Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Germination, emergence, and early seedling development patterns were analyzed for red rice (Oryza sativa L.) and the rice (Oryza sativa L.) cultivars Mars, Saturn, Lemont and Bellemont. Red rice had the highest germination percentage, fastest emergence rate, and earliest development of both shoots and roots. These results suggest that the competitive ability of red rice is based on these characteristics which enable it to preempt more resources at early stages of stand development. Interaction between red rice and Lemont or Mars was evaluated by comparing morphological and physiological characteristics of these plants when grown in pure stands and in 50:50 mixtures. Plant height, top dry weight, tiller and leaf number, leaf area index, and leaf area duration of the cultivars were reduced significantly in the presence of red rice in the mixture. The effects of the interaction were detected as early as 28 days after emergence in the cultivars, first as a reduction in leaf area index and then as reduced top dry weight. When red rice was grown in mixture it produced more tillers and leaves and greater top dry weight than when grown in monoculture. These growth attributes may also be responsible for its competitive ability. Effects of end-of-day light quality on early growth and development of red rice, Lemont and Mars were examined in a controlled environment. Exposure of the base of the plants to red light at the end of the day promoted an increase in the number of tillers per plant. The magnitude of the increase was greater for red rice than for the cultivars. The results support the hypothesis that tillering is controlled by a shift in spectral quality of the light reaching the bottom of the canopy. Root interaction between red rice and Lemont or Mars reduced nitrogen and phosphorus content of shoots for Lemont and the phosphorus content of shoots for Mars. The high root cation exchange capacity exhibited by red rice could be the root property associated with its greater nutrient uptake and below ground competitive ability.