Alternative soilless media for growing Petunia x hybrida and Impatiens wallerana: physical behavior, effect of fertilization and nitrate losses

The use of alternative soilless media for the production of potted plants requires knowledge of their physical and chemical characteristics to result in the best conditions for plant growth. We investigated the use of alternative soilless media based on river waste and Sphagnun sp. and Carex sp. from Argentinean peatlands on Petuniaxhybrida and Impatiens wallerana production at two fertilization levels (200 and 400mgl(-1)N). River waste or 'temperate peat' is the name given to a material, resulting from the accumulation of aquatic plant residues under an anaerobic subtropical environment, which is dredged from river banks. Our results showed that alternative substrates based on river waste can be used to grow high quality plants. This result was not fully explained on the basis of established methods to evaluate substrate quality. Highly concentrated fertigation solution decreased the substrate quality parameters and plant growth. Nitrate leaching from the alternative substrates containing river waste was lower than the standard peat-based materials, which makes river waste desirable from a sustainable pot production system perspective. River waste and Carex peat are suitable alternatives to Sphagnum peat from the Northern Hemisphere.     

Kin recognition: Competition and cooperation in Impatiens (Balsaminaceae)

The ability to recognize kin is an important element in social behavior and can lead to the evolution of altruism. Recently, it has been shown that plants are capable of kin recognition through root interactions. Here we tested for kin recognition in a North American species of Impatiens that has a high opportunity of growing with kin and responds strongly to aboveground competition. We measured how the plants responded to the aboveground light quality cues of competition and to the presence of root neighbors and determined whether the responses depended on whether the neighbors were siblings or strangers. The study families were identified by DNA sequencing as members of the same species, provisionally identified as Impatiens pallida (hereafter I. cf. pallida). We found that I. cf. pallida plants were capable of kin recognition, but only in the presence of another plant's roots. Several traits responded to relatedness in shared pots, including increased leaf to root allocation with strangers and increased stem elongation and branchiness in response to kin, potentially indicating both increased competition toward strangers and reduced interference (cooperation) toward kin. Impatiens cf. pallida responded to both competition cues simultaneously, with the responses to the aboveground competition cue dependent on the presence of the belowground competition cue.     

Photoperiodic studies on growth and development of Impatiens balsamina L.

Summary In the short-day plant Impatiens balsamina it was found that, while floral buds are initiated with 3 short-day (SD) cycles, at least 8 such cycles are required for flowering. The numbers of floral buds and open flowers bear a linear relationship with the number of SD cycles. The induced floral buds revert to vegetative growth unless the plants receive the minimum number of SD cycles needed for flowering, this reversion occurring in a basipetal direction. The rate of extension growth of the stem increases with increasing numbers of SD cycles. The high rate is maintained longer in plants receiving 32 or more SD cycles, but the subsequent fall is also steeper in these plants than in plants receiving less inductive cycles. Senescence also occurs in these plants and appears to be related to the magnitude of reproductive development and the high rate of extension growth.     

Non-reversion of Impatiens in the absence of meristem commitment

Purple-flowered plants of Impatiens balsamina maintained floral development on transfer from inductive short days (SD) to long days (LD), a treatment in which red-flowered plants of Impatiens are known to revert to leaf production. An investigation into the non-reverting nature of purple-flowered plants was carried out to establish whether these plants achieved meristem commitment or whether their non-reverting state was controlled by the leaves. When the leaves that had unfolded during the inductive SD treatment were removed at the time of transfer to LD, the purple-flowered plant did revert. This result suggests that, as in red-flowered Impatiens, meristem commitment is absent, but that purple-flowered plants maintain flowering in LD conditions because of a more permanent supply of signal from their leaves than occurs in red-flowered plants. A working hypothesis is proposed to explain how a signal from the leaves can retain a controlling role during flower development.Key words: Floral commitment, Impatiens, floral reversion, floricaula.      

Nectar properties of the sunbird-pollinated plant Impatiens sakeriana: A comparison with six other co-flowering species

Adaptations of the nectar traits in bird-pollinated flowers are amongst the most discussed aspects of floral evolution. In the case of sunbird-pollinated plants, data on nectar traits originate almost exclusively from the South African region and are very scarce for tropical Africa, where paradoxically the highest sunbird diversity occurs. Here we present a study on the nectar properties of a sunbird-pollinated plant, Impatiens sakeriana, growing in the West African mountains, including the nectar production, diurnal changes in the nectar standing crop, the nectar concentrations, the nectar volumes, total sugar amounts and sugar composition. Moreover we compare the nectar traits of I. sakeriana with six other co-flowering insect-visited plant species.Our results showed that many nectar properties, including high volume (approx. 38 μL in flowers unvisited by sunbirds), low sugar concentration (approx. 30% w/w) and high sucrose content (95%), are specific to I. sakeriana, compared to the insect-visited plants. These are in accordance with the most recent theory that nectar properties of the sunbird-pollinated plants are similar to those pollinated by hummingbirds.     

Plant community dynamics, nutrient cycling, and alternative stable equilibria in peatlands

Although observational data and experiments suggest that carbon flux and storage in peatlands are controlled by hydrology and/or nutrient availability, we lack a rigorous theory to account for the roles that different plant species or life-forms, particularly mosses, play in carbon and nutrient flux and storage and how they interact with different hydrologic sources of nutrients. We construct and analyze a model of peatlands that sheds some light on this problem. The model is a set of six coupled differential equations that define the flow of nutrients from moss and vascular plants to their litters, then to peat, and finally to an inorganic nutrient resource pool. We first analyze a simple version of this model (model 1) in which all nutrient input is from precipitation and enters the moss compartment directly, mimicking the dynamics of ombrotrophic bogs. There is a transcritical bifurcation that results in a switch of stability between two equilibrium bog communities: a moss monoculture and a community where mosses and vascular plants coexist. The bifurcation depends on the magnitudes of the input/output budget of the peatland and the life-history traits of the plants. We generalize model 1 to model 2 by dividing nutrient inputs between precipitation and groundwater, thus also allowing the development of minerotrophic fens that receive nutrient subsidies from both groundwater and precipitation and adding intraspecific competition (self-limitation) terms for both moss and vascular plants. Partitioning precipitation inputs between moss and the nutrient pool resulted in the greatest changes in model behavior, including the appearance of a lake and a vascular plant monoculture as well as the moss monoculture and coexistence equilibrium. As with model 1, these solutions are separated by transcritical bifurcations depending on critical combinations of parameters determining the input-output budget of the peatland as well as the life-history characteristics of the plant species. Model 2 also allowed for an early transient spike in vascular plant dominance followed by approach to near moss monoculture and then eventual approach to coexistence equilibrium. This generalized model mimics the broad features of successional development of peatlands from fens to bogs often found in the paleorecords of peat cores.     

Photoperiodic studies on growth and development of Impatiens balsamina L.

Summary Seedlings of Impatiens balsamina raised under ND and LD conditions were divided into two sub-groups each when they had reached 5-leaf stage. While one sub-group was left under the same condition (NDND or LDLD), the other was transferred to the other photoperiod (NDLD or LDND). NDND plants were subdivided into 2 lots. One of these was transferred to SD in May. The dates of emergence of individual branches and floral buds were recorded and the vegetative period was calculated in each case.It was found that in NDND plants floral buds were produced from all the nodes except the lowermost which produced a single vegetative branch. In LDND plants the vegetative branches were produced from the lower 9 nodes but floral buds from those above these. Small leafy structures which ultimately dried up were produced from a few top nodes in both these cases. In contrast to this in LDLD plants only vegetative branches were produced from all the nodes. In NDLD plants floral buds were produced from the lower 3–5 nodes prior to transfer to LD condition, but vegetative branches were produced from the upper nodes after this transfer. Even some of the lower floral buds reverted to vegetative state under this condition.The production of floral buds or the vegetative branches as the case may be, occurred in acropetal succession under all the photoperiodic conditions and never in basipetal manner.LDLD and NDLD plants, which did not flower at all, continued to produce lateral branches without showing any sign of senescence, while LDND and NDND ones showed yellowing of the apical growing point which spread downwards and lead ultimately to the death of the plant. The senescence was hastened when these plants were transferred to SD condition towards the end of May. The senescence therefore, appears to be related with reproductive development. The results are discussed in the light of current literature.     

Gel electrophoretic studies of proteins in photo-induced and vegetative plants of Impatiens balsamina

In Impatiens balsamina L. var. Rose, a qualitative SD plant,the protein content of the leaves shows an upsurge at the timeof physiological induction. The electrophoretic pattern of watersoluble proteins, however, does not change except for a newprotein that appears in the stem after the plants have received1 SD cycle. ¹Present address: Department of Biology, Guru Nanak Dev. University,AMRITSAR (Punjab) 143005, India. (Received March 1, 1976; )     

Establishment of woody plants for secondary and tertiary dune stabilization along the mid-Atlantic coast

Secondary and tertiary sand dunes along the Atlantic coast were originally covered with dense vegetation, including trees and shrubs. Most of this vegetation has been destroyed by various forms of development. The objective of this study was to evaluate the effects of various establishment techniques on the survival and growth of native and naturalized woody plants for secondary and tertiary dune stabilization, using bare root transplants. All plantings were made on sand dunes. The actual site was approximately 300 m from the ocean and was covered with a sparse stand of American beachgrass. Establishment variables were (a) peat moss applied in the fall, followed by fall plantings; (b) peat moss applied in the fall, followed by spring plantings; (c) peat moss applied in the spring, followed by spring plantings; and (d) no peat moss with either fall or spring plantings. Each planting included a fertilizer variable of (a) 30 g of magnesium ammonia phosphate placed 8 cm below the bottom of the planting hole; (b) 30 g of 10-6-4 fertilizer, which contained 50% of its nitrogen in an organic form, sprinkled around the base of the plant in the spring of the second growing season; and (c) no fertilizer. All plants used were 1- or 2-year-old seedlings. The use of organic soil amendments had a favorable affect on the survival of some species. Rugosa rose showed an increase in survival rate when the organic additive was added in the fall, followed by fall planting. Bayberry was favorably affected by the use of additive and regardless of planting time. The use of the two fertilizers produced no consistent or measurable response.Presented at the Seventh International Biometeorological Congress, 17–23 August 1975, College Park, Maryland, USA.     

Some factors affecting growth and survival ofRhizobium spp. in soil-peat cultures

Summary The growth and survival of rhizobium were studied in neutralized and sterilized soil-peat cultures containing alder bog peat, old moss peat, young reed peat, or young moss peat enriched with lucerne meal and sucrose. Although all these media proved to be excellent carriers for rhizobium, old moss peat from the 0–20 cm layer was less favourable than old moss peat from the 20–40 and 40–60 cm layer, while young moss peat proved to be the least satisfactory type of peat. A low storage temperature is always beneficial for the survival of rhizobia. Neutralization with CaCO₃ is to be preferred to that with CaCO₃+KH₂PO₄. Neutralization with NH₄OH exerted a detrimental effect. Much higher numbers of rhizobium were found in sterilized than in unsterilized soil-peat cultures. An antagonistic bacillus, isolated from peat, exerted a marked growth depression on rhizobium when both organisms were inoculated in sterilized soil-peat or in quartz sand media. Sterilization of the media permitted a rapid growth of the rhizobia and favoured their viability during storage, especially in autoclaved media containing nutrients. For the rhizobium ofLotonus bainesii sterilization of the peat proved essential for good growth. A harmful effect on the numbers of rhizobia was noted during the first week after the inoculation of the soil-peat mixtures when autoclaving had been carried out for 5 hours. This harmful effect proved, however, to be of a temporary nature.     

Plant regeneration from encapsulated nodal segments of Dalbergia sissoo Roxb., a timber-yielding leguminous tree species

One of the alternative methods adopted in recent years is to use biotechnological approaches for improving the tree species. The synthetic seeds offer several advantages, e.g., easy handling, storability, reduced size of propagules, and transportability. Germplasm can be effectively stored in the form of synthetic seeds. A protocol has been developed for plant regeneration from encapsulated nodal segments of Dalbergia sissoo Roxb. Nodal segments collected from basal sprouts of mature trees were encapsulated in calcium alginate beads. Inability of nodal segments entrapped in calcium alginate beads to form root was a major problem. To avoid this problem, an appropriate root induction treatment was given to nodal segments for 10 days, prior to encapsulation to allow formation of root primordia. For synthetic seeds production and subsequent conversion into plantlet, nodal segments with root primordia were encapsulated using sodium alginate and calcium chloride as gelling matrix. The best gel complexation was achieved using 3% sodium alginate and 75 mmol/L CaCl2 2H2O. Maximum percentage response (85%) for conversion of encapsulated nodal segments into plantlets was achieved on 1/2-MS medium without plant growth regulators, after 25 days of culture. The frequency of conversion of encapsulated nodal segments into plantlets affected by the concentration of sodium alginate, and the presence or absence of 1/2-MS nutrients in calcium alginate beads. Plantlets with well developed roots and shoots were transferred to pots containing autoclaved mixture of peat moss and soil (1:1). Plants were also established in pots. The conversion of encapsulated nodal segments into plantlets also occurred when calcium alginate beads having entrapped nodal segments were directly sown in autoclaved peat moss moistened with 1/2-MS0 medium. Out of 60 encapsulated nodal segments, in each experiments, stored at 4 degrees C for 30 days, 44 plants developed under in vitro conditions, and 27 on peat moss moistened with 1/2-MS0.     

Identification of mycobacteria in peat moss processing plants: application of molecular biology approaches

Peat moss processing plant workers are exposed to high concentrations of bioaerosols. Although mycobacteria have been cultured from peat moss, no study has examined the workers' exposure to mycobacterial bioaerosols. We evaluated the presence of mycobacteria in air samples from peat moss processing plants using molecular biology approaches (cloning-sequencing and polymerase chain reaction (PCR)) and the workers exposure using immunoglobulin G (IgG) complexes to mycobacteria. In addition, species detected in air samples and in peat moss were compared. Two peat moss processing plants were chosen among 14 previously studied. A total of 49 clones were sequenced. Real-time PCR was also performed on the same air samples to evaluate the airborne concentration of mycobacteria and estimate exposure levels. Several Mycobacterium species were present in the air samples (M. malmoense, M. smegmatis, M. graceum, M. bohemicum, and M. interjectum). Mycobacterium avium was recovered by culture in peat moss but not in the air using the molecular approach. Total airborne Mycobacterium concentration was estimated at 8.2 x 10(8)/m3. Workers had IgG against the mycobacterial mix and M. avium, suggesting significant exposure. The findings from air samples, supported by IgG measurements, demonstrate that peat moss processing plant workers are exposed to mycobacteria in addition to other biological agents.     

Floral induction by gibberellic acid in Impatiens balsamina,a qualitative short-day plant

Summary In the qualitative short-day plant Impatiens balsamina, gibberellic acid (GA₃) not only promoted the formation of floral buds in response to suboptimal photoinductive conditions and reduced the number of SD cycles that are required for their development into flowers, but also caused initiation of floral buds under non-inductive photoperiods. In plants treated with repeated applications of GA₃, the floral buds developed into flowers irrespective of whether the apex was left intact or was removed. In those that received a single application of GA₃ the floral buds developed into flowers only in decapitated plants.     

The effect of foliar nutrition on yield of greenhouse tomatoes and quality of the crop

Tomatoes grown in traditional mediums such as peat moss are usually supplied with essential nutrients by preplant fertilization and in the later growth stages by top dressing application to the root zone. According to the data from literature the efficient method of nutrient supply during the intensive stage of growth may be estimated as by foliar spraying. In the greenhouse experiment conducted in 1998–1999 a preplant fertilization by multicomponential fertilizer MIS-4 was applied to peat moss growing medium in full (4 kg per m³) and half (2 kg per m³) of recommended rate. Supplemental fertilization during the growing period was provided to the root zone or by using liquid multicomponential fertilizers Ekolist S and Mikrosol U in 5 sprays conducted at two week intervals. Results of the study proved that advantageous effect of foliar tomato nutrion grown in eat substrate was observed only in treatments with restricted supply of fertilizers to the growing medium. The maximum fruit yield was received from plots provided by the reduced preplant MIS-4 dose to 50 % of recommended rate combined with foliar sprays by Ekolist S. Such system of fertilization enhanced the marketable yield of fruit by 9.8 % and early yield by 11.3 % as compared to that obtained with preplant and top dressing soil application. Foliar nutrion did not change dry matter and vitamin C content and increased total and reducing sugars accumulation in tomato fruits.     

Floral bud reversion in Impatiens balsamina under non-inductive photoperiods

Summary All floral buds of Impatiens balsamina plants exposed to 4 short-day (SD) cycles and then returned to long days reverted to vegetative growth. The same happened with the upper buds of plants receiving a larger number of SDs, even as many as 90 cycles. The reversal proceeded in a basipetal order. The number of floral buds and flowers increased, and their reversion to vegetative growth was delayed with increasing numbers of SD cycles. Depending upon the stage attained by the floral bud before the transfer of the plant to noninductive photoperiods one or more inner whorls of the flower were replaced by a vegetative apex. The tip of the placenta was able to resume vegetative growth even after the formation of fertile anthers and an ovary with abortive ovules, showing that the potentiality for reversion is maintained till quite late stages in floral bud development. Continuous exposure to SD cycles is required not only for the continued production of floral buds, but also for their development to mature flowers, indicating that the floral stimulus in this plant is not self-perpetuating.     

An experiment on Impatiens New Guinea for 11–12 year olds

The following experiment describes an easy experiment for children 11–12 years old, performed during spring in a compulsory school near Karlstad, Sweden. Four different ripe fruits were placed under flowering plants of Impatiens New Guinea (Impatiens hawkeri) for four days on a table and with plastic bags around both plants and fruits. For one of the ethylene-producing fruits, apple, the result was very clear. The plants shed many flowers and buds on the first day, due to stimulated senescence caused by ethylene. For the other ethylene-producing fruit, kiwi fruit, the result was clear but not as explicit as for apple. On the other two fruits, orange and lemon, flowers and buds were shed in the same proportion as the control plants. From these results a discussion could focus on tips on how to stimulate the ripening of unripe fruit e.g. by putting apples in the same dish. The experiment is planned in a formal scientific manner and thus stimulates discussion about how to design experiments. Very few materials are required — just flowering pot-plants, fruits and plastic bags. These are easy to buy in a garden centre or a shop. Furthermore, the experiment is cheap, it is easy to perform and it stimulates practical work.     

Partitioning of latent heat flux at a northern peatland

The partitioning of latent heat flux (Q_E) to vascular plant and moss surface components was assessed for a Sphagnum-dominated bog with a hummock–hollow surface having a sparse canopy of low shrubs. Results from porometry and eddy covariance measurements of Q_E showed evaporation from the moss surface ranged from greater than 50% of total Q_E early in the growing season to less than 20% after a dry period toward the end of the growing season. Both soil moisture and vapour pressure deficit (D_a) affected this partitioning with drier moss and peat, lower water table, and smaller D_a all reducing moss Q_E. Daily maximum moss Q_E ranged from greater than 200 W m⁻² early in the growing season to less than 100 W m⁻² during a dry period. In contrast, vascular contribution to total Q_E increased over the season from a daily maximum of about 150 W m⁻² to 250 W m⁻² due to increase in leaf area by leaf replacement and emergence and to drying of the moss surface. Porometry results showed average daily maximum conductance from bog shrubs was near 8 mm s⁻¹. These conductance values were smaller than those reported for vascular plants from more nutrient-rich wetlands. The effect of increases in D_a on vascular Q_E were moderated by decreases in stomatal conductance. At constant available energy, vascular leaf conductance was reduced by as much as 2 mm s⁻¹ and moss surface conductance was enhanced by up to 3 mm s⁻¹ by large D_a. Considering vascular and non-vascular water transport characteristics and frequency of water table position and given the observed variations of Q_E partitioning with water table location and moss and peat water content, it is suggested that modelling efforts focus on how dry hummocks and wet hollows each contribute to Q_E, especially as related to D_a and soil moisture dynamics.     

Partial substitution by long days of short days required for floral induction in Impatiens balsamina

Two SD cycles are necessary for initiation of floral buds inImpatiens balsamina L., var. Rose. Floral buds are also initiatedin plants exposed to only one SD cycle +16- or 20-hr LDs; LDsby themselves are noninductive. Floral bud initiation is hastenedand the number of initiated flowers increases with longer darkperiods in the supplementary photoperiodic cycles. (Received May 6, 1972; )     

Laboratory experiments on the retention of micronutrients by peat humic acids

Summary The retention of some plant micronutrients (Cu, Zn, Mn, Mo) by insoluble peat humic acids has been quantitatively determined by laboratory investigations. The findings support the view that the symptoms of deficiency of these nutrients in plants growing on drained moor or peatland soils could well be caused by such retention. In addition a strong retention of Co was observed which could be the cause of the well-known Co-deficiency in animals feeding on Co-deficient plant material.     

Density-dependent flowering phenology,outcrossing, and reproduction in Impatiens capensis

Summary We investigated the effects of plant density on cleistogamous (CL) and chasmogamous (CH) flowering phenology and seed production in a natural Impatiens capensis population, by censusing individually marked plants at experimentally reduced and natural densities. CL flowering was earlier at natural density. This plastic density response may have resulted from a stress-related threshold for CL flowering; slower growing plants at natural density flowered earlier. Although apparently triggered by slow early growth, early CL flowering also involved an additional cost for later growth rate. In contrast, CH flowering was unrelated to relative growth rate, but apparently required a size threshold. Experimental density reduction resulted in earlier CH flowering and a dramatic increase in the percentage of plants producing CH flowers. Individual CL and CH flowering duration and flower production were greater at reduced density. These density-dependent effects caused differences between treatments in the shape and location of population flowering phenology curves. Moreover, the percentage of CH seeds produced per individual was much higher at reduced density. At natural density total seed production per plant was lower and more hierarchical than at lower density, suggesting that dominance and suppression shape jewelweed fitness distributions.