Call number: LD2668 .T4 1985 M62 / Master of Science

Call number: LD2668 .T4 1985 R422 / Master of Science

No description available.

A study was conducted in the field to test whether stomatal sensitivity to water stress can be used as a selection criterion for drought tolerance in two pearl millet genotypes. In both cultivars, stomatal aperture was significantly reduced by the water stress. However, the proportion of reduction per 20 mm decrease in applied water was much higher for the hybrid than for the female parent. This is clearly an indication of a higher stomatal sensitivity in the hybrid, which probably explains the superior performance under water stress that was previously observed in this genotype.

No description available.

Eleven full season hybrid grain sorghums, representing seven commercial sources, were grown on a silty clay soil south of Duncan. The test plots were managed the same as the rest of the field planted to DeKalb 69. Grain yields ranging from 6911 to 4546 pounds per acre were obtained, with DeKalb 69 the top yielder.

Nine medium to medium -late maturing grain sorghum hybrids were compared for yield, percent moisture at harvest, bushel weight, plant height, percent bird damage and standability. The highest yielding entry in the trial was a new hybrid from Northrup King (NK 2656). Its yield of 6185 pounds per acre was 11% higher than the most, commonly grown hybrid in the area.

The capability to measure the magnitude of water stress in plants is useful for precision irrigation scheduling and other purposes. This paper reports an evaluation of leaf (TL) and canopy (Tc) temperatures, leaf minus air (TL -Ta) and canopy minus air (Tc -Ta) temperatures, and leaf water stress index (LWSI) and crop water stress index (CWSI) in detecting stress in pearl millet (Pennisetum americanum (L.) Leeke) over two growing seasons. Baselines which were used to compute LWSI and CWSI were obtained. The upper and lower baselines for the Tc data, respectively, were Tc -Ta = 4.10 C and Tc -Ta = 3.87- .2001VPD where VPD is vapor pressure deficit in mbars. For the TL data, the upper and lower baselines, respectively, were TL -Ta = 1.97oC and TL -Ta = 1.308- .03006VPD. Tests against photosynthesis, transpiration, and grain yield showed that LWSI and CWSI are better indices of stress than TL -Ta, Tc -Ta, TL, Tc, or Ta. Average seasonal LWSI and CWSI ranged from approximately 0.03 for non- stressed to 0.80 for stressed plants. The reliability of LWSI and CWSI to detect stress and their relation with grain yield suggested the possibility of using these indices for irrigation scheduling decisions.

Ce travail a pour objectif de développer un nouvel indicateur quantitatif des conditions hydrologiques passées fondé sur la composition isotopique en hydrogène (δD) d’un biomarqueur sédimentaire spécifique du millet commun (Panicum miliaceum), la miliacine. L’étude de la pertinence spatio-temporelle de cet indicateur révèle que le δD miliacine de plants de millet dans un champ, bien que dispersé, suit une loi gaussienne. Le δD miliacine du sol correspond au δD miliacine des plantes cultivées l’année précédente. L’évolution interannuelle du δD miliacine est globallement parallèle à celle du δD des eaux météoriques, les différences pouvant être attribuées à des différences d’humidité. La comparaison des valeurs de δD miliacine dans des sédiments du même âge prélevés sur deux archives distinctes dans le Lac du Bourget témoigne que l’archivage de cet indicateur est intègre de manière homogène les conditions climatiques ayant régné dans le bassin versant. La culture de millet en chambre climatique démontre que, si le δD de l’eau de source est le principal facteur controlant le δD miliacine, ce dernier est très étroitement corrélé au δD de l’eau de la feuille. De légères différences de fractionnement biosynthétique net entre n-alcanes et miliacine sous deux conditions d’humidité laissent supposer que l’analyse combinée de biomarqueurs sédimentaires issus de voies synthétiques distinctes permettrait d’accéder à la fois aux variables paléoenvironnementales clé que sont le δD de l’eau de source et l’humidité. / This work aims at developing a new proxy of past hydrological conditions based on the hydrogen isotopic composition (δD) of a sedimentary biomarker that is specific for broomcorn millet (Panicum miliaceum), miliacin. Analysing the spatio-temporal relevancy of this proxy reveals that miliacin δD values of plants cultivated in the field, although dispersed, follow a Gaussian law. Soil miliacin δD values are the same as those found for plants grown the year before. Interannual variations in plant miliacin δD values roughly parallel those of precipitation δD values, slight differences being attributed to differences in relative humidity. The comparison of miliacin δD values in sediments deposited in two distinct settings at the same time in Lake le Bourget attests that this proxy homogeneously integrates climatic conditions over the whole catchment. Cultivation of millet plants in climatic chambers allowed demonstrating that, although source water δD is the principal controlling miliacin δD values, this later is closely correlated to leaf water δD. Slight differences in net biosynthetic fractionation between n-alcanes and miliacin under two relative humidity levels imply that the combined analysis of sedimentary biomarkers produced through distinct biosynthetic pathways could help discriminating between source water δD and relative humidity in paleoenvironmental studies.

Cette thèse intitulée "Le temps en métamorphose dans les œuvres de Richard Millet" s’appuie judicieusement sur quatre œuvres (La gloire des Pythre, L’amour des trois sœurs Piale, Lauve le pur, Ma vie parmi les ombres) dont la dernière ferme le cycle de Siom. Elles forment un cycle dense qui se prête parfaitement au questionnement sur le temps. Dans ce cycle, Millet écrit en effet pour retenir le temps, en témoin d’une civilisation rurale finissante et dans une posture d’ "antimoderne" (selon la définition d’Antoine Compagnon). Il y conduit une méditation ininterrompue sur le temps, la finitude, la langue que nous avons essayé d’analyser de très près. / This thesis on "Time in metamorphosis in the works of Richard Millet" wisely based on four works Pythres Glory, The love of three Piale sisters, Lauve le pur, My life in the shadows which closes the last cycle Siom. They form a dense cycle that lends itself perfectly to the questioning time. In this cycle, Millet wrote indeed to retain over time, witnessed a graduate rural civilization and a posture of "anti-modern" (as defined by Antoine Compagnon). He led an uninterrupted mediation on time, finitude, language that we have tried to analyse closely.