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Thesis (Ph. D.)--University of Michigan, 1931. / Cover title. Published also as Michigan Agricultural experiment station Technical bulletin no. 118, January, 1932. Bibliography: p. 63-67.

The response of Phaseolus vulgaris L. cv. Contender grown in controlled environmental conditions, at either ambient or elevated (360 and 700 μmol mol ̄¹, respectively) CO₂ concentrations ([CO₂]), was monitored from 10 days after germination (DAG) until the onset of senescence. Elevated CO₂ had a pronounced effect on total plant height (TPH), leaf area (LA), dry weight (DW) accumulation and specific leaf area (SLA). All of these were significantly increased by elevated [CO₂] with the exception of SLA, which was significantly reduced. Except for higher initial relative growth rates (RGR) in CO₂-enriched plants, RGR did not differ significantly between the two CO₂ treatments throughout the remainder of growth period. While growth parameters clearly differed between CO₂ treatments, the effects of CO₂ on many physiological processes including net assimilation rate (NAR), Rubisco activity, and some foliar nutrient concentrations were largely transient. For example, CO₂ enrichment significantly increased NAR, but from 20 DAG onward, NAR declined to levels measured on plants grown under ambient CO₂. Similarly, the decline in both foliar N concentration and Rubisco activity in CO₂-enriched plants after 20 DAG was significantly greater than the decline observed for ambient CO₂ plants. Soluble leaf protein and total chlorophylls (a+b) were also significantly reduced in plants grown under elevated CO₂. Chlorophyll (a/b) ratios increased with time underelevated CO₂, indicating that the rate of decline of chlorophyll b was higher than that of chorophyll α. No significant changes in total carotenoid (x+c) levels were observed in either CO₂ treatment. Under enhanced CO₂, the foliar concentrations of K and Mn were increased significantly, while P, Ca, Fe and Zn were reduced significantly. However, changes in Mg and Cu concentrations were not significant. High CO₂-grown plants also exhibited pronounced leaf discoloration or chlorosis, coupled with a significant reduction in leaf longevity. The levels of non-structural carbohydrates (sucrose, glucose, fructose and starch) and nitrogenous compounds (nitrogen, total soluble proteins and free amino acids) were determined for leaves and developing seeds of P. vulgaris. Leaf tissue of elevated CO₂-grown plants accumulated significantly higher levels of both soluble sugars and starch. Leaf ultrastructure revealed considerable erilargement of starch grain sizes with surface areas more than five times larger compared to those of control plants. No apparent differences in structure and membrane integrity of chloroplasts in both CO₂ treatments were noted. Although ambient CO₂-grown plants had comparatively low levels of non-structural carbohydrates (NSC), they accumulated significantly higher levels of nitrogenous compounds. The levels of NSC were consistently higher in seeds of plants grown under elevated CO₂. In comparison to plants grown at elevated [CO₂], pods and seeds of ambient CO₂-grown plants had significantly larger pools of free amino compounds and N. Stomatal conductance (gs) declined significantly, as expected for plants grown under elevated CO₂. This was accompanied by a decline in transpiration rates (E). Reduced gs and E led to high AlE ratio, which meant improved water use efficiency (WUE) values for CO₂-enriched bean plants. Leaf carbon isotope discrimination (∆) against the heavier isotope of carbon (¹³C), has been used to select for high WUE in C₃ plants. In plants grown at elevated CO₂ concentration, ,1 was significantly reduced. Although ∆ was negatively correlated with WUE in both CO₂ treatments, the correlation was steeper and highly negative for CO₂-enriched plants. These results indicate underlying differences in gas-exchange physiology, including stomatal responses between ambient and elevated CO₂-grown plants. Photosynthetic acclimation was investigated using the response of assimilation to internal carbon dioxide concentration (A/C₁ curves). At early stages of growth, the initial slope of the A/C₁ response curve did not differ with CO₂ treatment. In contrast, CO₂-saturated photosynthetic rate (Amax) was significantly higher in plants grown under elevated versus ambient CO₂ at 15 DAG. However, at subsequent stages of growth both the initial slope and Amax declined in bean plants grown in elevated CO₂. Apparent carboxylation efficiency (ACE, estimated from the initial slope of A/C₁ response) values followed a similar trend and were significantly reduced in CO₂-enriched plants. These results indicate that acclimation or negative adjustment of photosynthesis may have been caused by a combination of both stomatal and biochemical limitations. Bean plants grown under conditions of elevated atmospheric CO₂ flowered 3 to 4 days earlier, and produced significantly more flowers and pods than plants grown at ambient conditions. Plants grown at elevated CO₂ aborted 22 and 20% more flowers and pods, respectively, than plants grown at ambient CO₂. Elevated CO₂ also significantly increased the number of tillers or lateral branches produced by plants, which contributed to a significant increase in pod number and seed yield in these plants. Although plants grown at elevated CO₂ produced on average 8 seeds per pod, while plants grown under ambient CO2 conditions produced 5 seeds per pod, the greater number of seeds was offset by lower seed weights in plants grown under _ elevated CO₂. Thus, despite high seed yield in beans grown under elevated CO₂, the harvest index (HI) did not change significantly between CO₂ treatments.

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Application of 2,3,5-triiodobenzoic acid (TIBA) at 1, 2, 4, 5 and 12 g/ha to field-grown snap beans (Phaseolus vulgaris L.) at early bloom caused a reduction in plant height and width but not dry weight. Yield differences occurred with the cultural variables of cultivar ('Sprite' and 'Dark-Seeded Provider') and row spacing (single and double rows) but not with the chemical treatment. Low soil moisture at the time of TIBA application was suspected of interfering with absorption and action of the chemical. In the winter and spring of 1981 greenhouse studies were conducted with 2 g/ha TIBA treatment of double-row snap beans grown under 3 pre-flower moisture regimes. Early yield was increased with the TIBA treatment, but the total yield did not differ due to a reduced second harvest, such that TIBA functioned as a yield catalyst under these study conditions. Environment was a more important determinant of the snap bean productivity as yield increased with more available soil moisture in both trials and decreased with warmer temperatures during the second crop trial. The importance of environmental influences on TIBA effect is discussed. / M.S.

Call number: LD2668 .T4 1964 B57 / Master of Science

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The major objective of this study was to determine whether or not food production per unit space can be increased by intercropping summer squash (Cucurbita pepo L.) with mung bean (Phaseolus aureus Roxb.) or pinto bean (Phaseolus vulgaris L.), and to identify the factors associated with growth and yield of summer squash, mung bean and pinto bean under intercropping regimes. A series of experiments were conducted during the period: Summer, 1977 to February, 1980, at both the University of Arizona, Experiment Station, Marana, and in a greenhouse at the University of Arizona, Campbell Avenue Farm. Intercropping mung beans or pinto beans with summer squash in either adjacent rows or within the row did not significantly influence the bean seed yield, although adjacent row intercropping tended to outyield the within row intercropping. Summer squash yield was more significantly reduced by within row intercropping than adjacent row intercropping. Root and shoot dry weights of container grown mung beans or pinto beans were significantly reduced by intercropping with summer squash, but summer squash root and shoot dry weights were not significantly affected. Intercropping summer squash with either mung beans or pinto beans was more beneficial at low nitrogen and phosphorus fertility levels than at higher levels. Summer squash fruit and shoot dry weights per unit space increased with increase in plant population, but they were not significantly influenced by intercropping with either mung beans or pinto beans. Intercropping high population summer squash with low population mung beans or pinto beans reduced both seed and biomass yields of the beans. However, increasing the bean plant populations had no influence on their seed and biomass yields. Harvest index of mung beans or pinto beans was neither influenced by intercropping with summer squash nor by increasing the bean plant population. Leaf area per unit space increased with increase in plant population, but intercropping had no significant influence in all cases. Specific leaf weight, leaf area-to-leaf weight ratio, and leaf weight ratio were neither influenced by intercropping nor by varying the plant populations. Mung bean seed yield was significantly to highly significantly correlated with harvest index and biomass, but highly negatively correlated with leaf area index, while pinto bean seed yield was very highly correlated with biomass and harvest index. Summer squash fruit yield was significantly to highly significantly correlated with shoot dry weight, leaf area, leaf area index and specific leaf weight. Accumulations of nitrate nitrogen and/or phosphorus in the leaf petioles of mung beans, pinto beans or summer squash were neither influenced by intercropping nor by increasing the nitrogen or phosphorus fertility levels. The economic yields of field grown mung beans, pinto beans or summer squash were not significantly correlated with petiole accumulations of nitrate nitrogen and phosphorus. While summer squash exhibited autotoxicity, mung bean root leachates tended to promote growth of pinto beans and summer squash. Food production per unit space was increased by as much as 76% by intercropping summer squash with pinto beans, while intercropping summer squash with mung beans increased food production by 63%. Under certain plant combinations, dry matter yield per unit space was increased by as much as 185% by intercropping summer squash with mung beans, while intercropping summer squash with pinto beans increased the dry weight yield by as much as 81%.