Improved Root Development Research Articles

ALGAE EXTRACT AND MICRONIZED LEATHER AS BIOSTIMULANTS FOR EARLY-STAGE MAIZE FERTILIZATION

The application of biostimulants to crops could represent a significant opportunity in order to prevent plant nutrient stress and increase crop yield: this is particularly relevant in Mediterranean areas, which are characterised by hot and dry climate and soils poor in nutrient content and organic matter. On general terms, biostimulant properties are quite always associated to fertilizers based on algae extracts or hydrolysed proteins. An alternative approach could be recognized in the application of solid fertilizers with specific properties, such to improve root development and following nutrient uptake, especially at the early stage of crop growth. In the present study, in a short-term pot trial, we evaluated the effect of two different biostimulant products, a liquid and a solid, on maize root and shoot growth, under nutrient stress conditions. A biostimulant based on algae extract, in liquid form (LB) at the rate of 100 L L-1 and a solid (SB), based on micronized leather, at the rate of 100 mg L-1, were added to an inert growing substrate. Seedlings of maize (Zea mais L. ‘Suarta’) were transplanted in pots and then grown in a greenhouse. Standard nutrient solution at 50% of the optimal concentration was supplied or not supplied (0%) to the pots, in order to evaluate if the presence of nutrient solution could emphasize the biostimulant properties of the considered formulates. Results showed that both the maize primary root length and weight were significantly increased by both LB and SB application, particularly in absence of nutrient supply. Also shoot length and weight of maize treated with LB without any nutrient supply was comparable to those obtained with 50% of nutrient solution. The total fresh biomass produced with LB and SB addition without nutrient supply was the same obtained in presence of 50% of nutrient solution.

EFFECT OF BORON AND CALCIUM ON GROWTH AND QUALITY OF ‘EASY LOVER’ CUT ROSE

This study was conducted to determine the effects of boron (B) and calcium (Ca) treatments on growth, quality, and mineral concentration of ‘Easy Lover’ rose grown in soilless culture. The experiment was arranged in a factorial based on a randomized complete block design with four replications. Treatments were consisted three levels of B (25, 50 and 75 μM) and three levels of Ca (2.5, 5 and 7.5 mM). Increasing B and Ca concentration in nutrient solution improved root development. The tallest stems were obtained from the application of 75 μM B and 7.5 mM Ca. Application of B and Ca showed a further increase in stem diameter, with the thickest stem caused by 50 μM B and 7.5 mM Ca. Plants receiving 50 μM B and 2.5 mM Ca had highest number of flowering stem. High Ca level in the nutrient solution antagonized the B concentration in leaf and petal.

Microclimate Modification Using Eco-friendly Nets for High-quality Tomato Transplant Production by Small-scale Farmers in East Africa

Unfavorable environmental conditions, pests, and viral diseases are among the major factors that contribute to poor growth and quality of tomato (Solanum lycopersicum) seedlings in tropical areas. Improving crop microclimate and excluding insects that transmit viruses may improve transplant quality and yield in production fields. This study was carried out in two seasons at the Horticulture Research and Teaching Field of Egerton University in Njoro, Kenya, to investigate the effects of agricultural nets herein called eco-friendly nets (EFNs) on germination and performance of tomato seedlings. Tomato seeds were either raised in the open or under a permanent fine mesh net (0.4-mm pore diameter). Eco-friendly net covers modified the microclimate resulting in significantly higher day temperatures and relative humidity, compared with the open treatment. Nets increased temperature and relative humidity by 14.8% and 10.4%, respectively. Starting seeds under a net advanced seedling emergence by 2 days and resulted in higher emergence percentage, thicker stem diameter, more leaves, and faster growth leading to early maturity of seedlings and readiness for transplanting. Netting improved root development by increasing root quantity and length. Stomatal conductance (gS) and estimates of chlorophyll content were higher in seedlings under net covering compared with those in the noncovered control treatment. Insect pests and diseases were also reduced under net covering. The use of the net in the production of tomato transplants presented a 36.5% reduction in the cost of seeds, through improved emergence and reduced pest damage. All other factors held constant, healthy and quality transplants obtained under a net covering also translate into better field performance; hence, increasing economic returns for commercial transplants growers, as well as for tomato farmers. Results of this study suggest that EFNs can be customized not only for their effective improvement on growth and quality of tomato transplants but also for their pest and disease management in the nursery alone or as a component of integrated pest and disease management.

Effects of root zone composition and irrigation regime on performance of velvet bentgrass putting greens. II. Thatch, root development and playability

The use of velvet bentgrass (Agrostis canina L.) on putting greens is limited by sparse knowledge on optimal maintenance. The objectives of this study were to determine the effects of rootzone composition (SS, straight sand, or GM, sand amended with 20% v/v garden compost) and irrigation regime (LF, light and frequent, or DI, deep and infrequent) on thatch formation, root development and playability. A study was conducted from August 2007 to October 2009 on a USGA green seeded in June 2007 with velvet bentgrass ‘Legendary’ at a coastal location in Norway (Landvik, 58° N). Compared with light and frequent irrigation, deep and infrequent irrigation improved root development in the 10- to 20-cm soil layer in the second year after sowing. A decrease in turf visual quality on SS receiving light and frequent irrigation in the second year was associated with low infiltration rate. Neither thickness nor content of organic matter in the mat layer were significantly affected by the treatments. A 20% higher surface hardness on SS vs. GM persisted only during the first year of the study.

Estaquia caulinar de guaçatonga (Casearia sylvestris Swartz) nas quatro estações do ano, com aplicação de diferentes concentrações de AIB

Casearia sylvestris Swartz (Salicaceae) ou guaçatonga é uma árvore nativa do México, da América Central, e da América do Sul, com grande importância ecológica, farmacológica, e comercial. No entanto, como a maioria das espécies nativas de interesse medicinal no Brasil, a guaçatonga não é cultivada comercialmente, sendo obtida por extrativismo. O presente trabalho foi conduzido com o objetivo de testar um protocolo de propagação vegetativa de guaçatonga por meio da estaquia, visando identificar qual a melhor estação do ano para o enraizamento de estacas e avaliar o efeito da utilização do regulador vegetal ácido indolbutírico (AIB). No outono, inverno e primavera de 2007, e no verão de 2008, estacas caulinares semilenhosas de 12-14 cm de comprimento e com duas folhas foram preparadas e tratadas com AIB (0, 1000, 2000 e 3000 mg L-1), em solução alcoólica, através da imersão rápida por 10 segundos da base das estacas, e foram plantadas em tubetes contendo substrato Plantmax HT® em casa-de-vegetação sob nebulização intermitente. O delineamento experimental utilizado foi o inteiramente casualizado, com 4 repetições, 4 tratamentos, e 16 estacas por parcela. Todos os experimentos foram avaliados após 90 dias, sendo que para dois deles (primavera 2007 e verão 2008) prolongou-se o tempo de permanência em casa-de-vegetação para melhor desenvolvimento das raízes. Foram avaliados os parâmetros: porcentagem de estacas enraizadas, porcentagem de estacas vivas (com calos e sem raízes, sem calos e sem raízes), porcentagem de folhas retidas, porcentagem de estacas mortas, número de raízes, comprimento das três maiores raízes (cm), e média da massa seca das raízes (mg). Não ocorreu enraizamento nas estacas retiradas no outono e no inverno. Com as estacas retiradas na primavera obteve-se 39,1% de enraizamento. Estacas coletadas no verão não responderam como o esperado, apresentando, após 240 dias, 6,3% de enraizamento no tratamento com 3000 mg L-1 de AIB. O AIB até 3000 mg L-1 não estimulou o enraizamento de estacas de guaçatonga e a melhor estação do ano para a estaquia é a primavera.

Influence of nitrate fertilization on Hg uptake and oxidative stress parameters in alfalfa plants cultivated in a Hg-polluted soil

The mineral nutrition status of plants might affect the accumulation of heavy metals, which in turn could be reflected in altered plant sensitivity. Very little information is available about the effect of the nitrogen nutritional status on mercury (Hg) toxicity. We compared physiological stress parameters sensitive to Hg in alfalfa ( Medicago sativa) plants grown in Hg-polluted soils that were amended with two different fertilizers: without NO 3 − (PK) or with NO 3 − (NPK). Several parameters of oxidative stress, such as antioxidative enzymatic activities, lipid peroxidation, and chlorophyll content were analysed. The study was carried out in a green house with soil from an agricultural land plot located in Almadén (Spain), which contained an average Hg concentration of 12.4 mg kg −1, most of it found mainly as cinnabar (HgS). Our results suggest that nitrogen supply prevents oxidative stress in roots, but may improve root development and increase the uptake of Hg from the soil above safety consumption limits. This work highlights the importance of proper nitrogen fertilization towards future phytoremediation applications with alfalfa plants.

Response to Intracanal Medication in Immature Teeth with Pulp Necrosis: An Experimental Model in Rat Molars

Introduction The present study aimed at developing an experimental model in rat molars for evaluating treatment strategies in necrotic immature teeth. Methods To define the periods to be adopted in the experimental procedures and to confirm induction of periapical lesions and interruption of root embryogenesis, the left lower first molars of 4-weeks-old Wistar rats underwent pulpectomy and were left open to the oral environment. Comparisons with the right lower first molars (vital teeth) were performed in animals with ages of 7, 10, 13, and 16 weeks. In another group of animals the teeth were left open for 3 weeks, and then interventions for disinfection including the use of an antibiotic paste were carried out. Root formation was then assessed after 3 and 6 weeks on the basis of radiographic and histologic evaluation. Results Vital teeth showed increase of root length and hard tissue thickness throughout the experimental periods. On the other hand, induction of necrosis arrested root formation. Teeth subjected to disinfection with sodium hypochlorite associated with the triple antibiotic paste showed significant reduction of periapical lesions, gain in root length, and increased wall thickness compared with the control ( P < .05). Conclusions The root canal disinfection protocol used was able to reduce periapical lesion size and improve root development. The experimental model presented should contribute to studies that aim at improving therapeutic strategies for necrotic immature teeth by using a rat model.

Overexpression of transcription factor ZmPTF1 improves low phosphate tolerance of maize by regulating carbon metabolism and root growth

A bHLH (basic helix-loop-helix domain) transcription factor involved in tolerance to Pi starvation was cloned from Zea mays with an RT-PCR coupled RACE approach and named ZmPTF1. ZmPTF1 encoded a putative protein of 481 amino acids that had identity with OsPTF1 in basic region. Real-time RT-PCR revealed that ZmPTF1 was quickly and significantly up-regulated in the root under phosphate starvation conditions. Overexpression of ZmPTF1 in maize improved root development, enhanced biomass both in hydroponic cultures and sand pots, and the plants developed more tassel branches and larger kernels when they were grown in low phosphate soil. Compared with wild type, overexpressing ZmPTF1 altered the concentrations of soluble sugars in transgenic plants, in which soluble sugars levels were lower in the leaves and higher in the roots. Overexpression of ZmPTF1 enhanced the expression of fructose-1,6-bisphosphatase and sucrose phosphate synthase1 participated in sucrose synthesis in the leaves but decreased them in the root, and reduced the expression of genes involved in sucrose catabolism in the roots. The modifications on the physiology and root morphology of the plants enhanced low phosphate tolerance and increased the yield under low phosphate conditions. This research provides a useful gene for transgenic breeding of maize that is tolerant to phosphate deficiency and is helpful for exploring the relationship between sugar signaling and phosphate concentrations in cells.

Overexpression of Thellungiella halophila H+-PPase (TsVP) in cotton enhances drought stress resistance of plants

An H(+)-PPase gene, TsVP from Thellungiella halophila, was transferred into two cotton (Gossypium hirsutum) varieties (Lumianyan19 and Lumianyan 21) and southern and northern blotting analysis showed the foreign gene was integrated into the cotton genome and expressed. The measurement of isolated vacuolar membrane vesicles demonstrated that the transgenic plants had higher V-H(+)-PPase activity compared with wild-type plants (WT). Overexpressing TsVP in cotton improved shoot and root growth, and transgenic plants were much more resistant to osmotic/drought stress than the WT. Under drought stress conditions, transgenic plants had higher chlorophyll content, improved photosynthesis, higher relative water content of leaves and less cell membrane damage than WT. We ascribe these properties to improved root development and the lower solute potential resulting from higher solute content such as soluble sugars and free amino acids in the transgenic plants. In this study, the average seed cotton yields of transgenic plants from Lumianyan 19 and Lumianyan 21 were significantly increased compared with those of WT after exposing to drought stress for 21 days at flowering stage. The average seed cotton yields were 51 and 40% higher than in their WT counterparts, respectively. This study benefits efforts to improve cotton yields in arid and semiarid regions.

Subsoil improvement in a tropical coarse textured soil: Effect of deep-ripping and slotting

In many coarse textured soils, limited root development and biomass production are attributed to adverse physical conditions in the subsoil. The current study was undertaken on an Arenic Acrisol located in Northeast Thailand (i) to assess whether subsoil physical characteristics influence crop rooting depth, and (ii) to compare the benefits associated with conventional tillage with that of localised subsoil loosening on crop performance and selected soil attributes. Control plots consisted of disk ploughing; the implemented treatments were conventional deep-ripping and localised slotting below the planting line. A crop rotation consisting of a legume followed by maize was established annually to assess the impact of these treatments on crop performance. In the control treatment, root development was restricted to the topsoil (0–20 cm) due to high subsoil bulk density (>1.6 Mg m −3). After deep-ripping, no improvement was observed in bulk density, rooting depth and in crop performance. The implementation of a slotting treatment systematically improved root development in the slotted subsoil, root impact frequency increasing from <0.2 to 0.6–0.8 ( P = 0.01) despite no change in the bulk densities of the subsoil. This systematic improvement in root development could be explained by (i) reduced slumping that enable root development prior to recompaction and/or (ii) preferential drainage in the slot and therefore decreased resistance to root penetration. In a dry year maize yield was improved by 78% ( P = 0.01); the deep-rooting legume Stylosanthes was tested only a wet year and its biomass production increased by >40% ( P = 0.03). This study highlights the detrimental impact of subsoil compaction on root development and the potential role of slotting in coarse textured soils as a long-term management tool in addressing adverse subsoil physical characteristics that limit deep-rooting.

Response of apple trees to boron fertilization under conditions of low soil boron availability

The aim of the study was to examine the effect of boron (B) fertilization on the vegetative and the reproductive responses of apple ( Malus domestica Borkh.) trees grown at low soil B availability. The experiment was carried out in 2005 under a greenhouse on 5-year-old ‘Jonagold’ apple trees/M.9 EMLA planted singly in 50-L containers filled with a sandy loam soil with hot water-soluble B concentration of 0.32 mg kg −1. The trees were fertilized with B as foliar or soil application. Foliar B sprays were applied at the stage of pink bud, beginning of flowering, petal fall, and 10 days after flowering, at a solution concentration of 0.03%. Soil B fertilization was done at the bud break stage at a rate of 2 g per tree (27 mg B kg −1 soil). The trees untreated with B served as the control. The results showed that soil B fertilization improved root development and tree vigor. Leaves of trees supplied with B to the soil had higher B concentration and chlorophyll, net photosynthetic rate, stomatal conductance, and activity of catalase and glutathione reductase than those of the control plants. Boron fertilization, regardless of application mode, increased fruit yield; the efficiency of foliar B sprays was higher than soil B application. Apple fruits of trees fertilized with B to the soil were bigger, more colored, richer in B, and had higher soluble solids concentration, and titratable acidity compared to those of the control trees.

Mineral nutrition and water use patterns of a maize/cowpea intercrop on a highly acidic soil of the tropic semiarid

Due to global warming, water is expected to become scarce especially in semiarid regions. Therefore, there is a need to increase the efficiency in water use by crops under rainfed agriculture. The effect of nutrient availability on the growth, production, root development, water relations and water use efficiency (WUE) by the intercrop maize/cowpea was investigated in 2 contrasting years (dry and wet) in the semiarid region of Brazil. The crops were grown on a strongly acidic, sandy soil with three treatments: (i) application of NPK fertilizers plus lime (NPK + lime), (ii) application of NPK fertilizers (NPK) and (ii) control (Contr.) in low and high input regimes. The soil water balance was calculated with the crop model EPICSEAR. Application of fertilizers and lime increased biomass production and grain yield of the intercrop up to 400% and 550%, respectively, and maize suffered more from the effects of low nutrient availability and soil acidity than cowpea. The root development of both crops was strongly improved by the application of NPK and lime and cowpea developed a deeper root system which enabled this crop to keep a higher transpiration rate in the dry year. As a consequence of the shallow root system, maize was prone to water stresses caused by the dry spells and its harvest index was reduced when dry spells occurred during flowering and grain filling. Fertilizers and lime application reduced deep percolation and soil evaporation while increasing the productive transpiration flow. WUE were improved through the application of nutrients and lime and maize showed higher WUE than cowpea. The omission of lime showed only minor effects on the evaporation and transpiration WUE. The model probably over-emphasizes the effects of high Al saturation on the root growth and water uptake and consequently underestimated the transpiration rate of the crops. Nevertheless, the gross WUE was reduced up to 58% when lime was omitted and NPK applied at high inputs. A balanced fertilization in combination with lime improves the root development of a maize/cowpea intercrop in acid Acrisols of the semiarid NE of Brazil. The improved root development allows a better use of soil water reserves and increases the WUE of the system.

Enhancing root systems of waiting-bed strawberry plants grown on substrates

SummaryTo find techniques to improve root system development of waiting-bed strawberry plants ‘Camarosa’ grown in substrates, the influence of two substrates (peat and coconut coir dust), or plants from three waiting-beds at different altitudes, and of root treatments with different plant growth regulators (naphthalenacetic acid at 25, 50 and 75 mg g–1; indolebutyric acid at 10, 20 and 30 mg g–1; l-triacontanol at 0.02, 0.04 and 0.06 mg g–1) by dipping runners prior to planting, were studied in two experiments in the 1997–98 and 1998–99 seasons. In both years, plants from high elevation beds (HE) produced the greatest root development, and plants from medium elevation beds (ME) produced more new roots than those from low elevation beds (LE). Root development of plants grown in peat was greater than those grown in coconut coir dust in the first experiment and only on the first measuring dates (one month after planting). This difference was particularly high in plants from high or medium elevation nurseries, when the degree of root development was greater. No differences between substrates were observed in the second experiment. Treatments with the different growth regulators tested, at any of the concentrations used, did not improve root development on average for the other factors.

Controlled mycorrhizal initiation as a means to improve root development in somatic embryo plantlets of hybrid larch (Larix × eurolepis)

This study represents the first report of in vitro mycorrhization of somatic embryo‐derived plantlets. Effects of fungi on the rooting of plantlets as well as on their ultra‐structure were studied. Embryo‐derived plantlets of a hybrid larch (Larix × eurolepis Henry) were grown aseptically in the presence of four ectomycorrhizal fungi. One month after inoculation with Laccaria laccata, Hebeloma cylindrosporum and Pisolithus tinctorius, the number of plantlets which had developed a well‐growing root system was significantly improved compared with controls. Furthermore, root branching was strongly stimulated by L. laccata and H. cylindrosporum, which were more efficient species than P. tinctorius and Suillus grevillei. Development of the root system was concomitantly accompanied by an enhancement of shoot growth, except for plantlets inoculated with S. grevillei, which died after three to six months. At the ultrastructural level, cross‐sections of lateral roots made six months after inoculation, showed the presence of a Hartig net in the case of L. laccata and H. cylindrosporum, whereas no such net was observed with the two other fungi. With S. grevillei, some perforating hyphae penetrated the cortical cells and resulted in cell death. Evidence of a relationship between structure and efficiency of the association was found.

Controlled mycorrhizal initiation as a means to improve root development in somatic embryo plantlets of hybrid larch (Larix x eurolepis)

Controlled mycorrhizal initiation as a means to improve root development in somatic embryo plantlets of hybrid larch (Larix x eurolepis)

Concepts and methods for studying interactions of roots and soil structure

The central concept in present-day root ecological studies in agriculture is that reduced or improved root development may decrease or increase the efficiency of using water and nutrients and thus aggravate or reduce negative environmental impacts of agriculture. The normal root development of many agricultural crops is such that chemical fertility of the soil has to be so high that residues of NO 3 and P in the soil remain at harvest which are close to or higher than those acceptable to meet environmental standards on quality of ground- and surface water. Poor soil structures, with a large fraction of the soil at a relatively large distance to the nearest macropore or crack, may affect root penetration and functioning, and thus lead to even higher residues of macronutrients at harvest. If roots are not able to penetrate the matrix of the aggregates a clustered root distribution in the cracks is the result. Negative effects on nutrient and water uptake efficiency of non-regular root distribution and incomplete root-soil contact can now be estimated from the Root Position Effectivity Ratio, R per. Aeration of roots depends on the (maximum) distance between root tissue and the nearest “breathing section”, where part of that root is in contact with air-filled macropores or cracks, on the air-filled porosity of the root and on protection against leakage of oxygen out of the root. Methods are discussed for measuring: distance in pixel images, root distribution pattern on maps, synlocation of roots and other map features, root-soil contact, root position effectivity ratio, air-filled root porosity and continuity of air channels, and dynamics of root growth and decay.

Acid Soil Stress Tolerance in Tissue Culture‐Derived Sorghum Lines

Acid soil stress limits crop productivity on nearly one‐half of the nonirrigated arable land in the world. Improvement of acid soil tolerance in sorghum [Sorghum bicolor (L.) Moench] has been approached through conventional breeding programs and more recently through biotechnology. This study was initiated to determine if improved acid soil tolerant tissue culture regenerates could be developed from sensitive parental lines and whether tolerant regenerants with desirable agronomic traits could be selected under field stress conditions. Tissue culture regenerated lines of sorghum and their non regenerated checks were field tested for acid soil [Typic Kanhapludult] tolerance (50% Ai saturation at pH 4.2‐4.6) near Griffin, GA, from 1986 to 1990. Two R5 lines derived from ‘Hegari’ and two R5 lines from RTx430 demonstrated improved acid soil tolerance in 1989. Field test results indicated that these four lines had significantly higher ratings for vigor (2.6‐3.4 vs. 4.8‐4.9), plant survival (12–30 vs. panicles harvested (2–9 vs. 0), and seed yield (20‐85 g plot−1 vs. 0) than their nonregenerated checks. During 1990, selected R7 lines were advance tested on acid soils near Griffin with similar results. Three of these improved selections were then evaluated for early seedling development in a greenhouse soil study using the same acid soils from the field. These results showed that one Tx430 regenerated line had improved root development at low pH during the seedling stage. This research indicated that variation for acid soil stress tolerance was produced through tissue culture and that agronomically desirable genotypes were selected using appropriate field testing procedures and stress levels.

Effects of Subsoiling and Mechanical Impedance on Tobacco Root Growth

AbstractRelationships between mechanical impedance and root growth have not been extensively defined for field conditions, and as a result, it is usually impossible to know with certainty when soil layers of high mechanical impedance are limiting root growth or where subsoiling is needed to improve root development. The primary objective of this investigation was to describe relationships between mechanical impedance and root concentration for both subsoiled and nonsubsoiled tillage treatments in field studies. Experiments were conducted at three locations in the North Carolina Coastal Plain on soils that were coarse‐textured Typic and Arenic Paleudults with tillage pans. At each site, flue‐cured tobacco (Nicotiana tabacum L.) was grown in subsoiled and nonsubsoiled (moldboard plow/disk) tillage treatments replicated four times. Penetrometer readings were made in the row and 0.30 m to the side of the row at 6‐ to 14‐d intervals for periods of 28 to 42 d; these data were averaged by depth and position and were expressed as mean cone index (CI). At approximately 52 and 75 days following transplanting, roots were counted by the trench‐profile method. At all locations, numbers of roots below the Ap horizon were significantly greater for the subsoiled, as compared to nonsubsoiled treatments for both root count dates. Mean CI was significantly correlated with root concentration in the Ap and E‐B horizons at all locations with r values ranging from −0.79** to −0.88** for both root count dates. The three tillage pans examined had mean CI's between 2.8 to 3.2 MPa. Subsoiling reduced the CI of the tillage pans for up to 47 d from transplanting and permitted significantly greater root penetration of the subsoil.

Effects of Saline‐Sodic Soil Chemistry on Soybean Mineral Composition and Stomatal Resistance

AbstractSoybean [Glycine max (L.) Merr.] productivity is severely limited by saline‐sodic soil conditions that occur in isolated spots in the river bottoms of western Kentucky. Productivity of soybeans grown on a gradient of soils of increasing saline‐sodic character were studied in greenhouse experiments. Soils with electrical conductivity (EC) exceeding 3.20 dS m−1 would not support soybean growth. Soybean plants accumulated significant quantities of Na when soil solution sodium adsorption ratio (SAR) exceeded 6.4 and relative tissue Na accumulation was highly correlated with SAR. Estimates of potential productivity were made by stomatal diffusive resistance measurements at three vegetative growth stages. Potential productivity was severely limited under conditions of high soil salinity. In soils of lower EC (&lt; ≈ 2 dS m−1), soybean performance was affected to a greater extent by changes in SAR than by changes in EC. Dry matter production decreased with increasing SAR under low EC soil conditions.In a second experiment, saline‐sodic soil was amended with four rates of gypsum (CaSO4·2H2O), (0, 2.6, 6.0, and 12.9 g kg−1). Gypsum‐amended pots were leached until EC was &lt; 3.0 dS m−1. Plant dry matter production was minimized with the 2.6 g kg−1 amendment, which also produced plants with significantly reduced and negligible Na contents. At early growth stages (V4 and V7), stomatal diffusive resistance of plants grown on the gypsum‐amended soils was not affected by increasing SAR. Diffusive resistance measurements of large vegetative plants (V10) increased significantly at low soil solution SAR. The addition of gypsum apparently reduced the detrimental effects of physical impedence to root development and function in the poorly structured soil as well as soil solution SAR. The improved physical structure of the gypsum‐amended soil could improve root development, function, and crop productivity.

In Vitro Propagation of Mailing Merton Apple Rootstocks1,2

Abstract Rapid propagation of the apple rootstocks Mailing Merton (MM) 104, MM 106 and MM 109 (Malus sp.) achieved was by shoot tip proliferation using a Murashige and Skoog basal medium with 1 mg/liter 6-benzylamino purine (BA) and 1 mg/liter indolebutyric acid (IBA). Improved proliferation was achieved by using a liquid medium. Two media were selected for rooting: the first contained IBA for root initiation and the second was without IBA but plus 0.25% activated charcoal for improved root development. Plantiets were successfully transferred to soil.