The alkaloid fraction in tall rescue is associated with poor animal performance during summer grazing. In an effort to relate alkaloid response to field situations, the effects of water stress, temperature, N application, and harvest interval on accumulation of N‐acetyl and N‐formyl loline in G1‐307, a Lolium‐Festuca hybrid derivative (2n = 42) experimental strain of tall rescue, were studied in greenhouse and controlled environment chamber experiments. The N‐acetyl loline increased five‐times above control levels by the ninth week of severe water stress. The N‐formyl loline increased two‐times above control levels by the 12th week. Protein loss, decreased dry weight, and low plant water potentials were among possible causes for increased alkaloid concentrations. The N‐acetyl loline increased five‐fold and N‐formyl loline increased three‐fold from initial levels by the 10th week of 21/15 C temperature regime. The high (32/27 C) and low (16/10, 10/7 C) temperature regimes depressed alkaloid accumulation. Accumulation of N‐acetyl and N‐formyl lolines was not positively associated with N application. The largest N application tended to result in the least accumulation of alkaloids. Forage regrowth obtained after harvesting 6 to 8 weeks accumulated forage contained significantly higher concentrations of N‐acetyl and N‐formyl loline.

ceed plant needs or when fertilizer applications are not synchronized with plant uptake. Today, methods for Nitrogen fertilization is a required production practice for cotton predicting N status of cotton grown in the Midsouth are (Gossypium hirsutum L.) with risks arising from under-and overeither inaccurate or require additional studies before fertilization. Tissue testing for diagnosing N deficiencies in crops can use leaf blades and the total N concentration, but this practice has the critical values used in tissue testing can be accepted not been rigorously examined in cotton. The primary objective of and used by farmers and extension personnel (Bock and these experiments was to determine the leaf-N concentration of the Adams, 1980;Sabbe and Zelinski, 1990). Critical values uppermost, fully mature leaf blade below which yield loss could be are used in tissue testing to separate N-deficient from expected. Nitrogen-rate field experiments were conducted at 12 re-N-sufficient plants. Plants with tissue samples that consearch station and farm sites in the Midsouth USA in Louisiana, tain N levels above the critical value are considered Arkansas, Mississippi, and Alabama in 1996 and 1997. Leaf-blade sufficient in N and no N fertilizer would likely be needed total N concentrations associated with yield loss were 4.3% N at early while those plants with N concentrations below the critibloom (R 2 ϭ 0.50) and 4.1% N at mid-bloom (3 wk after early bloom, cal value are considered deficient in N and N applica-R 2 ϭ 0.32). The likelihood of applying N when not needed could be tions might be advisable. Inaccurate critical values can reduced by lowering the early bloom critical value to 3.9%. Only 4% result in the over-application or under-application of N. of all samples sufficient in N would have been incorrectly diagnosed N deficient at that critical value, but 44% of all deficient samples The principal method for assessing cotton-N status would have been misidentified as N sufficient. Reduced yields due under irrigated conditions is the petiole nitrate test. The to over application of N were evident in some samples with leaf N test is a snapshot of N movement to leaves because it between 4.6 and 4.8% at early bloom. These concentrations were also is an analysis of a transportable form of N, and because common for N-sufficient plants, making accurate diagnoses of the petioles or leaf stems are the conduit for nitrate transover application of N unlikely. Our leaf-N critical values probably port from roots. Petiole nitrate is a sensitive measure of differ from previously established values because earlier values were N movement to leaves, but it is probably hypersensitive derived via survey techniques and because faster fruiting cultivars because of soil moisture effects on petiole nitrate. Remay require higher leaf N.searchers have found petiole nitrate testing a better measure of soil moisture status than cotton-N status (Bock and Adams, 1980; Touchton et al., 1981). Another

The alkaloid fraction of tall rescue (Festuca arundinacea Schreb.) has been implicated in poor forage quality but the alkaloid content of tall rescue varies greatly amongrazing seasons, pastures, and individual plants. The objective of this research was to identify the association between the presence of E. typhina (Fr.) Tul. in the plant and the N‐formyl and N‐acetyl loline alkaloids. Plants were grown in benomyl‐treated soil in the greenhouse to control the fungus and treated plants and seed from treated plants were established in the field to provide seed and plant tissue for analysis. The fungus was eliminated or its development severely inhibited by growing tillers for 6 weeks in soil treated with benomyl.Accumulation of N‐acetyl loline and N‐formyl lollne in tall fescue was positively associated with the presence of the endophytic fungus, Epichloe typhina. Leaf tissue from treated plants contained very small amounts of N‐acetyl or N‐formyl loline. Plants from which E. typhina had been eliminated and that had been established in the field remained free of the fungus for at least 3 years.

In certain environments, reduced leaf‐open canopy cottons (Gossypium hirsutum L.) allow more light penetration and air circulation within their canopies than do normal leaf types. However, too much reduction in canopy can reduce overall productivity and economic yield. Removal of floral buds (squares) early in the season has been shown to result in larger plant size. Square removal was carried out in the field (fine‐silty, mixed, thermic, Aquic Fragiudalf soil type) on normal, okra, and super okra leaf type near‐isogenic lines of a ‘Stoneville 213’ background cotton for 3 and 6 weeks to determine i) if improved yield could be obtained in one or both open canopy types by enlarging the canopy and ii) if delaying fruit set produced differential responses in these leaf types. Results would form a basis for development of a boll weevil (Anthonomus grandis Boh.) trap crop system using exogenous chemicals to effect square abscission. Removal of squares increased plant height, leaf area index (LAI) and number of sympodial branches. The super okra leaf type produced the greatest responses to square removal. Fruit set was more rapid and occurred during a shorter interval for all leaf types undergoing square removal for 3 weeks, but the greatest response was obtained from super okra. Comprehensive analysis in 1983 indicated the rapid fruit set was due primarily to more sympodia fruiting simultaneously. The 3‐week treatment was more consistent in this response than the 6‐week treatment because of the generally shorter horizontal and vertical flowering intervals. Economic yield of normal and okra leaf types was generally not improved by square removal, whereas the super okra leaf type in the 3‐week square removal treatment produced an average 23.5% greater lint yield than its control. Differences in lint percentage were significant between treatments in 1981 with significant leaf type by treatment interactions in 1983. The data indicate that the super okra leaf type had the most consistent responses to 3 weeks of manual square removal. These results imply that this leaf type would produce the best response to exogenous chemical abscission of squares and the greatest chance of recovery from early season insect pressure.

Abscission or abortion of the initial cotton (Gossypium hirsutum L.) flower buds or bolls increases the importance of retaining fruit on adjacent or subsequent fruiting positions. Use of the plant growth regulator mepiquat chloride (MC) (N, N dimethylpiperidinium chloride) improves boll retention on lower reproductive branches (sympodia), reduces vegetative growth, and in some cases reduces upper sympodial productivity. Our objective was to determine the effect of doses and application timings of MC and different levels of early flower bud removal on within‐plant yield distribution. Zero or an average of two or four flower buds located at first positions on lower sympodia were removed from each plant prior to MC applications at two field locations in 1992. This bud loss resulted in higher retention at second positions on lower sympodia and on slightly higher sympodia. Two biweekly doses of 24.5 g ha−1 of MC applied at early bloom also enhanced compensation and yield on lower sympodial second positions. Primarily at one location, four weekly MC doses of 12.25 g ha−1 each beginning when buds were 1 cm long resulted in increased monopodial branch yield when there was moderate early bud loss. Depending on field location, one or the other of the MC treatments reduced the number of fruiting positions and yield on higher sympodia when fruit retention on lower sympodia was high. Loss of early buds, which resulted in small increases in vegetative growth, ameliorated this effect. The biological responses produced by early bud loss and MC treatments interacted positively. After early bud loss, plants treated with MC generally improved compensation on lower sympodia without negative effects on upper sympodia.