Shoot Dry Matter Accumulation Research Articles

CuCO3-painted Containers and Root Pruning Affect Apple and Green Ash Root Growth and Cytokinin Levels

CuCO3 at 100 g·liter-1 in a paint carrier applied to interior container surfaces effectively prevented root deformation in container-grown Malus domestica Borkh. and Fraxinus pennsylvanica Marsh. seedlings. CuCO3 treatments nearly doubled the number of white unsuberized root tips in both species. CuCO3 treatment increased some measures of root and shoot growth before and after transplanting to larger untreated containers. Root pruning at transplanting tended to reduce root and shoot fresh and dry matter accumulation in F. pennsylvanica seedlings and shoot extension in M. domestica seedlings. In some cases, root pruning of M. domestics at transplanting from CuCO3-treated containers increased root growth compared to unpruned CuCO3-treated and untreated seedlings. Changes in growth induced by CuCO3 and root pruning were not related to changes in trans -zeatin riboside-like activity in the xylem sap of-apple.

Nitrogen and phosphorus fertilization promotes rapid initial growth of Levcaena on Alfisol

Abstract Early growth of leucaena (Leucaena leucoceohala (Lam) de Wit) is often slow, especially on soils low in organic matter and total N. This study was conducted to determine whether small quantity of N fertilizer in combination with P will enhance early growth. Nitrogen as urea was applied at 0, 25, and 100 mg/kg soil with 50 mg P/kg soil as monocalcium phosphate or without P to leucaena seedlings in pots. All plants were inoculated with leucaena Rhizobium (LX 382). Growth rates declined from 0.3 cm/day at 14 to 0.22 cm/day at 42 days after planting (DAP) in no‐P plants. Fertilizer N and P application increased growth rates sharply thus hastening shoot and root dry matter accumulation. P uptake was enhanced with 25 mg N/kg soil at 42 and 84 DAP, but not at 126 DAP. It appears small amount of N applied with adequate P enhanced P uptake and hence early growth of leucaena.

Apple seedling response to calcium

Abstract Calcium plays an important role in the growth and development of apple trees as well as in high fruit quality. In the present study, solution cultures were carried out under climatically controlled conditions in a growth room to evaluate the response of apple seedlings to six levels of Ca (0.1, 0.2, 0.4, 0.8, 1.6, and 3.2 mM Ca). Foliar calcium deficiency symptoms were observed at Ca concentrations lower than 0.4 mM. The 3.2 mM Ca treatment resulted in the highest shoot dry matter accumulation and the greatest leaf area. However, both root length and dry matter accumulation were less affected by Ca levels. Calcium uptake parameters were significantly influenced by Ca treatment.

Root Distribution and Shoot Development in No‐Till Full‐Season and Double‐Crop Soybean

AbstractDry matter accumulation by soybean [Glycine max (L.) Merr.] has been studied extensively, but few data are available on the relationship between shoot development and root distribution of no‐till full‐season and double‐crop soybean. Row spacing and K availability effects on shoot growth are also well understood, but have not been thoroughly integrated with measures of root growth. The objectives of this research were to characterize soybean root length density and distribution as well as shoot dry matter accumulation under no‐tillage soil management for: (i) full‐season and double‐crop planting dates, (ii) high and low soil K fertility levels, and (iii) narrow and conventional row spacings. Potassium fertility did not alter total shoot weight at R1, R5, or R7, but did alter shoot dry matter partitioning at R7. Later planting dates reduced shoot growth at R1, R5, and R7. Seed yield was increased by greater K availability, earlier planting and a narrower row width. Dry soil conditions during vegetative growth reduced root length density (RLD). As water became more available during reproduction, RLD increased. With adequate soil moisture, full‐season soybean RLD was greater than double‐crop soybean RLD. Surface soil RLD was greater when soil K fertility was low. Leaf abscission was delayed by K stress. In crop development periods when root growth was most active, the root length/shoot dry weight ratio was greater in double‐crop than in full‐season soybean. Double‐crop soybean produced relatively more root length in support of shoot growth than did full‐season soybean. Root growth was more affected by soil K availability and less affected by plant spacial arrangement and density than was shoot growth.

Vegetative Establishment of Dwarf Elephantgrass: Effect of Defoliation prior to Planting Stems

AbstractCattle (Bos spp.) gains on ‘Mott’ dwarf elephantgrass (Pennisetum purpureum Schum.) have averaged 1 kg d−1 during 3 yr of summer grazing in Florida, but vegetative establishment of this cultivar has been problematic. The objective of this research was to determine the effect of defoliation prior to harvesting stems for vegetative planting on number of shoots produced, percentage of planted stems producing shoots, and shoot and root dry matter (DM) accumulation during 6 wk postplant. Responses were quantified for mid‐ and late summer planting dates in 2 yr on a Smyrna sand (sandy, siliceous, hyperthermic Aeric Haplaquods). Previously undefoliated plants were (i) grazed to remove 70 to 90% of leaf blade (grazed), (ii) grazed to remove the apical meristem and leaf blade of individual stems (meristem), (iii) not grazed, but leaf blades were stripped manually from stems (stripped), (iv) not grazed, but all herbage above the collar of the most recently expanded leaf was clipped manually (topped), or (v) not defoliated (undefoliated). More shoots emerged per row from undefoliated stems than from all other treatments except topped. Defoliation had no effect on percentage of planted stems that produced at least one shoot. Shoot DM was greater for undefoliated than for all but stripped stems, and root DM was greatest for undefoliated stems. Stems from the meristem treatment initiated shoot but not root growth during the first 2 wk postplant, and shoot and root DM production was low through 6 wk. Undefoliated stems produced little shoot DM by 2 wk, but root growth started soon after planting. Root and shoot growth responses were consistent with theories regarding apical dominance and auxin effects on early plant development from stem cuttings. Results suggest that successful establishment of Mott elephantgrass is most likely if undefoliated stems are planted.

COMPARISON OF MAIZE (Zea mays L.) GROWTH AND NITROGEN PARAMETERS UNDER HYDROPONIC AND FIELD CONDITIONS

A comparison of biomass and nitrogen (N) parameters from 23 maize (Zea mays L.) inbreds was conducted between hydroponic culturing during two growth chamber studies and soil in the field for two harvests during 1984. The growth chamber studies and first field harvests were sampled at a similar growth stage (approximately nine-leaf); the second field harvest was at anthesis. Shoot dry matter accumulation was greater under hydroponic than under field conditions at a similar vegetative growth stage. Significant inbred differences for shoot biomass, reduced and total N contents and reduced and total N concentrations were determined for the growth chamber and both field harvests. Correlation coefficients were low and not significant (P < 0.05) between inbred parameters in the growth chamber and in the field. In summary, traits from hydroponic plants were not predictive of those from field plants. However, N parameters and biomass of inbreds harvested in the field at a mid-vegetative stage were predictive of inbred performance at anthesis.Key words: Zea mays L., maize, biomass, nitrogen, field, hydroponic

Response of Alfalfa and Birdsfoot Trefoil to Shoot Removal and Root Anoxia

Shoot removal may accentuate potential plant injury when roots are under stress. Flood‐intolerant alfalfa (Medicago sativa L.) and flood‐tolerant birdsfoot trefoil (Lotus corniculatus L.) partition differing amounts of photoassimilate to roots during shoot regrowth, which may affect their ability to withstand stress. The objective of this study was to characterize plant response (growth and chemical composition) when root anoxia (severe hypoxia) and partial shoot removal were applied concurrently. Seedling plants (4–5 wk‐old) were grown in a growth chamber using nutrient solution. Alfalfa and trefoil roots were subjected to anoxia or O2 aeration (control) with shoots either clipped to 60‐ to 70‐mm stubble height or left unclipped. Root treatments were up to 5 d in duration. Alfalfa displayed greater damage (as measured by shoot dry matter accumulation) in response to root anoxia than did trefoil under both shoot treatments. Root anoxia significantly reduced root dry matter accumulation only in nonclipped plants, indicating that clipping had a more deleterious effect on root dry matter than did anoxia treatment. Both clipping and root anoxia had significant effects on root carbohydrates. A large increase in root sucrose concentration in response to anoxia was noted in alfalfa but not trefoil. Reducing sugar concentration declined in response to anoxia and clipping in alfalfa roots but only to clipping in trefoil roots. Root starch concentration increased in alfalfa and decreased in trefoil in response to root anoxia. There were no significant interactions between root aeration and shoot clipping in either species. Differential supply of photoassimilate did not appear to contribute to the differential tolerance to root anoxia displayed by these species. The data indicated that increased utilization of sugars may be important in trefoil's greater flooding tolerance.

EFFECTS OF SALINITY AND NITROGEN ON GROWTH AND WATER RELATIONS IN THE MANGROVE, AVICENNIA MARINA (FORSK.) VIERH.

Young plants of Avicennia marina (Forsk.) Vierh, were subjected to a factorial experiment with three concentrations of NaCl (0.1, 0.3, 0.5 M) and three of NH4 C1 (0.14, 1.4, 14 mg N I-1 ) in solution culture for three months. Nitrogen and salinity had significant effects on dry matter accumulation in shoots and roots. In general, growth of shoots and roots was significantly greater at 0.1 M NaCl than at 0.3 and 0.5 M NaCl. Added nitrogen at 14 mg N I-1 significantly increased shoot growth at 0.1 and 0.3 M NaCl. In roots, differences were significant at 0.3 M NaCl and 14 mg N I-1 . Nitrogen had no significant effect on shoot or root growth at 0.5 M NaCl. At lower salinities there was greater allocation of resources to shoots at 14 mg NI-1 . Increasing salinity decreased stomatal conductance, tissue water potentials and the concentrations of nitrogen and potassium in tissues. Nitrogen levels had no effect on tissue water potentials. These results are discussed in relation to the effects of salinity and nitrogen on productivity, nutrient uptake and on plant water relations.

Effect of Osmotic Stress on Ion Transport Processes and Phospholipid Composition of Wheat (Triticum aestivum L.) Mitochondria

The effect of osmotic stress on wheat (Triticum aestivum L.) mitochondrial activity and phospholipid composition was investigated. Preliminary growth measurements showed that osmotic stress (-0.25 or -0.5 megapascal external water potential) inhibited the rate of shoot dry matter accumulation while root dry matter accumulation was less sensitive. We have determined that differences in sensitivity to osmotic stress existed between tissues at the mitochondrial level. Mitochondria isolated from roots or shoots of stressed seedlings showed respiratory control and ADP/O ratios similar to control seedlings which indicates that stressed mitochondria were well coupled. However, under passive swelling conditions in a KCl reaction mixture, the rate and extent of valinomycin-induced swelling of shoot mitochondria were increased by osmotic stress while root mitochondria were largely unaffected. Active ion transport studies showed efflux transport by stressed-shoot mitochondria to be partially inhibited since mitochondrial contraction required the addition of N-ethylmaleimide or nigericin. Efflux ion transport by root mitochondria was not inhibited by osmotic stress which indicates that stress-induced changes in ion transport were largely limited to shoot mitochondria. Characterization of mitochondrial fatty acid and phospholipid composition showed an increase in the percentage of phosphatidylcholine in stressed shoot mitochondria compared to the control. Mitochondrial fatty acid composition was not markedly altered by stress. No significant changes in either the phospholipid or fatty acid composition of stressed root mitochondria were observed. Hence, these results suggest that a tissue-specific response to osmotic stress exists at the mitochondrial level.

Genotypic Variation for Cold Tolerance among Twelve Maize (Zea mays L.) Populations

AbstractThe objectives of this study were (1) to ascertain the genetic differences for cold‐tolerance traits in a series of diallel crosses among 12 maize populations grown in field experiments, and (2) to compare, in controlled environment rooms, the modification of various metabolic parameters of two sets of four F1 variety crosses which, according to the field experiments, differed largely in seedling early vigour (cold‐tolerant [Ct] vs cold‐sensitive [Cs] Fl sets). Under field conditions, cold‐tolerance adaptability, as monitored by shoot dry matter accumulation, appeared genetically controlled; moreover, considerable differences existed among genotypes. Field data suggested that shoot dry weight was a good indicator of plant adaptability to periods of unfavorable cool conditions. The growth‐chamber experiments showed that shoot dry weights of the two sets of hybrids (Ct vs Cs), were more uniform at the highest temperature regimes than under suboptimal temperatures. Moreover, the laboratory study indicated that the interval of time of attain a specific stage of development provided a meaningful and useful criterion for differentiating the capacity of maize plants to grow at low temperatures. Although a clear association between a particular metabolite and the capacity of plants to grow at low temperatures was not observed, it was of interest to note that the total N concentration in the shoot was significantly higher in the Ct plants compared to the Cs ones.

Progeny Screening of Sorghum Plants Regenerated from Sodium chloride-selected Callus for Salt Tolerance

Summary Sorghum bicolor (L.) Moench plants regenerated from callus cultures grown with and without salt (NaCl) were grown to maturity in a greenhouse. Seeds collected from these populations after self-pollination were germinated, and seedlings were screened in a hydroponics system for NaCl tolerance. Seedlings from the parent plants also were included in the screening. Progeny from the salt-selected plant had slightly longer roots than the parents when grown in normal nutrient solution. In nutrient solution containing NaCl, the salt-selected progeny had higher shoot dry matter than did the parent line. However, progenies from both the parent and salt-selected lines had decreased root weights and root lengths in the presence of NaCl. This suggests that seedlings from the salt-selected plant obtained adequate nutrients to allow higher shoot dry matter accumulation than that of the parent population.

Genetic Relationship between Turgor Maintenance and Growth in Cotton Germplasm1

Seventeen photoperiodic sensitive cotton (Gossypium hirsutum L.) stocks were grown for 2 years (1980 and 1981) at Big Spring, Tex. to evaluate the relationship between turgor maintenance and shoot dry matter accumulation (growth). During each year, leaf‐cutter thermocouple psychrometers were used to measure predawn and midday leaf water and osmotic potentials and to estimate turgor pressure at 50 and 80 days after planting (DAP). Shoot dry weights were measured also at 50 and 80 DAP. The 1st year was hot and dry while the 2nd year had about average temperatures and rainfall. Linear regressions between predawn and midday water and turgor potentials were used to estimate turgor maintenance as i) the change in turgor pressure per unit change of water potential (slope) and, ii) the osmotic potential where zero turgor pressure occurred (X intercept). Significant differences did not occur among the stocks for changes in turgor pressure per unit change in water potential (slope), but they did occur among stocks for osmotic potential at zero turgor (πo) all four sampling dates. Analysis over‐all of the sampling dates, identified a consistently low (T178) and high (T292) stock for πo. Linear correlation and regression coefficients between shoot dry weights and πo were negative and statistically significant during the sampling period (80 DAP, 1980) when the plants were water‐stressed. The linear correlation and regression coefficients were negative, but not statistically significant during the other sampling periods (50 DAP, 1980, and 50 and 80 DAP, 1981). Linear correlation coefficients between the change in shoot dry weights between 50 and 80 DAP in 1980 and the change in πo were negative (r = ‐0.82) and statistically significant. These relationships suggesthat if selection pressure is directed towards enhancing osmotic adjustment under water stress, a reduced growth potential may result.

Growth and the efficiency of root respiration of Pisum sativum as dependent on the source of nitrogen

Growth and efficiency of root respiration were investigated in Pisum sativum L. cv. Alaska and cv. Rondo. Plants were grown in culture solutions, either in symbiosis with Rhizobium leguminosanm, or with an abundant supply of nitrate or ammonium and completely lacking nodules. In comparison with plants utilizing nitrate or ammonium, Ni‐fixing plants showed lower rates of dry matter and nitrogen accumulation, as well as lower rates of total and cytochrome‐mediated root respiration. Rates of shoot dry matter accumulation and root respiration in plants utilizing ammonium were lower than in plants utilizing nitrate. The efficiency of root respiration was high in N2‐fixing plants, as indicated by a low activity of the SHAM‐sensitive, alternative, non‐phosphorylating pathway. In nitrate and ammonium grown plants of cv. Alaska, the efficiency of root respiration was about the same, and in both cases lower than in N2‐fixing plants. The efficiency of root respiration in non‐symbiotically grown pea plants was generally higher than in many non‐legumes. Comparison of the ATP costs of synthesis of root dry matter for different N‐sources was complicated by large differences in relative growth rate of the root and in shoot to root ratio between N‐treatments. A quantitative correction of the ATP production during synthesis of root dry matter for differences in shoot to root ratio and root maintenance respiration has been made. It is concluded that ATP costs of root dry matter production are highest in the case of N2‐fixing plants. In plants utilizing ammonium, ATP costs of synthesis of root dry matter were slightly lower than in plants utilizing nitrate. The physiological significance of the alternative pathway in root metabolism is discussed in relation to the assimilation of different sources of nitrogen.

Nitrate Assimilation during Vegetative Regrowth of Alfalfa

Dry matter accumulation, nitrate reductase activity of various organs, nitrate accumulation, nitrogen derived from nitrate, and nitrogen content were studied during 17 days of vegetative regrowth of harvested (detopped) alfalfa (Medicago sativa L.). Seedlings were grown in the glasshouse and treated with 0, 40, and 80 kilograms N per hectare applied as K(15)NO(3) to determine whether reduced nitrogenase activity after shoot harvest limited vegetative regrowth. The role of nodules in reducing NO(3) (-) during this period of low nitrogenase activity was also investigated.Applied nitrogen had no effect on shoot dry matter accumulation during the regrowth cycle. This observation suggests that reduced nitrogenase activity after shoot removal does not limit vegetative regrowth. Nitrate reductase activity was present in all tissues and ranked leaves > nodules > stems > roots. Root nitrate reductase did not respond to applied K(15)NO(3), while leaf, stem, and nodule nitrate reductase increased significantly. Significant increases in total plant nitrate reductase activity were highly correlated with shoot regrowth. Nodules incorporated N from (15)NO(3) (-), and calculations showed that 1.5% of the total plant N formed during regrowth could have been derived through nodule nitrate reductase. Nitrate accumulated in tissues of all plants, including those grown in the absence of added K(15)NO(3). Accumulation of NO(3) (-) in plant tissues ranked leaves > stems > roots. Analysis of the percentage of (15)N showed that plants grown in either 40 or 80 kilograms N per hectare derived 65 to 75% of the N that accumulated during regrowth from NO(3) (-). Approximately 23 milligrams of N . plant(-1) accumulated during the regrowth period. Leaves accounted for 80% of this net increase, while stems accounted for 20%. There was no net change in root N.These results indicate that, although alfalfa will efficiently utilize low levels of applied N in lieu of nitrogen fixation, N fertilization of seedling alfalfa after shoot removal will be of little value to increase yields. These data also indicate that nodules reduce NO(3) (-), but their contribution to total plant N during regrowth is relatively small.

Exotic Cottons as Genetic Sources for Drought Resistance1

As irrigation water becomes more limited and energy costs increase on the Southern Great Plains, more cotton (Gossypium hirsutum L.) acreage will be diverted to dryland production. Because water is the most limiting resource for cotton production in this region, production will be positively related to changes which increase the water supply or make more efficient use of water. The purpose of this study was to evaluate plant (shoot) dry matter accumulation in photoperiodic (exotic) cotton strains under irrigated (water optimal) and dryland (water stressed) field conditions, to estimate their water‐use efficiency under dryland, and to determine the relationship between field growth parameters, laboratory evaluations of heat tolerance, and greenhouse estimates of root growth. Fifteen photoperiodic strains and one commerciacl ultivar were planted in irrigated and dryland field tests at Big Spring, Texas and in acrylic tubes in the greenhouse at Temple, Texas. In the Big Spring test, dry weight harvests from both the irrigated and the dryland plots were made at 44, 58, 72, and 86 days after planting (DAP). Soil‐water use was measured with a neutron probe in the dryland plots, and leaf discs were taken from both the irrigated and the dryland tests to measure heat tolerance. In them Temple test, shoot dry weight, leaf area, taproot length, and the number of major root laterals were measured 35 DAP. Analyses of variance and regression analyses were used to evaluate the data.Significant variability was demonstrated among entries for shoot dry weights under both irrigated and dryland conditions, for water‐use efficiency in the dryland test, for heat tolerance at Big Spring, and for root growth at Temple. The number of lateral roots measured in the greenhouse was positively associated with shoot dry weights in the dryland plots, but not in the irrigated plots. Root morphology and root growth potentials appear to be important traits in the adaptation of cotton to conditions where limited soil‐water availability is a major constraint on plant growth.

Recovery Growth Following Water Deficits of Different Duration in Prairie Grass

Recovery of rates of leaf emergence, leaf extension, tiller number, leaf number, leaf area and shoot dry weight per plant following water deficits lasting for between 10 and 28 days was measured in Bromus catharticus in a controlled environment. The rate of leaf extension recovered to the rate of control plants within 4-6 days of rewatering and then exceeded the control rate for up to 28 days. During this time, four or five new leaves emerged. The maximum rate of leaf extension for individual leaves during recovery was up to 20% higher than rates typical for leaves of the same insertion on well watered control plants. During an initial recovery phase which followed the 28-day water deficit, and which lasted 20 days from rewatering, the rates of increase in tiller number, leaf number, and leaf area per plant were greater than control rates by 38, 48 and 51%, respectively. Rates for these components of yield then normalized. Relatively small differences among treatments were measured for rate of shoot dry matter accumulation. Final shoot dry weight was approximately proportional to the number of 'non- drought' days, which were defined as those days on which the leaves showed no sign of wilting. This also corresponded to day-time leaf water potentials higher (less negative) than - 1400 kPa.

Chemical Control of Yield of Sennosides in Senna Leaves

In the present studies an attempt has been made to evaluate the effect of various plant growth regulators on the yield of sennosides in C. angustifolia. The growth regulators which increased the yield of sennosides either by increasing their percentage or by increasing the total growth of plants were N, N–Succinic acid dimethylhydrazide (B9), (2–Chloroethyl) trimethyl ammoniumchloride (CCC), 2–Chloroethyl phosphonic acid (Ethrel), Maleic hydrazide (MH) and 6–Furfuryl–aminopurine (Kinetin). Treatments with Indole–3–acetic acid (IAA), Gibberellic acid (GA) and Phosfon–D were not beneficial in increasing either sennosides content or dry matter accumulation in shoot.