Vegetative Plant Parts Research Articles

Partitioning of biomass in water‐ and nitrogen‐stressed cotton during pre‐bloom stage

Abstract The partitioning of biomass between aboveground parts and roots, and between vegetative and reproductive plant parts plays a major role in determining the ability of cotton (Gossypium hirsutum L.) to produce a crop in a given environment. We evaluated the single and combined effects of water and N supply on the partitioning of biomass in cotton plants exposed to two N supply levels, 0 and 12 mM of N, and two water regimes, well irrigated and water‐stressed at an early reproductive stage. The N treatments began when the third true leaf was visible, while water deficit treatments were imposed over the N treatments when the plants were transferred into controlled‐environment chambers at a leaf area near 0.05 m2. Both water deficits and N deficits inhibited total biomass accumulation and its partitioning in cotton. Water deficit alone and N deficit alone inhibited the growth of leaves, petioles, and branches, but did not inhibit growth of the stem and enhanced the accumulation of biomass in squares. ...

Dry Matter Partitioning in Tomato: Validation of a Dynamic Simulation Model

A model for dynamic simulation of dry matter distribution between reproductive and vegetative plant parts and the distribution among individual fruit trusses in glasshouse tomato, is validated. The model is part of the crop growth model TOMSIM and is based on the hypothesis that dry matter distribution is regulated by the sink strengths of the plant organs, quantified by their potential growth rates, i.e. the growth rates at non-limiting assimilate supply. Within the plant, individual fruit trusses are distinguished and sink strength of a truss is described as a function of its development stage. Truss development rate is a function of temperature only. The same potential growth curve, proportional to the number of fruits per truss, is adopted for all trusses. In a simple version of the model, vegetative plant parts are lumped together as one sink with a constant sink strength. In a more detailed version, vegetative sink strength is calculated as the sum of sink strengths of vegetative units (three leaves and stem internodes between two trusses). The model was validated for six glasshouse experiments, covering effects of planting date, plant density, number of fruits per truss (pruning at anthesis), truss removal (every second truss removed at anthesis), single- and double-shoot plants and a temperature experiment conducted in climate rooms at 17, 20 or 23 °C. Daily increase in above-ground dry weight, average daily temperatures and number of set fruits per truss were inputs to the model. Both the simple and the more detailed model showed good agreement between measured and simulated fraction of dry matter partitioned into the fruits over time. For the simple version of the model, the slope of the lines relating simulated to measured fraction partitioned into the fruits (16 data sets), varied between 0.92 and 1.11, on average it was 1.04, implying 4% over-estimation for this fraction. For the detailed model these numbers were slightly better: 0.89, 1.08 and 1.01, respectively. The temperature experiment revealed no important direct influence of temperature on the ratio between generative and vegetative sink strength. Simulated truss growth curves showed reasonable agreement with the measurements, although both models over-estimated (17% on average) final dry weight of the lower trusses (truss 1 –3) on a plant. Modelling dry matter partitioning based on sink strengths of organs is promising, as it is a general, dynamic and flexible approach, showing good agreement between measurements and simulation for a range of conditions. Applicability of the model is, however, still limited as long as the number of fruits per truss (flower and /or fruit abortion) is not simulated, as this is a major feedback mechanism in plant growth.

In Vitro Micropropagation and Flowering in Artemisia annua

A protocol for quick regeneration of a large number of plantlets of Artemisia annua (source of a potent antimalarial drug) is being reported. Multiple shoots were obtained in large numbers from juvenile as well as vegetative parts of mature plant on Murashige and Skoog’s medium (MS) having 3% sucrose and 800 μM myoinositol and supplemented with NAA (0.5 μM) + BAP (13.0 μM) + GA3 (0.3 μM) + Asp (300.0 μM) + Glu (700.0 μM) + Arg (300.0 μM) + Cys - HCl (30.0 μM). Reversal of reproductive to vegetative phase and back to reproductive phase could be achieved in the cultured flower buds. The shoots obtained on the above medium could be induced to flower. In addition, new shoots that differentiated from vegetative parts of juvenile and mature explants also produced flowers when cultured on MS with GA3 (0.3 μM). Since artemisinin estimation is correlative to flowering, our results would facilitate better understanding of biosynthesis of this drug in vitro.

Involvement of phenolic acids in disease resistance of potato tubers from CEPA-treated plants

Treatment of vegetative parts of potato plants two weeks before the harvest with 0.2% 2-chloroethylphosphonic acid (CEPA) delayed the sprouting of tubers and increased the resistance of tubers to infections caused byPhytophthora infestans, Erwinia carotovora andFusarium spp. during the storage period. Levels of free, soluble ester- and glycoside-bound phenolic acids and cell wall-bound phenolics were determined in cortical parenchyma of tubers (periderm). The enhancement of phenolic acids in tubers from treated plants was caused primarily by the increase in the contents of free vanillic, caffeic andp-hydroxybenzoic acids and cell wall-bound ferulic, vanillic andp-coumaric acids.

Separation of desulphoglucosinolates by micellar electrokinetic capillary chromatography based on a bile salt

Micellar electrokinetic capillary chromatography (MECC) has been developed as a promising method for the determination of 40 desulphoglucosinolates. A sodium cholate based MECC method was found to be efficient for the qualitative and quantitative analysis of desulphoglucosinolates produced in an on-colum, enzymatic step form the corresponding intact glucosinolates. Separation conditions and sensitivity of the method have been optimised with respect to different parameters, including capillary types, where the 75-μm I.D. capillary increased the sensitivity 2.5 times over that of a 50-μ capillary. With use of a high-sensitivity optical cell assembly (Z-cell), the sensitivity was further increased ten times, resulting in detection of picogram amounts, or concentration levels corresponding to 10 −6 M. Repeatability with a 75-μm capillary was good, with the relative standard deviation varying between 0.2% and 0.9% for relative migration times and for relative normalised areas between 1.0% and 3.0%. Linearity of the optimised method gave correlation coefficients between 0.99 and 0.9999 for the 50-μm capillary and 0.99 and 0.9997 for the 75-μm capillary. Separation efficiency expressed as number of theoretical plates ( N/m) was in the range 250 000–300 000 for the 50-μm capillary and 210 000–250 000 for the Z-cell. Limitations and possibilities of the MECC method here presented are discussed with respect to analyses of glucosinolates occuring in a wide range of cruciferous seed, vegetative plant parts including cabbage varieties, feed and food.

Effect of temperature on biomass allocation in tomato (Lycopersicon esculentum)

Temperature may influence dry matter partitioning between fruits and vegetative plant parts either directly or indirectly through its influence on development, flower and/or fruit abortion. The objective of the present work was to investigate whether there is any direct effect of temperature on dry matter partitioning between fruits and vegetative plant parts in tomato. A greenhouse experiment was conducted, with alternating 3‐week periods of high (23°C) and low (18°C) temperature setpoint. Dry matter partitioning during these 3‐week periods was determined from destructive plant harvests at two levels of fruit pruning (3 and 7 fruits per truss). Indirect temperature effects on dry matter partitioning were excluded by fruit pruning.On average, the fraction of dry matter distributed to the fruits during a 12‐week period, starting with the flowering of the fifth truss (28 days after planting), was 0.53 (3 fruits per truss) and 0.70 (7 fruits per truss). These ratios were also calculated for every 3‐week period separately and did not depend on the average temperature (18–24°C) during that period.It is concluded that dry matter distribution in tomato is not significantly affected by temperature directly, which means that the temperature effect (18–24°C) on the generative sink strength is not much different from the temperature effect on the vegetative sink strength.

Efficient nitrogen economy: Key to the success ofPolygonum bistorta in an abandoned mountain meadow

The dominance ofPolygonum bistorta in abandoned mountain meadows was studied. Successional and seasonal changes in biomass, nitrogen concentration and content were studied at the community level. During the successionP. bistorta increases its biomass both in absolute and mainly in relative values compared to the surrounding species. Nitrogen stored in its rhizomes seems to be quickly translocated into above-ground parts at the beginning of the growing season. High amounts of nitrogen allow rapid growth of both vegetative and generative plant parts. The success ofP. bistorta is probably the result of efficient use of stored nitrogen, suppression of surrounding vegetation by above-ground cover of leaves and by decrease in the level of soil nitrogen, and the effect of a large amount of litter. Management consisting in the combination of mowing and fertilization is proposed.

Macro‐nutrient Status of Brassica napus and Brassica juncea Grown Under Swedish Conditions

AbstractConcentrations and amounts of macro‐nutrients (N, P, K, Ca, Mg, S) in shoots, vegetative and generative plant parts in B. napus and B. juncea and nutrient inflow per unit root length in B. napus were studied in a field experiment at Uppsala, Sweden. Concentrations in vegetative plant parts were, except for Ca in B. napus, highest at the beginning of the season, and N and K were higher in B. napus than in B. juncea. The higher N concentration in vegetative parts (leaves, stems and pods) in B. napus was probably due to differences in growth pattern between the species. Seed concentrations of N, P, Ca, Mg and, most pronounced of all, S were higher in B. juncea. Nutrient amounts were, with the exception of K, throughout the season higher in B. juncea than in B. napus due to a higher dry matter production. Nutrient inflow per unit root length in B. napus was highest during the rosette stage for all nutrients. During flowering, the inflow decreased for N and K and increased for P and Ca. After root growth had stopped, no net inflow of K and S was found and inflow rates of other nutrients were at very low levels.

Seasonal Allocation and Efficiency Patterns of Biomass and Resources in the Perennial Geophyte Sparaxis grandiflora Subspecies fimbriata (Iridaceae) in Lowland Coastal Fynbos, South Africa

The seasonal allocation and efficiency of biomass and resources (starch, soluble carbohydrates, N, P, K, Ca, Mg, Na, Zn, Fe, Mn and Cu) within and between the constituent plant parts of Sparaxis grandiflora subspecies fimbriata , a deciduous, synanthous geophyte, are described. The sequential production of roots, leaves and a new daughter corm, with fruit production phased in during the development of the daughter corm, results in continual transfer of resources when the plant is not dormant. The new daughter corm serves as the major sink for the allocation of dry matter and resources during the vegetative, reproductive and senescent periods. The parent corm is the major source of resources in the early stages of the vegetative period. The amount of resources allocated to the reproductive structures was comparatively low when compared with that allocated to vegetative plant parts. The corms have highly flexible storage capacities for a variety of nutrients, particularly the better conserved nutrients such as nitrogen, phosphorus, potassium, and carbohydrates. The dynamic patterns for the majority of the resources revealed high allocation when metabolic activity was also highest. Efficient recovery or recycling of important resources from senescing organs results in a similar or greater allocation to the daughter corm than the amount that was present in the parent corm of the previous growth season. This is seen as an advantage to these plants that grow in a seasonal environment where soils are of low nutrient status.

Efficiency of Nitrogen Utilization in C3 and C4 Cereals.

Addition of nitrogen leads to increased dry matter accumulation in vegetative plant parts and to increased final yields in cereal crops (Hageman and Lambert, 1988). The efficiency with which nitrogen is used varies with plant species and with environmental conditions. For example, plants that possess a C4 pattem of photosynthesis have, in addition to a superior method for trapping COz from the atmosphere, a greater nitrogen use efficiency (g dry matter gain per mg nitrogen utilized) than do C3 plants (Brown, 1978). Although there are many differences in the metabolism of C3 and C4 plants, the major difference between these two pattems of photosynthesis is the contribution of photorespiration to both carbon and nitrogen metabolism. When photorespiration is reduced in C3 plants either by increasing ambient levels of COz or reducing levels of 02, both the yield (vegetative dry matter) and nitrogen use efficiency are enhanced (Evans, 1989). As indicated in Table I, this effect is apparent in wheat, a C3 cereal, but not in maize, a C4 cereal (Hocking and Meyer, 1991).

A Simulation Model for Dry Matter Partitioning in Cucumber

A dynamic model is developed for the simulation of the daily dry matter distribution between the generative and vegetative plant parts and the distribution among individual fruits in greenhouse cucumber. The model is based on the hypothesis that dry matter partitioning is regulated by the sink strengths of the plant organs. The sink strength of an organ is defined here as its potential growth rate, i.e. the growth rate at non-limiting assimilate supply. The sink strength of each individual fruit is described as a function of its temperature sum after anthesis and the actual temperature, that of the vegetative plant parts as a function of actual temperature only. The formation rate of non-aborting fruits is essentially a function of the source/sink ratio.Model results agreed well with the measured fluctuating distribution of dry matter between fruits and vegetative parts. The measured effects of three intensities of fruit removal were also simulated satisfactorily. When simulating the partitioning among individual fruits the final fruit size was simulated quite well. However, the growth rate of young fruits was usually overestimated and that of old fruits underestimated, because of dominance among fruits. This phenomenon could be accounted for by incorporating priority functions into the model. Finally, a sensitivity analysis of the model was performed to investigate the effects of some climatic factors, manipulations of the number of fruits on a plant and model parameters on dry matter distribution. Strategies to manipulate the dry matter distribution are discussed.

A Simulation Model for Dry Matter Partitioning in Cucumber

A dynamic model is developed for the simulation of the daily dry matter distribution between the generative and vegetative plant parts and the distribution among individual fruits in greenhouse cucumber. The model is based on the hypothesis that dry matter partitioning is regulated by the sink strengths of the plant organs. The sink strength of an organ is denned here as its potential growth rate, i.e. the growth rate at non-limiting assimilate supply. The sink strength of each individual fruit is described as a function of its temperature sum after anthesis and the actual temperature, that of the vegetative plant parts as a function of actual temperature only. The formation rate of nonaborting fruits is essentially a function of the source/sink ratio. Model results agreed well with the measured fluctuating distribution of dry matter between fruits and vegetative parts. The measured effects of three intensities of fruit removal were also simulated satisfactorily. When simulating the partitioning among individual fruits the final fruit size was simulated quite well. However, the growth rate of young fruits was usually overestimated and that of old fruits underestimated, because of dominance among fruits. This phenomenon could be accounted for by incorporating priority functions into the model. Finally, a sensitivity analysis of the model was performed to investigate the effects of some climatic factors, manipulations of the number of fruits on a plant and model parameters on dry matter distribution. Strategies to manipulate the dry matter distribution are discussed.

Effect of fruit growth, temperature and irradiance on biomass allocation to the vegetative parts of cucumber

Cucumber plants were grown in a greenhouse at 18 or 25 degrees C with four intensities of fruit removal (1 fruit remaining for every 1, 3 or 6 leaf axils, or all fruits removed) or at three different levels of irradiance (shading with cheesecloth to give 100, 50 or 30% transmittance) in order to analyse the effects of fruit growth, temperature and irradiance on the dry matter allocation to leaves, stems, petioles and roots. With increasing irradiance, the dry weight of the vegetative part of the shoot increased, but the proportion of the total dry matter distributed to this part decreased. An increase in irradiance enhanced stem dry matter production less than leaf and petiole dry matter production which was in turn less stimulated than root dry matter production. In fruit-bearing plants, an increase in temperature had no effect on the dry matter allocation to the leaves, stems and petioles, but reduced the allocation to the roots. Fruit growth strongly reduced dry matter production of all vegetative plant parts, but the distribution between stems, leaves and petioles was only slightly affected. At 25 degrees, the dry matter distribution between the roots and the vegetative part of the shoot was not affected by fruit growth, but at 18 degrees, the root to vegetative shoot dry weight ratio decreased with increasing number of fruits on the plant. The biomass allocation between roots and shoot is discussed in relation to the functional equilibrium concept.

Effect of fire on soil, rice, weeds and forest regrowth in a rain forest zone (Coˆte d'Ivoire)

In south-western Coˆte d'Ivoire mature forest is felled and burned and one crop of upland rice is grown. Forest is then allowed to regenerate for 15 or more years before being cropped again. Soils are very gravely, clayey, acid, thoroughly leached and chemically poor. Forest, soil, rice, weeds and regrowth were studied in the fields of local farmers in permanent plots during 2–5 years. The fields (16) covered all currently cultivated soil types and forest types. Burning leads to an instant mineralisation of organic matter and the ashes produce a marked decrease in acidity (before burning pH 4.4–5.2, after burning pH 5.4–6.2). The nutrient availability is further stimulated by the reduction of Al activity in the soil solution. Fire is a decisive factor in cultivation: slightly burnt or unburnt areas are wholly unproductive. The rice thrives on the nutrients contained in the ash of the burnt forest rather than on the nutrients of the mineral soil: the nature of the soil is of relatively little importance, as long as large quantities of biomass are burnt. A fire of normal intensity destroys enough buried seeds and vegetative parts of forest plants to avoid weed stress, yet allows the survival of a sufficient number of forest plants for forest regrowth after the rice crop. Excessive burning kills sprouts and buried seeds. Regeneration comes then from seeds dispersed into the field after the fire, mainly grasses and forbs. Grassy shrub land or thickets are thus formed.

The N2-fixing capacity of peanut cultivars with differing assimilate partitioning characteristics

The contribution of symbiotic N2 fixation to the total N budget of irrigated crops of peanut (Arachis hypogaea L.) during vegetative and reproductive growth was investigated using four peanut cultivars with differing patterns of dry matter (DM) partitioning to developing pods. Estimates of NZ fixation were obtained with the 15N natural abundance procedure by using a non-nodulating peanut genotype as a non-N2-fixing reference plant. Partitioning was assessed on the basis of vegetative DM equivalents, with adjustments to pod DM based on relative synthesis costs of vegetative and pod DM. Cultivars differed in crop duration, DM production and yield of pods and kernels. Despite large differences in derived DM partitioning coefficients among cultivars (0.68 to 1.03), both total crop N and fixed N increased as a constant proportion of accumulated, energy-adjusted DM. Crop duration was the primary factor determining both total crop N and fixed N. In addition to fixation, all cultivars continued to accumulate soil mineral N throughout the season. However, in all cultivars except TMV-2, crop N uptake during reproductive growth was insufficient to meet the demands of developing pods and N was renlobilized from vegetative plant parts. Remobilized N was almost exclusively N derived originally from N2 fixation. Despite relatively high levels of N2 fixation (from 140 to 210 kg N ha-1, depending on crop duration), all cultivars except Virginia Bunch showed a negative apparent N balance when the amounts of N2 fixed were compared to N removed in pods at final harvest. This was primarily due to high N harvest indices (0.62 to 0.73), and is likely to be a feature of many recently released, high yielding cultivars.

Determination of flavonoids by micellar electrokinetic capillary chromatography

HPCE based on cetyltrimethylammonium bromide (CTAB) or cholate micellar electrokinetic capillary chromatography (MECC) was found suitable for the separation of individual flavonoid glycosides following a rapid and simple technique of isolation, purification and group separation. Kaempferol and quercetin glycosides with varying degrees of glycosylation, and with or without additional esterification on the carbohydrate part, were included in the study. The influence of temperature and voltage as well as electrolyte, CTAB and organic modifier concentrations in the buffer on the migration order, migration times, and peak areas of the flavonoids was investigated. The method developed gives possibilities for the separation and specific determination of flavonoids isolated from vegetative parts of cruciferous plants.

Fruit growth and biomass allocation to the fruits in cucumber. 2. Effect of irradiance

Cucumber plants were grown at three different irradiances in a glasshouse for a short (4 day) and an extended period (62 day). The biomass allocation to the fruits increased with increasing irradiance when plants were grown over an extended period (62 day) at different irradiances. In the short-term (4 day) the allocation to the fruits did not increase with increasing irradiance. The positive long-term effect of high irradiance on the biomass distribution to the fruits could primarily be ascribed to an increase in the number of fruits growing at the same time on the plant. The growth rate of individual fruits increased with increasing irradiance resulting in a shorter growing period from anthesis until harvest of a fruit. The dry-matter percentage of both the fruits and the vegetative plant parts increased with increasing irradiance.

Fructan exohydrolase from grasses.

In grasses, fructan reserves are mobilized from vegetative plant parts during seasonal growth, after defoliation during grazing and from stems during seed filling. Well-illuminated leaves show a diurnal pattern of fructan accumulation during the light and mobilization during the dark. In expanding leaves, fructans are accumulated in cells of the elongation zone and when mobilized are considered to contribute assimilate for synthetic processes. Even in leaves which do not contain high fructan concentrations, high rates of fructan turnover occur. The process of fructan mobilization appears to be regulated in relation to ontogenic events, demand for assimilate during growth and in response to environmental stress. Hydrolysis of fructans in bacteria is catalyzed by both endo- and exohydrolases. However, in higher plants only fructan exohydrolases (FEH) (EC 3.2.1.80) have been reported. FEH has been extracted from only a limited number of grass species. The pH optimum of FEH activities varies between pH 45-5-5, the temperature optimum ranges from 25-40 °C and FEH is considered to be entirely localized in vacuoles. Estimates of the Km for FEH assayed using high molecular weight fructan substrates vary widely and should be considered carefully because most substrates are ill-defined. Many studies indicate that crude and partially-purified FEH activity is highest when assayed using a fructan substrate extracted from the species that was the source of the enzyme activity. Inulin extracted from members of the Asteraceae is generally less readily hydrolyzed and levans from bacteria are relatively poor substrates for FEH from grasses. Glycosidic-linkage-specific hydrolysis has been demonstrated for an FEH activity extracted from barley. This FEH activity hydrolyzed β-2,1-glycosidic linkages more rapidly than β-2,6-linkages. Most other studies are less conclusive because ill-defined fructan substrates were used. Two isoforms of FEH are reported in leaves of Lolium spp., but the roles of isoforms and their kinetic characteristics are not known. FEH activity in different tissues may be regulated by metabolic concentrations, sucrose (5-10 mw) being a strong inhibitor in vitro of FEH from some species. Results of experiments with Dactylis glomerata indicate control of expression of FEH activity at the gene level. In stem bases, FEH activity increased after defoliation. The increase was abolished by applications of inhibitors of protein synthesis and was apparently repressed by application of various sugars. Although the rates of fructan hydrolysis measured in vitro are sufficient to explain the in vivo rates of fructan hydrolysis, it is yet to be shown whether fructan hydrolysis in vivo is due to the activity of FEH exclusively, or FEH and invertase-like activities. The overriding conclusion is that the various studies of FEH from grasses present a confusing and incomplete picture of the function, activity and kinetics of this enzyme. This is due in part to the lack of defined, commercially-available substrates. The chromatographic techniques available to most laboratories do not permit purification of sufficient quantities of high molecular weight fructans of specific degree of polymerization, or fructan oligosaccharides with glycosidic linkages which differ from that of the inulin series for enzyme characterization. It is recommended that a few well-defined oligosaccharides be adopted as substrate standards for future research.

Ineractions between a mild and a severe strain of potato spindle tuber viroid in doubly infected potato plants

Potato (Solarium tuberosum) plants co-infected with a mild and a severe strain of potato spindle tuber viroid (PSTVd) were analyzed by return-polyacrylamide gel electrophoresis for the presence of both strains in vegetative and reproductive plant parts. Both strains were detected in the anthers, flowers, inflorescences, leaves, ovaries, ovules, petals, pistils, roots, sepals, stolons and tubers. Only mild strain was detected from pollen in the cultivars tested. True potato seed (TPS) were not doubly infected when they were obtained from co-infected maternal parent plants pollinated with pollen from healthy plants. Also, when maternal plants infected with severe strain were pollinated with pollen from healthy plants or from those infected with the mild strain, TPS were not doubly infected. A small number of TPS with double infection was obtained when co-infected or mild-strain-infected plants were pollinated with pollen containing the severe strain (singly or doubly infected). The number of TPS containing mild strain predominated in a ratio of 7:1 over TPS containing the severe strain. This study indicates that segregation of strains from doubly-infected plants probably takes place during pollen formation and persists through seed development.

Faecal Analysis as a Method of Describing Diets of Apes: Examples from Sympatric Gorillas and Chimpanzees at Lope, Gabon.

Faecal analysis has proven to be a useful method of studying the diets of wild apes. This is especially true for populations living in tropical forest habitat in central Africa where dense vegetation makes systematic observation of feeding difficult. The method developed and used for faecal analysis in the Lope Reserve, Gabon, where gorillas (Gorilla g. gorilla) and chimpanzees (Pan t. troglodytes) co-occur, are described and some examples given of some of the ways in which data can be qualified and analised. Faecal analysis alone cannot give a complete picture of diet as some foods leave no recognisable remains and others, particularly vegetative plant parts, are difficult to identify taxonomically. However, standard application of the methods allow some comparisons to be made between years, species and sites.