Shoot Growth Parameters Research Articles

Effect of Copper on Antioxidant Enzyme Activities and Mineral Nutrition of White Lupin Plants Grown in Nutrient Solution

ABSTRACT We analyzed the effect of different copper (Cu) concentrations (0.10, 0.15, 0.20 and 0.35 mM) and time (1 day to 9 days) on several growth and biochemical parameters of roots and shoots of white lupin plants (Lupinus albus cv Estoril) grown in nutrient solution. A significant decrease in leaf fresh weight and leaf area was detected. Copper accumulated in the roots, and an impairment of nutrient translocation was only observed after six days at the highest Cu concentrations applied. A transient increase in the activity of polyphenoloxidase (EC 1.10.3.1) enforces a role for lignification as a defense strategy under enhanced Cu levels. The activities of several antioxidative enzymes were enhanced after Cu application. Our results indicate that Lupinus albus cv ‘Estoril’ is a rather resistant plant that can cope with moderate concentrations of copper, mostly by controlling up to a certain point, the uptake of excessive amounts of this metal.

Vegetative Growth Responses of Pinot gris (Vitis viniferaL.) Grapevines to Infestation by Potato Leafhoppers (Empoasca fabaeHarris)

The potato leafhopper (<i>Empoasca fabae</i> Harris) can be a damaging pest of vineyards throughout eastern North America, causing leaf curling and yellowing in sensitive cultivars. To determine the relationship between infestations by this insect and vine growth and resource allocation, potted and fruitless Pinot gris (<i>Vitis vinifera</i> L.) grapevines grafted to rootstock 1103 Paulsen (<i>V. berlandieri</i> Planch. x <i>V. rupestris</i> Scheele) were infested for 7 days with 0.0 to 4.5 potato leafhopper (<i>E. fabae</i>) nymphs per leaf. Shoot growth, leaf growth, and infestation symptoms of the leaves were quantified before and after the infestation period, and biomass of vegetative vine structures was measured at the end of the experiment. Leaf symptoms of cupping and discoloration were positively correlated with infestation severity, while shoot and leaf growth declined with increasing leafhopper density. Root mass at the end of the experiment was lower in vines with higher infestation levels. Analysis of these results enabled damage symptom and leaf growth thresholds to be determined at between 0.5 and 1.0 <i>E. fabae</i> per leaf. However, recovery of vines after infestation was observed in leaf and shoot growth parameters, and vine biomass was reduced only when <i>E. fabae</i> densities exceeded 3.0 nymphs per leaf. This study reveals the negative effect of low densities of <i>E. fabae</i> on a sensitive grape cultivar and suggests that vines can recover from low infestation levels during the postinfestation period.

Pear plantlets cultured ‘in vitro’ under lime-induced chlorosis display a better adaptive strategy than quince plantlets

In many fruit trees species lime-induced chlorosis causes serious economic damage. In the last few years, the in vitro culture technique has been applied to test rootstocks for susceptibility to iron chlorosis and to study biochemical and molecular aspects of the syndrome. In this study in vitro shoot cultivation of quince rootstocks MA, BA29 and pear cv. 'Conference' was used to unravel the relationship between iron deficiency, presence of bicarbonate, and growth development and chloroplast pigment behav- iour. Stresses were obtained by using MS medium supplemented with various concentrations of FeNa- EDTA and/or KHCO3. Substrate pH, shoot growth and development parameters, total leaf iron and photosynthetic pigment contents of plantlets were independently determined after 24 days of culture. The medium was acidified by the species under all stress conditions. Iron deficiency and bicarbonate condition led to different growth patterns and mod- ular development among the genotypes. This reflects a different sensitivity and plastic adaptation to the elements of this stress. Iron concentration in leaves and the shoot apex of plantlets decreased in all genotypes. However, chloroplast pigments only decreased in quince plantlets under iron deficiency and bicarbonate condition while they did not change in pear plantlets. Our results demonstrate firstly that a plantlet without a root system, which is cultivated in vitro, is able to sense iron deficiency and bicarbonate enriched conditions and, consequently, activates biochemical and physiological responses. Secondly, acidification appears to be related to iron concentra- tion in tissues of quince rootstocks and pear cultivar. Finally, chloroplast biochemical elements are strongly and differently regulated under both stress conditions and between genotypes.

Performance of prohexadione-calcium on shoot growth and fruit quality of apple — Effect of spray surfactants

Vegetative growth control of apples (Malus × domestica Borkh.) is necessary to maintain a balance between growth and cropping. Pruning is a labour-intensive management practice to achieve this and intrinsically stimulates new growth. Prohexadione-calcium (PC) is a plant bio-regulator that effectively regulat es the shoot extension growth of apples and other tree fruits. Previous research has demonstrated that its efficacy can vary based on the use of spray surfactants and adjuvants. This study investigated the efficacy of two rates of Apogee™, the commercial form of PC, used in combination with the spray surfactants Sylgard 309 and LI 700, on extension shoot growth and yield parameters. Experiments were conducted in Ontario on Empire and Nova Scotia on Royal Court™ Cortland apples. Treatments of 0, 75 or 125 mg L-1 PC, with and without either 0.5% (vol/vol.) LI 700 surfactant or 0.05% (vol/vol) Sylgard 309 surfactant were applied to Empire trees, and 75 or 125 mg L-1 PC, with or without 0.5% (vol/vol) LI 700, were applied to Royal Court™ trees. An untreated control treatment was also included for comparison purposes. A total of two sprays were applied to the Empire trees and a total of three sprays were applied to the Royal Court™ trees. PC significantly decreased the vegetative growth of Empire and Royal Court™ trees by approximately 18 to 44%, respectively, and the efficacy of PC was enhanced when combined with either Sylgard 309 or LI 700 surfactant. No additional benefit in vegetative growth control was gained when using Apogee™ at rates of 125 mg L-1 PC, relative to 75 mg L-1 PC. The rate of Apogee™ did not influence the number of fruit or yield per tree or mean fruit size of either cultivar. For Empire, LI 700 and Sylgard 309 significantly reduced the number of fruit per tree, resulting in lower yields and crop densities. In addition, higher mean fruit weights, and a greater distribution of fruit in the larger size categories were observed for LI 700. Fruit from Royal Court trees treated with the highest rate of Apogee™ had higher crop densities, poorer coloured fruit, and a higher percentage of fruit less than 60 mm in diameter. These data provide support for the use of alternative surfactants with Apogee™ other than those listed on the US and Canadian product labels. Key words: Apogee™, Empire, Cortland, Regalis, calcium 3-oxido-5-oxo-4-propionylcyclohex-3-enecarboxylate, surfactant

Bioassay for Determining Sensitivity to Sulfosulfuron on Seven Plant Species

This study presents a bioassay procedure, based on the root and shoot growth parameters, for the determination of the herbicide sulfosulfuron (1-(4,6 dimethoxypyrimidin-2-yl)-3-(2-ethylsulfonylimidazo[1,2-a]pyridin-3-ylsulfonil)urea) sensitivity on seven vegetal species. Plant response to sulfosulfuron was calculated with the equations fitted to the root growth data as a function of the logarithm of the herbicide concentration by non-linear regression and was used to calculate the doses for 10, 30 and 50% inhibition of root growth (EC10, EC30 and EC50). The results indicate that the phytotoxic effect of sulfosulfuron in all the species assayed followed the order: flax > maize > onion > vetch > lepidium sativum > tomato > barley. These species showed phytotoxicity at low levels of sulfosulfuron and flax appeared to be the most susceptible species to sulfosulfuron (0.001 mg/L).

Municipal garbage as a component of potting media for the growth of rosewood (Dalbergia latifolia Roxb.) seedlings in the nursery

To evaluate the effect of potting media containing municipal garbage on the growth of Rosewood (Dalbergia latifolia Roxb.) seedlings in the nursery, a series of studies were carried out at the College of Forestry, Kerala Agricultural University, Vellanikkara, Thrissur. Treatments T1 (soil), T2 (soil: sand), and T3 (soil: sand: cowdung) recorded 100 per cent initial survival rate. In most of the treatments containing municipal garbage, initial establishment were found to be good. Growth and vigour in terms of shoot growth parameters were found to be most promising when the seedlings were grown in potting media containing 4 weeks decomposed municipal garbage and soil: sand: cowdung. Physiological growth parameters did not show any systematic pattern. No uniform trend could be observed with regard to chlorophyll content also. Seedlings grown in potting media containing soil: sand: cowdung recorded maximum content of nitrogen, phosphorus and potassium in the tissues. Media containing 4 weeks decomposed municipal garbage also recorded high content of tissue nitrogen and phosphorus. It was observed that at the end of the study period, percentage of nutrient elements in different potting media slightly increased compared to the initial content.

Effects of different N-sources on growth, nutritional status, chlorophyll content, and photosynthetic parameters of shoots of the apple rootstock MM 106 cultured in vitro

The effects of five different N-sources (KNO3 + NH4NO3 = control, KNO3, NH4NO3, NH4H2PO4, L-alanine) on growth, nutritional status, chlorophyll (Chl) content, and photosynthetic parameters of the apple rootstock MM 106 shoots cultured in vitro were investigated. In comparison to all the other treatments, control explants grown on a MS medium containing KNO3 + NH4NO3 had the highest fresh mass, Chl content, net photosynthetic rate, transpiration rate, and stomatal conductance.

The Effects of Litter Cover on the Early Growth of Manchurian Wild Rice (Zizania latifolia)

ABSTRACT The effects of a standing layer of litter on the shoot emergence and subsequent growth of Zizania latifolia were evaluated by removing the litter layer in three plots. Three other plots were kept as controls with litter layer. Shoot emergence and growth parameters were observed for seven months. Light incidence through the litter layer was measured. New shoots emerged about a month earlier in the plots without litter than in the plots with litter layer. The maximum shoot density in the plots where the litter layer was removed was 590 m−2 at the time when average shoot height was 61 cm, whereas the shoot density was 316 m−2 with an average shoot height of 71 cm in the control plots. Maximum shoot density was reached three weeks later in the plots with litter. Although removal of standing litter significantly increased initial shoot density, plant growth was essentially comparable regardless of the presence or absence of accumulated litter.

New Guinea Impatiens Growth Response and Nutrient Release from Controlled-release Fertilizer in a Recirculating Subirrigation and Top-watering System

New Guinea impatiens (Impatiens hawkeri Bull.) `Illusion' were grown in a recirculating subirrigation system under various rates and placements of 14N-6.1P-11.6K (Osmocote; Scotts-Sierra, Marysville, Ohio) resin-coated, controlled-release fertilizer (CRF). Four CRF placements (incorporated, top-dressed, bottom, and dibble) were tested. Incorporated placement yielded slightly greater dry weights than the other placements. A rate experiment tested incorporating from 0.5 to 2 times the fertilizer manufacturer's recommended rate of 7.11 kg·m-3. All shoot growth parameters (height, leaf number, shoot, and root fresh and dry weight) exhibited a significant quadratic response, as exemplified by shoot dry weight, where shoot dry weight increased up to the 1.5× rate, after which shoot dry weight decreased. A quadratic response surface model revealed that the optimum rate response ranged from 1.16× rate for height to 1.47× rate for shoot dry weight. The lower bound of the 95% confidence interval (CI) would be the lowest rate at which one could expect maximum growth response. The lower bound of the 95% CI varied from 0.56× rate for height to 1.30× rate for shoot dry weight. Thus, the lowest rate that would be within the 95% CI for all growth parameters, and thus yield maximum growth response, would be the 1.30× rate. Electrical conductivity (EC) of the growing media increased significantly with increasing CRF rate. At all rates, EC was significantly greater in the top layer than in the middle and bottom layers. Only in the 1.75× and 2× rates did EC exceed the recommended EC levels in the middle and bottom layer. All rates &gt;0.75× exceeded recommended EC in the top layer. Release characteristics and total nutrient balance of the CRF was compared in subirrigated and top-watered systems. There was no significant difference between top-watered and subirrigated treatments for the amount of K recovered in plant tops and released from prills. By day 84, in subirrigation, 46% of the K was still in the prills, 41% was recovered in the plant tops, and 22% was recovered in the medium. Similar results were obtained in the top-watering treatment, except that a lesser amount was recovered in the medium (9%) and a small amount (4%) was recovered in the leachate. The uptake of K by plants and release of K by the CRF were inversely proportional and linear with respect to time. Of the K released from the prills, 77% and 83% were recovered in the plant tops for subirrigation and top-watering, respectively, indicating very high fertilizer use efficiency.

Concentrações de ANA e BAP na micropropagação de abacaxizeiro L. Merrill (Ananas comosus) e no cultivo hidropônico das plântulas obtidas in vitro

O efeito de diferentes concentrações de ANA e BAP na micropropagação do abacaxizeiro, bem como no cultivo em hidroponia das plântulas obtidas in vitro, foram estudados em brotos de abacaxizeiro da variedade Pérola, inoculados em meio de cultura básico MS, suplementado com os fitorreguladores BAP e ANA em diferentes concentrações. Caracteres morfológicos quantitativos relacionados ao crescimento dos brotos e das plântulas de abacaxizeiro foram avaliados respectivamente durante os cultivos in vitro e em hidroponia e mostraram que, o tratamento T1 (BAP = 1,0 mg L-1e ANA = 0,5 mg L-1) proporcionou a maior taxa média de regeneração de brotos e conseqüentemente uma maior produção de matéria fresca. Entretanto, a altura dos brotos e a formação de suas raízes foram maiores nos tratamentos T2 (BAP = 0,5 mg L-1 e ANA = 0,25 mg L-1 ) e T3 (BAP = 0,25 mg L-1 e ANA = 0,12 mg L-1 ). Após sessenta dias de cultivo em hidroponia, todas as plântulas oriundas do tratamento T1 apresentaram um bom desenvolvimento, expresso pela maioria dos caracteres morfológicos avaliados. O sistema de micropropagação utilizado neste trabalho possibilitou a obtenção de brotos de abacaxizeiro Pérola, em quantidade suficiente e ao mesmo tempo de fácil individualização, seguida da regeneração de plântulas que foram cultivadas em hidroponia.

Changes in the Rooting and Growth of Willows and Poplars Induced by Cadmium

Growth parameters of six fast growing trees showed that the roots responded to Cd treatment more sensitively than the shoots. Cd-treatment suppressed rooting and root growth (length and biomass production) as well as its development in all tested species. Root systems of Salix cinerea, Salix alba, and Populus cv. Robusta were more tolerant to Cd stress than the root system of the other studied species. Shoot growth parameters of Salix species were significantly reduced unlike Populus species, which were not affected by Cd treatment.

Nursery studies in Terminalia paniculata Roth. Seedlings

A nursery study was conducted in College of Forestry, Kerala Agricultural University, Vellanikkara to find out the effect of potting media containing different types of waste materials like garbage and coir dust on establishment, growth and vigour of seedlings of Terminalia paniculata Roth. The seedlings raised in potting media T1 (Soil: sand: cowdung), T5 (Soil: fresh garbage: cowdung) and T12 (Soil: coirdust: cowdung) recorded 100 per cent success with regard to both initial establishment after one week of planting and final survival after eight months. In most of the treatments, the initial establishment was found to be good. The initial establishment and survival were very poor when fresh garbage alone was used as a planting medium. With regard to growth and vigour in terms of shoot and root growth parameters and other physiological attributes, potting mixtures of soil and cowdung with four weeks decomposed garbage were found to be most promising. Growth and vigour was generally found to be less when seedlings were grown in coirdust. The relative growth rate and other physiological attributes were also found to be less for this treatment. Generally, the chlorophyll A content was found to be slightly higher when compared to chlorophyll B. Stomatal distribution did not show a specific pattern with regard to treatments. Nutrient uptake particularly nitrogen was found to be more when cowdung and partially decomposed garbage were used as components of potting media. However, the potting media did not affect the uptake of potassium and phosphorus.

Influence of water deficit and low air humidity in the nursery on survival of Rhamnus alaternus seedlings following planting

SummaryThe effect of irrigation and air humidity on the water relations and root and shoot growth of Rhamnus alaternus L. during the nursery phase was considered to evaluate the resulting degree of hardening obtained by these treatments. R. alaternus seedlings were pot-grown in two greenhouses of equal characteristics. In one of these greenhouses air humidity was controlled using a dehumidifying system, while in the other one the environmental conditions were not artificially modified. In each greenhouse, two irrigation treatments were used. Thus, four different treatments were applied during the nursery phase (January-May): 1) control air humidity + control irrigation; 2) control air humidity + deficit irrigation; 3) low air humidity + control irrigation; 4) low air humidity + deficit irrigation. In May, plants of all treatments were transplanted and grown in good environmental and irrigation conditions for one month (17 May–20 June), after which they received no irrigation until the end of the experiment (14 July). Low air humidity and water deficit reduced all shoot growth parameters during the nursery phase, however the root growth was not significantly affected by air humidity and even increased under the water deficit. The reduction in leaf water potential under water stress was induced by tissue dehydration since leaf turgor potential also decreased and non-osmotic adjustment was observed. The drought effects on water relations were similar in both low and high air humidity. The leaf stomatal conductance was also reduced by both types of stress, leading to a decrease in the rate of photosynthesis at the end of the nursery phase. Both water deficit and low air humidity showed their value as nursery acclimation processes, improving the survival of seedlings following transplanting and non-irrigation conditions (establishment phase). The stomatal regulation and a shift in the allocation of assimilates from shoot to root were the acclimation mechanisms showed by R. alaternus under both types of stress. The accumulated effects in low air humidity and water deficit plants could explain the highest percentage of survival at the end of the establishment period (97%) for the combined treatment.

Microbial Inoculants on Woody Legumes to Recover a Municipal Landfill Site

Tree and shrubby legumes have great potential in degraded land rehabilitation because of their ability to form symbiotic associations with nitrogen fixing rhizobia and mycorrhizal fungi. Extensive soil disturbance reduces natural microbial propagules thus preventing the formation of be- neficial plant-microbes symbiosis. Reintroduction of selected microbial symbionts may improve the recovery rate of disturbed ecosystems. We inoculated selected rhizobia and arbuscular mycorrhizal fungi on two woody legume species, the mediterranean shrub Spartium junceum L. and the exotic tree Acacia cyanophylla Lindl. in order to recover a sealed municipal landfill (Palermo, Sicily, Italy). Inoculated plants showed shoot growth parameters 2 to 12-fold higher than uninoculated plants. After transplanting on the municipal landfill site, inoculated plants showed no transplant shock and low mortality (6-15%). The chemical analysis of P and N plant content showed no differences between inoculated and uninoculated plants suggesting that a dilution effect occurred due to higher biomass production of the inoculated plants. The beneficial effects of mycorrhization and rhizobium inoculum on growth parameters were still detectable one year after transplanting in S. junceum.

Growth, Water Relations and Accumulation of Organic and Inorganic Solutes in the Halophyte Limonium latifolium cv. Avignon and its Interspecific Hybrid Limonium cas pia x Limonium latifolium cv. Beltlaard During Salt Stress

Summary Plants of two genotypes, Limonium latifolium cv. Avignon and its interspecific hybrid Limonium caspia X Limonium latifolium cv. Beltlaard, grown in a hydroponics culture were submitted to 140 mmol/L NaCl nutrient solution for 20 days (saline treatment). The physiological traits of salt tolerance that differ among these cultivars have been studied. Shoot growth parameters of Beltlaard plants showed that they were affected by salinity, inducing a significant reduction in shoot dry weight and leaf area with respect to the control treatment, while these parameters remained unchanged in Avignon. The behaviour of leaf water relations under saline stress was not different between both genotypes, which indicated that the osmotic effect was similar for both cultivars. At the end of the experiment the cultivars studied were able to achieve the same degree of osmotic adjustment. However, in L. Beltlaard the maintenance of turgor did not permit the maintenance of the growth rate. Leaf growth reductions in response to salinity were associated with higher tissue levels of Na+ and Cl− and changes in the contribution to leaf osmotic potential of K+ and NO3−. The rates of NaCl absorption by roots and the net transfer from roots to shoots was higher in Beltlaard than in Avignon; this fact suggests that the radical exclusion mechanisms are more operative in Avignon. In conclusion, although Avignon showed lower NaCl uptake rates, the growth reduction was more pronounced in Beltlaard because the accumulation of salt in the tissue generated toxicity and nutritional disturbances.

Effect of Fall Defoliation and Spring Shading on Shoot Carbohydrate and Growth Parameters among Individual Branches of Alternate Bearing `Kerman' Pistachio Trees

Early fall (September) defoliation and late spring (early June) shading of “off” and “on” pistachio trees were used to test two hypotheses: that 1) fall defoliation would reduce carbohydrate storage sufficiently to suppress spring growth and 2) spring shading would reduce carbohydrate status and increase inflorescence bud abscission. Defoliation suppressed initial leaf area expansion the following spring on current year shoots of “off” but not “on” trees respectively. Suppression of leaf size was correlated with the initial low concentration of carbohydrates in organs of individual branches of the tree. Fruiting and artificial shading in June had more dramatic effects on growth parameters than defoliating. Shading “off” trees for 14 days in early June accelerated abscission of inflorescence buds, reduced dry mass of individual leaves, buds, current year and 1-year-old shoots. Shading also reduced the concentration of total nonstructural carbohydrates (TNC) of these organs in “off” and “on” trees. Fruiting suppressed leaf size and leaf dry mass by 20% and 30% among individual branches of undefoliated and defoliated trees respectively. Low carbohydrate concentrations in individual branches and inflorescence buds following shading were closely correlated with the abscission of inflorescence buds.

Effects of nitrogen nutrition on salt-stressedNicotiana tabacumvar. Samsunin vitroplantlets

Tobacco shoots were grown in vitro for 35 d, in MS culture medium modified to include various sources (nitrate-N, ammonium-N or a mixture) and levels (0-120 mM) of N, and in the presence of 0-180 mM NaCl or iso-osmotic concentrations of mannitol. Growth of control plantlets was significantly inhibited when NH 4 + -N was the sole N source, and at high (120 mM) NO 3 - N supply. Under conditions of salt stress (90 and 180 mM NaCl) growth was repressed, with roots being more severely affected than shoots. Salinity also inhibited root emergence in vitro. The only alleviation of the salt stress by nitrate nutrition observed in this study was on shoot growth parameters of plantlets grown on 60 mM NO 3 - -N and 90 mM NaCl

Gauging Turfgrass Salinity Responses in Whole‐Plant Microculture and Solution Culture

New methods for assessing salinity responses of turfgrass lines are required to identify selections for use on marginal sites. This study was conducted to quantify whole turfgrass plant responses to salt in solution‐culture and microculture test environments, and to evaluate the latter as an alternative system for identifying salt‐resistance characteristics. Paired cultivars of bermudagrass (Cynodon spp.), creeping bentgrass [Agrostis stolonifera L. var. palustris (Huds.) Farw. syn.] and St. Augustinegrass [Stenotaphrum secundatum (Walt.) p. Kuntze] were tested in treatments ranging from control (no supplemental salt) to 32.4 dS m−1 conductivity (NaCl in the growth medium). Direct comparison between test environments of the regression slopes for osmotic adjustment revealed no significant differences for bermudagrass, and salt‐sensitive cultivars of St. Augustinegrass and creeping bentgrass. Linear or quadratic regressions characterized reductions in all shoot growth parameters with increasing salt levels in both solution and microculture environments. More severe regressions were frequently observed for relatively salt‐sensitive cultivars. Root length and area data did not exhibit consistent regressions on medium conductivity level in either test system. These results demonstrate that the small‐scale microculture environment can be used to nonintrusively monitor turfgrass plant responses to salinity.

Rice Shoot Response to Root Confinement within a Membrane

AbstractA porous membrane has been used for root studies of upland crops but not for crops grown under submerged conditions. A field study was conducted to compare the growth of paddy rice (Oryza sativa L.) with and without root confinement within a porous membrane. Three membrane configurations were compared: (i) a narrow membrane; (ii) a wide membrane; and (iii) a modified wide membrane. Root confinement within membranes reduced all shoot growth and yield parameters compared to soil‐grown plants (control). Reductions in shoot growth and yield parameters were usually least for the modified wide membrane and greatest for the narrow membrane.

Root Temperature and Calcium Level Effects on Winter Wheat Forage: I. Shoot and Root Growth

AbstractWheat pasture poisoning is a metabolic disorder of ruminants, that occurs particularly in the spring, during a sudden spurt in plant growth, under conditions of optimum temperature, ample soil moisture and adequate mineral supply. To determine the effects of an increase in root temperature and four Ca levels on the shoot and root growth of winter wheat (Triticum aestivum L. ‘Centurk’), seedlings were grown under three root temperature regimes (constant 8 °C, constant 16 °C, and increasing from 8‐16 °C), in nutrient solutions with four Ca levels (0.2,0.6,2.0, and 5.0 mM). No significant differences due to Ca levels were found for growth rates of the shoots and roots (dry weight basis), nor for root extension rates. Growth rates of the shoots and roots (dry weight basis), and root extension rates were significantly slower for plants grown at 8 °C compared to those grown at 16 °C. Lateral root growth, in particular, was depressed in plants grown at a cold root temperature. The mean root diameter was significantly greater at 8 °C than at 16 °C, apparently due to the greater proportion of main root axes with larger root diameters at a cold root temperature. Plants transferred to 16 °C had growth rates of the shoots and roots that were intermediate, relative to those grown at constant low or constant high root temperatures. A lag period of 1 wk was observed before shoot and root dry weights of plants transferred to 16 °C increased, compared to those maintained at 8 °C. Thus, root temperatures play a major role in modifying shoot and root growth parameters.