Using in vitro systems, numerous authors have cited the sensitivity of pollen tube growth to high temperature as a major cause of low yields for crops with valuable reproductive structures. We investigated the hypothesis that in vivo fertilization efficiency would be negatively affected by heat stress-induced changes in energy reserves and calcium-mediated oxidative status in the pistil. Gossypium hirsutum plants exposed to optimal (30/20 degrees C) or high day temperature (38/20 degrees C) conditions during flowering were analyzed for fertilization efficiency via UV microscopic observation of pollen tube-containing ovules and for soluble carbohydrates, adenosine triphosphate (ATP), calcium, antioxidant enzyme activity and NADPH oxidase (NOX; EC 1.6.3.1) activity in the pistil. Leaf measurements included gas exchange, chlorophyll content, quantum efficiency and ATP content of the subtending leaf on the day of anthesis. In the pistil fertilization efficiency, soluble carbohydrates, ATP content and NOX activity declined significantly, whereas water soluble calcium and glutathione reductase (EC 1.8.1.7) activity increased, and superoxide dismutase (EC 1.15.1.1) activity remained unchanged. In leaves, heat stress decreased photosynthesis, quantum efficiency and chlorophyll content, but increased stomatal conductance. We conclude that decreased source leaf activity either inhibits pollen development, tube growth through the style or guidance to the ovules as a result of an insufficient energy supply to the developing pistil. We further conclude that a calcium-augmented antioxidant response in heat-stressed pistils interferes with enzymatic superoxide production needed for normal pollen tube growth and fertilization of the ovule.

Jefferson counties in Arkansas to assess nonpoint source water pollution. During these 3 years, 59-62 lake and river/ stream sites were sampled eight times and screened for 17 pesticides commonly used in Arkansas. Pesticides were extracted by solid-phase extraction (SPE) disks. Extracts were analyzed by gas chromatography-electron capture detection (ECD) and high-performance liquid chromatography-UV detection (LCUV). Detections were confirmed by gas chromatography-mass spectroscopy (MS) or co-chromatography. The 256 detections during the survey represented 14 pesticides. Metolachlor (25% of total detections), atrazine (22%), norflurazon (16%), and cyanazine (14%) were the most commonly detected compounds. A total of 5% of the total detections was above health advisories. Spring and summer samples provided 73% of the total pesticide detections. Rivers and streams were responsible for 62% of the detections. The highest number of repeated detections of the same pesticide at a site was for cyanazine (six of eight sampling periods).

The stability of various pesticides in water at 4 °C was compared with their stability on C-18 SPE disks under three storage regimes. The disk storage regimes involved using the disk to extract the chemical from water, removing the disk and placing it in a plastic bag, and then storing it at either -20 or +4 °C for 1 day and then -20 °C for the remainder of the storage period. The storage periods included 0, 3, 30, 90, and 180 days. The percent recovery of each chemical was determined and used to compare storage treatments. Results indicate that the pesticides have equivalent or greater stability on solid-phase extraction disks compared to their storage in water at 4 °C. The data suggest that freezing the disk after pesticide loading is the most favorable storage option. Results show that field extraction/storage methodology is feasible, which could improve the reliability of future environmental water sampling procedures.

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Japanese honeysuckle presents a serious problem to the economically attractive natural regeneration of loblolly and shortleaf pine. This research investigated the potential allelopathic interference mechanisms of Japanese honeysuckle in relation to pine regeneration and growth, which may provide insight into overcoming this problem. The allelopathic potential of root exudates and leaf litter from Japanese honeysuckle was tested against loblolly and shortleaf pine seedlings. When Japanese honeysuckle and loblolly pine seedlings were grown using the same irrigation reservoir, there was no significant effect on the growth of either pine species. Exudates of Japanese honeysuckle grown as a pure culture in donor cups also produced no growth effects on pure-cultured pine seedlings grown in acceptor cups. In other assays, aqueous extracts of Japanese honeysuckle leaf tissue were toxic to duckweeds at concentrations well below levels where plasmolysis might cause effects. When Japanese honeysuckle leaf tissue was added to soil at a rate of 2 g tissue 100 g−1 soil, mean seedling height at 128 d after planting was reduced by as much as 40%. Moreover, pine seedlings grown in the presence of Japanese honeysuckle tissue exhibited significant chlorosis of the shoot and needles. Gas chromatography–mass spectroscopy analyses and high-performance liquid chromatography of Japanese honeysuckle leaf tissue aqueous extracts confirmed the presence of five compounds previously identified as possible allelochemicals: 4-hydroxycinnamic acid; 2-hydroxycinnamic acid; 3,4-dihydroxybenzoic acid; 3,4-dihydroxycinnamic acid; and chlorogenic acid. Results indicate that allelopathy plays at least a partial role in Japanese honeysuckle interference with loblolly and shortleaf pine.