Thomas Marler - Academia.edu (original) (raw)

Papers by Thomas Marler

Horticulturae

The literature covering the biology, invasion chronology, host plant responses, and control effor... more The literature covering the biology, invasion chronology, host plant responses, and control efforts of the armored scale Aulacaspis yasumatsui Takagi (Hempitera: Diaspididae) is reviewed. The small size of this cycad pest and complex surface morphology of the host cycad organs combine to make visual detection of every cryptic infestation difficult or impossible to achieve. The international movement of Cycas revoluta Thunb. nursery plants and the presence of C. revoluta nursery industries in so many countries have enabled this pest to wreak havoc on the international cycad horticulture trade over the last 25 years. The short pre-oviposition period and considerable female fecundity lead to rapid population expansion on the plants initially infested in newly invaded regions. A depletion of non-structural carbohydrates accompanies long-term infestations and precedes plant death. Enemy escape within the invasive range allows the scale population growth to remain unchecked until anthropo...

Functional Plant Biology, 2006

Neurotoxins contained in the seeds of Cycas micronesica K.D. Hill have been implicated in the Gua... more Neurotoxins contained in the seeds of Cycas micronesica K.D. Hill have been implicated in the Guam neurological disease cluster, amyotrophic lateral sclerosis–parkinsonism dementia complex (ALS–PDC). Some of these neurotoxins remain in the washed cycad seed flour that was historically an important part of the Chamorro diet. Of these, variant steryl glucosides have been identified by us as a possible etiological factor in the disease. In vitro and in vivo animal studies have strongly supported a role for these molecules in some forms of neurodegeneration. As part of a series of studies, we have now determined the concentrations of several steryl glucosides and their sterol precursors as affected by the age of C. micronesica seeds. The concentration of these molecules declined with seed age from 2.0 to 30.5 months. Following log-transformation of both axes, the decline was linear. Similarly, concentration of all but one of the molecules declined with age when samples were restricted t...

Cycas micronesica leaf and strobili expansion patterns were measured in three locations and seaso... more Cycas micronesica leaf and strobili expansion patterns were measured in three locations and seasons on Guam and then were fitted with non-linear models to evaluate the use of the parameters for informing management decisions. All growth curves except for microstrobili height conformed to a negative exponential function. Microstrobili height development could not be fitted with any traditional linear or non-linear function, so spline models were used to smooth the effect of elapsed days. Leaf and leaflet expansion patterns were influenced by habitat and season, indicating development of the vegetative organ is plastic. In contrast, the models that described development of megasporophyll length, microstrobili height, and microstrobili diameter were not influenced by habitat or season. Moreover, seed diameter developmental patterns were only minimally influenced by location. These results indicate developmental patterns of the reproductive structures were primarily constitutive. We have demonstrated two empirical approaches to fitting models of Cycas micronesica organ growth and development and that both methods are useful for determining the influence of spatial or temporal factors in the timing of organ development. This approach may be used to inform horticultural or conservation questions of other rare cycad species.

Hortscience, Aug 1, 1996

To determine when a paper is to be presented, check the session number in the Program Schedule or... more To determine when a paper is to be presented, check the session number in the Program Schedule or the Conference at a Glance charts. The Author presenting the paper is indicated by an asterisk.

HortScience

Leaflets of carambola were restricted to a horizontal position for 3.5-h during late morning and ... more Leaflets of carambola were restricted to a horizontal position for 3.5-h during late morning and early afternoon on sunny days to determine the influence of natural leaflet movement on temperature and chlorophyll fluorescence. Adaxial temperature of these horizontal leaflets was 5-9 C higher than that of leaflets that were allowed to move in response to high light. Chlorophyll fluorescence was similarly affected. Leaflets that were allowed to move had a higher Fv/Fm than leaflets that were restricted in movement The results indicate that the presence of a pulvinus at the base of each leaflet of carambola leaves allows movement of the leaflet to avoid incident light. This natural leaflet movement under sunny conditions results in a lower temperature and a higher level of photochemical efficiency when compared with leaflets that are exposed to high light due to restricting their movement.


HortScience

The Abstracts that follow are arranged in numerical sequence by the abstract number. For Poster S... more The Abstracts that follow are arranged in numerical sequence by the abstract number. For Poster Sessions, the number preceded by PB (i.e., PB XXX) indicates the poster board number on which the poster will be mounted. Abstracts for Oral Sessions, Colloquia,and Workshops are grouped by sessions. To determine when a paper is to be presented, check the session number in the Program Schedule or the Conference at a Glance charts. The author presenting the paper is indicated by an asterisk.

HortScience

Leaf gas-exchange responses of A. souamosa seedlings to salinity were studied in sand culture in ... more Leaf gas-exchange responses of A. souamosa seedlings to salinity were studied in sand culture in a series of glasshouse experiments. Trees were irrigated with a complete nutrient solution as the control, or with this solution amended to 3 or 6 dS/m with sea salt. Inhibition of net CO2 assimilation, stomatal conductance of CO2, and transpiration was apparent 14 days after treatments were imposed, and continued to decline until day 30 to 35. The diurnal pattern of leaf gas exchange was not altered by salinity. Salinity reduced CO2, light energy, and water use efficiencies. Dark respiration and internal partial pressure of CO2 were unaffected by salinity stress. Results indicated that substrate salinity inhibited photosynthesis of A. souamosa via limitations on mesophyll capacity for CO2 assimilation and had little effect on gas phase limitations.

HortScience

The eyecare industry has used various instruments and methods for determining intraocular pressur... more The eyecare industry has used various instruments and methods for determining intraocular pressure. Some of the methods may be applicable for measurement of fruit firmness in the horticultural industry. We determined fruit firmness with an applanation tonometer, currently one of the most popular instruments in the eyecare industry. We then measured firmness of the same sample using a penetrometer with an 8-mm probe. Kiwi, mango, peach, strawberry, tomatillo, and tomato fruit were included in the study. With the exception of mango, tonometer and penetrometer measurements within a species were significantly correlated. The contact area of the tonometer probe was 1.5 mm2, which was less than 3% of the contact area of the penetrometer probe. The heterogeneous nature of mango mesocarp due to fibers and this large difference in contact area between the two instruments may have caused the lack of correlation for that species. The data indicate that tonometry may be useful for determining f...

HortScience

To determine when a paper is to be presented, check the session number in the Program Schedule or... more To determine when a paper is to be presented, check the session number in the Program Schedule or the Conference at a Glance charts. The Author presenting the paper is indicated by an asterisk.

HortScience

Cycas micronesica is an arborescent cycad with sclerophyllous, long-lived compound leaves that ar... more Cycas micronesica is an arborescent cycad with sclerophyllous, long-lived compound leaves that are produced in synchronized pulses. The photosynthetic characteristics of leaves in two sequential cohorts of ≈2 and ≈11 months after leaf expansion were determined in this study. Fluorescence yield following 30-min of light exclusion or from leaves engaged in photosynthesis under ambient light was measured throughout several 24-h periods to determine maximum quantum efficiency of PSII photochemistry and quantum efficiency under ambient light. Maximum quantum efficiency was similar for the two cohorts throughout the nocturnal period. Maximum quantum efficiency and quantum efficiency under ambient light declined following exposure to daily direct sun but recovered quickly each afternoon. This daily decline was greater for the older cohort than the younger cohort. Net carbon dioxide assimilation (Pn) was also determined using gas exchange, and light saturated Pn of the older cohort was 75% ...

HortScience

Two studies were conducted with `Known You 1' and `Sunrise' papaya seedlings to determine... more Two studies were conducted with `Known You 1' and `Sunrise' papaya seedlings to determine the combined influence of wind and drought stress on growth. For each study, 4-week-old nursery plants were transplanted into 2.6-L containers and placed in a protected site with rain exclusion provided by polypropylene cover. Industrial fans were used to provide unidirectional wind of ≈2 m/s for 12 hours per day to half of the plants; the remaining half of the plants received no wind. One half of the plants for each cultivar and wind combination were designated as well-watered and received daily irrigation. The remaining half of the plants were designated as drought-stressed and received 25% to 50% of the water applied to the well-watered plants. Plants were grown for 3 weeks under these experimental conditions. There were no interactions between the drought and wind main effects. The reduction in height, trunk cross-sectional area, total plant dry weight, and relative growth rate belo...


HortScience

The influence of plant size on recovery following defoliation of `Tainung 1' papaya was used ... more The influence of plant size on recovery following defoliation of `Tainung 1' papaya was used to study the role of respiratory sink size relative to photosynthetic surface area and the carbohydrate pool size available for remobilization. Defoliated (D) plants at three different ages: oldest, 24 weeks posttransplant (PT), supporting ≈8 weeks of fruit set; intermediate, 10 weeks PT, ≈2 weeks from initial flowering; and youngest, 4 weeks PT, were compared to an equal number of control plants. The oldest plants abscised all fruit <5.5 cm in diameter as a result of defoliation. Increase in stem height and basal circumference ceased on all plants and increase in fruit circumference ceased on the oldest plants following defoliation. Increase in stem height of D plants began again 3 weeks postdefoliation (PD) and returned to that of control plants by 6 weeks PD. Increase in basal circumference of D plants began again 6 weeks PD. Root density was observed on observation windows, and fi...


HortScience

Seedlings of Carica papaya L. `Waimanalo' (papaya) were transplanted into 27-L containers fil... more Seedlings of Carica papaya L. `Waimanalo' (papaya) were transplanted into 27-L containers filled with nonsterile composted landscape yard trimmings passed through a 1.3-cm screen. At transplanting, papaya plants were inoculated with either one of three different AMF communities or were not inoculated as control plants. Two of the AMF communities were from Arizona citrus orchards, and one AMF community was from an undisturbed western Chihuahuan Desert soil. After transplanting, papaya plants were grown for 4 months under well-watered conditions in a temperature-controlled (32 °C day/24 °C night) glasshouse (45% light exclusion). Control plants remained non-mycorrhizal. Total colonization of papaya roots by AMF communities ranged from 56% to 94%. Depending on mycorrhizal treatment, AMF arbuscules and internal hyphae were present in 30% to 60% and 20% to 24% of roots, respectively. Noticeably absent in papaya roots were AMF vesicles. Papaya height, trunk diameter, and leaf phosphor...

HortScience

The frequency of tropical cyclones is a major factor affecting the vegetation of the Mariana Isla... more The frequency of tropical cyclones is a major factor affecting the vegetation of the Mariana Islands, where these storms are called typhoons. An average of about one typhoon per year has passed within ≈100 km of Guam during the past 50 years. The physiognomy of Guam's natural and urban forests is largely determined by these typhoons. The impact of each typhoon is determined by a long list of interacting factors such as species characteristics; environmental and horticultural conditions preceding the typhoon; the intensity, direction, and duration of winds; the amount of rainfall associated with the typhoon; and the environmental and horticultural conditions following the disturbance. Many species survive typhoons by reducing aerodynamic drag of the canopy by abscising inexpensive leaves or breakage of small stems which results in an intact major structural framework. Speed of recovery for nonlethal damage following disturbance depends on nonlimiting conditions during recovery. T...

HortScience

Trade winds are a widespread horticultural consideration throughout the tropics. Growth and produ... more Trade winds are a widespread horticultural consideration throughout the tropics. Growth and productivity of most horticultural crops are not optimal on sites that are exposed to these chronic, unidirectional winds. We conducted four container studies on an exposed site, using clear plastic or screening material to provide three levels of wind exposure: 0%, 36%, or 100%. Two studies were conducted with direct-seeding, such that seedling emergence and early growth were determined for 7 weeks. Two studies were conducted using 8-week-old nursery plants that had been grown in a protected nursery. These plants were transplanted to the experimental site and grown for 6 weeks. Cultivars were `Known You 1', `Sunrise', and `Tainung 2'. Full exposure to wind reduced height up to 32%, increased root: canopy ratio up to 36% and exhibited no influence or slightly reduced stem cross-sectional area when compared with full protection from wind. Net carbon dioxide assimilation (Pn) was me...

Hortscience, May 1, 1994

The Abstracts that follow are arranged in numerical sequence by the abstract number. For Poster S... more The Abstracts that follow are arranged in numerical sequence by the abstract number. For Poster Sessions, the number preceded by PB (i.e., PB XXX) indicates the poster board number on which the poster will be mounted. Abstracts for Oral Sessions, Colloquia,and Workshops are grouped by sessions. To determine when a paper is to be presented, check the session number in the Program Schedule or the Conference at a Glance charts. The author presenting the paper is indicated by an asterisk.

HortScience, 2007

The concentration of two steryl glucosides and their sterol precursors were measured in gametophy... more The concentration of two steryl glucosides and their sterol precursors were measured in gametophyte tissue of Cycas micronesica K.D. Hill seeds before and after two storage treatments. For one study, intact 14-month-old seeds were stored at room temperature for 10 months. For the second study, cleaned (sarcotesta tissue removed) 22-month-old seeds were sown in perlite propagation beds, and ungerminated seeds were harvested after 14 months. Concentration of the steryl glucosides and sterols in the gametophyte tissue did not differ between the fresh seeds and the seeds after storage. The function of these metabolites is not known, but their unexpected stability for up to 14 months of storage indicates they are not metabolized during storage and may be vital during germination and early seedling growth. Implications on human exposure to their neurotoxic effects from gametophyte flour ingestion are discussed.

HortScience, 2001

Subsoil from an acid soil series was amended with CaSO 4 , MgO, or Ca(OH) 2 to identify chemical ... more Subsoil from an acid soil series was amended with CaSO 4 , MgO, or Ca(OH) 2 to identify chemical factors that may enhance papaya (Carica papaya L.) root growth in these soils. Root length of 'Red Lady' and 'Waimanalo' seedlings at two stages of development was increased by the addition of each of the materials. The increase in root length was similar for CaSO 4 or MgO amendments, and was greatest for Ca(OH) 2 amendment. These amendments increased dry weight of new roots for 'Red Lady' and increased root length per unit dry weight in one experiment for 'Waimanalo'. The results indicate that both Ca deficiency and Al toxicity may be responsible for limiting papaya root growth in the subsoils of the acid soils of Guam. Correcting these chemical factors should improve rooting depth, thereby increasing the volume of soil from which resources are accessible and lessening the susceptibility to toppling during tropical cyclones.

Horticulturae

The literature covering the biology, ecology, horticulture, and conservation of the critically en... more The literature covering the biology, ecology, horticulture, and conservation of the critically endangered tree Serianthes nelsonii Merr. was reviewed. The roots, stems, and leaves of this charismatic legume tree revealed highly plastic traits and responded positively to horticultural manipulations to improve the quality of container-grown transplants. Pre-sowing seed treatments of seed coat scarification and 1 h of imbibition generated 85% to 90% germination at a temperature optimum of 26 °C. Adventitious root formation on air layers and successful unions on approach grafts were 100%. Seedling and sapling growth was maximum under 25% to 50% sunlight transmission, limited irrigation to ensure adequate root zone aeration, repetitive stem tip pruning to increase root:shoot quotient, and thigmic stress to retain an orthotropic orientation of stems. In situ regeneration on Guam was substantial but recruitment from seedling to sapling was nil. High quality leaf litter chemistry enabled ra...

Horticulturae

The literature covering the biology, invasion chronology, host plant responses, and control effor... more The literature covering the biology, invasion chronology, host plant responses, and control efforts of the armored scale Aulacaspis yasumatsui Takagi (Hempitera: Diaspididae) is reviewed. The small size of this cycad pest and complex surface morphology of the host cycad organs combine to make visual detection of every cryptic infestation difficult or impossible to achieve. The international movement of Cycas revoluta Thunb. nursery plants and the presence of C. revoluta nursery industries in so many countries have enabled this pest to wreak havoc on the international cycad horticulture trade over the last 25 years. The short pre-oviposition period and considerable female fecundity lead to rapid population expansion on the plants initially infested in newly invaded regions. A depletion of non-structural carbohydrates accompanies long-term infestations and precedes plant death. Enemy escape within the invasive range allows the scale population growth to remain unchecked until anthropo...

Functional Plant Biology, 2006

Neurotoxins contained in the seeds of Cycas micronesica K.D. Hill have been implicated in the Gua... more Neurotoxins contained in the seeds of Cycas micronesica K.D. Hill have been implicated in the Guam neurological disease cluster, amyotrophic lateral sclerosis–parkinsonism dementia complex (ALS–PDC). Some of these neurotoxins remain in the washed cycad seed flour that was historically an important part of the Chamorro diet. Of these, variant steryl glucosides have been identified by us as a possible etiological factor in the disease. In vitro and in vivo animal studies have strongly supported a role for these molecules in some forms of neurodegeneration. As part of a series of studies, we have now determined the concentrations of several steryl glucosides and their sterol precursors as affected by the age of C. micronesica seeds. The concentration of these molecules declined with seed age from 2.0 to 30.5 months. Following log-transformation of both axes, the decline was linear. Similarly, concentration of all but one of the molecules declined with age when samples were restricted t...

Cycas micronesica leaf and strobili expansion patterns were measured in three locations and seaso... more Cycas micronesica leaf and strobili expansion patterns were measured in three locations and seasons on Guam and then were fitted with non-linear models to evaluate the use of the parameters for informing management decisions. All growth curves except for microstrobili height conformed to a negative exponential function. Microstrobili height development could not be fitted with any traditional linear or non-linear function, so spline models were used to smooth the effect of elapsed days. Leaf and leaflet expansion patterns were influenced by habitat and season, indicating development of the vegetative organ is plastic. In contrast, the models that described development of megasporophyll length, microstrobili height, and microstrobili diameter were not influenced by habitat or season. Moreover, seed diameter developmental patterns were only minimally influenced by location. These results indicate developmental patterns of the reproductive structures were primarily constitutive. We have demonstrated two empirical approaches to fitting models of Cycas micronesica organ growth and development and that both methods are useful for determining the influence of spatial or temporal factors in the timing of organ development. This approach may be used to inform horticultural or conservation questions of other rare cycad species.

Hortscience, Aug 1, 1996

To determine when a paper is to be presented, check the session number in the Program Schedule or... more To determine when a paper is to be presented, check the session number in the Program Schedule or the Conference at a Glance charts. The Author presenting the paper is indicated by an asterisk.

HortScience

Leaflets of carambola were restricted to a horizontal position for 3.5-h during late morning and ... more Leaflets of carambola were restricted to a horizontal position for 3.5-h during late morning and early afternoon on sunny days to determine the influence of natural leaflet movement on temperature and chlorophyll fluorescence. Adaxial temperature of these horizontal leaflets was 5-9 C higher than that of leaflets that were allowed to move in response to high light. Chlorophyll fluorescence was similarly affected. Leaflets that were allowed to move had a higher Fv/Fm than leaflets that were restricted in movement The results indicate that the presence of a pulvinus at the base of each leaflet of carambola leaves allows movement of the leaflet to avoid incident light. This natural leaflet movement under sunny conditions results in a lower temperature and a higher level of photochemical efficiency when compared with leaflets that are exposed to high light due to restricting their movement.


HortScience

The Abstracts that follow are arranged in numerical sequence by the abstract number. For Poster S... more The Abstracts that follow are arranged in numerical sequence by the abstract number. For Poster Sessions, the number preceded by PB (i.e., PB XXX) indicates the poster board number on which the poster will be mounted. Abstracts for Oral Sessions, Colloquia,and Workshops are grouped by sessions. To determine when a paper is to be presented, check the session number in the Program Schedule or the Conference at a Glance charts. The author presenting the paper is indicated by an asterisk.

HortScience

Leaf gas-exchange responses of A. souamosa seedlings to salinity were studied in sand culture in ... more Leaf gas-exchange responses of A. souamosa seedlings to salinity were studied in sand culture in a series of glasshouse experiments. Trees were irrigated with a complete nutrient solution as the control, or with this solution amended to 3 or 6 dS/m with sea salt. Inhibition of net CO2 assimilation, stomatal conductance of CO2, and transpiration was apparent 14 days after treatments were imposed, and continued to decline until day 30 to 35. The diurnal pattern of leaf gas exchange was not altered by salinity. Salinity reduced CO2, light energy, and water use efficiencies. Dark respiration and internal partial pressure of CO2 were unaffected by salinity stress. Results indicated that substrate salinity inhibited photosynthesis of A. souamosa via limitations on mesophyll capacity for CO2 assimilation and had little effect on gas phase limitations.

HortScience

The eyecare industry has used various instruments and methods for determining intraocular pressur... more The eyecare industry has used various instruments and methods for determining intraocular pressure. Some of the methods may be applicable for measurement of fruit firmness in the horticultural industry. We determined fruit firmness with an applanation tonometer, currently one of the most popular instruments in the eyecare industry. We then measured firmness of the same sample using a penetrometer with an 8-mm probe. Kiwi, mango, peach, strawberry, tomatillo, and tomato fruit were included in the study. With the exception of mango, tonometer and penetrometer measurements within a species were significantly correlated. The contact area of the tonometer probe was 1.5 mm2, which was less than 3% of the contact area of the penetrometer probe. The heterogeneous nature of mango mesocarp due to fibers and this large difference in contact area between the two instruments may have caused the lack of correlation for that species. The data indicate that tonometry may be useful for determining f...

HortScience

To determine when a paper is to be presented, check the session number in the Program Schedule or... more To determine when a paper is to be presented, check the session number in the Program Schedule or the Conference at a Glance charts. The Author presenting the paper is indicated by an asterisk.

HortScience

Cycas micronesica is an arborescent cycad with sclerophyllous, long-lived compound leaves that ar... more Cycas micronesica is an arborescent cycad with sclerophyllous, long-lived compound leaves that are produced in synchronized pulses. The photosynthetic characteristics of leaves in two sequential cohorts of ≈2 and ≈11 months after leaf expansion were determined in this study. Fluorescence yield following 30-min of light exclusion or from leaves engaged in photosynthesis under ambient light was measured throughout several 24-h periods to determine maximum quantum efficiency of PSII photochemistry and quantum efficiency under ambient light. Maximum quantum efficiency was similar for the two cohorts throughout the nocturnal period. Maximum quantum efficiency and quantum efficiency under ambient light declined following exposure to daily direct sun but recovered quickly each afternoon. This daily decline was greater for the older cohort than the younger cohort. Net carbon dioxide assimilation (Pn) was also determined using gas exchange, and light saturated Pn of the older cohort was 75% ...

HortScience

Two studies were conducted with `Known You 1' and `Sunrise' papaya seedlings to determine... more Two studies were conducted with `Known You 1' and `Sunrise' papaya seedlings to determine the combined influence of wind and drought stress on growth. For each study, 4-week-old nursery plants were transplanted into 2.6-L containers and placed in a protected site with rain exclusion provided by polypropylene cover. Industrial fans were used to provide unidirectional wind of ≈2 m/s for 12 hours per day to half of the plants; the remaining half of the plants received no wind. One half of the plants for each cultivar and wind combination were designated as well-watered and received daily irrigation. The remaining half of the plants were designated as drought-stressed and received 25% to 50% of the water applied to the well-watered plants. Plants were grown for 3 weeks under these experimental conditions. There were no interactions between the drought and wind main effects. The reduction in height, trunk cross-sectional area, total plant dry weight, and relative growth rate belo...


HortScience

The influence of plant size on recovery following defoliation of `Tainung 1' papaya was used ... more The influence of plant size on recovery following defoliation of `Tainung 1' papaya was used to study the role of respiratory sink size relative to photosynthetic surface area and the carbohydrate pool size available for remobilization. Defoliated (D) plants at three different ages: oldest, 24 weeks posttransplant (PT), supporting ≈8 weeks of fruit set; intermediate, 10 weeks PT, ≈2 weeks from initial flowering; and youngest, 4 weeks PT, were compared to an equal number of control plants. The oldest plants abscised all fruit <5.5 cm in diameter as a result of defoliation. Increase in stem height and basal circumference ceased on all plants and increase in fruit circumference ceased on the oldest plants following defoliation. Increase in stem height of D plants began again 3 weeks postdefoliation (PD) and returned to that of control plants by 6 weeks PD. Increase in basal circumference of D plants began again 6 weeks PD. Root density was observed on observation windows, and fi...


HortScience

Seedlings of Carica papaya L. `Waimanalo' (papaya) were transplanted into 27-L containers fil... more Seedlings of Carica papaya L. `Waimanalo' (papaya) were transplanted into 27-L containers filled with nonsterile composted landscape yard trimmings passed through a 1.3-cm screen. At transplanting, papaya plants were inoculated with either one of three different AMF communities or were not inoculated as control plants. Two of the AMF communities were from Arizona citrus orchards, and one AMF community was from an undisturbed western Chihuahuan Desert soil. After transplanting, papaya plants were grown for 4 months under well-watered conditions in a temperature-controlled (32 °C day/24 °C night) glasshouse (45% light exclusion). Control plants remained non-mycorrhizal. Total colonization of papaya roots by AMF communities ranged from 56% to 94%. Depending on mycorrhizal treatment, AMF arbuscules and internal hyphae were present in 30% to 60% and 20% to 24% of roots, respectively. Noticeably absent in papaya roots were AMF vesicles. Papaya height, trunk diameter, and leaf phosphor...

HortScience

The frequency of tropical cyclones is a major factor affecting the vegetation of the Mariana Isla... more The frequency of tropical cyclones is a major factor affecting the vegetation of the Mariana Islands, where these storms are called typhoons. An average of about one typhoon per year has passed within ≈100 km of Guam during the past 50 years. The physiognomy of Guam's natural and urban forests is largely determined by these typhoons. The impact of each typhoon is determined by a long list of interacting factors such as species characteristics; environmental and horticultural conditions preceding the typhoon; the intensity, direction, and duration of winds; the amount of rainfall associated with the typhoon; and the environmental and horticultural conditions following the disturbance. Many species survive typhoons by reducing aerodynamic drag of the canopy by abscising inexpensive leaves or breakage of small stems which results in an intact major structural framework. Speed of recovery for nonlethal damage following disturbance depends on nonlimiting conditions during recovery. T...

HortScience

Trade winds are a widespread horticultural consideration throughout the tropics. Growth and produ... more Trade winds are a widespread horticultural consideration throughout the tropics. Growth and productivity of most horticultural crops are not optimal on sites that are exposed to these chronic, unidirectional winds. We conducted four container studies on an exposed site, using clear plastic or screening material to provide three levels of wind exposure: 0%, 36%, or 100%. Two studies were conducted with direct-seeding, such that seedling emergence and early growth were determined for 7 weeks. Two studies were conducted using 8-week-old nursery plants that had been grown in a protected nursery. These plants were transplanted to the experimental site and grown for 6 weeks. Cultivars were `Known You 1', `Sunrise', and `Tainung 2'. Full exposure to wind reduced height up to 32%, increased root: canopy ratio up to 36% and exhibited no influence or slightly reduced stem cross-sectional area when compared with full protection from wind. Net carbon dioxide assimilation (Pn) was me...

Hortscience, May 1, 1994

The Abstracts that follow are arranged in numerical sequence by the abstract number. For Poster S... more The Abstracts that follow are arranged in numerical sequence by the abstract number. For Poster Sessions, the number preceded by PB (i.e., PB XXX) indicates the poster board number on which the poster will be mounted. Abstracts for Oral Sessions, Colloquia,and Workshops are grouped by sessions. To determine when a paper is to be presented, check the session number in the Program Schedule or the Conference at a Glance charts. The author presenting the paper is indicated by an asterisk.

HortScience, 2007

The concentration of two steryl glucosides and their sterol precursors were measured in gametophy... more The concentration of two steryl glucosides and their sterol precursors were measured in gametophyte tissue of Cycas micronesica K.D. Hill seeds before and after two storage treatments. For one study, intact 14-month-old seeds were stored at room temperature for 10 months. For the second study, cleaned (sarcotesta tissue removed) 22-month-old seeds were sown in perlite propagation beds, and ungerminated seeds were harvested after 14 months. Concentration of the steryl glucosides and sterols in the gametophyte tissue did not differ between the fresh seeds and the seeds after storage. The function of these metabolites is not known, but their unexpected stability for up to 14 months of storage indicates they are not metabolized during storage and may be vital during germination and early seedling growth. Implications on human exposure to their neurotoxic effects from gametophyte flour ingestion are discussed.

HortScience, 2001

Subsoil from an acid soil series was amended with CaSO 4 , MgO, or Ca(OH) 2 to identify chemical ... more Subsoil from an acid soil series was amended with CaSO 4 , MgO, or Ca(OH) 2 to identify chemical factors that may enhance papaya (Carica papaya L.) root growth in these soils. Root length of 'Red Lady' and 'Waimanalo' seedlings at two stages of development was increased by the addition of each of the materials. The increase in root length was similar for CaSO 4 or MgO amendments, and was greatest for Ca(OH) 2 amendment. These amendments increased dry weight of new roots for 'Red Lady' and increased root length per unit dry weight in one experiment for 'Waimanalo'. The results indicate that both Ca deficiency and Al toxicity may be responsible for limiting papaya root growth in the subsoils of the acid soils of Guam. Correcting these chemical factors should improve rooting depth, thereby increasing the volume of soil from which resources are accessible and lessening the susceptibility to toppling during tropical cyclones.

Horticulturae

The literature covering the biology, ecology, horticulture, and conservation of the critically en... more The literature covering the biology, ecology, horticulture, and conservation of the critically endangered tree Serianthes nelsonii Merr. was reviewed. The roots, stems, and leaves of this charismatic legume tree revealed highly plastic traits and responded positively to horticultural manipulations to improve the quality of container-grown transplants. Pre-sowing seed treatments of seed coat scarification and 1 h of imbibition generated 85% to 90% germination at a temperature optimum of 26 °C. Adventitious root formation on air layers and successful unions on approach grafts were 100%. Seedling and sapling growth was maximum under 25% to 50% sunlight transmission, limited irrigation to ensure adequate root zone aeration, repetitive stem tip pruning to increase root:shoot quotient, and thigmic stress to retain an orthotropic orientation of stems. In situ regeneration on Guam was substantial but recruitment from seedling to sapling was nil. High quality leaf litter chemistry enabled ra...