Dry Matter Formation Research Articles

Nitrogen fixation and assimilation efficiency in Ethiopian and German pea varieties

Dinitrogen (N2) fixation and assimilation efficiency in a German and two Ethiopian varieties of Pisum sativum L. was studied in a pot experiment during vegetative and reproductive growth. The objective of the study was to assess whether genotypes having contrasting growth habits showed differences in physiological processes that affect the efficiency of N2 fixation and assimilation. Dry matter formation, nodulation and nitrogen assimilation were compared between two treatments where one depended solely on N2 fixation while the other was nourished with nitrate. Moreover, carbon (C) costs of N2 fixation and the capacity of different respiratory chains in roots and nodules were determined at vegetative and reproductive growth. As compared to the Ethiopian cultivars, the German variety displayed a more rapid vegetative growth with intensive N2 fixation and assimilation and highly efficient individual nodules. However, during reproductive growth, N2 fixation in the German variety declined sharply, while continuing in the Ethiopian varieties. Lowest C costs of N2 fixation coincided with most efficient individual nodules in both growth intervals. C costs of N2 fixation were lower during reproductive growth in all varieties which was accompanied by a shift in root/nodule respiratory capacity towards more C efficient respiratory pathways. The results provide further evidence that unreliable nitrogen fixation rates during reproductive growth of pea can be connected with restricted C supply to nodules. One strategy of pea plants to adapt to critical C availability is an increase in capacity of more C efficient root/nodule respiration.

Effects of supplied nitrogen form on growth and water uptake of French bean ( Phaseolus vulgaris L.) plants

In order to investigate the effect of N form on dry matter (DM) formation and water uptake rate, French bean (Phaseolus vulgaris L. `Sotaxa') plants were grown with a split-root system. Three treatments were compared: sole nitrate (NO− 3) supply (NN), sole ammonium (NH+ 4) supply (AA) and spatially separated supply of NO− 3 and NH+ 4 (NA). The pH of the nutrient solutions was kept constant at 6.3 using a pH-stat system. 9 days after onset of the treatments, NN plants had higher root (36%) and shoot dry matter (11%) than AA plants. N form drastically influenced partitioning of assimilates: in the NA treatment, the root half exposed to NO− 3 revealed a 170% higher DM than the root half exposed to NH+ 4. N form affected stable carbon-isotope discrimination (δ) of leaf tissue. In leaves of plants which were supplied with NH+ 4 (AA; NA) δ was significantly more negative (–29.4‰, –29.6‰) than in NN treatment (–28.2‰). We explain this effect by differences in stomatal conductance. We suppose that the significantly less negative δ of root tissue under NH+ 4 supply is most probably related to higher PEP-case activity. The water uptake rate was higher in NN than in AA grown plants. This effect was found in both, short- and long-term experiments. In case of NA plants, the water uptake in the root part being exposed to NO− 3 was 104% higher than in those receiving NH+ 4. At least in the case of the NA treatment we can exclude shoot growth effects as being responsible for differences in water uptake. We therefore assume that differences in root hydraulic conductivity are responsible for the observed effects.

Efficiency of N2 fixation inVicia faba L. in combination with differentRhizobium leguminosarum strains

The efficiency of symbiotic dinitrogen (N2) fixation in Vicia faba L. in combination with 3 different Rhizobium leguminosarum strains was studied in a pot experiment during vegetative and reproductive growth. The objective of the experiments was to assess variability among Rhizobium strains inoculated on single legume species and determine possible reasons for observed variations. Dry matter formation, N 2 fixation and the carbon (C) costs of N2 fixation were determined in comparison with nodule free plants grown with urea. Nodule number and the capacity of different respiratory chains in the nodules were also measured. The plants inoculated with the Rhizobium strain A 37 formed less dry matter and fixed less N compared to the other two Rhizobium strains (Vic 1 and A 150). This coincided with a lower number of nodules and higher C costs of N 2 fixation. The C costs for N 2 fixation were in all cases significantly lower during reproductive growth compared to vegetative growth. Neither the latter nor the differences in C expenditure for N 2 fixation between the Rhizobium strains could be explained in terms of differences or shifts in the capacity of different respiratory chains in the nodules.

Formation of microsclerotia of Verticillium dahliae on various crops

In 2 pot experiments, potato (cultivars Element, Mirka, Ostara and Astarte), pea, sugarbeet, onion, flax, spring barley, faba beans, spring wheat and spring rape were inoculated with V. dahliae by root dipping or by growing the plants in artificially infested soil. In both treatments the dry matter yield and formation of microsclerotia were determined for aerial parts. In plants grown in infested soil, the DW and microsclerotia formation were determined in stubbles and roots as well. The highest numbers of microsclerotia per g plant material and per pot in the root dipping treatment were found on potato, flax and barley. The microsclerotia density on potato cv. Element, pea and barley was higher in the root dipping treatment than in the soil infestation treatment. The reverse was true for potato cultivars Ostara and Mirka. Dry matter yield of the harvestable organs of potato cultivars Element and Astarte, flax, sugarbeet and barley was lower in the root dipping treatment than in the soil infestation treatment. The greatest inter-crop differences in the microsclerotia yield/pot were in the aerial parts. Flax gave the highest numbers of microsclerotia/pot, followed by the 4 potato cultivars. The other crops had a much lower microsclerotia yield. It is suggested that the results will be useful for modelling effects of various crops on the soil population at crop and farm level.

Field investigations of ammonia exchange between barley plants and the atmosphere. II. Nitrogen realiocation, free ammonium content and activities of ammonium‐assimilating enzymes in different leaves

ABSTRACTThe activities of glutamine synthetase (GS) and glutamate synthase (GOGAT) in different leaves of field‐grown spring barley were measured during the reproductive growth phase in 2 consecutive years. Concurrently, the contents of soluble ammonium ions and free amides in the leaves were determined. The studies were carried out to investigate the relationship between variations in these parameters and emission of NH3 from the plant foliage. GS and GOGAT activities declined very rapidly with leafage. The decline in enzyme activities was followed by an increase in soluble ammonium ions and amides in the leaf tissues. During the same period, about 75% of leaf and stem nitrogen was reallocated to the developing ear. The amount of NH3 volatilized from the foliage during the reproductive growth phase amounted to about 1% of the reallocated nitrogen. The experimental years were characterized by very favourable conditions for grain dry matter formation and for re‐utilization of nitrogen mobilized from leaves and stems. Ammonia volatilization occurring under conditions with declining GS and GOGAT activities and increasing tissue concentrations of NH4+ may be useful in protecting the plant from accumulation of toxic NH3 and NH4+ concentrations in the tissues.

Field investigations of ammonia exchange between barley plants and the atmosphere. I. Concentration profiles and flux densities of ammonia

ABSTRACTThe exchange of ammonia between the atmosphere and the canopy of spring barley crops growing at three levels of nitrogen application (medium N, high N and excessive N) was studied over two consecutive growing seasons by use of micrometeorological techniques. In most cases, ammonia was emitted from the canopy to the atmosphere. The emission started around 2 weeks before anthesis, and peaked about or shortly after anthesis. The volatilization of ammonia only took place in the daytime. During the night‐time, atmospheric ammonia was frequently aborbed by the canopy. Occasionally, plants in the medium and high N treatments also absorbed ammonia from the atmosphere during the daytime. Daytime absorption of ammonia never occurred in the excessive N canopy. The loss of ammonia from the canopy amounted in both years to 0.5–1.5 kg NH3‐N ha−1 and increased with the N status of the canopy. In agreement with the small losses of ammonia, the content of 15N‐labelled nitrogen in the plants did not decline during the grain‐filling period. The experimental years were characterized by very favourable conditions for grain dry matter formation, and for re‐utilization of nitrogen mobilized from leaves and stems. Consequently, a very high part of the nitrogen in the mature plants was located in grain dry matter (80–84% in 1989; 74–80% in 1990). The efficient re‐utilization of nitrogen may have reduced the volatilization of ammonia.

ハウス栽培におけるニホンナシ‘幸水’の器官別乾物重構成, 貯蔵養分および花芽着生の特徴

ハウス栽培におけるニホンナシ‘幸水’の器官別乾物重構成, 貯蔵養分および花芽着生の特徴

Some effects of mineral nutrient deficiencies on the growth ofActinidia chinensisPlanch.

SummaryA study was made of the deficiency symptoms and effects on the growth of young, rooted kiwi cuttings when grown in nutrient solutions lacking P, K, N or Mg. Leaf yellowing with N deficiency, dark green leaves with lack of P, and typical lesions with insufficient K and Mg supply resembled symptoms in other species. Major effects on dry matter production, stem and leaf growth, top:root ratios and contents of chlorophyll, P and K contents, as well as water contents, are described, and an attempt made to assess the relative importance of the effects of leaf numbers, area or net assimilation rates in determining dry matter formation. A marked sensitivity of kiwi to ammonium toxicity was also revealed. The results are discussed in relation to previous studies on nutrient deficiencies with other crop species.

Effect of Ammonium and Nitrate Supply on Dry Matter Production and Nitrogen Distribution in Urtica dioica

Summary The influence of low (3 mM) and high (22 mM) nitrate or ammonium supply on biomass and nitrogen distribution of Urtica dioica L. was studied under controlled environmental conditions. With respect to biomass production growth on nitrate was more effective than on ammonium irrespective of the concentration of the nitrogen source. Low nitrogen supply favoured dry matter formation of the root plus rhizome fraction, whereas high nitrogen supply resulted in a preferential growth of the leaf plus stalk fraction. Growth on 22 mM nitrate or ammonium caused a significant higher content of total nitrogen, nitrate and free amino acids (particularly asparagine and arginine) in all plant parts as compared to that found in plants grown on the 3 mM nitrogen sources. The distribution of total nitrogen between the various plant parts was similarly affected by the concentration of the nitrogen supply as was that of biomass. The main nitrogen storage compounds were nitrate on the one hand and the free amino acids on the other when nitrate or ammonium were the nitrogen sources. Nitrate was preferentially accumulated in the leaves and the stalks, whereas the free amino acids were more equally distributed between leaves, stalks and roots; however, their concentrations were significantly highest in the stalks, if ammonium was the nitrogen source.

A Dynamic Model for Above-Ground Growth and Dry Matter Production in a Forest Community

(1) A dynamic model for estimating the dry matter production rate of a plant community is described. The model is used to simulate the production rate of above-ground dry matter by trees and by the ground vegetation in a Scots pine (Pinus sylvestris) stand. Only formation of structural dry matter during the vegetative growth phase is considered. (2) The model assumes that growth and production rates are affected by environmental factors, but they are also dependent upon the internal state of the plant. Temperature is the only environmental factor considered. The physiological stage of development of the plant during the annual cycle is estimated as a function of temperature. Its effect on growth rate is brought into the model by means of inherent growth rhythm. (3) The concept of potential production rate, PPR, is introduced. It combines the effect of the inherent growth rhythm, number of growing compartments and the amount of available carbohydrates on the growth rate into one variable. The actual production rate of the community is obtained by multiplying PPR by the temperature factor. (4) Strong correlation was found between measured and modelled values for daily growth and production.

Estudos sobre a nutrição mineral do arroz: XVIII - efeito das deficiências de macro e micronutrientes e da toxidez de alumínio, cloro e manganês na morfologia, crescimento, produção e composição mineral das variedades IAC-164 e IAC-165 cultivadas em solução nutritiva

O arroz das variedades IAC-164 e IAC 165, foi cultivado em solução nutritiva (Hoagland nº 2) completa, com deficiência de N, P, K, Ca, Mg, S, B, Cu e Zn e com excesso de Al, Cl e Mn. Foram observados sintomas associados aos desequilíbrios nutricionais provocados pelos tratamentos. A produção de matéria seca na var. IAC -164 foi afetada pelos tratamentos na seguinte ordem: -N, -K, -P, -Mg, -B, -Ca -Zn, -S e -Cu; no caso da var. IAC-165 observou-se: -B, -N, -P, -K, -Mg, -Ca, -S e -Zn. Não houve produção de grãos nos tratamentos -Ca e -B. Os excessos Al, Cl e Mn afetaram significativamente a produção de matéria seca, sendo o efeito prejudicial do Mn maior que o do Al. A variedade IAC-164 foi mais afetada pela toxidez de Al e Cl. Consideram-se adequados os seguintes teores, encontrados na lâmina das folhas medianas por ocasião do perfilhamento pleno, respectivamente para as variedades IAC-164 e IAC-165: N -2,32 e 2,70%; P -0,28 e 0,49; K -2,83 e 4,21; Ca -0,94 e 0,94; Mg -0,93 e 0,88; S -0,13 e 0,16%.

Partitioning and Utilization of Net Photosynthate in a Nodulated Annual Legume

The economy of carbon in nodulated white lupin (Lupinus albus L.) was studied in terms of consumption of net photosynthate in nitrogen fixation, in maintenance of respiration, and in the production of dry matter and protein. Net photosynthesis rose to a maximum in early fruiting and then fell abruptly due to shedding of leaves. Nodulated roots acquired translocate equivalent to 51% of the plant's net photosynthate, 78% of the carbon of this translocate being respired, 10% entering dry matter, and 12% returning to the shoot attached to products of nitrogen fixation. Nodules utilized 4-0-6-5 g C in fixing 1 g nitrogen. Photosynthate was utilized most effectively for nitrogen fixation in late vegetative growth. Fruits sequestered 16% of the plant's net photosynthate, shoot night respiration 17%, and dry matter formation in shoot vegetative parts 22%. Averaged over growth, 9-9 g net photosynthate was required to produce 1 g seed dry matter and 31 g net photosynthate to produce 1 g seed protein. Budgets for utilization of the carbon of net photosynthate were constructed for 10 d intervals of the plant's growth cycle. Feeding of shoots with 14C02 resulted in radiocarbon becoming partitioned approximately as predicted by these budgets. The dependence of root respiration on recent photosynthate was assessed by following the time course of release of 14C02 to the rooting medium of the 14CTabelled plants.

Einfluß der verschiedenen K-Ernährung auf die Dynamik von RNS- und DNS-Gehalt in jungen Maispflanzen

The effect of K-deficiency on dry matter formation, DNA and RNA content was investigated in developing corn seedlings. Nucleic acid contents are severely decreased but can be restored after re-addition of potassium into the nutrient solution.

The effect of different sowing densities and nutrient levels on leaf area index, production and distribution of dry matter in maize (zea mays l.)

The course of biological curves of accumulation of total (Ybiol), vegetative (Yveg) and grain dry matter (Ygr) in maize(Zea mays L.)was investigated in a field experiment. The different population densities from 27 777 to 121 418 plants per ha were tested in interaction with increasing fertilizer rates (NPK) ranging from zero to 780 kg of pure nutrients per ha. The grain yield (Fgr) plotted against the population density shows a parabolic trend with a maximum at densities from 64 000 to 79 000 plants per ha. An asymptotic trend was obtained for the curve of biological yield (Fbiol) in relation to the population density. The optimum densities for Ygr and Fbiol were identical in the unfertilized control plot. At optimum and higher population levels the application of optimum rate of pure nutrients was 260 kg per ha. Leaf area index(L) was rising with the increasing stand density. Its value was also increased by increasing mineral nutrition but only at plant densities higher than 64 000 plants per ha. The proportion of Ygr/ Ybiol showed an optimum atL value within 2.03 and 2.68. Its value declined with further increase of both, stand densities and levels of NPK. The optimumL estimated for Ygr was within 2.65 and 3.87 and that for Yol in the control variant was 2.65. Tn fertilized plots even the highestL values (5.17) did not influence neither the biological nor the vegetative dry matter yields. Relative photosynthetic potential for dry matter formation (RPP gr) was decreasing with the increasing stand density.

The physiological activity of volatile substances of plants in air and water media

Physiological effects of volatile substances released by the overground as well as by the underground organs of higher plants were studied. The activity of the volatile substances was tested both when these substances were allowed to act directly in the air and when they were dissolved in water in the form of solutions. Plants which do not contain essential oils or which are not rich in them as well as those abounding in essential oils and other volatiles were used in the experiments. The physiological activity of the volatile substances was tested on rye seedlings.The overground as well as underground mature organs of the tested plants were found to release volatile substances causing, when acting directly, in the majority of cases an inhibition of the growth in length and of the formation of dry matter in rye seedlings. A pronounced inhibition of the growth of rye seedlings was brought about especially by the volatile substances of “aromatic” plants such as common dill, wild thyme, yarrow milfoil, garden thyme, marjoram, etc. The volatile substances released by the organs of “non-aromatic” plants like sugar-beet, common sunflower, quackgrass, etc., were found to bring about a significant inhibition of the growth of rye seedlings, too.The volatile substances released by the plant organs were found to be altogether absorbable in water and physiologically active also in the form of water solutions. With the exception of volatile substances from hemp and quackgrass leaves, which brought about a mild stimulation of the dry matter formation in rye seedlings, inhibitory effects of these solutions were found to prevail in all cases. Most effective were the solutions of the volatiles from some of the “aromatic plants”.An assay for olefines in the atmosphere of the experimental vessels demonstrated that in almost all cases ethylene is being released by the plant organs.

Contribution to the study of heterogeneity in the leaves of a spring wheat plant

The effect of the individual leaf blades of spring wheat on the dry matter of stalks, chaff and grain (caryopses), of spikes and total overground part, was studied. In the experimental plants the individual leaf blades were detached according to the scheme given, at the beginning of shooting, (A), at the beginning of earing (B), and at the beginning of flowering (C). The dry matter (fresh weight) of the stalk was least decreased if either the lowest or the uppermost leaf blade was severed during the developmental phase of shooting. The dry as well as the fresh weights of chaff were least affected in those plants where the leaf blade was removed during the developmental phase of flowering. Both the dry and fresh weights of caryopses were least decreased if either the lowest or the uppermost leaf blade was removed during the developmental phase of flowering. The dry weight as well as the relative water content of chaff and ear grains were most decreased following removal of leaf blades during the developmental phase of shooting. The relative water content of chaff, grains and ears was most decreased following removal of developed leaf blades during the developmental phase of earing. It was confirmed that in addition to the photosynthetic activity of leaves the photosynthesis of other parts of the stem system (stalk internodes, ear awns etc.) participated in the production of total dry matter of experimental plants. The photosynthetic activity of leaf blades was particularly high up to the earing phase, while subsequently the photosynthesis of extrafoliar area (stalk internodes and ears) predominated. In spite of this, participation of the total leaf area is very high in the formation of grain dry matter (over 50%), as well as of the total dry matter of plant (over 80%).

Effect of local x-irradiation on albumen formation by the hen's oviduct.

X-irradiation of the surgically exposed oviduct of the hen reduces the formation of albumen dry matter (which is composed essentially of protein). Over a dosage range of 0–4000 r, the irradiation effect is logarithmically related to the dose, with the albumen (dry basis) formation being reduced 40% at 4000 r. At higher doses (5000 r) irreversible changes apparently take place, since very few birds so treated return to egg production. Radioinhibition of albumen formation requires direct irradiation of the oviduct magnum tissue and, once established, appears to be more or less permanent. The functional status of the magnum tissue, relative to albumen secretion, at the time of irradiation does not appear to influence the result.

Analytic studies in plant respiration VII—Aerobic respiration in barley seedlings and its relation to growth and carbohydrate supply

Preliminary to a study of seedling respiration as affected by varying concentrations of oxygen, some sets of experiments were carried out in air as a standard oxygen medium. In these experiments growth was also measured and the relation between the rates of these two processes was determined. The major features of the carbon metabolism in the young seedling are, (1) hydrolysis of starch in the endosperm, (2) formation of new dry matter in the embryo by growth, (3) respiration of carbohydrates to carbon dioxide and water in both endosperm and embryo. By relating (1) with (2) and (3) we arrive at (4) the rate of translocation of carbohydrates from endosperm to embryo. All these activities may be expressed, for numerical comparison, in terms of hexose units per unit of time, so that it is possible to survey, on this common basis, the balance and relative rates of these processes. The rates of the component parts of the system are to be labelled as follows: H , production rate of liexoses by hydrolysis of carbohydrate reserves in the endosperm; R 1 ,respiration rate of hexoses in the endosperm; T , translocation rate of hexoses from the endosperm to the embryo; R 2 , the respiration rate of the embryo; G , the rate of growth of dry weight of the embryo material. We may add to this series P (as a subsection of G ) the rate of transitory deposition in the embryo of mobile reversible carbohydrate reserves such as starch, which are later available for respiration. G less P would stand for the irreversible growth of new tissue substance, in a restrictive sense, while G stands for the whole dry-weight increase.