Search Results

You are looking at 1 - 10 of 12 items for

  • Author or Editor: Jean C. Stutz x
Clear All Modify Search
Free access

Chris A. Martin and Jean C. Stutz

Sour orange (Citrus aurannum L.) seedlings were inoculated with geographic isolates of an endomycorrhizal fungus, Glomus intraradices Smith and Schneck, from a xeric (New Mexico) or mesic (Florida) climate or not inoculated as controls, and were grown for 5 months under high (soil water potential more than or equal to –0.1 MPa, irrigated once every 3 days) or low (more than or equal to –1.0 MPa, irrigated once every 12 to 15 days) irrigation frequency regimens. Similar leaf P concentrations were achieved in all plants by giving more P fertilizer to nonmycorrhizal plants than mycorrhizal plants. Plants inoculated with the xeric isolate had more arbuscules and fewer vesicles than those inoculated with the mesic isolate. Mycorrhizal fungi had little affect on plant growth under high irrigation frequency. Low irrigation frequency reduced plant growth compared with high irrigation frequency. Under low irrigation frequency, shoot and root growth increased for mycorrhizal plants; however, the magnitude of increase of shoot growth was greatest for plants inoculated with the xeric isolate. Additionally, low irrigation frequency was associated with a dramatic decrease in vesicle formation in roots inoculated with the mesic isolate. This study showed that sour orange plants especially benefited from inoculation with an isolate from a xeric climate under low irrigation frequency, independent of P nutrition.

Free access

Chris A. Martin and Jean C. Stutz

Prosopis alba (mesquite) in 27-liter containers, either infected or noninfected with the VAM fungi, Glomus intraradix Schenk & Smith, during the container production phase were transplanted into a simulated landscape and irrigated at regular intervals or nonirrigated (irrigated only once at transplanting time). Mesquite shoot extension (SE), trunk diameter, rooting density (RD), specific root length density (SRLD), and VAM colonization levels were measured at 6 months and 1 year after transplanting. At 6 months, VAM colonization was observed only in the roots of inoculated mesquite, but by 12 months, roots of inoculated and noninoculated mesquite were colonized by VAM fungi. There were higher levels of VAM colonization in roots of irrigated mesquite (23%) in comparison to nonirrigated mesquite (5%). Irrigation promoted SE and VAM inoculation inhibited SE of nonirrigated trees. Trunk diameter was greater for irrigated trees than for nonirrigated trees and was not affected by VAM fungal treatment. At 6 months after transplanting, VAM fungal and irrigation treatments interacted to affect mesquite RD and SRLD. For irrigated mesquite, RD and SRLD were highest for VAM-inoculated mesquite, whereas for nonirrigated trees, RD and SRLD were highest for noninoculated trees. At 12 months after transplanting, mesquite RD and SRLD were higher for irrigated than for nonirrigated trees and were not affected by previous VAM inoculation.

Full access

Chris A. Martin and Jean C. Stutz

A distance learning course called Southwest Home Horticulture was developed and implemented at Arizona State University using video and Internet technologies to give nonhorticulture students an overview of urban horticulture in the southwestern United States. Fourteen, one-half-hour video programs about topics in southwestern residential landscaping, plants materials and landscape best-management practices were produced in ≈800 working hours. The video programs are now telecast weekly, each academic semester, on the regional public television station and the educational channel of several cable television systems. We found that students who enrolled in the course were most likely to tape the programs on a video cassette recorder and watch them at their own convenience, one to three times. A World Wide Web (Web) site on the Internet was developed as a supplement to the video programs. The Web site was organized into a modular format giving students quick access to auxiliary course-related information and helpful resources. When asked, ≈90% of the students indicated that the Web site was a helpful supplement to the video programs. Use of video and Internet technologies in tandem has enabled nonhorticulture major students to learn about home horticulture in an asynchronous or location and time independent fashion.

Full access

Lucy K. Bradley and Jean C. Stutz

The Univ. of Arizona Cooperative Extension home horticulture World Wide Web site for Maricopa County, “Environmentally responsible gardening and landscaping in the low desert,” provides the public with timely, research-based, regionally appropriate information. This delivery method enables self-service access to prepared text information and high-quality images that could not be economically distributed via traditional print methods, and interactive opportunities for submitting questions.

Free access

Chris A. Martin, Jean C. Stutz and Robert W. Roberson

Effects of VAM fungal inoculum, Glomus intraradices Schenk & Smith, on the growth of Chilean mesquite in containers were investigated as part of a nursery container system for production of xeric trees. Seedling liners of Chilean mesquite were transplanted into 27-liter containers filled with a 3 pine bark : 1 peat moss : 1 sand medium. Before transplanting, 50% of the trees were band-inoculated at a depth of 8 to 12 cm below the growth medium surface with 35 g per container of Glomus intradices (Nutrilink, NPI, Salt Lake City, UT), approximately 1,000 spores g-1. All trees were top-dressed with 15 g Osmocote 18N-2.6P-9.9K (Grace-Sierra, Milpitas, CA) and 3 g Micromax (Grace-Sierra, Milpitas, CA) fertilizers and grown in a fiberglass greenhouse under 50% light exclusion. After 4 months, all inoculated tree root systems were colonized, and the percent infection was 47%. Noninoculated trees remained nonmycorrhizal. There were no differences in height, total shoot length, shoot dry weight, or root dry weight between inoculated and non-inoculated trees; however, total root length and specific root length of inoculated trees were less than those of noninoculated trees. These results suggest that the VAM fungi altered the root architecture of inoculated trees such that root systems of these trees had thicker roots with fewer fine roots elongating into the growth medium profile.

Free access

Chris A. Martin, Sean A. Whitcomb and Jean C. Stutz

Leucophyllum frutescens I. M. Johnst. (Texas sage) and Nerium oleander L. (oleander) shrubs grown for 2 years in the southwest United States under well-watered conditions in outdoor field plots were either sheared every 6 weeks or not pruned (control) to determine if frequent shearing had an effect on root growth and mycorrhizal colonization. During February and June of the second year after transplanting, leaf gas exchange, shoot and root growth, and arbuscular mycorrhizal fungi (AMF) colonization of shrubs were studied. Shearing reduced shrub volume of Texas sage and oleander by 84% and 82%, respectively. Leaf carbon assimilation (A) and conductance of both shrub taxa were stimulated by frequent shearing, especially during June. Shearing decreased root mass density (RMD) and root length density (RLD) of Texas sage but had no impact on RMD or RLD of oleander. Shearing decreased the length of Texas sage roots colonized by AMF but increased AMF colonization of oleander roots. Soil respiration and temperatures were less under all shrubs that were frequently sheared than those that were not pruned and were higher under all shrubs in June than in February. From these data we conclude that under well-watered conditions, the rejuvenative capacity and resilience of oleander to the practice of frequent shearing is greater than Texas sage and recommend that Texas sage shrubs not be frequently sheared in southwest landscapes.

Free access

Ruth H. Copeman, Chris A. Martin and Jean C. Stutz

Tomato (Lycopersicon esculentum Mill. `Heinz 1350 VF 402') seedlings were inoculated with populations of vesicular–arbuscular mycorrhizal (VAM) fungi collected from saline or nonsaline soil or remained nonmycorrhizal as a control. Plants then were salinated for 8 weeks at 1.0, 2.0, 5.0, or 10.0 dS·m–1 produced by dilutions of 1 m NaCl: 1 m CaCl2 in deionized water. Inoculation with VAM fungi from nonsaline soil enhanced shoot growth, while VAM fungi from saline soil suppressed shoot and root growth. Plants inoculated with VAM fungi from nonsaline soil and non-VAM control plants showed a quadratic increase in leaf Cl concentration in response to an increased salinity level, whereas plants inoculated with VAM fungi from saline soil showed a linear increase in leaf Cl concentration. Mycorrhizal-induced growth responses and changes in leaf Cl concentration were not associated with any apparent alterations in tomato plant P status. Although VAM fungi originating from saline soil did not promote plant growth, reduction in leaf Cl concentration mediated by these VAM fungi at moderate salinity levels may have beneficial implications for plant survival in saline soil.

Free access

Matthew W. Fidelibus, Chris A. Martin and Jean C. Stutz

Four AM fungal isolates (Glomus sp.) were screened for effects on growth of `Volkamer' lemon (Citrus volkameriana Ten. and Pasq.) under well-watered conditions. Plants were inoculated with an isolate of AM fungi, or non-inoculated. Non-mycorrhizal plants received more phosphorus (P) fertilizer than mycorrhizal plants because mycorrhizae enhance P uptake. Mycorrhizal and non-mycorrhizal plants were grown in 8-liter containers for 3 months in a glasshouse. Plants were then harvested, and root length colonized by mycorrhizal fungi, leaf P concentration, and plant growth were determined. Root length colonized by AM fungi differed among isolates; control plants were non-mycorrhizal. Leaf P concentration was in the optimal range for all plants; however, plants colonized by Glomus mosseae Isolate 51C had higher leaf P concentration than non-mycorrhizal plants. Plants colonized by Glomus AZ112 had higher leaf P concentration than all other plants. All plants had similar canopy leaf area, shoot length, and shoot dry mass. Plants colonized with AM fungi, except Glomus mosseae Isolate 51C, had longer root length and greater root dry mass than non-mycorrhizal plants. All mycorrhizal plants had lower shoot:root dry mass and leaf area:root length ratios than non-mycorrhizal plants. Our results showed that under optimal P nutrition and well-watered conditions, AM fungal isolates differentially altered the morphology of citrus plants by stimulating root growth.

Free access

Chris A. Martin, Jean C. Stutz and Shanyn Goodnight

Pepper (Capsicum sp. L.) seedlings were inoculated with either Glomus sp. AZ 112 (isolated from Wickman, Ariz.), Glomus intraradices Smith and Schneck (isolated from Santa Theresa, N.M.), a mixture of the two isolates, or a nonmycorrhizal control, and were grown for 8 weeks in a moderate (20.7 to 25.4C) or high temperature (32.1 to 38.0C) environment. Plants in moderate temperatures were larger and had lower specific soil respiration (Rspsoil) (μmol CO2/m2/s per gram root tissue dry weight) compared with those in high temperatures. In moderate temperatures, mycorrhizal plants were smaller and had higher Rspsoil than nonmycorrhizal controls. In high temperatures, plants inoculated with the isolate mixture grew nearly twice as large and had lower Rspsoil compared with plants inoculatedwith the individual isolates or the nonmycorrhizal control. Results suggest an improved carbon economy and a synergistic enhancement of pepper growth caused by the mixture of VAM fungal isolates that was not achieved by inoculation with single isolates alone under conditions of high-temperature stress.

Free access

Chris A. Martin, Jean C. Stutz and Shanyn Goodnight

Pepper (Capsicum sp. L.) seedlings were inoculated with either Glomus sp. AZ 112 (isolated from Wickman, Ariz.), Glomus intraradices Smith and Schneck (isolated from Santa Theresa, N.M.), a mixture of the two isolates, or a nonmycorrhizal control, and were grown for 8 weeks in a moderate (20.7 to 25.4C) or high temperature (32.1 to 38.0C) environment. Plants in moderate temperatures were larger and had lower specific soil respiration (Rspsoil) (μmol CO2/m2/s per gram root tissue dry weight) compared with those in high temperatures. In moderate temperatures, mycorrhizal plants were smaller and had higher Rspsoil than nonmycorrhizal controls. In high temperatures, plants inoculated with the isolate mixture grew nearly twice as large and had lower Rspsoil compared with plants inoculatedwith the individual isolates or the nonmycorrhizal control. Results suggest an improved carbon economy and a synergistic enhancement of pepper growth caused by the mixture of VAM fungal isolates that was not achieved by inoculation with single isolates alone under conditions of high-temperature stress.