Effect of top excision and replacement by 1-naphthylacetic acid on partition and flow of potassium in tobacco plants

The effect of removal of the shoot apex of 92-d-old tobacco plants and its replacement by 1-naphthylacetic acid (NAA) on sink-source relationships and on the flows and partitioning of potassium and water has been studied over a short-term period of 7 d (intact control plants) or 8 d (decapitated and NAA-treated plants). For determining flows an upper, middle and lower stratum of three leaves each were analysed. Within the study period three new leaves were formed in control plants and 57.7% of the total dry matter increment during the experimental period was allocated to the apex and these newly formed leaves. An even higher proportion of the K+ taken up (93.8%) was deposited in these organs and this was imported via xylem (72%) and phloem (28%). Only 18.7% and 9.8% of the total dry matter increment were found in the previously present upper leaves and the roots, respectively, and substantial net K+ export occurred from middle and lower leaves and roots. Decapitation removed the dominant phloem sink and caused marked changes in sink-source relationships. After decapitation the net increase in root dry matter was twice that of control plants. 56.2% of the total net increments in dry matter and 70% of the absorbed K+ were deposited in upper leaves (below the excised apex). There was only slight net K+ export from the middle leaves. Application of NAA on the cut surface of the stem stump did not change the growth of plants that much, apart from a substantial increase in stem growth, correspondingly it stimulated the partitioning of K+ into the upper leaves and most dramatically into the stem, which deposited 64.5% or 27% of the K+ uptake, respectively. In these plants K+ uptake was increased and the K+ concentrations in upper, middle and lower leaves were increased from 4.7, 5.4 and 5.6 to 5.1, 6.1 and 6.1% of dry matter, respectively. Possible mechanisms of this effect of NAA on the improvement of K+ concentration in tobacco leaves are discussed in detail.     

The effects of irradiance on growth, respiration and nitrate reductase activity of Terminalia ivorensis and Terminalia superba

Controlled-environment experiments were conducted to determine the effect of three irradiance levels obtained by artificial shading (40%, 65% and 100% light) on the growth, distribution of photosynthate, relative growth rate, net assimilation rate, respiration and nitrate reductase activities in the leaves of seedlings of Terminalia ivorensis and Terminalis superba, two important tropical tree species. Total dry weights of both species increased with increasing irradiance level during growth. Shading affected the percentage dry matter in the roots and number of leaves of both species. Relative growth rate, net assimilation rate, respiration and nitrate reductase in the leaves of both species increased with increases in irradiance level during growth. Significant differences between the species were observed in most of the parameters studied.     

The Effect of Different Root Temperatures on Dry Matter and Carbohydrate Changes in Rooted Leaves of Phaseolus Spp.

Weekly estimates of dry matter in rooted dwarf-bean leaves (Phaseolusvulgaris) and rooted runner-bean leaves (Phaseolus multiflorus)were made with roots held at 13°, 17°, 21°, or 25°C. Most dry matter accumulated in the lamina of both speciesat the coldest root temperature. Roots of runner bean grew morethan dwarf bean at all temperatures compared, especially at13° and 17° C and the greater net assimilation rate,i.e. dry matter increase per dm1 per week, of runner-bean leavesat cold temperatures, is attributed to faster root growth. Shading lessened accumulation in the lamina, especially at coldroot temperatures, because a greater proportion of assimilatewas transferred to roots. Rates of root growth are mainly influenced by temperature, andno effect could be detected of carbohydrate accumulation inthe lamina at cold temperatures on root growth after the rootswere kept warmer. Water content of the lamina per unit areaincreased as dry matter increased. For any particular dry-mattercontent, the water content was greater with roots at 20°than at 13°, i.e. the leaves were more succulent with warmerroots. When roots first formed on the petioles the lamina lost sugarand subsequently regained it, faster when roots were cold. Whentransferred from warm to cold root temperature, sugars accumulatedin the lamina. Starch changed more than sugars in response tochanging root temperatures. Starch in the lamina progressivelydeclined when roots were warm, but increased when they werecold. The starch content of the lamina was rapidly influencedby root temperature. Sugars and starch together account forless than half of the dry-matter increase in the lamina. Theunidentified fraction is little influenced by changes of roottemperature; it may be largely structural because the palisadecells continued to grow after the leaves were excised, althoughthe lamina was fully expanded before the leaves were rooted.Palisade cells were larger with roots at 20° than at 13°C.     

土壤碳氮比对平邑甜茶幼苗生长和碳氮分配的影响

为探讨土壤碳氮比(C:N)对苹果(Malus pumila)植株生长和碳氮分配特性的影响, 采用碳氮双标记示踪技术, 以二年生平邑甜茶(Malus hupehensis)幼苗为试验材料, 研究了6个不同土壤C:N处理(T1-T6分别为4.70、9.78、14.70、19.96、25.60和28.83)下平邑甜茶的生长状况和氮素吸收、利用分配以及碳水化合物的运转特性。结果表明, 随着土壤C:N的逐渐增大, 平邑甜茶幼苗根系干重逐渐增加, 而株高、茎粗、地上部干重和植株总干重呈先增加后降低的趋势, 以T4处理最大。土壤C:N显著影响了平邑甜茶幼苗的 ¹⁵N利用率, 从T1到T4处理, 植株的 ¹⁵N利用率逐渐升高, T4处理(18.46%)是T1处理(10.65%)的1.73倍; 随着土壤C:N的进一步增加, 植株的 ¹⁵N利用率逐渐降低, T5和T6处理分别比T4处理降低了1.59%和2.58%。土壤C:N较低的T1和T2处理, 平邑甜茶幼苗各器官从肥料中吸收分配到的 ¹⁵N量对该器官全氮量的贡献率(Ndff)大小顺序为根>叶>茎, 随着土壤C:N的进一步增大, 叶片的Ndff均为最大, 其次是根, 茎最少。随着土壤C:N的增大, 叶片 ¹⁵N分配率逐渐升高, ¹³C分配率逐渐降低; 而根系 ¹⁵N分配率逐渐降低, ¹³C分配率逐渐升高。综合考虑植株生长和氮素利用状况, 本试验条件下适宜平邑甜茶生长的土壤C:N为21-23。     

Growth and Maintenance Respiration in Whole Plants, Tops, and Roots of Lolium multiflorum

Continuous measurements of CO₂-exchange were separately carried out on tops and roots of small swards of Lolium multiflorum grown in nutrient solution in growth chamber during 3–4 weeks. From these measurements, a daily carbon balance and accumulated dry matter could be established. The data were used to distinguish between two components of respiration, one proportional to growth or photosynthesis (growth respiration), the other proportional to plant dry weight (maintenance respiration). The separation of respiration in the two components was made by multiple regression analyses with daily photosynthesis or growth rate and accumulated dry matter as the independent variables. To ensure independency between the independent variables during the growth period, photosynthesis was varied by application of alternate three-day periods of high and low irradiance. From the two regression coefficients, the efficiency of converting assimilates into constructive growth (Y_G) and the maintenance coefficient (M) could be derived. Three experiments with varying length of photoperiod and dark period were carried out. The analyses were carried out for whole-plant respiration, respiration of tops and respiration of roots separately. Growth respiration for whole plants as well as for tops and for roots was lower — and hence the efficiencies higher — the longer the photoperiods were. Growth respiration and maintenance respiration were higher for roots than for tops. The high rate of root respiration may originate from release of HCO₃^? in exchange for NO₃^?. The parameters found can be utilized quantitatively in computer models of crop photosynthesis and respiration.     

HCO−3 uptake through the roots and its effect on the productivity of willow cuttings

Abstract Young willow plants (Salix‘aquatica gigantea’) were grown in hydroponic culture media, and ¹⁴C–labelled sodium bicarbonate was fed to the roots. Uptake of ¹⁴C-label in the leaves and shoots was assayed after two different feeding periods (6 h, 48 h). Even during the shortest feeding period, ¹⁴C-label had been transferred to the leaves and shoots. Compared with the longer feeding period, after the 6 h feeding period more label was in the form of acid-labile products, whereas after the 48 h feeding period most of the label was in acid-stable products. A second experiment was designed to test whether carbon uptake by roots affects the growth of young willow plants. Uniform rooted cuttings were grown in hydroponic cultures at five different levels of bicarbonate: 0, 0.015, 0.147 0.737, and 1.473 mol m^?3 NaHCO₃. After a 4-week growing period we determined the biomass of leaves, shoots, roots and cuttings. Production of total dry matter (shoots, leaves and roots) increased with increasing bicarbonate concentration. Saturation of dry matter production was reached at 0.737 mol m^?3 NaHCO₃, but a higher concentration of NaHCO₃ (1.470 mol m^?3) caused a slight decrease in the dry matter production. At 0.737 mol m^?3 NaHCO₃ the total dry weight increased by 31.1%, which suggests that uptake of dissolved carbon dioxide through the roots might affect carbon budgeting in young willow plants.     

Response of purely symbiotic and NO3-fed nodulated plants of Lupinus luteus and Vicia atropurpurea to ultraviolet-B radiation

The effects of elevated UV-B radiation on growth, symbiotic function and concentration of metabolites were assessed in purely symbiotic and NO3-fed nodulated plants of Lupinus luteus and Vicia atropurpurea grown outdoors either on tables under supplemental UV-B radiation or in chambers covered with different types of plexi-glass to attenuate solar ultraviolet radiation. Moderately and highly elevated UV-B exposures simulating 15% and 25% ozone depletion as well as sub- ambient UV-B did not alter organ growth, plant total dry matter and N content per plant in both L. luteus and V. atropurpurea. In contrast, elevated UV-B increased (P <0.05) flavonoid and anthocyanin concentrations in roots and leaves of L. luteus, but not of V. atropurpurea. Feeding nodulated plants of L. luteus under elevated UV-B radiation with 2 mM NO3 increased (P <0.05) nodule, leaf and total dry matter, and whole plant N content. With V. atropurpurea, NO3 reduced (P <0.05) nodule activity, root %N and concentrations of flavonoids, anthocyanins in roots and leaves and soluble sugars in roots, in contrast to an observed increase (P <0.05) in nodule dry matter per plant. Similarly, supplying 2 mM NO3 to L. luteus plants exposed to sub-ambient UV-B radiation significantly reduced individual organ growth, plant total biomass, nodule dry matter, nodule %N, and whole plant N content, as well as root concentrations of flavonoids, anthocyanins, soluble sugars, and starch of L. luteus, but not V. atropurpurea plants. These results show no adverse effect of elevated UV-B radiation on growth and symbiotic function of L. luteus and V. atropurpurea plants. However, NO3 supply promoted growth in L. luteus plants exposed to the highly elevated UV-B radiation.     

Nitrate Nutrition and Temperature Effects on Wheat: a Synthesis of Plant Growth and Nitrogen Uptake in Relation to Metabolic and Physiological Processes

Lawlor, D. W., Boyle, F. A., Keys, A. J., Kendall, A. C. andYoung, A. T. 1988. Nitrate nutrition and temperature effectson wheat: a synthesis of plant growth and nitrogen uptake inrelation to metabolic and physiological processes.—J.exp. Bot. 39: 329-343. Growth of spring wheat was measured in cool (13°C day/10°Cnight) or warm (23°C/18°C) temperatures, combined withlarge and small amounts of nitrate fertilizer. The rate of growthof dry matter was less at cool temperatures but total growthover the same period of development was slightly greater inthe cool than in the warm. Main-shoot and tiller leaves grewslower and, despite growing for a longer period, were shorterin the cool than in the warm. They had greater fresh and drymass and content of starch and fructosans per unit area. Coolconditions increased root dry mass, root to shoot ratio andnitrogen content in dry matter. Additional nitrate increasedleaf area of main shoots slightly but of tillers greatly; itincreased leaf and tiller dry matter and total plant dry mass.Additional nitrate decreased the proportion of dry matter inroots and in stems and the N content of dry matter in all plantparts. Regulation of growth by temperature, nitrate supply andthe rôle of photosynthesis and nitrogen uptake, is consideredin relation to the mechanisms of incorporation of carbon andnitrogen into biochemical constituents. It is concluded thattemperature regulates the rate of protein synthesis, which determinesplant growth rate. Nitrogen flux into the plant is not directlylinked to protein synthesis so that the content of NO^–₃and of amino acids is related both to growth and to conditionsgoverning NO^–₃ uptake and its reduction. When nitrogensupply is large, growth is limited by temperature, not NO^–₃.Inadequate nitrate supply decreases protein synthesis (and thereforegrowth) more than it decreases carbon assimilation, so thatorgans such as roots and stems increase in dry matter relativeto shoots and all tissues have smaller proportions of nitrogenin dry matter. Cool conditions, although decreasing the rateof protein synthesis, increase its duration and decrease thesize of leaves, so that the content of protein per unit leafarea is greater in cool than in warm grown leaves. Consequencesof changes in the balance of N and C supply and growth ratefor dry matter distribution in plants are discussed. Key words: Wheat, nitrate nutrition, temperature     

A role for young leaves in vernalization of cauliflower: I. Analysis of leaf development during curd induction

Growth analysis techniques are used to test the hypothesis that chilling induces curd (flower) initiation in the cauliflower ( Brassica oleracea Botrytis L. cv. Perfection) through inhibiting leaf growth, thereby increasing the availability of growth factors to the stem apex and enabling differentiation of the curd. Effects of chilling on leaf growth and curd induction are compared in juvenile and mature, vegetative plants. Chilling at 5°C reduced dry matter accumulation in the total leaf complement by ca 60% in juvenile plants and 40% in mature plants, compared to control plants growth at 20°C. Juvenile plants showed slower rates of leaf initiation than mature plants. Leaf initiation was retarded by chilling in both plant types with the most marked effect seen in the juvenile plants. This was consistent with dry matter availability to the stem apex limiting differentiation more severely in juvenile plants than in mature plants. The rate of dry matter accumulation in existing leaves, however, was faster in juvenile plants than in mature plants at 20°C. Plants that were juvenile during chilling produced an average of 43 leaves below the curd whereas those that were mature produced 25.
Dry matter accumulation in younger leaves was more markedly inhibited by chilling than in older leaves. Chilling also reduced the rate at which enlarging leaves became positionally more remote from the stem apex. Possible roles for such leaves in regulating apical development are considered.     

Partitioning of shoot and root dry matter and carbohydrates in bean plants suffering from phosphorus, potassium and magnesium deficiency

The influence of varied supply of phosphorus (10 and 250 mmolP m^–3) potassium (50 and 2010 mmol K m^–3) and magnesium(20 and 1000 mmol Mg m^–3) on the partitioning of dry matterand carbohydrates (reducing sugars, sucrose and starch) betweenshoots and roots was studied in bean (Phaseolus vulgaris) plantsgrown in nutrient solution over a 12 d period. Shoot and rootgrowth were quite differently affected by low supply of P, K,and Mg. The shoot/root dry weight ratios were 4.9 in the control(sufficient plants), 1.8 in P-deficient, 6.9 in K-deficientand 10.2 in Mg-deficient plants. In primary (source) leaves,but not in trifoliate leaves, concentrations of reducing sugars,sucrose and starch were also differently affected by low nutrientsupply. In primary leaves under K deficiency and, particularlyMg deficiency, the concentrations of sucrose and reducing sugarswere much higher than in control and P-deficient plants. Magnesiumdeficiency also distinctly increased the starch concentrationin the primary leaves. In contrast, in roots, the lowest concenfrationsof sucrose, reducing sugars and starch were found in Mg-deficientplants, whereas the concentrations of sucrose and starch wereparticularly high in P-deficient plants. There was a close relationshipbetween shoot/root dry weight ratios and relative distributionof total carbohydrates (sugars and starch) in shoot and roots.Of the total amounts of carbohyd rates per plant, the followingproportions were parti tioned to the roots: 22.7% in P-deficient,15.7% in control, 3.4% in K-deficient and 0.8% in Mg-deficientplants. The results indicate a distinct role of Mg and K in the exportof photosynthates from leaves to roots and suggest that alterationin photosynthate partitioning plays a major role in the differencesin dry matter distribution between shoots and roots of plantssuffering from mineral nutrient deficiency. Key words: Bean, carbohydrates, magnesium nutrition, phosphorus nutrition, potassium nutrition, shoot/root growth     

Competitiveness and dry matter allocation of oilseed rape (Brassica napus L.) and two mustards (Sinapis alba L. and S. arvensis L.) under water stress conditions

In Morocco, oilseed rape is commonly exposed to mustards competition which are not totally controlled by herbicides. To understand the competitiveness of each species, growth parameters should be studied notably dry matter allocation. The objective of this study was to confirm the competitiveness of oilseed rape with regard to Sinapis alba and S. arvensis and to investigate how the dry matter is allocated. A pot experiment was undertaken with a quartz sand as substrate. Two plant densities were tested (one and two plants). The binary density was either a monoculture or a mixture. Half the pots were maintained at field moisture capacity and the other half was irrigated up to 70% of its water holding capacity. Dry matter allocation of each species at density two was compared to that of the same species at density one. Results of replacement series diagrams and those of the relative crowding coefficient (based on total dry matter) showed that Brassica napus was more competitive than S. alba. S. arvensis was the least competitive. Under competition, B. napus irrigated at water holding capacity allocated more dry matter to stem when compared to its dry matter at density one. Under the same condition, when reducing water supply, B. napus allocated more dry matter to leaves. In case of S. alba, dry matter percent in leaves and roots were respectively low and high in normally irrigated plant and inversely under water shortage. S. arvensis allocated high and low dry matter percent respectively to root than to leaves when sufficiently irrigated. But no clear tendency was noticed under water shortage, for this species.     

Partitioning of Dry Matter in Tanier (Xanthosoma spp.) Irrigated with Fractions of Evapotranspiration

The accumulation and partitioning of dry matter was determinedin tanier plants irrigated with fractions of the water lostthrough evapotranspiration (WLET) in an effort to establishgrowth analysis data from which a tanier growth (simulationmodel could be developed. The irrigation regimes were basedon Class A pan factors ranging from 0·33 to 1·32with increments of 0·33. Tanier plants were planted inthe field and harvested for biomass production about every 6weeks during the growing season. At each harvest, plants wereseparated into various plant parts, and their dry matter contentwas determined. The first 90 d after planting (DAP) were characterizedby low rates of dry matter accumulation, with only leaves andpetioles showing substantial growth. A grand growth period followedin which leaves, petioles, and roots rapidly accumulated drymatter until 278 DAP. During this period, plants that received0·99 and 1·32 WLET exhibited similar total drymatter content, and this was significantly greater than in plantssupplied with 0·33 and 0·66 WLET. Cormel dry mattercontent peaked at 29% of total plant dry matter by 322 DAP inplants replenished with 1·32 WLET. Partitioning of drymatter to cormels in other treatments was significantly reduced.Partitioning of dry matter to corms increased linearly throughoutthe growing season in all treatments. Dry matter partitioningto suckers and the number of suckers formed from plants replenishedwith 0·33 and 0·66 WLET was greater than in themore irrigated treatments.Copyright 1994, 1999 Academic Press Tanier, Xanthosoma spp., growth, dry matter partition, irrigation, evapotranspiration     

Growth of the Tops of Sweet Potato and the Translocation of the Nutrients from Leaves

1. Experiments were carried out in Hangchow on the increase of dry matter in the tops of sweet potato plants. The increase can be divided into three periods: (1) slow accumulation of dry matter; (2) rapid increase of accumulation of dry matter, reaching a maximum; (3) decline of accumulation of dry matter, later on account of senility and the dropping of leaves, there was a marked reduction in the dry matter of the tops. The increase in dry matter is in proportion to the leaf area. The amount of fertilizer used is closely related to the increase of dry matter and leaf area. 2. The yield of sweet potato is related to the increase in dry matter of the tops of the plant. To a certain extent, the greater the amount of dry matter, the more rapidly will the tubers enlarge, finally results in a higher yield. Excessive use of fertilizer leads to an abnormal elongation of the plant. During this period an increase in dry matter of the tops not only fails to induce the enlargement of the tubers, but also leads to the consumption of the dry matter, and consequently causes a reduction in yield of sweet potato. From the curve of T/R ratio, the sooner the downward translocation of the tops nutrients occurs, the faster the tubers will form and enlarge. 3. Experiments with p32 show that the various growth conditions of the tops are closely correlated with the translocation of the tubers. With well growing and high yielding plants the nutrients move from the tops to the tubers as soon as the root enlarges. This translocation is even accelerated during the later stage. During the earlier stage of development, much of the plant nutrition is translocated to the stems and leaves, particularly to the latter; then gradually it is diverted to the leaves and the root system, and finally concentrates in the roots. The increase of the area of green leaves and the number of branches during the period of early growth, and the promoting of favourable conditions for the formation and enlargement of the roots, as well as the facilitating of the translocation of nutrients to the roots during the later stage are the determinative factors necessary for obtaining high yield of sweet potato.     

Assimilation,respiration and allocation of carbon inPlantago major as affected by atmospheric CO2 levels

The response ofPlantago major ssp,pleiosperma plants, grown on nutrient solution in a climate chamber, to a doubling of the ambient atmospheric CO₂ concentration was investigated. Total dry matter production was increased by 30% after 3 weeks of exposure, due to a transient stimulation of the relative growth rate (RGR) during the first 10 days. Thereafter RGR returned to the level of control plants. Photosynthesis, expressed per unit leaf area, was stimulated during the first two weeks of the experiment, thereafter it dropped and nearly reached the level of the control plants. Root respiration was not affected by increased atmospheric CO₂ levels, whereas shoot, dark respiration was stimulated throughout the experimental period. Dry matter allocation over leaves stems and roots was not affected by the CO₂ level. SLA was reduced by 10%, which can partly be explained by an increased dry matter content of the leaves. Both in the early and later stages of the experiment, shoot respiration accounted for a larger part of the carbon budget in plants grown at elevated atmospheric CO₂. Shifts in the total carbon budget were mainly due to the effects on shoot respiration. Leaf growth accounted for nearly 50% of the C budget at all stages of the experiment and in both treatments.Abbreviations LAR leaf area ratio - LWR leaf weight ratio - RGR relative growth rate - R/S root to shoot ratio - RWR root weight ratio - SLA specific leaf area - SWR stem weight ratio     

Transfer of water from roots into dry soil and the effect on wheat water relations and growth

This investigation was performed to study the effect on plant water relations and growth when some of roots grow into dry soil. Common spring water (Triticum aestivum) plants were grown from seed in soil in 1.2 m long PVC (polyvinyl chloride) tubes. Some of the tubes had a PVC partition along their center so that plants developed a split root system (SPR). Part of the roots grew in fully irrigated soil on one side of the partition while the rest of the roots grew into a very dry (-4.1 MPa) soil on the other side of the partition. Split root plants were compared with plants grown from emergence on stored soil moisture (STOR) and with plants that were fully irrigated as needed (IRR). The experiment was duplicated over two temperature regimes (10°/20°C and 15°/25°C, night/day temperatures) in growth chambers. Data were collected on root dry matter distribution, soil moisture status, midday leaf water potential (LWP), leaf relative water content (RWC) and parameters of plant growth and yield.Some roots were found in the dry side of SPR already at 21 DAE (days after emergence) at a soil depth of 15 to 25 cm. Soil water potential around these roots was -0.7 to -1.0 MPa at midday, as compared with the initial value of -4.1 MPa. Therefore, water apparently flowed from the plant into the dry soil, probably during the night. Despite having most of their roots (around 2/3 of the total) in wet soil, SPR plants developed severe plant water stress, even in comparison with STOR plants. Already at 21 DAE, SPR plants had a LWP of -1.5 to -2.0 MPa, while IRR and STOR had a LWP of -0.5 MPa or higher. As a consequence of their greater plant water stress, SPR as compared with IRR plants were lower in tiller number, ear number, shoot dry matter, root dry matter, total biomass, plant height and grain yield and had more epicuticular wax on their leaves.It was concluded that the exposure of a relatively small part of a plant root system to a dry soil may result in a plant-to-soil water potential gradient which may cause severe plant water stress, leading to reduced plant growth and yield.     

Matter-economical roles of the evergreen foliage ofAucuba japonica,an understory shrub in the warm-temperate region of Japan

Leaf demography and productivity ofAucuba japonica, an understory shrub in the warm-temperate region, were examined and dry matter economy was analyzed to evaluate the roles of the evergreen foliage. Turnover of leaves occurred during a short period in spring. The mean leaf life span was about 2.6 years. Annual NAR (net assimilation rate) of each sample shoot was calculated from the biomass and the total dead mass estimated from scars of leaves and floral parts. The average NAR was 1.34±0.22 g·g⁻¹·yr⁻¹. The ratio of dry matter produced by leaves during their whole life span to the initial investment was 3.45±0.37. The annual NAR calculated for individual plants was negatively related to the life span of their leaves. The seasonal change in SLW (specific leaf weight) showed that the reserve material in leaves was accumulated from autumn to early spring and was consumed for the growth of new organs in the following season. The dry matter withdrawn in spring from the overwintering foliage amounted to 40% of dry mass of the new organs developed.     

Virus diseases of cacao in West Africa; effect of virus infection on growth and water content of cacao seedlings

Apparently healthy cacao seedlings were compared with those infected before planting with 'swollen shoot' viruses. The leaf area and the fresh and dry weights of each organ were measured. Infected plants were lower in dry weight, leaf area, relative growth rate and net assimilation rate; a smaller proportion of the dry matter was in the leaves and lateral roots, a larger proportion in stems and tap roots. Infection caused extensive necrosis of the lateral roots, and reduced the rate of depletion of reserves in the cotyledons and the water content of the plant. Many of these effects were apparent within a month of infection and planting.     

Accumulation of cadmium, zinc, and copper by Helianthus annuus L.: impact on plant growth and uptake of nutritional elements

We investigated the effects on physiological response, trace elements and nutrients accumulation of sunflower plants grown in soil contaminated with: 5 mg kg(-1) of Cd; 5 and 300 mg kg(-1) of Cd and Zn, respectively; 5, 300, and 400 mg kg(-1) of Cd, Zn, and Cu, respectively. Contaminants applied did not produce large effects on growth, except in Cd-Zn-Cu treatment in which leaf area and total dry matter were reduced, by 15%. The contamination with Cd alone did not affect neither growth nor physiological parameters, despite considerable amounts of Cd accumulated in roots and older leaves, with a high bioconcentration factor from soil to plant. By adding Zn and then Cu to Cd in soil, significant were the toxic effects on chlorophyll content and water relations due to greater accumulation of trace elements in tissues, with imbalances in nutrients uptake. Highly significant was the interaction between shoot elements concentration (Cd, Zn, Cu, Fe, Mg, K, Ca) and treatments. Heavy metals concentrations in roots always exceeded those in stem and leaves, with a lower translocation from roots to shoots, suggesting a strategy of sunflower to compartmentalise the potentially toxic elements in physiologically less active parts in order to preserve younger tissues.     

Specific features of source-sink relations in alloplasmic hybrid of winter wheat with alien cytoplasm of goatgrass with emphasis on resistance to low temperature stress

We studied the influence of alien cytoplasm of spring goatgrass Aegilops ovata L. on some physiological parameters in winter wheat (Triticum aestivum L.), Mironovskaya 808, under normal conditions and in the case of modified source-sink relations. Measurements of relative rates of plant dry matter growth and its distribution among organs, CO₂ exchange (photosynthesis upon light saturation and dark respiration), content of sugars (sucrose + glucose + fructose) and their ratio in leaves, frost hardiness, and indices of membrane stability and damage of leaves by frost have shown that, on average, alloplasmic hybrid differed from the initial cultivar by almost all parameters. Reduced frost hardiness, increased index of leaf damage by frost, lowered leaf content of sugars, and reduced sucrose/(glucose + fructose) ratio in the alloplasmic hybrid were combined with higher roots/leaves ratio, relative rate of dry matter growth, and photosynthesis and respiration rates. The alloplasmic hybrid was more tolerant to decreased source strength in source-sink relations as compared to the initial cultivar.     

Effects of flooding on carbohydrate and ABA levels in roots and shoots of alfalfa

Alfalfa is sensitive to waterlogging, and its yields are significantly reduced under this condition. We investigated the effects of soil flooding on free abscisic acid (ABA) accumulation in shoots and roots of alfalfa in relation to plant growth and stomatal conductance responses. The production of dry matter in alfalfa was significantly affected by flooding mainly as a result of a rapid reduction in root growth. Shoot dry matter accumulation was maintained during the first 10 d of treatment and started to decline thereafter. Foliar concentration of the major mineral elements (N, P, K) was reduced by flooding, whereas only K concentration decreased in roots of flooded plants. Regrowth declined with duration of flooding and was less than 50% of controls after 2 weeks. While no changes in ABA concentration could be detected in flooded roots, an increase was noted within a few days in leaves when compared to unflooded controls. This increase in free ABA coincided with the accumulation of large quantities of starch in leaves and a rapid decline in leaf stomatal conductance. Our results support the suggestion that leaf ABA originates from the leaf itself and may be accumulating along with starch as a result of reduced translocation to the roots. Our observation of large accumulations of sucrose in flooded roots agrees with previous reports that supply of carbohydrates is not a limiting factor to root anaerobic metabolism in flooded alfalfa.