Glyphosate treatments to glyphosate-resistant (GR) cotton have been associated with poor pollination and increased boll abortion. Anatomical studies were conducted to characterize the effect of glyphosate treatments on the development of male and female reproductive organs of cotton flowers at anthesis. In comparison with nontreated plants, glyphosate applied at both the four-leaf stage postemergence (POST) and at the eight-leaf stage POST directed inhibited the elongation of the staminal column and filament, which increased the distance from the anthers to the receptive stigma tip by 4.9 to 5.7 mm during the first week of flowering. The increased distance from the anthers to the stigma resulted in 42% less pollen deposited on stigmas of glyphosate-treated plants than in nontreated plants. Moreover, pollen from glyphosate-treated plants showed numerous morphological abnormalities. Transmission electron microscopy showed the presence of large vacuoles, numerous starch grains, and less organized pockets of the endoplasmic reticulum containing fewer ribosomes in pollen from glyphosate-treated plants than from nontreated plants. Pollen development in glyphosate-treated plants is likely inhibited or aborted at the vacuolate microspore and vacuolate microgamete stages of microgametogenesis, resulting in immature pollen at anthesis. Although stigmas from glyphosate-treated plants were 1.2 to 1.4 mm longer than those from nontreated plants, no other anatomical differences in stigmas were visibly evident. The presence of the GR 5-enolpyruvylshikimate-3-phosphate synthase (CP4-EPSPS) enzyme from Agrobacterium sp. strain CP4 was quantified in reproductive and vegetative tissues using enzyme-linked immunosorbent assay. The content of CP4-EPSPS in the stigma, anther, preanthesis floral bud (square), and flower petals was significantly less than that in the vegetative leaf tissue. Glyphosate effects on the male reproductive development resulting in poor pollen deposition on the stigma, as well as production of aborted pollen with reduced viability, provide a likely explanation for reports of increased boll abortion and pollination problems in glyphosate-treated GR cotton.

With green sugarcane (interspecific hybrids of Saccharum spp.) harvesting, 6 to 24 Mg ha 21 of postharvest residue is deposited on the field surface covering the sugarcane stubble that must reemerge for several ratoon crops. The objectives of this research were to: (i) determine if postharvest residue possesses allelopathic, autotoxic, and hormetic properties; (ii) determine the interaction of soil type with possible autotoxic effects; and (iii) identify a reliable indicator species. Extract concentrations consisted of 0, 0.1, 10, 25, and 100% of the original solution of a 1:28 tissue to water extract. The higher concentrations of residue extracts exhibited autotoxicity by delaying early leaf development. The lower extract concentration of 10% increased sugarcane bud germination by 45% compared with the control, indicating hormetic effects. Allelopathic activity on tall morninglory (Ipomoea hederacea Jacq.) was more pronounced on a light soil; germination and radical length were reduced by all concentrations by an average of 42% and 8 mm, respectively, compared with the control. Seedling dry weights were reduced by an average of 10 mg by the 10, 25, and 100% extract concentrations relative to the control. On the heavy soil, only the 100% concentration reduced radical length and weight by 5 mm and 4 mg, respectively, relative to the control. Extract effects on oat (Avena nuda L.), rye (Secale cereale L.), and tomato (Lycopersicon esculentum Mill.) showed poor correlation with effects on sugarcane. Chemical analysis by gas chromatography/ mass spectrotometry indicated the extract contained benzoic acid. Further studies are needed to establish the impact of benzoic acid in natural settings.

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degree days during cotton BMAP, which is defined as the number of days from open bloom to open boll (Gip-Degree days are often used for cotton (Gossypium hirsutum L.) son and Joham, 1968). Boll maturation period has been growth monitoring and management. The objectives of this research are to determine if 15.5؇C is an accurate lower-threshold temperature shown to increase with the advance of the growing seato monitor the boll maturation period (BMAP) for cotton in the son because of the gradual reduction of temperature northern, rainfed region of the U.S. Cotton Belt, to investigate other during the season (Anderson and Kerr, 1938; Hawkins climatic factors in this cotton region that may improve the accuracy and Servis, 1930). Gipson and Joham (1968) reported of the current degree day system for cotton, and to evaluate degree day that mean night temperature was more influential on models that include both an upper-and lower-threshold temperature. BMAP than mean day temperature as mean night tem-Cotton was planted at three different timings in 2001 and 2002 to peratures in this study were considerably lower than provide different climatic regimes during the BMAP. On 10 typical mean day temperatures. For night temperatures ranging plants per plot, all first-position flowers were individually tagged with from 5 to 25ЊC, BMAP was increased by 3.4 d per degree date of flower opening and were then harvested at full maturity.decrease in mean temperature (Gipson and Joham, 1968).Daily weather data consisted of maximum, minimum, and average air temperature; maximum and average soil temperature; average soil Conversely, Yfoulis and Fasoulas (1973, 1978) reported moisture; maximum and average solar radiation; and maximum and that both day and night temperatures are highly influenaverage photosynthetically active radiation. The 17؇C degree day tial on BMAP. Reddy et al. (1997) reported that BMAP model, which used 17؇C as the lower threshold, provided the best was reduced by 6.9 d per degree of increased mean adjusted r 2 (0.2715) of all the single-variable models; the degree day temperature from 21.5 to 30.5ЊC. 15.5؇C model had an adjusted r 2 of 0.2276. The best model using both Although, mean temperatures influence BMAP, the upper and lower temperature thresholds was DD3017, using 30 and limiting factor for boll development in many growing 17؇C as the thresholds, and had an adjusted r 2 of 0.2452. Adding averareas is the minima and maxima, not necessarily the age, minimum, and maximum air temperatures to the DD15.5, DD17, mean temperature (Liakatas et al., 1998; Yfoulis and and DD3017 models reduced coefficient of variation and mean square Fasoulas, 1973). Research has indicated that optimal error and increased adjusted r 2 values.