Plant Growth Variables Research Articles

Both nitrogen and phosphorus limit plant production on young Hawaiian lava flows

We applied fertilizers in a 23complete factorial design to determine the effects of nutrient amendments on plant growth in Hawaiian montane forests growing on two different volcanic substrates: ‘a‘ā and pāhoehoe lava. Both sites were about 140 years old and their overstories were nearly monospecific stands of Metrosideros polymorpha. Fertilizer applications included N, P, a mixture of essential macro- and micronutrients excepting P and N, and all combinations thereof in each of four blocks. Additions of nutrients other than N or P had no significant effects on measured plant-growth variables. In contrast, additions of either N or P significantly increased tree height growth, diameter increments, biomass growth, and height growth of the understory fern Dicranopteris linearis in both sites. The effect of N was greater than that of P. Greatest growth rates occurred in plots receiving both N and P, and signficant N*P interactions occurred in several cases, suggesting a synergistic effect between these two elements. Plant growth on these young, poorly weathered, basaltic lavas is colimited by N and P availability. Growth in a similar-aged stand growing on a mixture of volcanic ash and cinders is N but not P limited, indicating that the texture of the parent material influences nutrient-availability patterns during early primary succession.

The effect of stem and cob borers on maize subjected to different nitrogen treatments

AbstractThe influence of four nitrogen levels (0, 60, 90 and 120 kg N/ha) on growth of maize and development of lepidopterous pests was investigated in a field trial. Nitrogen had a positive effect on both plant growth variables (plant height, stem diameter and yield), and development and survival of Sesamia calamistis and Eldana saccharina, and thereby increased the incidence of dead hearts and stem tunneling. However, the percent yield loss due to artificial infestation decreased with increasing N application rate from 20% to 11% in the in the 0kg/ha and 120kg/ha treatment, respectively. Using a multiple regression analysis, plant height, plant diameter and stem tunneling were found to be the most important variables explaining the variability in maize yield.

Effects of Crop Residue and Phosphorus Application on the Spatial Variability of Non-destructively Measured Millet Growth in the Sahel

SUMMARYSpatial variability in soil parameters and plant growth in the Sahel are still poorly understood and may hamper the interpretation of experimental results. This paper examines whether or not soil amendments such as phosphorus and crop residues affect the variability of final dry matter production in pearl millet (Pennisetum glaucum). Within- and between-plot variation in millet growth was studied in a three-year experiment with three levels of crop residues and four levels of phosphorus. The effects of different rates of application on within-plot variation in number of tillers, number of heads, maximum tiller height, and total above-ground dry matter of single mature millet plant stands (pockets) were calculated. Above-ground dry matter, estimated non-destructively using an equation derived from numbers of tillers and heads and from maximum plant height, gave good predictions of total dry matter for a range of genotypes across the 12 treatments. Crop residue and phosphorus application reduced the number of missing pockets, leading to a more uniform stand with fewer pockets which did not produce grain. With amendments, pockets were also taller and of more uniform height but a decrease in variability of total dry matter production only became evident after standardization of the data. The results show the need for a clear definition of ‘growth variability’ in millet and indicate that both chemical and non-chemical factors govern its expression in the Sahel.Efectos de los residuos de las cosechas y del fósforo en la variabilidad del mijo

Critical Petiole Nitrate‐Nitrogen for Lint Yield and Enhanced Maturity in Pima Cotton

AbstractPetiole NO3‐N concentration (PNN) has been recommended as an indicator of midseason N deficiency in upland cotton (Gossypium hirsutum L.). Its use in Pima cotton (G. barbadense L.) management, exspecially when early maturity is the goal, is not well documented. A 3‐yr study evaluated PNN as an indicator of N status in Pima cotton in order to identify a critical minimum PNN level for yield and early maturity. Treatments were five preplant applied N rates of 0 to 180 kg ha−1 in 1990 and 0 to 269 kg ha−1 in 1991 and 1992. The PNN was measured throughout boll development, starting ≈ 2 wk before or at first flower. Applied N significantly (P ≤ 0.05) affected PNN in 1991 and 1992, when residual soil N was low, but not in 1990, when residual N was high; differences among treatments in 1991 and 1992 were largest during early flowering. PNN was a good indicator of plant N status within but not across seasons. Based on early‐flowering samples, the critical PNN level for lint yield was 3.84 g kg−1 in 1991 and only 1.75 g kg−1 in 1992; in 1990, residual soil N alone resulted in PNN much higher than the critical levels in the other years. PNN < 2 g kg−1 in 1991 and < 1 g kg−1 in 1992 resulted in earlier maturity, but also resulted in less lint yield. Pima cotton PNN did not exceed an average of 11 g kg−1, in contrast to 24 to 30 g kg−1 reported for upland cotton. Plant growth or petiole anatomical variables that cause year‐to‐year variation in PNN should be identified and the necessary normalization made before PNN can be used as a midseason diagnostic tool in Pima cotton.

Chronic ozone exposure increases the susceptibility of hybrid Populus to disease caused by Septoria Musiva

Rooted cuttings of hybrid Populus (DN34, Populus deltoides X nigra) were grown outdoors in pots in open-top chambers at Ithaca, NY (74·5° W, 42·5° N), during 1988 and 1989 (Experiment 1) and during 1989 and 1990 (Experiment 2). Ambient air was passed through charcoal filters to produce a 0·5 times ambient ozone treatment, and ozone generated from oxygen was added to produce one and two times ambient ozone treatments. In Experiment 1, treatments were applied for 8–12 h each day for 112 days of the 1988 growing season; then the plants were grown outdoors with ambient ozone in 1989. In Experiment 2, treatments were applied for 9 h each day for 98 days of the 1989 growing season; then the plants were grown outdoors with ambient ozone in 1990. Shallow wounds were made into the bark tissue and inoculated with either an aqueous suspension of conidia of Mycosphaerella populorum or sterile water on 1 and 2 September 1988 (Experiment 1) or 16 and 17 August 1989 (Experiment 2). In Experiment 1, wounds were inoculated either 0, 7, or 14 days after wounding. In Experiment 2, wounds were inoculated either 0, 3, or 6 days after wounding. Canker development was measured after harvest on 16 and 17 July 1989 (Experiment 1) and 28 May 1990 (Experiment 2). In both experiments, chronic exposure to ozone significantly increased the incidence of canker formation in inoculated wounds, and no cankers formed in wounds that received only sterile water. In Experiment 1, cankers formed only on plants inoculated the same day as wounding. No cankers formed on plants inoculated either 7 or 14 days after wounding. In Experiment 2, cankers formed on plants inoculated on the same day as wounding, and on a few plants inoculated 3 days after wounding. No cankers formed on plants inoculated 6 days after wounding. Additionally, in Experiment 2, exposure to increased concentrations of ozone caused a significantly higher number of plants to die during the subsequent winter. Analysis of partial correlation coefficients among plant growth and plant disease variables suggested that the observed ozone-induced increase in the susceptibility of the plants to disease was not mediated by alterations in plant growth.

Parent‐Offspring Regression Estimates of Heritability for Salt Tolerance during Germination in Tomato

Salinity impositions can markedly delay and decrease germination rates of tomato (Lycopersicon esculentum Mill.) seed. Wide phenotypic variability in plant growth and germination responses to salinity stress has been reported, but scant documentation concerning genotypic variation for salt responsiveness has restricted breeding efforts. This study evaluated the heritability of germination performance under salinity stress by parent‐offspring regression. Germination distribution data were collected for Fz and F3 seeds derived from a cross between a saltsensitive (UCT5) and a salt‐tolerant (PI 174263) cultivar under moderately high salinity levels (150 mM synthetic sea salt). Individuals germinating at different response time intervals were recovered and advanced to produce F3 and F4 progeny seeds. Progeny families were evaluated for mean times to selected germination quantiles of 25, 50, and 75% under salt stress and the family means were regressed on the individual parental values. Heritability estimates for the F2:3 regression at the selected quantiles were 0.78, 0.76, and 0.58, respectively. These results were comparable with the F3:4 regression estimates of 0.65, 0.73, and 0.58, respectively. The similarity of the estimates obtained in both parent‐offspring regressions suggests the absence of significant dominance genetic effects and when considered with the moderately high heritabilities estimated (r = 0.58‐0.78), reasonably rapid response to selection in early segregating generations would be expected for this important seed trait in tomato.

Growth and yield of potato (Solanum tuberosum L.) cultivars Atlantic and Monona as influenced by seed type and size

Growth and yield of potato plants grown from several weight classes of whole “B” seed, unsorted “B” seed, and 56 g cut seed pieces were compared in Ohio in 1988 and 1989. Whole “B” seed classes were 8 g ranges with means of 35 g, 43 g, 51 g, and 58 g. Unsorted “B” seed was used as an experimental control. Treatment responses were inconsistent. Few significant differences were evident at bloom in leaf area, number of main stems, and total plant dry weight (without tubers) per hill. However, the number of tubers greater than 1 cm in diameter per hill at bloom was less for cut seed as compared with several whole seed treatments. Percent stand at four weeks was also less for cut seed compared with 51 g and 58 g whole tuber treatments. Significant differences in total and U.S. No. 1 yields were absent despite differences in several plant growth variables early in the 1988 and 1989 growing seasons.

Yield Losses to Iceberg Lettuce Due to Corky Root Caused byRhizomonas suberifaciens

Plant growth and yield variables of closely related resistant and susceptible lettuce cultivars (440-8 and Salinas, respectively) were compared in microplots at Davis, CA, in soil infested with Rhizomonas suberifaciens, the causal agent of corky root of lettuce. To validate the results for large scale lettuce production, the same variables were compared for 440-8 and Salinas in fumigated soil and soil naturally infested with R. subenfaciens at Salinas, CA. Most plant growth variables for 440-8 in infested microplots were not significantly different from those for 440-8 or Salinas in uninfested microplots (...)

Effects of Dinitroaniline Herbicides, Carboxin-Pentachloronitrobenzene Seed Treatment, and Rhizoctonia Disease on Soybean

The effect of trifluralin, pendimethalin, and ethalfluralin and disease caused by Rhizoctonia solani on soybean (Glycine max) was determined with field and growth chamber studies. In field studies, oats infested with R. solani placed in furrow at planting significantly reduced plant growth variables. No significant interactions were observed between herbicides and inoculum treatments. Effects of inoculum were significantly reduced with carboxin-pentachloronitrobenzene seed treatment, in growth chamber studies, steamed and nonsteamed field soil were used (...)

Phosphorus uptake and utilization in wild and cultivated oats (avenaspp.)

Abstract In a solution culture experiment, the growth and nutrient uptake of wild oat plants (Avena fatua L.) was compared with that of cultivated oat plants (Avena sativa L. cv. Pennlo) at both low (5 μM P) and high (100 μMP) levels of phosphate. Solution phosphate depletions and plant growth variables were measured through daily solution sampling and destructive tissue harvests. Wild oat produced more root mass and accumulated P more rapidly than the cultivar in both low and high P levels. Wild oat plants also produced significantly more dry matter for a given accumulation of P than the cultivated oat plants in both low and high P solutions. We conclude that wild oat is likely to be competitively superior to the Pennlo cultivar under conditions of moderate P limitation due to its greater allocation of dry matter to roots and higher P use efficiency.

Biological control of the cassava mealybug, Phenacoccus manihoti (Hom., Pseudococcidae) by Epidinocarsis lopezi (Hym., Encyrtidae) in West Africa, as influenced by climate and soil

Population data concerning the cassava mealybug (CM) Phenacoccus manihoti Matile-Ferrero, the introduced parasitoid Epidinocarsis lopezi (De Santis), and indigenous antagonists were collected, together with ecological and plant growth variables, during a survey of 414 fields covering all ecological zones of Nigeria and Benin, for evaluation in multiple regression analyses. The choice of fields was unbiased, and insect populations were estimated from large random samples. Seven years after the first release of E. lopezi, the entire area, with the exception of an isolated CM population near Lake Chad, had been colonized by the parasitoid. Within the area of distribution of E. lopezi, average CM populations were very low (1.6 CM per shoot tip), highest densities being found in the forest transition zone. The mean tip damage score on a scale from 1 to 5 was only 1.2. Only 3.2% of all tips were strongly stunted, the same percentage had more than 10 CM, and no tip had over 1000 CM. However, significant tip damage persisted on the 4.8% of fileds with unmulched, sandy soils in the forest zone. In these fields, 3.3 times fewer CM were needed to cause heavy stunting than on less stressed plants on soils with mulch, or clay, or less rain. This deleterious effect of leaching and lack of crop rotation was alleviated completely in the fields which had a small amount of mulch. Thus, agronomic factors, mediated through the condition of the plant, influenced biological control.

The Microclimate and Transpiration of a Greenhouse Cucumber Crop

ABSTRACT Point source sensors and plant growth variables were used to characterize the microclimate of a greenhouse grown cucumber crop. Diurnal cycles and/or vertical profiles of solar radiation, air movement, leaf and air temperature, humidity, transpiration rate, and stomatal resistance, as well as plant architectural parameters were reported. Canopy leaf temperature with high solar radiation was found considerably lower than greenhouse air temperature due to high transpiration rate.

Plant Growth Analysis of Field-grown Cowpeas

Abstract Plant growth aspects of field-grown cowpea [Vigna unguiculata (L.) Walp.] were investigated under four N regimes: No N, rhizobial inoculation (cowpea “EL” inoculum), 100 kg fertilizer N/ha (NO3-N) at planting, and inoculation + 50 kg fertilizer N/ha at flowering. Five indeterminate cultivars, Brown Crowder, California Blackeye No. 5, Mississippi Silver, Tennessee White Crowder, and Lady, and one determinate cultivar, Bush Purple Hull, were compared. Plant growth variables were measured biweekly starting at the 4th week. Dry matter and leaf area per plant reached maximum at 56 days after planting in all five indeterminate cultivars, and 1 week later in the determinate cultivar. Large-seeded cultivars, California Blackeye No. 5, Mississippi Silver, Brown Crowder, and Tennessee White Crowder, generally produced larger leaves throughout the season than did ‘Bush Purple Hull’ and ‘Lady’. The relative growth rate (RGR) declined linearly with harvest time, irrespective of N treatment. The RGR of ‘Bush Purple Hull’ was lower than that of the indeterminate cultivars throughout the growth period. The net assimilation rate (NAR) of the indeterminate cultivars declined slowly from maximum values at 4 weeks and became negative during pod development. However, ‘Bush Purple Hull’ NAR increased during pod development, but declined very rapidly during late pod development. The leaf area ratio (LAR) declined curvilinearly with time in all N treatments and cultivars. The LAR values were lowest for the determinate cultivar, and the differences among indeterminate cultivars were not significant. Total dry matter, leaf area per plant, and average leaf size of inoculated and N-fertilized plants were greater than the uninoculated and unfertilized control. Nitrogen treatments did not affect physiological components RGR, NAR, and LAR.

Catastrophic Events Reveal the Dynamic Nature of Salt-Marsh Vegetation in Southern California

Recent hydrological disturbances, including flooding, dry-season streamflow, and drought, greatly altered coastal wetland habitats in sourthern California. At Tijuana Estuary, a six-year study of salt-marsh vegetation patterns during these rare conditions documented substantial temporal variability in plant growth and distribution. Important to cordgrass (Spartina foliosa Trin.) dynamics were the amount and timing of streamflows, which reduced soil salinity and alleviated stresses on plant growth. Poorest growing conditions occurred in 1984 when both river and tidal flows were lacking; soils had low moisture and extreme salinities (avg.=104‰ in September). Plant stress was documented in 1984 as high mortality (62% fewer stems than in 1983) and reduced height (19% less than in 1983). Cordgrass height was greatest in 1980 following winter flooding (20% increase over 1979); densities were greatest in 1983 with summer freshwater influxes (60% increase over 1982). A carbon allocation model is proposed to explain the varied responses.

Insecticide Effects on Potato Leafhopper and Nabids, 1982

Abstract Insecticides were applied to the second cutting of alfalfa planted in the spring near Blacksburg, VA, using a CO2-powered boom sprayer with 19 gal water/acre 18 lb psi. Treatments were replicated 5 times in 50 ft x 50 ft plots in a randomizer block design. Insect samples consisted of 10 pendular sweeps per plot using a 15 in net. Insect counts were transformed to square root of (X + .05) prior to analysis of variance. Treatments were applied Jul 14 when 2nd growth alfalfa was 6 in tall, the mean nymphal leafhopper density estimate was 0.9 per sweep, and the pretreatment adult leafhopper density estimate was 3.4 per sweep. No yield or forage quality samples were taken because of high intraplot variability in plant growth.

Fusarium Blight and Physical, Chemical, and Microbial Properties of Kentucky Bluegrass Sod

SMILEY, R. W., M. M. CRAVEN, and J. A. BRUHN. 1980. Fusarium blight and physical, chemical, and microbial properties of Kentucky bluegrass sod. Plant Disease 64:60-62. Kentucky bluegrass (Poa pratensis) may become severely damaged by Fusarium blight. When the disease occurred on a well-established plot, its dependence on the environment, a relationship that is not well understood, was studied. Factor analysis was performed to identify associations between Fusarium blight and the other variables. The disease was positively correlated with the thatch decomposition rate, negatively correlated with the plant growth variables, and not correlated with any microbial group including all species, sections, and composite numbers of Fusarium. Sod pH and Fusarium numbers were associated with thatch decomposition rates. Fusarium blight was least severe when the percentage of Fusarium-infected plant crowns was highest. These results are considered in relation to the possible role of phytotoxic substances that are produced during thatch decomposition and act as incitants of Fusarium blight of Kentucky bluegrass. Fusarium blight of Kentucky bluegrass (Poa pratensis L.), reportedly caused by Fusarium roseum (Lk.) emend. Snyd. & Hans. f. sp. cerealis and by F. tricinctum (Cda.) emend. Snyd. & Hans. f. sp.poae (4), destroys bluegrass stands in several regions of the United States. The disease occurs on seeded bluegrass stands that are usually older than 4 yr but may occur earlier on stands established from sod. Occurrence of Fusarium blight on mature turfgrasses is very dependent upon the environmental conditions (3,20), but these conditions remain poorly defined due to the unpredictable nature of the disease in well-controlled experiments. We investigated the longterm (3 yr) effects of fungicide applications on nontarget microbial activities and soil processes in closely monitored Kentucky bluegrass sod (14-16). Fusarium blight occurred on the plot in 1977 (18), and the disease was unexpectedly controlled by several fungicides that have been ineffective in all 1-yr studies. Several properties of sod also appeared to be associated with the incidence of Fusarium blight. An understanding of the relationships between this disease and certain characteristics of host growth and of sod and microbial numbers may allow more complete characterization of the conditions favoring or causing disease. This is especially important because several fungicides that control the disease in the field are not fungitoxic to the alleged pathogens in vitro (12,17). This investigation was conducted as part of Hatch Project NY(C)153434. Accepted for publication 21 March 1979. 00191-2917/80/000010$03.00/0 01980 American Phytopathological Society This report presents the results of correlative and multivariate analyses performed to identify associations between Fusarium blight of Kentucky bluegrass and certain turfgrass characteristics. Because a significant level of multicollinearity existed among variables, simple correlation coefficients could not be interpreted. Factor analysis was used to identify a set of independent patterns of association among the variables. The results of the factor analysis allowed estimation of partial correlation coefficients that provided a statistical measure of the degree of linear association between Fusarium blight and each of