[Show abstract][Hide abstract] ABSTRACT: ADDITIONAL INDEX WORDS. biocontainer, biodegradable container, plantable container, water use, plastic container, sustainable nursery crop production SUMMARY. Market researchers have found that nursery and greenhouse production practices that reduce plastic use can increase consumer interest. However, there are broader crop performance, production efficiency, and environmental factors that must be considered before adopting containers made with alternative materials. This review highlights current commercially available alternative containers and parent materials. In addition, findings from recent and ongoing nursery, greenhouse , and landscape trials are synthesized, identifying common themes, inconsistencies , research gaps, and future research needs.
[Show abstract][Hide abstract] ABSTRACT: The green industry has identified the use of biodegradable containers as an alternative to plastic containers as a way to improve the sustainability of current production systems. Field trials were conducted to evaluate the performance of four types of 1-gal nursery biocontainers [keratin (KR), wood pulp (WP), fabric (FB), and coir fiber (Coir)] in comparison with standard black plastic (Plastic) containers on substrate temperature, water use, and biomass production in aboveground nurseries. Locations in Kentucky, Michigan, Mississippi, and Texas were selected to conduct experiments during May to Oct. 2012 using 'Green Velvet' boxwood (Buxus sempervirens · B. microphylla) and 'Dark Knight' bluebeard (Caryopteris ·clandonensis) in 2013. In this article, we were focusing on the impact of alternative container materials on hourly substrate temperature variations and plant growth. Substrate temperature was on an average higher (about 6 °C) in Plastic containers (about 36 °C) compared with that in WP, FB, and Coir containers. However, substrate temperature in KR containers was similar to Plastic. Substrate temperature was also influenced by local weather conditions with the highest substrate temperatures recorded in Texas followed by Kentucky, Mississippi, and Michigan. Laboratory and controlled environment trials using test containers were conducted in Kentucky to evaluate sidewall porosity and evaporation loss to confirm field observations. Substrate temperature was similar under laboratory simulation compared with field studies with the highest substrate temperature observed in Plastic and KR, intermediate in WP and lowest in FB and Coir. Side wall temperature was higher in Plastic, KR, and FB compared with WP and Coir, while side wall water loss was greatest in FB, intermediate in WP and Coir, and lowest in plastic and KR. These observations suggest that the contribution of sidewall water loss to overall container evapotranspiration has a major influence on reducing substrate temperature. The porous nature of some of the alternative containers increased water use, but reduced heat stress and enhanced plant survival under hot summer conditions. The greater drying rate of alterative containers especially in hot and dry locations could demand increased irrigation volume, more frequent irrigation, or both, which could adversely affect the economic and environmental sustainability of alternative containers.
[Show abstract][Hide abstract] ABSTRACT: Containers made from natural fiber and recycled plastic are marketed as sustainable substitutes for traditional plastic containers in the nursery industry. However, growers' acceptance of alternative containers is limited by the lack of information on how alternative containers impact plant growth and water use (WU). We conducted experiments in Michigan, Kentucky, Tennessee, Mississippi, and Texas to test plant growth and WU in five different alternative containers under nursery condition. In 2011, 'Roemertwo' wintercreeper (Euonymus fortunei) were planted in three types of #1 (%1 gal) containers 1) black plastic (plastic), 2) wood pulp (WP), and 3) recycled paper (KF). In 2012, 'Green Velvet' boxwood (Buxus sempervirens · B. microphylla siebold var. koreana) was evaluated in 1) plastic, 2) WP, 3) fabric (FB), and 4) keratin (KT). In 2013, 'Dark Knight' bluebeard (Caryopteris ·clandonensis) was evaluated in 1) plastic, 2) WP, and 3) coir fiber (Coir). Plants grown in alternative containers generally had similar plant growth as plastic containers. 'Roemertwo' wintercreeper had high mortality while overwintering in alternative containers with no irrigation. Results from different states generally show plants grown in fiber containers such as WP, FB, and Coir used more water than those in plastic containers. Water use efficiency of plants grown in alternative containers vs. plastic containers depended on plant variety, container type, and climate. P lastic is the most commonly used material for containers in nursery and greenhouse operations. Schrader (2013) estimated that the green industry uses over 750 million kilograms of petroleum plastic for containers per year. Plastic containers are lightweight, easy to ship, and inexpensive (Helgeson et al., 2009). However, the disposal of plastic containers has raised concerns about the sustainability of this product. Today, the primary method of plastic container disposal is still in the landfill, and long-term risks of soil and groundwater contamination from ultraviolet light stabilizers and additives used in plastic products are unknown (Hopewell et al., 2009; Teuten et al., 2009). In 2012, 32 million tons of plastic waste were generated; however, only 9% of the total plastic was recovered for recycling (U.S. Environmental Protection Agency, 2014). Containers made from various new materials such as bioplastic, coir, poultry feathers, paper fibers, rice hulls, and processed cow manure have emerged as alternative options to plastic containers (Hall et al., 2010; Nambuthiri et al., 2015a). As plant growth is an important factor in growers' consideration when choosing containers, experiments have been carried out to investigate the impact of alternative containers on plant growth. Evans and Hensley (2004) reported that the shoot dry weight of impatiens (Impatiens walleriana) and vinca (Catharanthus roseus) plants in poultry feather containers was greater than that of peat and plastic containers when they were irrigated according
[Show abstract][Hide abstract] ABSTRACT: . The performance of biocontainers as sustainable alternatives to the traditional petroleum-based plastic containers has been researched in recent years due to increasing environmental concern generated by widespread plastic disposal from green industry. However, research has been mainly focused on using biocontainers in short-term greenhouse production of bedding plants, with limited research investigating the use of biocontainers in long-term nursery production of woody crops. This project investigated the feasibility of using biocontainers in a pot-in-pot (PIP) nursery production system. Two paper (also referred as wood pulp) biocontainers were evaluated in comparison with a plastic container in a PIP system for 2 years at four locations (Holt, MI; Lexington, KY; Crystal Springs, MS; El Paso, TX). One-year-old river birch (Betula nigra) liners were used in this study. Results showed that biocontainers stayed intact at the end of the first growing season, but were penetrated to different degrees after the second growing season depending on the vigor of root growth at a given location and pot type. Plants showed different growth rates at different locations. However, at a given location, there were no differences in plant growth index (PGI) or plant biomass among plants grown in different container types. Daily water use (DWU) was not influenced by container type. Results suggest that both biocontainers tested have the potential to be alternatives to plastic containers for short-term (1 year) birch production in the PIP system. However, they may not be suitable for long-term (more than 1 year) PIP production due to root penetration at the end of the second growing season.
[Show abstract][Hide abstract] ABSTRACT: As high-input systems, plant production facilities for liner and container
plants use large quantities of water, fertilizers, chemical pesticides, plastics, and
labor. The use of renewable and biodegradable inputs for growing aesthetically
pleasing and healthy plants could potentially improve the economic, environmental,
and social sustainability of current production systems. However, costs for production
components to integrate sustainable practices into established systems have
not been fully explored to date. Our objectives were to determine the economic costs
of commercial production systems using alternative containers in aboveground
nursery systems. We determined the cost of production (COP) budgets for two
woody plant species grown in several locations across the United States. Plants were
grown in plastic pots and various alternative pots made from wood pulp (WP),
fabric (FB), keratin (KT), and coconut fiber (coir). Cost of production inputs for
aboveground nursery systems included the plant itself (liner), liner shipping costs,
pot, pot shipping costs, substrate, substrate shipping costs, municipal water, and
labor. Our results show that the main difference in the COP is the price of the pot.
Although alternative containers could potentially increase water demands, water is
currently an insignificant cost in relation to the entire production process. Use of
alternative containers could reduce the carbon, water, and chemical footprints of
nurseries and greenhouses; however, the cost of alternative containers must become
more competitive with plastic to make them an acceptable routine choice for
[Show abstract][Hide abstract] ABSTRACT: Independently controlled irrigation plots were designed to test two container nursery irrigation regimes on oakleaf hydrangea (Hydrangea quercifolia ‘Alice’) in both nursery and controlled greenhouse environments. The experiments were conducted in both 3.8 and 11.4 L containers. Plants were automatically irrigated by one of two soil moisture sensor-based regimes: (1) a daily water use (DWU) system that delivered the exact amount of water that had been lost in the previous 24 h and (2) an on-demand (OD) irrigation system based on a specific substrate moisture content derived from the relationship between substrate moisture and photosynthetic rate. In this system, irrigation was applied when the substrate moisture level fell below 33% container capacity, which corresponded to 90% maximum predicted photosynthetic rate. Both treatments delivered the volume of water required to return the containers to container capacity by overhead irrigation, but the DWU system was static, irrigating once per day, whereas OD was dynamic and irrigated whenever the substrate moisture reached the 33% threshold level. Gas exchange was measured at the driest point prior to the next irrigation event. Periodical growth index, water use, and final dry weight were recorded. OD used less water than DWU outdoors, reduced leaching fraction among greenhouse experiments, and had either no or a positive impact on biomass in all but one trial. For 3.8 L plants, photosynthesis and stomatal conductance were consistently greater when irrigated by the OD program. Both treatments used significantly less water than the industry standard of 2.5 cm per day. This research demonstrated that both DWU and OD are a dramatic improvement over conventional irrigation scheduling and could be adopted as conservative irrigation systems for nursery production.
Scientia Horticulturae 11/2014; 179:132–139. DOI:10.1016/j.scienta.2014.09.008 · 1.50 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To improve nursery sustainability, nursery containers constructed of wood fiber, woven recycled plastic, keratin and coir were compared to standard high density polypropylene containers in 4 states. Containers were used for a one-year growing season. Plants were irrigated based on daily water use determined with moisture sensors. Plant growth, quality and mortality and container physical properties were measured over the growing season. Plant and container performance will be discussed in relation to water use and implications on sustainable nursery production.
[Show abstract][Hide abstract] ABSTRACT: Birch (Betula nigra) bare root liners were planted into two types of fiber containers (seven gallon, Kord® Fiber Grow, Western Pulp) and one plastic container (seven gallon, GL 2800, Nursery Supplies® Inc), which were used as the production pots in a pot-in-pot production system (PIP). Production pots were inserted into a GL 6900 (15 gallon) socket pot. The study was initiated in mid-June 2011 at four locations, KY, MI, MS and TX, and lasted through October 2012. Plant height, widths (Plant growth index (PGI) = (height+ width + perpendicular width)/3), and plant caliper (20 cm above ground) were measured at all locations at monthly intervals. Substrate moisture was determined with a calibrated theta probe (ML2, Dynamax Inc.) in KY with daily irrigation applied to replace 100% of daily water use (DWU). At the end of each growing season, a visual and tactile evaluation of the fiber containers was conducted to assess container strength. Birch plants were destructively harvested in October 2012. Above ground dry weight, root dry weight, and total dry weight were determined. There was no significant difference in plant height, plant dry weight, plant caliper or PGI among plants grown in different container types in MS, KY, or TX. Data from KY showed that there was no significant difference of DWU of plants grown in all three container types. At the end of the 2011 growing season fiber containers were still intact but by the end of the experiment roots had penetrated the bottom of the containers. In MS, bottom of fiber containers were severely penetrated by birch roots by October 2012 due to vigorous root growth; whereas, in KY, plant growth was less vigorous with only a few roots found penetrating the bottom of the pots.
[Show abstract][Hide abstract] ABSTRACT: Studies were conducted at the University of Kentucky to evaluate side wall water loss and substrate temperature of quart size alternative containers derived from paper, card board, peat, cow’s manure, rice hull or coir, bio degradable plastic, and plastic (control). An environmental chamber controlled for temperature and relative humidity was used to obtain a VPD of 2.6 k Pa. The containers were filled to their rim with saturated Fafard potting mix. Top part of each container was sealed using plastic sheet to prevent evaporation through the open surface. Five replicates of containers were moved to the chamber and hourly substrate water loss was measured. Another five replicates were used to determine light reflectance, wall temperature and substrate temperature in room temperature at 20⁰C and relative humidity 50%. Two 100 watts incandescent bulbs were installed 6 inches away from pots to provide heating for 90 minutes to warm up the substrate. After 90 minutes, radiation flux density of pot side wall was measured using a pyranometer (Licor-LI200). After measuring the radiation, the light was turned off, the temperature of pot wall was determined using an Infra-Red thermometer. Substrate temperature was obtained at one inch depth of the substrate at the center of pot and between the pot side wall and center of pot.
It was found that on an average plastic and bio-plastic containers lost 2.5 ml water whereas containers manufactured using rice hull, coir and straw containers lost 10 to 20 ml and peat, wood pulp and cow manure containers lost 25 to 30 ml in an eight hour period in the chamber. Light reflectance was lowest for black containers (20Wm-2) and it was higher for all alternative containers and it varied around 70 to 120 Wm-2 for rice, coir and straw containers. Container wall temperature was highest for plastic and bio-plastic containers (40ºC) followed by rice hull, coir and straw containers (30 ºC) and peat, wood pulp and cow manure based containers showed lowest wall temperature of around 24 ºC. Substrate temperature near to sidewall was highest for plastic and bio-plastic (28ºC), followed by all other alternative containers (22 ºC), same trend was noticed for temperature at the center of the container with plastic showing the highest (25ºC) and all alternative containers showing lower values (21ºC). Light reflectance and porous nature of container walls prevented higher substrate temperature buildup of some of the alternative containers.
[Show abstract][Hide abstract] ABSTRACT: Plant production facilities for perennial plug and container plants are high input systems using large quantities of water, fertilizers, chemical pesticides, plastics, and labor. The use of renewable and biodegradable inputs while growing an aesthetically pleasing and healthy plant will improve the economic, environmental, and social sustainability of current production systems. However, costs, such as poor integration of sustainable practices into established systems, increased carbon footprints, increased product shrinkage, and reduced plant health, which may be associated with sustainable production practices, have been ill defined. Our objectives are to determine the environmental and economic costs of commercial production systems using biocontainers (including greenhouse, above ground nursery, and pot-in-pot nursery production). The costs of all of the production inputs including water, fertilizers, chemical pesticides, disinfectants, and containers were collected for each system in each participating state. Labor inputs of potting, watering, applying chemicals, inspecting plants, harvesting, and cleaning pots and production area were also recorded. Use of “Green” processes based upon quantitative data will result in improved farm incomes while sustaining environmental quality by reducing the carbon, water, and chemical foot prints used in nurseries and greenhouses. Any strategy that can reduce expense and benefit the environment is a priority for the long-term sustainability of the industry.
[Show abstract][Hide abstract] ABSTRACT: Current best management practices recommend single irrigation to occur during early morning hours to reduce drift and evaporative loss of water for container grown nursery plants. A pot-in-pot (PIP) study was conducted at the University of Kentucky Horticulture Research Farm in Lexington, KY to evaluate optimal timing of daily cyclic irrigation in eastern redbud (Cercis canadensis ’Forest Pansy‘) growth and daily water use. Liners were grown in either 7-gallon or 15 gallon containers filled with 85% pine bark: 15% peat (vol/vol) in PIP systems in a completely randomized experiment design. Substrate moisture content was continuously monitored using EC5 (Decagon, IL) moisture sensors inserted into three representative containers per irrigation treatment. Irrigation was scheduled to replace 100% daily water use applied in three equal amounts and applied at the following times: cyclic irrigation starting at (i) 7, 8, and 9 am; (ii) 12, 1, and 2 pm; or (iii) at 5, 6,and 7 pm. Water use was approximately double in plants grown in 15-gal containers compared to 7-gal containers. The timing of cyclic irrigation impacted total and daily use in 7-gal, but not 15-gal containers. In the 7-gal containers, the least amount of water was used in the 7AM cyclic irrigation schedule. Containers required greater irrigation volumes when irrigation was scheduled at noon (19%) and at 4PM (5%) compared to the 7AM irrigation.
Plant physiological measurements as well as plant water status were collected just before the start of cyclic irrigation event and it varied on an average from about 9 μmol CO2 m‐2·s‐1 in the morning to 11 μmol CO2 m‐2·s‐1 in the noon and to 13 μmol CO2 m‐2·s‐1 in the afternoon irrespective of irrigation timing. Sap flow varied from about 23 cm hr-1 in the morning and to 54 cm hr-1 in the afternoon for plants grown under various irrigation treatments. Leaf water potential became more negative as day progresses irrespective of cyclic irrigation timing as observed right before the morning (-7 kPa), noon (-16 kPa) and afternoon irrigation (-22 kPa) events. The study highlights the water savings under sensor based cyclic irrigation and that when water is not limiting, environmental variables such as air temperature, relative humidity and solar radiation are more closely coupled to changes in plant physiological characteristics and water status.
[Show abstract][Hide abstract] ABSTRACT: This one-factor completely randomized experiment was conducted in Michigan, Kentucky, Mississippi, and Texas, in order to test plant growth and water use in containers made from material other than virgin plastic. From July 2011 to June 2012, Euonymus fortunei ‘Roemertwo’ were planted in three types of #1 (~3.8 L) containers (treatments) and evaluated. Container treatments were: 1) polyethylene PF400-SM (control); 2) Western Pulp 7X7RD (WP); and 3) Kord 07.50 Fiber Pot (Kord). From June 2012 to May 2013, Buxus x ‘Green Velvet’ were evaluated in four types of #1 containers: 1) control; 2) WP; 3) root pouch 15–20 month (RP) 4) keratin pot (KP). Substrate volumetric moisture content (SVMC) was determined by EC-5 moisture sensors in 2011, GS3 and EC-5 sensors in 2012 (Decagon Devices, Inc., Pullman, WA). Plant daily water use (DWU) was calculated as SVMC 5 minutes after irrigation minus SVMC immediately before the following irrigation period multiplied by container volume. Plants were irrigated to replace 100% DWU. For E. fortunei, in all states, plant growth and biomass were not different between treatments. A higher mortality rate in plastic than Kord and WP container was observed at the end of 2011 growing season. The DWU for WP and Kord varied by states in both years. The root zone temperature of KP was similar to control, and for WP and RP was 9% and 15% lower than control in Michigan, container temperature in other states varied. Mortality of Buxus was 0% for all states by October 2012; mortality will be evaluated in May 2013.
[Show abstract][Hide abstract] ABSTRACT: Biocontainers are being considered as more environmentally sustainable alternatives to plastic containers. However, the use of biocontainers may have unforeseen challenges including increased water use and poor durability in long-term nursery production settings. The objective of this research was to investigate the suitability of using biocontainers in a pot-in-pot (PNP) nursery production system. This study was conducted in Mississippi, Texas, Kentucky, and Michigan. Two types of 7-gallon fiber containers, KordFiber Grow and Western Pulp, and a 7-gallon standard plastic container were used in this study as inner pots (production pots). A plastic container was used as the in-ground socket pot. Birch (Betula nigra) bare root liners were planted in mid-June 2011 into the production pots filled with pine bark and peat (85:15, v/v). At the end of the first growing season, there was no significant difference in plant growth index and daily water use among the three container types in all four locations. Visual inspection of the biocontainers showed that the side walls and the bottom of the containers were intact. At the end of the second growing season, there was still no significant difference in plant growth index and daily water use among the three container types. However, the visual inspection of the biocontainers showed some degrees of degradation, especially the bottoms of the pots. The results suggested that the biocontainers we tested might be suitable for short-term rather than long-term PNP production.
[Show abstract][Hide abstract] ABSTRACT: The current study was conducted at the University of Kentucky Horticulture Research Farm in Lexington in conjunction with locations at Mississippi, Michigan, Texas, and West Virginia under the USDA–SCRI program. Buxus x Green Velvet 'Boxwood’ were planted in four types of #1 (~3.8 L) containers (treatments): 1) polyethylene PF400-SM (control) (Nursery Supplies Inc., PA); and alternative containers 2) Western Pulp 7X7RD (Western Pulp Products Co.,TX); 3) Keratin (Horticultural Research Institute, Washington, D.C.); and 4) Root PouchTM (Root Pouch Inc., OR). This one-factor completely randomized design experiment was conducted in Kentucky, Texas, Mississippi, Michigan, and West Virginia from June to October 2012. All plants were irrigated at 7 am and 7 pm to replace 100% daily water use. Two thermocouples (Type T copper-constantan thermocouple wires; Omega Engineering, CT) in each plot measuring substrate temperature were placed in the container of central growing beds at one inch below the substrate surface at one inch away from container wall facing south and at the center of container. Data were recorded using a datalogger (CR1000; Campbell Scientific) programmed to scan every 30 s and determined maxima, minima, and averages hourly. Average substrate temperature showed around 6°C to 9°C increase in black plastic containers as compared to alternative containers at one inch away from container wall and an increase of about 2°C to 4°C at the center of container during August in Kentucky. Substrate temperature was exposed to critical temperature (>37.8°C) for more than 3 hours on 15 different days in black plastic containers and about 9 days in keratin containers and none was observed for wood pulp and fabric containers during the study in Kentucky. Substrate temperature was increased by about 16°C (plastic), 14°C (keratin), 10°C (wood pulp), and 7°C (root pouch) from sun rise to midafternoon and substrate started cooling down from late afternoon with root pouch and plastic cooling the fastest, followed by keratin and wood pulp containers. Other locations observed similar trend in thermodynamics among the containers. Plastic containers exposed plant roots to rapid changes in substrate temperature than alternative containers types causing decreased plant root dry weight at harvest compared to plants grown in wood pulp. Highest substrate temperature observed in plastic was attributed to its black, non-porous and thin container walls. Porous walls of wood pulp and root pouch containers improved heat exchange and also allowed increased evaporative cooling resulting in reduced heat buildup.
[Show abstract][Hide abstract] ABSTRACT: Nursery irrigation scheduling based on two methods were compared (1) daily water use (DWU) and (2) a recently proposed plant demand-based irrigation system that assumes that growth would not be compromised when basing the irrigation set point on the substrate water content where photosynthesis begins to decline due to water stress. Buxus microphylla ‘Boxwood’ 4-inch liners were potted into 1 gallon containers with 85% pine bark : 15% peatmoss (vol:vol). Each irrigation zone was controlled by a 13DE04K solenoid valve (Rain Bird Corporation). Irrigation was applied through four overlapping Toro 570 Shrub Spray Sprinklers (The Toro Co., Riverside, CA) per irrigation zone. Emitters were mounted on 1.3-cm diameter risers at a height of 66 cm. DWU was calculated based on the average soil moisture readings of ECHO-5 probes (Decagon Devices, Pullman, WA) inserted into two containers per irrigation zone and irrigation was applied daily at 9 am. The demand-based irrigation system was designed to apply irrigation to return the moisture to container capacity (0.53 cm3) after substrate moisture set point (0.28 cm3) has been reached. Acquisition and control were monitored using a data logger (CR 1000, Campbell Scientific, Logan, UT). Gas exchange and pH and electrical conductivity of leachate were monitored during the experiment. Plant biomass metrics were measured at the termination of the experiment. Plant water use efficiency (WUE) was estimated by dividing total dry weight at the time of harvest by total water volume applied (irrigation plus precipitation; L per container). Plant physiological parameters such as leaf water potential, photosynthetic rate, transpiration rate and stomatal conductance were not different among plants in both the treatments. The average growth index and average plant dry weight at the end of study were not different among plants grown in DWU and demand-based irrigation treatments. Total irrigation water applied was greater (35%) for the DWU-based treatment than the on-demand irrigation treatment. Plants under on-demand treatment had greater WUE (31%) than plants in the DWU treatment. In general, the DWU treatments were irrigated when the volumetric water content was about 23% above the plant demand treatment’s set point. The pH and electrical conductivity of leachate were similar between the treatments and were within the acceptable range. These results suggest that for woody plants with low water requirement, such as boxwood, irrigation based on plant physiological parameters can significantly reduce water use compared to DWU based irrigation methods.
[Show abstract][Hide abstract] ABSTRACT: Biocontainers have been successfully marketed as sustainable alternatives to petroleum-based containers in greenhouse production. Despite this appeal, past research has shown that biocontainers, especially those constructed from more porous plant materials (e.g., peat and wood fiber), tend to require more frequent watering than conventional plastic products. However, no research to date has investigated how the use of a plastic filling/carry tray (commonly used facilitate production using small diameter containers) influences water demand in biocontainer production. This project evaluated plant growth and water consumption for 10 different containers (a plastic control and nine biocontainer alternatives) used to grow a short-term greenhouse crop (Vinca minor) at three different greenhouse sites in Fayetteville, AR; Lexington, KY;and Crystal Springs, MS. Containers were either left exposed or surrounded by an excised filling/carry tray pocket for the duration of the five-week study. Results indicate that both container type (P < 0.0001, all sites) and the absence/presence of a tray (P < 0.0001, AR; P = 0.0093, KY; P = 0.0023, MS) influence total water consumption. Trays generally reduced watering demand (up to 40% for straw pots); however, the benefit offered by the addition of a tray was not as significant for the more impervious containers made of plastic, bioplastic, and pressed rice hulls. In contrast with water use, growth responses (i.e. leaf area, dry shoot weight, and dry root weight) generally did not differ among the treatment combinations (with the exception of leaf area at the Arkansas site), indicating that water consumption was driven largely by the treatment combinations and was not confounded by differences in growth. We conclude that filling/carry trays can be an effective means of managing the overall sustainability of greenhouse production when using more porous biocontainers, especially if water use is a key concern. Additionally, past research may overestimate differences in watering demand in production systems where plastic filling/shuttle trays are used.
[Show abstract][Hide abstract] ABSTRACT: Seeds of Echinacea species have endogenous physiological dormancy. Dormancy release is induced by moist chilling stratification, but seeds treated with ethylene can show increased germination comparable to stratification. The primary aims of this work were to discover whether endogenous ethylene production was required for dormancy release and germination in Echinacea seeds and to investigate the physiological basis for stratification and ethylene-induced dormancy release. There were no significant differences in ethylene production in untreated versus stratified seeds. Seeds subjected to a dormancy release treatment showed reduced sensitivity to exogenous abscisic acid (ABA). Isolated embryos were completely released from dormancy when the outer envelope surrounding the embryo was removed. Isolated embryos with the envelope intact were also induced to germinate when treated with ACC (1-aminocyclopropane-1-carboxylic acid) to increase ethylene production. It was determined that the covering envelope was derived from enlargement of the endothelium layer surrounding the egg sac (integumentary tapetum) plus several crushed layers of the outer integument. Ethylene does not appear to be required for dormancy release and germination in Echinacea seeds. Two possible physiological mechanisms were discovered to explain stratification and ethylene-induced dormancy release. These included a change in seed sensitivity to ABA and changes in the tissues covering the embryo. The data suggests that ethylene-induced dormancy release is independent of stratification and possibly acts by inducing physiological events that are normally downstream of stratification.
Scientia Horticulturae 06/2013; 156:63–72. DOI:10.1016/j.scienta.2013.03.010 · 1.50 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background and AimsPhysical dormancy (PY) occurs in seeds or fruits of 18 angiosperm families and is caused by a water-impermeable palisade cell layer(s) in seed or fruit coats. Prior to germination, the seed or fruit coat of species with PY must become permeable in order to imbibe water. Breaking of PY involves formation of a small opening(s) (water gap) in a morpho-anatomically specialized area in seeds or fruits known as the water-gap complex. Twelve different water-gap regions in seven families have previously been characterized. However, the water-gap regions had not been characterized in Cucurbitaceae; clade Cladrastis of Fabaceae; subfamilies Bombacoideae, Brownlowioideae and Bythnerioideae of Malvaceae; Nelumbonaceae; subfamily Sapindoideae of Sapindaceae; Rhamnaceae; or Surianaceae. The primary aims of this study were to identify and describe the water gaps of these taxa and to classify all the known water-gap regions based on their morpho-anatomical features.Methods
Physical dormancy in 15 species was broken by exposing seeds or fruits to wet or dry heat under laboratory conditions. Water-gap regions of fruits and seeds were identified and characterized by use of microtome sectioning, light microscopy, scanning electron microscopy, dye tracking and blocking experiments.Key ResultsTen new water-gap regions were identified in seven different families, and two previously hypothesized regions were confirmed. Water-gap complexes consist of (1) an opening that forms after PY is broken; (2) a specialized structure that occludes the gap; and (3) associated specialized tissues. In some species, more than one opening is involved in the initial imbibition of water.Conclusions
Based on morpho-anatomical features, three basic water-gap complexes (Types-I, -II and -III) were identified in species with PY in 16 families. Depending on the number of openings involved in initial imbibition, the water-gap complexes were sub-divided into simple and compound. The proposed classification system enables understanding of the relationships between the water-gap complexes of taxonomically unrelated species with PY.
Annals of Botany 05/2013; 112. DOI:10.1093/aob/mct094 · 3.30 Impact Factor