oxalate. Depending on the N-concentration of the medium, the malate content will be a bit more than the amount of citrate in case of maximum yield. If there is a lack or toxicity in the medium the citrate content will be higher than the malate content. The yield per dry weight correlates positivly with the quotients of citrate and malate.  相似文献   

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Phosphate mobility in relation to fertilizing effects in raised-bog peat The phosphate solubility of raised-bog peat soils is very different from the phosphate solubility of mineral soils. Compared to mineral soils the losses of phosphates by leaching are 10 to 20 times higher. This mobility of phosphates is destined by the quantity, kind and time of fertilizing, land use (grassland or arable land) and fertilizing technique. Field and lysimeter trials with raised-bog peat soils show: 1. Water soluble phosphates are quickly translocated and leached. 2. Water insoluble phosphates are quickly solved and leached in raised-bog peat soils. The mobility of the phosphates decreases with increasing pH-value of the top soil and topdressing. At a pH-value of 4,O nearly 80% of Thomasphosphat and nearly 70% of Hyperphos phosphates are leached in lysimeter trials; at pH-value of 4 3 only 17 % of Thomasphosphat and 15 % of Hyperphos phosphates are leached. 3. To minimize leaching losses phosphate fertilizingin spring is recommended to reduce the phosphate leaching. 4. The phosphate leaching in grassland is twice or thrice less than in arable land.  相似文献   

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Uptake and translocation of 42 and 86Rb by young seedlings in relation to different calcium levels in the root medium The uptake of 42K and 86Rb by 8-d.-old barley seedlings was studied after 4 h period in solutions containing either 42K or 86Rb (1 mmol 42KNO3 + 1 mmol KCl; 1 mmol 86RbCl + 1 mmol RbNO3). The amount of 42K was 56% and 20% higher than that of 86Rb in the roots and shoots respectively (Pict. 1). Increasing the level of Ca in the root medium enhanced 42 86Rb uptake. However the translocation rate of 86Rb in the shoot was relatively lower than that of 42K. In view of the content in the roots both elements were translocated to the shoot in a similar percentage (Table 1).  相似文献   

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The growth and Zn-, Fe- and P-contents of higher plants in relation to Zn-supply The influence of varied supply of zinc was studied on nine different plant species growing in water culture under controlled experimental conditions. The results of the trials were as follows: 1. The vegetative development of the plant was enhanced by increasing supply of zinc in the nutrient solution. Visible symptoms of zinc deficiency were observed in all plants tested up to a level of 10 μg Zn/l in the nutrient medium. Latent zinc deficiency is to be expected when the zinc supply lies between 10 and 100 μg/l. Normal plant development was recorded in the 100 μg/l Zn/l treatment. 2. The zinc content of all plant organs (except in the trial series without zinc) rose with increasing zinc supply. Zinc contents differed greatly depending on plant species. In onions deficiency symptoms appeared during plant development at a zinc content below 7.8 ppm in the dry matter of the leaves. The corresponding value for flax was 21.5 ppm Zn. The range of latent zinc deficiency was characterized by zinc contents between 13.8 and 37.5 PPm. The optimal zinc content differs depending on plant species. For these very varied Zn-treatments and different species, values between 15.8 and 52.0 were found. 3. Leaf Zn content does not always provide a reliable measure of the Zn-nutritional status of the plant. This is, because zinc contents are extremely dependent upon plant species, the age of the plant, and experimental conditions, etc. 4. A higher zinc concentration was measured in older than in younger leaves. 5. The phosphorus contents in all organs were depressed by increasing zinc supply in the nutrient solution. The leaves of the plants in the trial series without zinc had the heighest phosphorus content. The P:Zn ratio at optimal plant growth differs between species. In the control plants this ratio, measured in the younger leaves, was 100 in millet and 262 in soybean. When the symptoms of zinc deficiency are very pronounced, these values lie above 1000. Zinc deficiency does not occur if the P:Zn ratio is below 250 (except in Cotton and beans). 6. Increasing zinc supply led to a decrease in the iron content in the plant organs of all species tested. The iron content was particularly high in those plants which did not receive any zinc.  相似文献   

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