Browsing by Subject "Roots (Botany)"
Now showing 1 - 13 of 13
Results Per Page
Sort Options
Item Cambial periodicity in the rhizome of Ephedra coryi(Texas Tech University, 1956-08) Scott, Billy DaveNot availableItem Environmental influences on Bradyrhizobium sp. survival and nodulation potential on peanut(Texas Tech University, 2003-12) Radtke, Michelle LeighPeanut (Arachis hypogaea) is an important legume crop currently grown in West Texas and obtains much of its nitrogen through a symbiotic relationship with compatible Bradyrhizobium strains. However, West Texas soils may not contain the specific bradyrhizobial strain required and, therefore, inoculation is essential. The success of inoculation is often limited by several factors, including high sandy soils, and high soil temperature commonly found in West Texas. The goal of this research was to determine if these environmental conditions have an effect on the survivability of bradyrhizobial inoculants and the ability of inoculants to infect peanut plants under these conditions. Three commercial bradyrhizobia inoculants were tested for their ability to survive at temperatures 30°, 37°, and 40°C and pHs 6, 7, and 8 in laboratory culture. The inoculants were differentially affected in their ability to survive the higher temperature regimes. Experiments were also conducted to determine the effect of high root temperature on nodulation of peanut. One peanut variety (Flavor Runner 458) was inoculated and exposed to diurnal temperatures of 25°C/10°C and 40°C/25°C. Nodulation was strongly affected by the high temperature regime, while pHs tested did not significantly influence inoculant effectiveness. Results have practical implications for West Texas peanut farmers who plant into hot, dry soil even if fields are irrigated within 24 hours.Item Identification of molecular markers linked to root penetration ability in rice (Oryza sativa L.)(Texas Tech University, 1998-08) Pathan, Md. SafiullahDrought is a major abiotic factor that reduces rice production in rainfed lowland environment. More than 90% of the world'e rice is grown and consumed in Asia. One third of the South and Southeast Asian rice is grown in rainfed lowland environment with shallow rooted indica genotype. In rainfed lowland environment, soils are subjected to compaction and periodic water deficiencies at any stage of the crop growth. Rice root traits such as a high number of penetrated roots, thick penetrated roots, and high root penetration ability through the compacted soil layers play a vital role in the drought resistance mechanism. Breeding for root traits related to drought resistance has been limited due to a lack of suitable techniques for evaluating these traits under field conditions. In this situation, mapping and tagging of drought related root traits using molecular markers is a novel approach for varietal improvement. The main objective of this study is to identify molecular markers like restriction fragment length polymorphiem (RFLP) associated with total root number, penetrated root number, penetrated root thickness, and root penetration ability of indica rice through wax-petrolatum layers simulated as compacted soil layers. The mapping population of thie study was composed of 166 recombinant inbred lines (RILs) developed from two indica genotypes. This population wae evaluated twice in the greenhouse, in the summer and the fall. Between the two experiments, total and penetrated root numbers were higher in the summer than those of the fall experiment. Favorable environmental conditions, like higher temperature, longer day length, and higher solar radiation contributed to the optimum growth of the plants in the summer season. Data were collected for total root number (TRN), penetrated root number (PRN), and penetrated root thickness (PRT). Root penetration index (RPI) wae derived as the ratio of penetrated root number with total root number. Significant genetic variation was observed for all traits and significant correlation was also found between different traits. The TRN varied from 71-328 in the summer and 45-213 in the fall. The PRN varied from 14-122 in the summer and 6-57 in the fall. The RPI varied from 0.08-0.56 in the summer and 0.06-0.55 in the fall experiment. The PRT varied from 0.40-1.18 mm in the summer and 0.40-1.10 mm in the fall.Item Influence of varying replacement of potential evapotranspiration on water use efficiency and nutritive value of three Old World bluestems (Bothriochloa spp.)(Texas Tech University, 2004-05) Philipp, DirkForage systems offer alternatives to traditional cropping systems in the Texas High Plains, but information on water management is lacking. This research investigated whether differences in water use efficiency (WUE; kg total seasonal dry matter [DM] yield ha"' mm"' water [precipitation, irrigation, and soil water depletion]) existed among species of old world bluestems (Bothriochloa spp.). Additionally, effects of irrigation amounts on forage nutritive value and plant morphology were explored. Established stands of three Bothriochloa species ('Dahl' [bladhii]; 'Caucasian' [caucasica]; and 'Spar' [ischaemum]) were surface drip-irrigated weekly during the growing season to replace: 1) 0% (dryland); 2) 33% (low); 3) 66% (medium); and 4) 100% (high) of potential evapotranspiration minus precipitation during 2001,2002, and 2003. Soil organic carbon as influenced by irrigation level and optimum metabolic temperature for growth were investigated in 2003. Each species and water treatment was replicated three times in a complete randomized block design with a split plot treatment arrangement. In 2001 and 2002, no differences in water use efficiencies among species were found. Averaged across these 2 yr, WUE of 19.0, 19.3, and 15.3 kg ha"' mm"' were observed for Caucasian, Dahl, and Spar, respectively. In 2003, Caucasian produced 16.9 kg ha" mm', differing (P < 0.05) in slope fi-om Spar (7.4 kg ha"' mm"') but Dahl (12.4 kg ha"' mm"') was not different in slope from either Caucasian or Spar. Maximum seasonal DM yield was obtained with Caucasian under high irrigation (18.0 Mg ha"') vs. Dahl (15.2 Mg ha") and Spar (12.55 Mg ha"') averaged over all years. Percentage dry matter digestibility (DMD) was higher (P < 0.05) in all forage species irrigated at a low level (58% DMD) than for other water treatments (57, 56, and 55% DMD for dryland, medium, and high irrigation, respectively). Dahl generally averaged higher (P < 0.05) percentage crude protein (CP) than other species during the growing season. More differences in percentage CP were observed between dryland and irrigated forages than within the irrigated treatments but CP would have met nutritional needs of most livestock only in May. In all species, percentages total nonstructural carbohydrates (TNC) and DMD and leaf: stem ratio declined while percentage cell wall increased with increased irrigation amount in the first half of the growing season. Effects of irrigation on cell wall, TNC, and DMD appeared related to changes in plant morphology (leaf:stem) and to an increase in physiological age as indicated by growth stage (mean stage count and mean stage weight). Leaf:stem ratio following hay harvest in July showed fewer effects of irrigation treatments but ratios of live:dead plant material generally increased during the growing season in response to increased irrigation (linear effects; P < 0.05). Soil organic carbon was higher (P < 0.05) in all irrigated soils (5.5 g 100 g"') compared with dryland (4.6 g 100 g"') but did not differ among irrigation treatments. Optimum metabolic temperatures for growth of Caucasian, Spar, and Dahl old world bluestems were 24, 24, and 28°C, respectively. Our data suggest that differences in WUE among Bothriochloa species can be identified, and that yield, chemical composition, and morphology can be manipulated through irrigation management to optimize total nutrient yield and nutritive value.Item Intercropping of sorghum and cowpeas under dryland conditions: effect on water use, root distribution, and plant growth(Texas Tech University, 1984-12) Davis, Jessica GNot availableItem Relationship between observations in mini-rhizotrons and true root length density(Texas Tech University, 1985-08) Upchurch, Dan RoyceThis project has resulted in the development of two models which can be applied to the mini-rhizotron technique for root observations. The models are based on probabilistic assumptions concerning root growth directions in the soil. The models apply to the average number of roots which intersect the wall of several tubes buried in the soil, and not to individual observation tubes. The usefulness of the mini-rhizotron technique has been expanded to include indications of the orientation of the root system through the ratio hypothesis. The conversion of root counts to root length density (RLD) has been given a mathematical basis, with few assumptions. The primary disadvantage of the system is the number of samples required. By determining the ratio of the number of roots which intersect the top to the number which intersect the bottom, the model predicts the direction of deviation from a random orientation. Observations made on the wall of a trench confirmed the horizontal orientation of a cotton root system and the existence of upward growth which had been predicted by the model from observations in mini-rhizotrons. A model, relating the number of root intersections on a mini-rhizotron to the bulk soil RLD, predicted a linear relationship. The average length to associate with each intersection was determined assuming that root growth was affected only after an intersection occurred, that roots can be represented by straight line segments, and that root growth direction followed some probability density function. The assumption that roots can be represented by straight lines can be removed if the tortuousity of the path of root growth is known. The length can be weighted by the probability of root growth in that direction, if it is known. The correlation coefficient between RLD determined by applying the model to mini-rhizotron observations and that from soil cores was low but significant at the 99% level, when all treatments and angles were considered. The correlation was largest, 0.70, in the dryland treatment at the 30 installation angle. The higher correlation in the dryland treatment may have resulted from of the reestablishment of the natural soil structure at the interface as the soil dried. The statistical properties of the mini-rhizotron system emphasize the need for a large sample size. The number of samples required to detect specific differences in RLD is large for both soil cores and mini-rhizotrons when the difference is small. The decision about the number of tubes to install will be affected by the reported variance, the magnitude of the expected RLD, the difference in RLD which is important to the project, and the resources of the project. The variance of the mini-rhizotron was larger than soil cores in this project, but in another project reported in the literature this result was reversed.Item Root and top growth of annual legume forages using the slant-tube technique(Texas Tech University, 1986-12) Bojorquez Reyes, Custodio LucioNot availableItem Root carbohydrates in sand shinnery oak (Quercus havardii rydb.).(Texas Tech University, 1974-12) Boo, Roberto MiguelNot availableItem Root Development in Four Sorghums as Measured by Soil Placement of Radiophosphorus(Texas Tech University, 1961-05) McClure, Jerry WeldonNot Available.Item Root development in four sorghums as measured by soil placement of radiophosphorus(Texas Tech University, 1961-05) McClure, Jerry WeldonNot availableItem Root Development of Two Native Grasses using Radiophosphorous and Soil-Block Techniques(Texas Tech University, 1965-05) Pettit, Russell DeanNot Available.Item Root growth and water uptake patterns of cotton, sunflower and kochia, and their relationship to caliche(Texas Tech University, 1986-08) Georgen, Paul GNot availableItem Rooting behavior and soil water extraction of several grain sorghum genotypes(Texas Tech University, 1981-08) Moore, Terry JackNot available