The effects of extracts from purple nutsedge tubers were determined on the germination, growth, root leakage, water status, and photosynthesis of an Upland cotton, DPL 5415, and a Pima cotton, Pima S-7. Tubers extracts inhibited secondary root growth of seedlings more than primary root growth. At 500 ppmw, primary root growth was inhibited 44 percent whereas inhibition of secondary root growth was 64 percent. Non-polar extracts were more inhibitory to growth than polar extracts. Cotton plants grown in soil treated with hexane extracts of tubers containing non-polar allelopathic substances also lost electrolytes from their roots indicating an effect on root function. The effects on root function resulted in perturbations to the capacity of the plants to maintain efficient water status. At 250 ppmw of the hexane extract, the plant water potential, the leaf water content, and the leaf osmotic potential decreased from -0.7 to -1.3 MPa, from 89 to 79 percent, and from -0.8 to -1.0 MPa, respectively. In addition, the photosynthetic capacity of cotton was decreased 50 percent in both cotton cultivars in the second and third day after transplanting to soil treated with 62 ppmw of the hexane extracts. Leaf dehydration to below 70 percent relative water content and a reduction of quantum yield was detected in DPL 5415 at 125 ppmw of the hexane extracts. However, Pima S-7 was capable of tolerating higher levels of dehydration and did not show the reduction of quantum yield. Leaf expansion and epicotyl growth were also inhibited by 30 and 37 percent, respectively, by the hexane extracts at 250 ppmw. Purple nutsedge tubers released volatile substances that inhibited growth when trapped and tested on cotton seedlings, and caused root leakage. GC analyses showed that both the hexane extracts of purple nutsedge tubers and the volatile compounds released from the tubers contained substances with retention times that are characteristic of sesquiterpenes. These results demonstrate that purple nutsedge tubers contain allelopathic substances capable of inhibiting the growth of cotton by interfering with membranes of root cells, disrupting water status, and affecting photosynthesis.

Biophysical models were developed for biomass accumulation, transpiration and carbon dioxide (CO₂) assimilation of Agave pacifica as functions of air CO₂ concentration, photosynthetic photon flux (PPF) and irrigation interval. Parameter estimation and validation were performed for the Gompertz's equation for biomass accumulation and for the Penman-Monteith equation for transpiration. A new biophysical model for CO₂ assimilation is proposed consisting of four components: stomatal opening and CO₂ fixation; malic acid accumulation; malic acid depletion; and photosynthetic carbon assimilation. The main and interactive effects of air CO₂ concentration, PPF and irrigation interval on biomass accumulation, transpiration and CO₂ assimilation of Agave pacifica were also determined.

Epicuticular wax (EW) forms the outermost layer over aerial portions of a plant. EW has been studied in plants for more than 100 years, yet there is a great deal that is still not known about epicuticular wax. The work in this dissertation has taken a broad view in investigating EW of Arabidopsis thaliana. In this dissertation I examined EW chemistry, EW structure, and mapped positions of existing and novel eceriferum or cer mutants. Additionally, I worked to develop new EW pathway models, establish correlations between EW chemistry and structure, and examine a possible functional role for EW in insect interactions. More specifically this dissertation project has attempted to expand the baseline knowledge of EW and of EW mutants in A. thaliana.

Many factors influence the salt tolerance of plants. This study investigated the effects of form and concentration of nitrogen fertilizer on the salt tolerance of 'Tifway' bermudagrass grown under four salinity levels in a nutrient solution. The design was a 4 x 2 x 2 factorial in an RCB design. The four salinity levels were 0 (1.6 to 3.6), 10, 22, and 42 dS m⁻¹. Nitrogen was applied in the NH₄⁺ and NO₃⁻ form and at 52.5 and 210.0 mg N L⁻¹ of nutrient solution. The results indicated that NH₄⁺ improved the salt tolerance of 'Tifway' bermudagrass in terms of aesthetic value (color and leaf firing), osmotic adjustment (free amino acid content), and tolerance of specific ion effects (Na, Ca, and the Na:K ratio). The 210.0 mg N L⁻¹ concentration improved the root:shoot ratio of 'Tifway' bermudagrass and reduced salt ion accumulation in shoots.

Eight-day-old mung bean seedlings (Vigna radiata L.) grown in hydropondic medium were osmotically stressed by exposing roots to increasing concentrations of NaCl up to 4 bars. They were transferred after 16 to 18 hours to a similar solution containing tritiated water (THO). Periodic samples were taken of water transpiring from the leaves and of tissue water obtained from the same leaves, frozen and ground; specific radioactivity was determined by a scintillation counter. Proportional to increasing stress, the labelling of tissue water was increasingly delayed, the time for equilibration of the specific radioactivity in the two fractions lengthened, and equilibration occurred at higher concentrations of THO. Thus stress causes transpirational water to be increasingly restricted to extra-cellular pathways. Further investigations of stomatal function by leaf surface, of anatomy and of growth patterns were unsuccessful in finding an explanation for this behavior but did reveal a transpirational circadian rhythm and a continual layer of (air?) space between the palisade and spongy mesophyll, the latter organized into two compact rows.

Improvements in the external color of Regreened 'Valencia' oranges were studied using ethylene gas. Twelve hour cycles of gassing were followed by the restoration of normal air concentrations with high humidity. Two temperatures, 14°C and 22°C were used with ethylene concentrations of 5, 10 μl/l as well as normal generated ethylene concentration in air for two weeks. The reflectance of the fruit was measured to indicate chlorophyll concentration changes. Chroma measurements were used to mimic the human eye response. The oranges treated at 22°C with either 5 or 10 μl/l ethylene gas lost their chlorophyll (greenness) and gained orange pigment (redness). Brightness increased more in the 10 μl/l ethylene than in the 5 μl/l concentrations. At 5 μl/l little evidence of stem-end decay was observed which indicates senescence was not accelerated. Some stem-end decay was observed in oranges treated with 10 μl/l of ethylene at 22°C an indication that shelf life had been reduced because of the treatments.

A two year study was conducted to determine the optimum timing of the initial post-plant irrigation for cotton (Gossypium hirsutum L.). A short-season Upland variety, DPL 20, was planted on 19 April 1993 and 15 April 1994 at the Marana Agricultural Center. Daily midday leaf water potential measurements were taken using the pressure chamber technique. Treatments, designated T1, T2, and T3, received the initial post-plant irrigation when the midday LWP measured -1.5, -1.9, and -2.3 MPa, respectively. Soil-water data was collected at 25 cm depth increments using neutron attentuation. Yields were 1263, 1244, and 1110 kg lint/ha in 1993 and 1229, 1176, and 1095 kg lint/ha in 1994 for T1, T2, and T3, respectively. When treatments were initiated, approximately 84 (T1), 62 (T2), and 32% (T3) of the total plant-available water was present in the upper 150 cm of the soil profile.

Pima pineapple cactus (Coryphantha scheeri var. robustispina) (PPC) is listed as endangered by the US Fish and Wildlife Service. This taxon occurs south of Tucson, Arizona and Sonora, Mexico. Knowledge of this plant's distribution, growth, and reproduction is important for management. Research has documented reduced plant vigor and lack of reproduction within Lehmann lovegrass stands. PPC density and seedling presence were described at five sites in two different vegetation types. Field observations of 72 plants at five sites were monitored from fall 1993 through summer of 95 and shadehouse studies were conducted. This research resulted in five conclusions: (1) fire-induced mortality of PPC may be related to Lehmann lovegrass, (2) PPC grows vegetatively in the spring, (3) flower buds are initiated in May and open after a few summer rains, (4) seed germination follows several summer rains, and (5) cross-pollination produces significantly more PPC seeds than self-pollination.

A highly sensitive photometric method for the quantitation of protein separated in SDS-PAGE micro-slab gels was used to determine the relative amounts of rubisco in palisade, spongy and guard cells of Vicia faba L. Cell types were obtained by dissection from freeze-dried leaf or by protoplast isolation. Protein profiles of palisade and spongy mesophyll were virtually identical. The rubisco large subunit (ls) was the most abundant protein in both mesophyll cell types (32-35%, protein basis). A comparison of mesophyll and guard-cell protein profiles indicated considerable differences. For guard cells from lyophilized tissue, the maximum possible contribution of the rubisco ls to total protein was 1.08%. Among guard-cell protoplast preparation, the maximum contribution of the rubisco ls was variable and greater (2-5%, protein basis), which is consistent with contamination by mesophyll. On a cell basis, these data indicate that the upper limit for guard-cell rubisco is 0.2% of that of mesophyll. These findings indicate that rubisco activity in guard cells is negligible, if it is present at all. / Kinetic properties of phosphoenolpyruvate carboxylase (PEPC) of guard cells of Vicia faba L. in different stage of stomatal opening were determined at two pHs and in the presence of malate. PEPC was "extracted" from individually excised cells in microdroplets of reagent. After fewer than 15 second, the reaction progress was monitored in real-time. Dephosphorylation of phosphoenolpyruvate (PEP) by endogenous phosphatase activity was corrected for by parallel assays with no Mg$\sp{2+}$. A pH increase from 7.0 to 8.5 decreased Km(PEPMg) 3.5-fold. Malate inhibited Km(PEPMg) at both pHs, but inhibition was 3-fold greater at pH 7.0. These data indicate that the combined effects of pH and malate can produce changes in enzyme velocity by more than 10-fold. However, PEPC Km(PEPMg) and maximum enzyme velocities of guard cells of closed, opening, and open stomata were affected similarly by pH and malate. These findings are consistent with a role of PEPC in cytoplasmic pH maintenance in guard cells. We discuss the physiological implications of the kinetics of PEPC in relation to guard-cell function. / Source: Dissertation Abstracts International, Volume: 50-03, Section: B, page: 0817. / Major Professor: William H. Outlaw. / Thesis (Ph.D.)--The Florida State University, 1989.

A rapid, quantitative stomatal bioassay was developed to test abscisic acid (ABA)-like inhibition of stomatal opening by ABA-conjugates in epidermal peels of Commelina communis L. The one-hour bioassay was sensitive to 0.02 $\mu$M (+)-S-ABA and was insensitive to 20 $\mu$M ($\pm$)-S-ABA-1-methyl ester, which is consistent with previous work. Replacement of the C-4$\sp\prime$ carbonyl on ABA with hydrazone conjugates rendered these ABA-conjugates ineffective in inhibiting stomatal opening. Competition assays between ABA and excess ABA-conjugates demonstrated that ABA-conjugates did not interfere with ABA inhibition of stomatal opening. Together, these findings demonstrate the unlikelihood of producing anti-idiotype antibodies against C-4$\sp\prime$-substituted ABA for identification of receptor(s) involved in stomatal closure. / In a separate study, the interactions of ABA, Ca$\sp{2+}$, and osmoticum on ABA accumulation, $\sp{35}$S-amino-acid accumulation and incorporation into protein and protein synthesis were investigated in "isolated" guard cells of Vicia faba L. The effects of eight permutations, $\pm$ ABA, $\pm$ Ca$\sp{2+}$ (EGTA) and $\pm$ osmoticum (mannitol), on $\sp{35}$S-protein synthesis were investigated during two one-hour radiolabelling periods: the first and the fifth hours of incubation. Guard cells were "isolated" by sonication of epidermal peels. Ca$\sp{2+}$ depletion (EGTA) and osmoticum inhibited ABA accumulation in guard cells. $\sp{35}$S-amino-acid accumulation was inhibited to $<$50% of control values by ABA during the first hour of incubation and to varying extents by ABA, Ca$\sp{2+}$ depletion and osmoticum during the fifth hour of incubation with combinations of effectors causing greater inhibition. Incorporation percentages were not significantly different between incubation conditions of the same time interval, indicating a correlation between $\sp{35}$S-amino-acid accumulation and incorporation into protein. Computer-assisted analysis of autoradiographs of $\sp{35}$S-proteins following separation by two-dimensional-micro-polyacrylamide-gel electrophoresis determined that changes in guard-cell $\sp{35}$S-protein profile were elicited by all three effectors and incubation duration. Although Ca$\sp{2+}$-dependent synthesis of proteins was discerned consistently during the fifth hour of incubations, Ca$\sp{2+}$-dependent synthesis of ABA-induced proteins was not discerned. ABA- and osmotic-induced synthesis of similar protein(s) was not discerned consistently during either radiolabelling period. These results are based on a conservative interpretation of changes in $\sp{35}$S-protein profiles that allowed for comparisons among all incubation conditions. / Source: Dissertation Abstracts International, Volume: 56-04, Section: B, page: 1770. / Major Professor: William H. Outlaw, Jr. / Thesis (Ph.D.)--The Florida State University, 1995.