The Effects of Rootzone Salinity and Hypoxia on Shoot and Root Growth in Trifolium Species

The effect of concurrent salinity (0-60 mM NaCl) and rootzonehypoxia (flooding for up to 15 d) on shoot and root growth andshoot ion concentrations of six species of Trifolium (T. subterraneumL., T. fragiferum L., T. michelianum Savi., T. isthmocarpumBot., T. purpureum Lois., and T. repens L.), was studied intwo greenhouse experiments. There was a significant salinityx flooding effect for shoot yield but no significant salinityx flooding x species interaction although individual speciesdiffered significantly (P < 0·001) in their growthresponse to the saline or flooded conditions separately. Concentrationsof Na and Cl in the shoots of all species increased with increasingperiods of saline flooding and there was a significant salinityx flooding interaction. Sodium and Cl concentrations were significantlyhigher (P < 0·001) in T. purpureum, the species inwhich shoot growth was most depressed by saline flooding, thanother species. In T. michelianum, T. fragiferum and T. repens,fresh and dry weight of roots increased with flooding underboth saline and non-saline conditions while in T. subterraneumroot growth decreased. A significant proportion of the increasedroot growth in the first three species occurred as new adventitiousroots. These roots had higher percentages of internal gas spaceswithin the root tissue even in the presence of salinity comparedwith roots from non-flooded conditions. There were also significantlymore gas spaces in the total root tissue in T. fragiferum andT. repens under saline-flooding than in roots of T. subterraneum.Electron micrographs of the root cross sections illustratedthe presence of these gas spaces or aerenchyma. Trifolium fragiferum, T. repens and T. michelianum are morelikely to be suited to growth in soils prone to high salinityand to flooding than are T. subterraneum, T. purpureum and T.ishmocarpum.Copyright 1993, 1999 Academic Press Trifolium subterraneum, Trifolium fragiferum, Trifolium michelianum, Trifolium isthmocarpum, Trifolium purpureum, Trifolium repens, salinity, flooding, hypoxia, adventitious roots, aerenchyma, subterranean clover, white clover, strawberry clover, purple clover, balansa clover     

Shoot and Root Growth of Lettuce Seedlings Following Root Pruning

Hydroponically-grown lettuce seedlings with 13 to 18 primarylateral roots were root pruned in one of four ways; the rootapices were removed from the main root only (1) or from allthe root membranes (2), or half the total root system was removedwith the remaining apices left intact (3) or removed (4). Duringthe following 8 d the rate of lateral root production on prunedplants increased, decreased, and then increased again relativeto the unpruned control. Conversely, the rate of increase intotal root length decreased, then increased, and if all theroot apices were removed, declined again, prior to increasingon day 8. These changes in the rates of lateral root productionand growth resulted in similar, but less pronounced, patternsof change in the total root length and the total number of lateralroots with time. The changes in total lateral root productionwere related to differences in the rates of primary, secondaryand tertiary root emergence. The shoot d. wt of the most severely root pruned seedlings (treatment4) fell below that of the control 4 d after pruning and remainedlower than the control on day 14, whereas the root d. wt hadrecovered to the control level by day 6. The root: shoot d.wt ratio, which was reduced by root pruning, rose above thatof the control on days 6 and 8. Lactuca sativa L., lettuce, root pruning, root growth, lateral root, nutrient solution     

Effects of the Photoperiod Genes Ppd1 and Ppd2 on Growth and Development of the Shoot Apex in Wheat

Two major genes influencing the photoperiod response in wheat,Ppd1 and Ppd2, have been identified on the group 2 chromosomes.Substitution lines, which had been characterized on the basisof time of ear emergence as carrying either the insensitiveor sensitive alleles of the two Ppd genes, were used to investigatethe effect of these genes on development. They were grown undershort photoperiods, and growth and development of the shootapex was measured. The primary influence of the Ppd genes was on ear growth. Inthe plants carrying the insensitive alleles, Ppd1 and Ppd2,the relative growth rate of the floral apex was faster thanthat of plants with the sensitive alleles, ppd1 and ppd2. Therewere no differences in the rate of spikelet initiation, butthe spikelets of the ppd lines grew and developed more slowly. The Ppd2 material segregated for another gene located on chromosome2B affecting duration of the life cycle. This gene also affectedthe relative growth rate of the ear. It was considered that the major effect of the Ppd1, Ppd2 andthe second genetic factor on chromosome 2B is on floral growthrate. Differences in apex morphology, stem growth and ear emergenceare thought to be due to the differences in floral apex growthand size. Wheat, photoperiod genes, shoot apex development, shoot apex growth     

Shoot and Root Activities During Steady-state Plant Growth

A simple model for steady-state plant growth is described. Thegrowth constant, measured during steady-state exponential growth,is related to the specific activities of the shoot and the root,enabling the effects of certain environmental variables (light,carbon dioxide and nitrogen) on the growth constant to be examined.The model is used to interpret data on the growth kinetics ofwheat (Macdowall, 1972a, b, c).     

Adverse Effect of Shoot Growth on Root Growth in Rooted Cuttings of Aspen

In experiments with rooted cuttings of aspen (Populus tremula L). with a small leaf area, it was found that the roots grew well as long as there was no shoot growth. The onset of shoot growth was followed by a period of decreased root growth. When the leaf area had increased sufficiently, root growth recovered. Decreasing the shoot growth by removal of growth points in the shoot or by short day treatment increased the fraction of photosynthesis products used for root growth, leading to increased root/shoot ratios. Competition between growing shoots and roots for carbohydrates formed in photosynthesis is considered to cause the effects noted and to be of importance for maintaining the balance between the root and shoot systems.     

Photoperiod and Temperature Interactions in Growth and Flowering of Strawberry

Growth and flowering of strawberry cultivars were studied in controlled environments. Early cultivars adapted to marginal growing areas in Scandinavia initiated flower buds in all photoperiods including continuous light at temperatures of 12 and 18°C. At 24°C they remained vegetative in photoperiods above 14 or 16 h. The later cultivars ‘Senga Sengana’ and ‘Abundance’ did not initiate flower buds in 24-h photoperiods at any of these temperatures. Their critical photoperiod changed from above 16 h at 12°C to about 14 and 13 h at 18 and 24°C, respectively. It is concluded that at high latitudes temperature is as important as photoperiod in controlling flowering in the strawberry. Stolon formation, petiole elongation, and leaf area growth were stimulated by high temperature and long days, usually with optima at 16 h and 18°C for petiole elongation and 16 h and 24°C for stolon formation. Although growth and flowering responses in general were opposite, the results indicate that they are to some extent independent. The photoperiodic growth responses were mainly of morphogenetic nature. Dry weight of stem and leaves was little influenced by photoperiod when the irradiance was kept constant.     

Some Effects of Light Intensity and Temperature on Dry Weight and Shoot Growth of Grape-Vine

Prerooted cuttings of grape-vine (Vitis vinifera L., cultivarMuscat Gordo Blanco, syn. Muscat of Alexandria) were grown ingrowth cabinets for 13 weeks after bud-burst. Environmentalconditions were light intensities of 3600 foot candles (f.c.),18oo f.c., and 9oo f.c. in all combinations with temperaturesof 30 ?C day/25 ?C night, 25 ?C/20 ?C, and 20 ?C/15 ?C. Daylengthwith both fluorescent and incandescent lighting was 16 h with8-h nights. Measurements of main and lateral shoot lengths,leaf numbers, and leaf areas were made at weekly intervals for9 weeks. At 13 weeks the plants were harvested and dry weightsof roots, parent canes, stems, and leaves measured. Dry weights increased with increasing light intensity and weregreaert at 25 ?C than at 20 ?C or 30 ?C. The new shoot: rootratio remained at approximately 7.o under all conditions, butincreasingly more dry weight was in leaves and correspondinglyless in stems with increased temperature. Stem lengths and leafarea values were in most cases greatest at 25 ?C followed inturn by 30 ?C and 20 ?C values. Light intensity had no cleareffect. Apical dominance increased with increasing temperature.Internode length was stable under all conditions. The erraticgrowth of lateral shoots was one factor making the results difficultto interpret.     

Temperature Effects on Shoot and Root Development From Begonia × cheimantha Petiole Segments Grown in vitro

The effect of different temperatures on the shoot and root formation in isolated petiole segments of Begonia × cheimantha was determined after 10 weeks on a modified White medium containing 0.1 mg/1 NAA and 0.5 mg/1 BA. Temperature proved to be important for the induction of shoot and root formation. At a constant temperature the best plants were obtained at 18 to21°C. If the temperature was higher, fewer cultures survived and the number of roots and shoots were lower. Lower temperatures inhibited the development of plants. A pretreatment at 15 or 18°C for two to four weeks improved the number and size of the shoots developed during a following 24°C treatment. High temperatures throughout the growing period reduced the number of shoots severely. A pretreatment of three days at 24°C or one day at 28°C reduced the shoot number by 50 %. After seven days at 28°C there was not a single shoot in any of the cultures. However, after two weeks at 15 or 18°C it was no longer possible to inhibit the shoot formation by a 24°C treatment. It is concluded that the formation of shoots in petiole segments takes place during the first two weeks after excision, and that high temperature is detrimental to the shoot initiation process.     

Effects of Temperature and Photoperiod on Assimilate Partitioning in Potato Plants

The effects of temperature and photoperiod on d. wt partitioningand ¹⁴C translocation were studied in three potato varieties.High temperatures and long days enhanced plant growth in termsof plant height and number of leaves, and also affected d. wtpartitioning between the plant organs. However, no temperatureeffect was noted on total plant d. wt, nor on the export of¹⁴C from the source leaf. Translocation of ¹⁴C to the vegetativeorgans (leaves and stems) was greater at higher temperatures,while translocation to the tubers was less under these conditions.We suggest that, under the temperature regimes studied, themain effect of high temperature is on assimilate partitioningand not on total plant productivity. Differences in responseto high temperatures were observed among varieties, with Norchipshowing the least and Up-to-Date showing the most sensitivity. High temperature, partitioning of assimilates, ¹⁴C-translocation, potato, Solanum tuberosum var. Desirèe, Solanum tuberosum var. Norchip, Solanum tuberosum var. Up-to-Date     

Root and Shoot Growth of Plants Treated with Abscisic Acid

Young seedlings of Capsicum annum L., Commelina communis L.and maize (Zea mays L.) were subjected to a mild water-stressingtreatment and/or treated with abscisic acid (ABA). Plants rootedin soil received a soil-drying treatment and their leaves weresprayed with a 10–⁴ M solution of ABA. Plants grown insolution culture were stressed by the addition of polyethyleneglycol (PEG) to the rooting medium and ABA was also added tothe rooting medium, either with or without PEG. The effectsof both treatments on the growth of roots and shoots and theultimate root: shoot dry weight ratio were very similar. Shootgrowth was limited both by water stress and by ABA application;while there was some evidence that mild water stress and/orABA application may have resulted in a stimulation of root growth.More severe water stress reduced the growth of roots but theoverall effect of stress was to increase the ratio of rootsto shoots. Capsicum annum L., Commelina communis L., Zea mays L., water stress, abscisic acid     

Effects of Temperature and Photoperiod on Growth and Development of Tillers and Rhizomes in Poa pratensis L. Ecotypes

The vegetative growth of four Norwegian ecotypes of Poa pratensisL. was compared at day/night temperatures of 21/12, 21/6, 12/12and 12/6 °C and at photoperiods of 12, 16, 20 and 24 h,the irradiation being approximately equal in all treatments.Tillering within tufts was most abundant in short days and atthe large temperature amplitude. Rhizome formation and elongationwere stimulated by long days and, more strongly, by high daytemperature, but a greater proportion of the rhizomes formedaerial tillers in short days. Long day stimulation of heightgrowth and dry matter accumulation differed between ecotypesbut was generally most pronounced at low temperatures. The NorthNorwegian ecotype ‘Lavang’ had a higher relativegrowth rate and developed two to three times as many rhizomesas its South Norwegian counterparts. Day/night temperature, growth rate, leaf area, photoperiodicity, Poa pratensis L., rhizomes, roots, smooth meadow grass, tillering, weight gain     

Effect of Root and Shoot Meristem Temperature on Shoot to Root Dry Matter Partitioning and the Internal Concentrations of Nitrogen and Carbohydrates in Maize and Wheat

Maize (Zea mays L.) and spring wheat (Triticum aestivum L.)were grown in nutrient solution at uniformly high air temperature(20 °C), but different root zone temperatures (RZT 20, 16,12 °C). To manipulate the ratio of shoot activity to rootactivity, the plants were grown with their shoot base includingthe apical meristem either above (i.e. at 20 °C) or withinthe nutrient solution (i.e. at 20, 16 or 12 °C). In wheat, the ratio of shoot:root dry matter partitioning decreasedat low RZT, whereas the opposite was true for maize. In bothspecies, dry matter partitioning to the shoot was one-sidedlyincreased when the shoot base temperature, and thus shoot activity,were increased at low RZT. The concentrations of non-structuralcarbohydrates (NSC) in the shoots and roots were higher at lowin comparison to high RZT in both species, irrespective of theshoot base temperature. The concentrations of nitrogen (N) inthe shoot and root fresh matter also increased at low RZT withthe exception of maize grown at 12 °C RZT and 20 °Cshoot base temperature. The ratio of NSC:N was increased inboth species at low RZT. However this ratio was negatively correlatedwith the ratio of shoot:root dry matter partitioning in wheat,but positively correlated in maize. It is suggested that dry matter partitioning between shoot androots at low RZT is not causally related to the internal nitrogenor carbohydrate status of the plants. Furthermore, balancedactivity between shoot and roots is maintained by adaptationsin specific shoot and root activity, rather than by an alteredratio of biomass allocation between shoot and roots.Copyright1994, 1999 Academic Press Wheat, Triticum aestivum, maize, Zea mays, root temperature, shoot meristem temperature, biomass allocation, shoot:root ratio, carbohydrate status, nitrogen status, functional equilibrium     

Distinct Influence of Root and Shoot Temperature on Nitrogen Fixation by White Clover

White clover (Trifolium repens L.) was grown in controlled environmentsto determine the distinct effects of root and shoot temperatureon the accumulation of total and fixed (¹⁵ N dilution) nitrogenat two levels of nitrate (10 and 75 mM). Nitrogen fixation(BNF) showed a positive response to higher shoot temperature(23 vs. 13 C day temperature), irrespective of whether or notroot temperature was increased in parallel. Low root temperature(5 C) caused a marked reduction in the accumulation of totalnitrogen at both nitrate levels, and led to a lower proportionof N derived from BNF. The temperature response of BNF was attributedfor the major part to an adaptation to the demand for fixedN. It is therefore concluded that BNF is not primarily responsiblefor the reduced clover growth at low temperatures. White clover, Trifolium repens L., temperature, nitrogen fixation, nitrate, root, shoot     

Effect of Photoperiod on Vegetative Growth in Two Natural Populations of Dactylis glomerata L.

The growth of two natural populations of cocksfoot from contrastingclimatic regions (Norway and Portugal) was studied at four temperaturesand two photoperiods. Serial harvests were taken and quadraticcurves were fitted to log dry weight and leaf area for eachreplicate in order to calculate growth attributes at a constantplant weight for all treatments. Interactions of population,temperature, and photoperiod on relative growth-rate (RGR) werefound, with the greatest population differences at 5 and 30°C in an 8-h photoperiod. Leaf-area ratio (LAR) played alarger part than net assimilation rate (NAR) in determiningthe differential population responses in RGR to daylength, andthese differences in LAR were primarily the result of differentpatterns of dry-matter distribution within the plant.     

Effect of Root/Leaf Temperature Differentials on Root/Shoot Ratios in Some Pasture Grasses and Clover

Twelve pasture species were grown in the same aerial environment,but with five constant soil temperatures ranging from 5 to 35°C, to determine the influence of root temperature on theweight of roots per unit weight of foliage (R/S ratio). Thisratio varied by a factor of 2 to 8 within species. Using maximum yield of foliage to indicate the optimum soiltemperature for each species, it was found that the R/S ratiowas lowest at the optimum soil temperature, and was progressivelyhigher at soil temperatures above and below the optimum withonly slight exceptions. This experimental manipulation of R/Sratios suggests that the partitioning of photosynthate is controlledby the relative rates of photosynthesis and root absorption,by inverse proportion: Root mass x rate_(abeorption)     

Effects of Temperature, Photoperiod and Seed Vernalization on Flowering in Faba Bean Vicia faba

Factorial combinations of three photoperiods (10, 13 and 16h), two day temperatures (18 and 28 °C) and two night temperatures(5 and 13 °C) were imposed on nodulated plants of six diversegenotypes of faba bean (Vicia faba L.). Plants were grown inpots in growth cabinets from both vernalized (1.5±0.5°C for 30 d) and non-vernalized seeds. The times from sowingto the appearance of first open flowers (f) were recorded. Seedvernalization decreased the subsequent time taken to flowerin almost all genotype x growing environment combinations (theexceptions were plants of the cv. Maris Bead grown in threecooler, short-day regimes). The influence of temperature andphotoperiod on the rate of flowering was quantified, using amodel applied previously to other long-day species of grainlegume in which positive linear relations between both temperatureand photoperiod and the rate of progress towards flowering areassumed to apply. A significant positive linear response ofrate of progress towards flowering to limited ranges of meandiurnal temperature was detected in all six genotypes, but inthree genotypes (Syrian Local Large, Aquadulce and Maris Bead)the 28 °C day temperature reduced the rate of progress towardsflowering - suggesting that the optimum temperature for floweringin these genotypes is below 28 °C. In four genotypes (MarisBead, Giza-4, Aquadulce and BPL 1722) a significant positiveresponse to photoperiod, typical of quantitative long-day plants,was observed only in plants grown from vernalized seeds. Incontrast, plants of the genotype Zeidab Local grown from bothnon-vernalized and vernalized seeds showed the same positiveresponse to photoperiod, whereas plants of the land-race SyrianLocal Large were consistently unresponsive to photoperiod. Theimplications of this range of responses amongst diverse genotypesare discussed in relation to screening germplasm. Vicia faba, faba bean, flowering, photoperiod, temperature, seed vernalization, germplasm screening     

Photoperiod and Temperature Effects on Late Developmental Stages of Stylosanthes guianensis

Seedlings of Stylosanthes guianensis var. guianensis cv. Cookand S. guianensis var. pauciflora cv. Bandeirante were defoliatedand placed in a naturally lit glasshouse at 23/18 °C, 28/23°C or 33/28 °C (day/night). After exposure to 14 h daysand after floral induction with 30 cycles of 11 h, plants wereallocated to 11, 12, 13 or 14 h during flowering and seed formation. Floral initiation occurred after 10–15 short-day cycles.Flower appearance was hastened by warm temperatures and spikenumber per plant at 20 d after flower appearance was negativelyrelated to temperature and greater in Cook than in Bandeirante.Exposure to 13- and 14-h days reduced the continued differentiationof inflorescences in Bandeirante, and in Cook in warm temperatures.Floret number per spike was greatest at 23/18 °C and a higherproportion of florets aborted in Bandeirante at 33/ 28 °C.Variations in seed setting of the bi-articulate loment of Bandeiranteare described. Highest potential seed yield occurred if afterfloral induction 11 or 12 h days were maintained with 23/18°C or 28/23 °C temperatures. Photoperiod, temperature, development, Stylosanthes guianensis, flowering     

The Effect of Root and Shoot Temperatures on Growth of Ceanothus greggii Seedlings

The effect of varying independently nutrient solution temperature(5, 15, 25 C) and air temperature (10, 20, 30 C) on hydroponicallygrown Ceanothus greggii (Rhamnaceae) seedlings was studied.Increasing both air and solution temperatures caused higherroot and shoot biomass and larger root and leaf areas. Root/shootbiomass ratio increased with increasing solution temperatureand decreased with increasing air temperature. The surface areaof individual leaves decreased with higher air temperaturesbut did not change with solution temperatures. These resultsare opposite to what is predicted from Davidson's balanced rootand shoot activity model. We suggest that nutrient solutiontemperature directly affected root growth and that air temperaturedirectly affected shoot growth. Ceanothus greggii (Trel.) Jeps., root temperatures, soot temperature, plant growth, biomass allocation     

Growth Responses of Sweet Orange Seedlings to Shoot and Root Pruning

Following combined shoot- and root-pruning treatments the growthof Citrus sinensis (L.) Osbeck seedlings was analysed into responsesto post-pruning size and to the part pruned. The treatmentswere shoots pruned by removing O, , or of their estimated weightin all combinations with roots pruned by removing O, , or oftheir estimated weight. Responses were measured a year laterand are discussed in terms of the mechanisms controlling increment.Total increment was linearly related to initial pruned weightboth within and between treatments and there were no interactionsbetween shoot and root pruning in increment of leaf, new stem,old stem, thorn, fibre-root, or tap-root. Root pruning, pergramme of pruned material, reduced increment more than did shootpruning. With increasing shoot pruning the ratio of new stem to old stemincreased while with increasing root pruning the ratio of fibre-rootto tap-root increased. Following shoot pruning the new-stemincrement was disproportionately large while following rootpruning the increment of top growth was proportionately largerthan that of roots. The results suggest that pruning citrus trees to a constantsize at planting could lead to a uniform tree size in the subsequentorchard but that maximum growth would occur on un-pruned trees.