Survival Percentage Of Seedlings Research Articles

Effect of sowing dates on the germination and seedling growth of Pinus wallichiana and Cupressus torulosa

A nursery trial of Pinus wallichiana and Cupressus torulosa with nine different sowing dates spread over autumn, winter and spring was conducted during 2002-2003. Germination in case of Pinus wallichiana was better where seeds were sown in the month of February, but in Cupressus torulosa germination during December, February and first fortnight of March was uniform. Survival percentage of seedlings was more in seeds sown in the month of February. Time taken for completion of germination decreased as sowing proceeded from autumn to spring. Seedling development in terms of height and diameter was better in seeds sown on 15th of November (autumn), but seedlings obtained from 1st February sown seeds are also of comparable good quality. The study concluded that in order to get good germination, better survival, good quality seedlings and cost effective nursery seeds should be sown in the nursery in the first fortnight of February (winter), instead of sowing in autumn season as is normally practiced.

A major QTL associated with cold tolerance at seedling stage in rice (Oryza sativa L.)

Chilling injury is one of the most important limiting factors affecting rice production in temperate and high-elevation areas. In this study, 146 microsatellite markers were employed to identify quantitative trait loci (QTL) conferring cold tolerance at seedling stage (CTS) .The mapping population consisted of 193 doubled haploid (DH) lines, which derived from a cross between a cold-tolerant japonica variety (AAV002863) and a cold-sensitive indica cultivar (Zhenshan97B). Tolerance to cold was assessed by the survival percentage of seedlings after cold treatment. In a climate chamber, after treatment at 6°C/10°C for 7 d, the measurement was taken on the sixth day of the recovery stage at room temperature. The phenotypic distribution of the DH population approximately fitted normality with skewness and kurtosis less than 0.3, and the difference among the three repetitions was not significant. Five main effect QTLs were identified with LOD > 4.0 on chromosomes 1, 2, 8 using a composite interval mapping approach. The accumulated contribution of the five QTLs was 62.28%, and a major QTL (LOD = 15.09) was identified on chromosome 2 flanked by RM561 and RM341, which explained 27.42% of the total phenotypic variation. Four significant epistatic interactions were also detected with a total contribution of 20.14%.

In vitro embryo rescue culture of F1 progenies from crosses between diploid and tetraploid grape varieties

The purpose of this study was to understand factors affecting in vitro embryo rescue culture from hybrids between diploid and tetraploid varieties of grape in creation new triploid germplasm resources. The effects of different media, removal ages of immature seeds and reciprocal crosses of parents on the germination and seedling survival of immature seeds from crosses between diploid and tetraploid grape varieties by in vitro embryo rescue culture were investigated. The results indicated that the medium consisting of NN-1969 + IAA 1.75 mg l−1 + GA3 0.35 mg l−1 + CH 400 mg l−1 + AC 2.0 g l−1 was better than other media. The optimal removal age of immature seeds for the best development of embryos was 35–45 days after pollination (DAP). The percentage of germination (PG) for immature seeds and the percentage of seedling survival (PSS) for immature seeds for diploid varieties used as female parents were 10.72% and 4.35% higher than when tetraploid varieties were used as female parents respectively. A total of 41 hybrid progenies from eight combinations were obtained, made up of 17 diploid, 9 tetraploid, 14 aneuploid, and 1 triploid progeny as determined by root-tip chromosome identification. The triploid progeny was from Fujiminori (2n = 4x = 76) × Jingxiu (2n = 2x = 38). These results implied that it was feasible to extend the hybridization range of grape and to create new germplasm resources by in vitro embryo rescue based on the conventional hybridization. The NN-1969 medium supplemented with GA3 and IAA was more propitious to the development of immature seeds sampled at about 45 DAP. It was easier to obtain plants using diploid as female parent, but triploid progeny was only obtained using tetraploid as female parent.

Effect of Arbuscular Mycorrhiza on the Drought Tolerance of Poncirus trifoliata Seedlings

The effects of Glomus mosseae colonization on the plant growth and drought tolerance of 1-year-old trifoliate Poncirus trifoliata seedlings in potted culture were studied in natural water stress and rewatering conditions. Results showed that arbuscular mycorrhizal (AM) inoculation significantly improved the height, stem diameter, and fresh weight of P. trifoliata seedlings before natural water stress. By the end of the experiment, the survival percentage of AM-transplanted seedlings was 8% higher than those of non-AM ones. During water stress and rewatering, AM significantly increased the contents of soluble sugars and proteins in leaves, and enhanced the activities of superoxide dismutase (SOD), guaiacol peroxidase (G-POD), and catalase (CAT) in either seedling leaves or roots, which indicated that AM colonization could improve the osmotic adjustment response of P. trifoliata, enhance its defense system, and alleviate oxidative damages to membrane lipids and proteins. These results demonstrated that the drought tolerance of P. trifoliata seedlings was increased by inoculation with AM fungi. The functional mechanism underlying the observation that mycorrhizas increased the host’s drought tolerance was closely related to enzymatic and nonenzymatic antioxidant defense systems such as SOD, G-POD, CAT, and soluble protein.

An Effective In-Vitro Selection of Water Spinach (Ipomoea aquatica Forsk.) for NaCl-, KH2PO4- and Temperature-Stresses

Inorganic substances found in wastewater (i.e. industrial, agricultural, and urban-sewage runoff) constitute a form of abiotic stresses for plants, negatively impacting their growth, development, and productivity. The aim of this investigation is to establish an effective in-vitro selection system, to identify water spinach varieties displaying higher tolerance to inorganic salts and evaluated temperature. High inorganic salt concentrations (171 mM NaCI or 125 mM KH2PO4) strongly retarded chlorophyll concentration and relative water content, led to growth reduction, and decreased the seedling survival percentage of a commercial variety of water spinach. The fresh weight, shoot height, and leaf number of seedlings grown under inorganic stresses were also strongly decreased when compared to unstressed control seedlings. Moreover, seedlings grown at high temperature (30±2°C) exhibited 4-folds reduction in survival percentage compared to those grown at low temperature (10±2°C) . An in-vitro selection system was then applied to screen 54 varieties of water spinach. The results indicated that 10 varieties processed increased tolerance to high inorganic salt levels and evaluated temperature. These tolerant varieties should be further investigated in filed trials for vegetable production, contaminant absorption, and wastewater treatment. Conversely, the sensitive varieties may potentially be used as indicators for pollutant contamination in wastewater.

Percent Dry Weight of the Ovule Predicts Peach Seed Viability

Percent Dry Weight of the Ovule Predicts Peach Seed Viability

Influence of temperature and watering frequencies on seed germination and seedling growth of Ornithogalum longibracteatum and Tulbaghia violacea

The effect of temperature and watering frequencies on seedling growth were investigated in Ornithogalum longibracteatum and Tulbaghia violacea. Temperature had a significant influence on seed germination with low (10 °C) and high (40 °C) temperatures resulting in poor germination in both species. The optimum temperature for seed germination of O. longibracteatum and T. violacea was 22.9 and 26.8 °C, respectively. Seedling survival rate for both species was higher at temperatures ranging from 10 to 25 °C. Bulb fresh weight of seedlings grown at 15–25 °C was significantly higher than for seedlings subjected to 30 and 35 °C. Leaf length increased with higher temperature. The highest number of roots was recorded at 25 °C in both species. Watering had a pronounced positive effect on the seedling survival percentage and seedling growth of O. longibracteatum and T. violacea. Watering three times a week (W3) resulted in rapid seedling growth compared to watering once or twice a week. These findings suggest that a combination of temperature (25 °C) and frequency of watering of the seedlings will result in better seedling quality for field planting.

Screening Malus Seedlings for Cold Hardiness

Twelve-week-old Malus seedlings were induced to cold harden by exposure to low temperature and freezing environments. The effectiveness of induced acclimation by exposure to stimuli such as low temperature (3 to 5 °C), frequency of exposure to freezing temperatures (-3 °C), storage time before and after induction and the effects of different screening temperatures (-20, -30, and -40 °C) were investigated with seedlings grown in a greenhouse from open-pollinated `Golden Delicious' apple (Malus pumila (Mill.), `Antonovka' apple (M. baccata (L.) Borkh. × (M. pumila) and `Rescue' apple (M. baccata) × (M. pumila). Differentiation of the seedling populations with respect to cold hardiness was not achieved until after acclimation at cool temperatures (3 to 5 °C) for 6 weeks. Further population differentiation was achieved by exposure to one or more frosts (-3 °C). Once the acclimation response had been initiated the seedlings could be held for up to 11 days, under the same conditions, with no significant decrease in hardiness. Hardiness levels of acclimated and nonacclimated open pollinated seedlings coincided with known inherent hardiness responses for all three maternal cultivars evaluated. A binomial form of regrowth data collection, percent seedling survival, was determined to be the most efficient and most precise measure of evaluation. Induction of cold hardiness in very young seedlings and the use of a controlled freeze testing protocol should facilitate rapid screening of large progenies and improve the rate of progress in breeding for cold hardiness.

Emergence, survival and growth of selected plant species in petroleum-impacted flare pit soils

One of the prerequisites to phytoremediation of hydrocarbon-contaminated soils is that plants be able to germinate and become established in the presence of contaminants. This 5-wk growth chamber study examined the tolerance of five grasses and one legume to petroleum hydrocarbons (PHCs) and associated salts in three weathered, fine-textured, flare pit soils obtained from NE British Columbia. Plant tolerance to these soils was measured by percent seedling emergence (PSE), percent seedling survival (PSS) and 5-wk dry shoot biomass; a non-contaminated control soil was included in the study. The contaminated soils showed a wide range in total PHC concentrations (Soil A: 0.1 %, Soil B: 1.8 %, Soil C: 16 % PHC by mass) and in the recently established Canadian Council of Ministers of the Environment (CCME) PHC Tier 1 fractions 1–4. Electrical conductivity in contaminated soils ranged from 3.00 (Soil B) to 5.16 (Soil A) dS m-1. Medicago sativa (alfalfa, cv. Peace) was sensitive (low PSS, PSE and shoot biomass) to high salinity of Soil A but flourished in Soil B, a soil with F3 a nd F4 (gravimetric) concentrations that exceeded CCME PHC Tier 1 Eco Contact standards for agricultural, residential and parkland soils. When considering the combined effects of PHC and salts, Bromus inermis (smooth brome, cv. Carlton) was the grass most tolerant of contaminants in the weathered industrial soils. Compared to other plants, it consistently produced relatively high PSS, PSE and shoot biomass. Soil C was slightly hydrophobic and all plants showed reduced shoot biomass compared to other soils; however, average shoot biomass for Bromus inermis was almost twice as great as any other plant species growing in this soil. More research on the properties and remediation of historic flare pit soils is warranted. Key words: Hydrocarbons, phytoremediation, soil contamination, soil remediation, CCME, soil toxicity

Improving seedling vigour of indigenous medicinal plants with smoke

The application of smoke and aqueous smoke solutions stimulates seed germination in a number of plant species. This study highlights the effects of aerosol smoke and smoke solutions on the germination and seedling vigour of three South African indigenous medicinal plants Albuca pachychlamys, Merwilla natalensis and Tulbaghia violacea. The vigour index of one-week-old seedlings of all three species examined was increased with the application of dry smoke and smoke extract dilutions, as compared to control treatments. Seedlings of A. pachychlamys germinated with smoke solutions showed a significant ( p ⩽ 0.05) gain in bulb and leaf mass (27.9 and 197.6 mg respectively) compared to untreated seedlings (9.9 and 124.7 mg respectively) when grown in vitro for 75 days. The leaf mass of smoke solution-treated seedlings of T. violacea was significantly ( p ⩽ 0.05) higher (120.4 mg) than that of untreated seedlings (47.6 mg). Subsequently, the height of seedlings in both species was also significantly ( p ⩽ 0.05) greater. Seedlings germinated in water and then transferred to smoke solutions (1:2000) showed enhancement of some of the growth parameters studied. Albuca pachychlamys and T. violacea seeds exposed to aerosol smoke exhibited higher seedling survival percentages than from non-smoked seeds, while no significant effect was observed for M. natalensis seedlings. This investigation shows that the application of smoke technology can be adopted to produce high vigour seedlings.

A major QTL conferring cold tolerance at the early seedling stage using recombinant inbred lines of rice ( Oryza sativa L.)

Cold tolerance at early seedling stage of rice ( Oryza sativa L.) is one of the major determinants for the stable stand establishment in temperate and high-elevation areas. In the current study, with 269 recombinant inbred lines derived from a cross between a japonica tolerant to cold and a sensitive indica of rice, the cold tolerance at early seedling stage was evaluated by the paper-roll tests in a two-replication trial with 10- and 13-day treatments at 10 °C, respectively. The phenotype data, in combination with a complete linkage map consisting of 198 marker loci, were used to conduct composite interval mapping to locate both main-effect and digenic epistatic QTL for the trait. Three main-effect QTL were identified. The comparison of the QTL identified in these two cold treatments resulted in an intriguing finding that seedling cold tolerance in the 10-day cold treatment was regulated by many loci each with minor effect while that in the 13-day cold treatment was controlled by a major QTL as well as minor ones. Of the three main-effect QTL, QTL qSCT-11, closely linked to microsatellite marker RM202 on chromosome 11, was found to increase its additive effect from 4.07 to 10.11% (seedling survival percentage) as the duration of cold stress was prolonged from 10 days to 13 days. In the 13-day cold treatment, QTL qSCT-11 was detected at a very high LOD score of 19, explaining up to 30% of the phenotypic variation. In addition, a total of nine digenic interactions were detected, each showing small effects on cold tolerance with R 2 ranging from 3.5 to 9.7%, with an average R 2 of 5.3%. In the 13-day cold treatment, the sum of absolute epistatic effects of all the interactions amounted up to 36% in seedling survival percentage, suggesting the importance of epistasis in the genetic control of cold tolerance. These results would favor our better understanding of the genetic control of cold tolerance in rice. The identification of QTL for the trait is important for the development of rice cultivars with a broader climatic adaptation.

Differential seed mortality among habitats limits the distribution of the invasive non-native shrub Ardisia elliptica

During the early phases of biological invasions, both limited dispersal and habitat preference may contribute to observed patterns of distribution for non-native species. In a disturbed area of Everglades National Park, the non-native Ardisia elliptica (Myrsinaceae) does not occur in all habitat types nor is it evenly distributed among habitats where it does occur. One goal of this study was to determine whether the patchy distribution of A. elliptica may be due to differential effects of habitat on seed fates and germination. Screen mesh bags containing seeds of A. elliptica were buried in the surface litter of five habitats and were later sampled periodically over a three month period to measure seed germination, survival and death. Seed mortality and mean germination speed was higher in open exposed habitats relative to closed canopied forests. During the study period, which coincided with the dry season, there was no germination of seeds that had been placed in pine forests or in Schinus thickets that were highly disturbed pine forests. Because hydroperiod is a critical determinant of habitat type in the Everglades ecosystem, a second goal of this study was to determine whether water availability was correlated with seed germination and seedling survival in five sites where A. elliptica has invaded. Seeds were sown under mesh boxes and monitored for germination and seedling survival for ten months. Estimates of water availability taken as predawn water potentials on A. elliptica were positively correlated with percent seed germination but not with percent seedling survival. Additionally, pre-dawn water potential of A. elliptica differed among sites. This study suggests that differential water availability among habitats may have influenced the patchy distribution of A. elliptica in Everglades National Park. Lack of sufficient moisture availability for seeds in exposed habitats such as pine forests and wetland prairies during the dry season has contributed to its distribution. Because some of the habitats where A. elliptica currently occurs were pine forests and wetland prairies prior to disturbance, this study suggests that substrate disturbance and canopy formation have altered the soil microenvironment, favoring the establishment of A. elliptica.

Efficacy of cultural methods in the control of rhizoctonia solani strains causing tomato damping off in Kenya

Rhizoctonia damping off of tomato caused by Rhizoctonia solani can be a serious problem in most intensive production environments. Recent increase in smallholder vegetable production of 0.5- 3.0 ha in Kenya has resulted in build up of the pathogen to above economic threshold levels. There is no effective chemical control or resistant varieties. Use of soil fumigants such as methyl bromide in the control of Rhizoctonia and other soil borne pathogens is not sustainable due to their high costs, and toxicity to ma n and environment. Cultural methods such as soil amendments, mode of planting and influencing soil moisture levels either alone or in combination with other methods are among the most likely substitute s to use of toxic fumigants for control of soil borne pathogens in agriculture. This study was undertaken to evaluate the effect s of cow manure application, transplanting , planting on raised beds and varying watering interval on Rhizoctonia damping off of tomato as measured by percent seedling survival at 5 -30 days after planting (DAP), disease severity at 30 DAP, percent crop stand at 60 DAP and fruit yield at maturity . The study was conducted in a field artificially inoculated with pathogenic strains of Rhizoctonia solani isolated from infected tomato plants and Rhizosphere soil sampled from the major production regions of Kenya. The efficacy of the various cultural strategies both singly and in combination on the Rhizoctonia damping off management was compared with the conventional disease control involving chemical fumigation with metham sodium and two chemical seed dressers (pencycuron, thiram, imidacloprid) and ( captafol) as the standard . Cow manure application and shorter watering interval when used singly or in combination with other cultural methods produced lower disease control and yield. Transplanting, planting on raised beds and medium irrigation interval when used singly or in combination with other cultural strategies produced good disease control resulting in higher yield that compared favorably with the conventional disease control involving soil fumigation and seed dressing. The various cultural disease control methods documented in this study can be used alone and in integration with other compatible Rhizoctonia damping off of tomato control strategies. Furthermore the promising non- chemical strategies may form part of the urgently sought for alternative to use of hazardous fumigants in agriculture and since they are not specific, there is low risk of resistant development over time.

Reliable and easy screening technique for salt tolerance of citrus rootstocks under controlled environments

Three salt tolerance experiments using 5 common citrus rootstocks were carried out to find a reliable and easy screening technique for salt tolerance in breeding programs. The experiments were: (1) in vitro seed culture where salt tolerance was mainly evaluated as germination percentage, (2) hydroponic culture of 2-month-old seedlings where salt tolerance was mainly evaluated as survival percentage, and (3) hydroponic culture of satsuma-rootstock combinations where salt tolerance was evaluated by leaf and fruit characters. Treatments were: 4 mm K2CO3 and 0-100 mm NaCl in Expt 1; 3.5 mm K2CO3 and 0-50 mm NaCl, with and without K2CO3, in Expt�2; and 25 mm NaCl in Expt 3. Volkamer lemon was the most salt-sensitive genotype during seed germination (Expt�1), whereas Troyer citrange was the most sensitive when used as rootstock of satsuma (Expt 3). For seedling survival (Expt 2), the trifoliate orange variety Flying dragon showed the highest survival percentage, and chloride content of satsuma leaves and fruit juice were high on this rootstock under salinity (Expt 3). Alkalinity (pH = 8.5) greatly affected seedling survival of Cleopatra mandarin and Volkamer lemon (Expt 2), probably due to major disturbances in seedling nutrition. Analysis of trait values for the rootstocks in the different saline treatments in both the in vitro germination and the seedling survival experiments revealed some significant changes compared with control conditions. Most of these changes were not consistent between genotypes, except for chloride concentration in both shoot ([Cl]s) and root ([Cl]r). The ordering of genotypes for salt tolerance found in the literature, which corresponds to the ordering as chloride excluders in our satsuma Expt 3, agrees with the inverse ordering of genotypes regarding the increment of both [Cl]s and the ratio [Cl]s/[Cl]r from control to low salinity, but does not agree with salt tolerance measured as a percentage of germination or seedling survival. The increments of both [Cl]s and the ratio [Cl]s/[Cl]r from control to low salinity are suggested as criteria for early selection of salt-tolerant citrus rootstocks. Three salt tolerance mechanisms have been observed: chloride exclusion, water saving, and accumulation of soluble solids. They all seem to be presented by Cleopatra mandarin when used as rootstock, supporting its utilisation as donor of salt tolerance in breeding programs of citrus rootstocks.

The role of facilitation in seedling recruitment and survival patterns, in the Strandveld Succulent Karoo, South Africa

Several studies in arid ecosystems have demonstrated that seedling establishment and survival were greater underneath the canopies of shrubs than in the open spaces between shrubs. These results led to the formulation of the hypothesis that seedling recruitment and survival were dependent on the shelter provided by shrub species (nurse-plant hypothesis). Seedling emergence and survival beneath and between the canopies of selected perennial shrub species were investigated at five localities in the Strandveld Succulent Karoo, each dominated by a different shrub species. Seedling emergence and survival were also examined at three localities dominated by annual species. In general, species richness and seedling densities were significantly higher in open areas than underneath shrubs, while seedling survival percentages did not differ significantly between microsites. Therefore, no evidence could be found to support the hypothesis that seedling recruitment and survival were facilitated by the presence of shrub species. Although most species will be able to establish in the absence of shrubs, the presence of woody species may have other advantages when restoring vegetation in mined areas.

Allelopathic Influence of Nine Forage Grass Extracts on Germination and Seedling Growth of Alfalfa

AbstractPoor establishment of alfalfa (Medicago sativa L.) often results when the alfalfa is sown with cool‐season perennial grasses. This study was conducted to screen the inhibitory characteristics of grasses that are often grown in combination with alfalfa in grass swards. Laboratory and greenhouse studies were conducted to determine the allelopathic potential of nine grasses to alfalfa germination and seedling growth. Alfalfa seeds were germinated in aqueous extracts of nine grasses, using distilled water as a control. Measurements were taken to determine the effect of the extracts on germination, seedling length, and weight. Alfalfa germination ranged from 64% for tall fescue (Festuca arundinacea Schreb.) extracts to 91% for the control. Total alfalfa seedling length was reduced by 39% for grain sorghum [Sorghum bicolor (L.) Moench] extracts. Dry weights of alfalfa cotyledons, hypocotyls, and radicles were reduced significantly by several grass extracts. Smooth bromegrass (Bromus inermis Leyss.), orchardgrass (Dactylis glomerata L.), and grain sorghum extracts were more inhibitory than other grass extracts. Alfalfa seedling emergence and survival percentage was affected by various grass root residues. Timothy (Phleum pratense L.) extracts caused the lowest survival percentage of 59% compared to the control of 88%. Redtop [Agrostis gigantea Roth; syn. Agrostis alba L. sensu auct. (American)] and reed canarygrass (Phalaris arundinacea L.) extracts had no effect on alfalfa seedling emergence and survival. Leached and nonleached residues significantly inhibited alfalfa height, leaf area, and dry weights of leaves and stems. The extent of reduction was greater in nonleached than in leached residues. These results suggest that grass residues may affect alfalfa growth and development because of inhibitory effects of allelochemicals present in grass residues.

Effects of salinity on germination and seedling growth of Prosopis flexuosa (D.C.)

Prosopis flexuosa, the most widespread arboreal legume found on saline soils in Argentina, is regarded as an especially attractive species for the productive recovery of arid and salt-affected areas. The effects of salinity on germination and seedling growth of this species were studied. Salt tolerance during germination was examined in seeds collected from two populations growing either on saline or non-saline soil. Germination was assessed under various NaCl concentrations: 0, 0.2, 0.4, 0.6 and 0.8 M. Significant decreases in germination percentage were observed above 0.2 M NaCl. Variability was higher among individual trees than between populations and highest at 0.4 M NaCl. Salt tolerance at the seedling stage was analysed in 20-day-old seedlings, grown in pots with soil, treated for 90 days with NaCl solutions ranging between 0 and 0.4 M. The average seedling survival percentage for the trial was above 96%. A 50% decrease in final height was observed in the treatment with 0.4 M NaCl, where substrate in the pots had reached a final salt concentration of nearly 1 M NaCl. In Prosopis flexuosa, salt tolerance at the seedling stage appears to be greater than at the germination stage, suggesting that seedlings could be used for afforestation of salt-affected areas.

Concurrent establishment of ground cover and hardwood trees on reclaimed mined land and unmined reference sites

A reclaimed mined site and an unmined reference site were compared to assess the effectiveness of reclaiming land according to United States Public Law 95-87, The Surface Mining Control and Reclamation Act of 1977, for forest land use. Red oak ( Quercus rubra L.) and black walnut ( Juglans nigra L.) seedlings were planted concurrently with K-31 fescue ( Festuca arundinacea Schreb.) and red clover ( Trifolium pratense L.), and maintained under the same levels of management on mined and unmined sites in Sullivan County, Indiana. Soil chemical and physical properties were evaluated, and ground-cover productivity was assessed for 4 years. Survival and growth of bareroot and container seedlings as influenced by chemical control of competing ground cover was followed for 7 years. After liming and fertilization, mine soil physical properties rather than chemical properties were apparent factors affecting survival of tree seedlings and productivity of both tree species and ground-cover vegetation. Survival percentage of black walnut and red oak seedlings on the mine site was adequate to meet the 450 trees acre −1 (≈ 1112 trees ha −1) stocking level specified by current laws only when ground cover vegetation was controlled. Survival and height growth of both tree species was greater on the reference site than on the mine site, especially when ground-cover vegetation was controlled. The poorer growth on the mine site was due to severe stem dieback on plots with no ground-cover control. The results show the importance of controlling the competing ground-cover vegetation during seedling establishment on reclaimed mine soils, particularly during the first 4 years following outplanting.

Growth ofVigna unguiculata L. var. GWL K3B in sub-optimal moisture conditions as influenced by certain antitranspirants

An experiment for differential water supply was set up. The effects of antitranspirants Phosfon-D and CCC on the growth ofVigna unguiculata L. Var K3B grown under suboptimal soil moisture conditions were recorded. An evaluation of the various aspects of growthe.g., seedling survival percentage, shoot growth, root growth, stomatal index and chlorophyll content indicated that application of CCC and Phosfon-D can help withstanding the adverse effects of sub-optimal soil moisture conditions to a certain extent. In the beginning of the paper effects of Phosfon-D CCC and MH on seedling growth are described.

Comparative mutagenicity of four organophosphorous insecticides in meiotic system of red pepper.

A study has been made of the effects of four organophosphorous insecticides: TARA 909, DDVP, phosphomidon (PMN) and monocrotophos (MCP) on ger-mination, survival and meiotic behaviour in Capsicum annuum. Soaked (24 h) seeds were treated with 0.1, 0.5 and 1.0% of the insecticides for 24h. There was a sig-nificant decline in germination and seedling survival percentage in all insecticidal treatments. All the insecticides were capable of inducing various types of meiotic alterations. Abnormalities consisted of univalents, multivalents, bridges, lagging chromosomes, non-synchronization, multipolar formation, micronuclei, unoriented and unequal disjunction of chromosomes at various divisional stages of PMCs. Stickiness and clumping of chromosomes was a common effect. As a result of these abnormalities, the tetrad formation were highly irregular and caused a high pollen sterility. Chromosomal aberrations and pollen sterility were dose-dependent and there was an apparent relationship between frequency of chromosomal damage and pollen sterility. Among the four insecticides, DDVP and TARA produced greater damage on chromosomes, which also caused significant reduction in ger-mination, survival and pollen viability followed by PMN and MCP.The present study has shown that the insecticides were effective mutagenic agents with radiomimetic action, and point out the need of adequate information concerning plant responses to agricultural chemicals to ensure their safe use.