Biomedical subjects

C G Poneleit

Publications and source records attributed to C G Poneleit.

3 recordsLinked to original sources

PubMed1987

Carbon dioxide exchange rates, ribulose bisphosphate carboxylase/oxygenase and phosphoenolpyruvate carboxylase activities, and kernel growth characteristics of maize.

Four high-yield-potential maize hybrids (FS854, CB596 x LH38, B73 x LH38, and B73 x Mo17) and four inbred lines (LH38, CB59G, Mo17, and B73) were grown in the field to study traits associated with leaf area duration (LAD) and the relationship between LAD and kernel growth characters. Based on decline in chlorophyll, leaf N concentration, CO(2) exchange rate, and ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) and phosphoenolpyruvate carboxylase (PEPCase) activities, the hybrid B73 x Mo17 had a significantly shorter LAD than the other three hybrids. The shorter LAD was not due to maturity because B73 x Mo17 is in a maturity class similar to the other hybrids except CB59G x LH38, which is approximately 1 week earlier. At the time of grain maturity, leaves of B73 x Mo17 had lost all chlorophyll and CO(2) exchange and carboxylase activities. The other three hybrids, however, retained green leaves which still had 20% of the maximum CO(2) exchange rate. In addition, B73 x Mo17 remobilized leaf N more extensively. For all hybrids, declines in CO(2) exchange were closely correlated with declines in PEPCase activity, whereas the relationship between CO(2) exchange and Rubisco activity was weak. Responses of the inbred lines predicted, to some extent, physiological characteristics of the hybrids. CB59G and LH38 both had a longer LAD than either B73 or Mo17 as judged by decline in chlorophyll, leaf N, CO(2) exchange rate, and Rubisco and PEPCase activities. With the exception of B73 x LH38, kernel growth characteristics of the hybrids were related to LAD. Effective filling period (EFP) measured in days was 32.9, 31.5, 30.8, and 30.4 for FS854, CB59G x LH38, B73 x LH38, and B73 x Mo17, respectively. For FS854 and CB59G x LH38, the longer EFP was associated with a larger kernel weight. These data suggested that late season photoassimilate resulting from longer LAD could be utilized by the kernels of these two hybrids. For B73 x Mo17, the shorter LAD and EFP was associated with a kernel dry matter accumulation rate (10.1 milligrams per kernel per day) which was significantly higher than for the other three hybrids. Thus, the more rapid leaf senescence of B73 x Mo17 appeared to be coordinated with efficient leaf N remobilization and a relatively short grain-filling period characterized by rapid kernel dry matter accumulation.

Journal Article↗

PubMed1987

Effect of Ear Removal on CO(2) Exchange and Activities of Ribulose Bisphosphate Carboxylase/Oxygenase and Phosphoenolpyruvate Carboxylase of Maize Hybrids and Inbred Lines.

The effects of ear removal on gas exchange traits, chlorophyll, and leaf N profiles, and activities of ribulose 1,5-bisphosphate carboxylase/oxygenase and phosphoenolpyruvate carboxylase were examined using four maize hybrids (B73 x Mo17, B73 x LH38, FS854, and CB59G x LH38) and four inbred lines (B73, Mo17, LH38, and CB59G) as experimental material. A diverse genotypic response to ear removal was observed which was generally typified by (a) greatly accelerated loss of chlorophyll, leaf N, enzyme activities, and CO(2) exchange relative to controls for B73, B73 x Mo17, and B73 x LH38, (b) intermediate rate of decline for leaf constituents for FS854, LH38, and Mo17, or (c) loss of leaf constituents at similar or slower rates than for control plants for CB59G and CB59G x LH38. For all genotypes which had accelerated senescence relative to controls, loss of CO(2) exchange activity was correlated with increased internal CO(2) concentrations. Thus, it was concluded that metabolic factors and not stomatal effects were responsible for loss of CO(2) exchange activity. Loss of chlorophyll, leaf N, and enzyme activities correlated well with loss of CO(2) exchange activity only for some of the genotypes. Accelerated leaf senescence in response to ear removal for the inbred line B73 and the hybrids B73 x Mo17 and B73 x LH38, as well as the apparent delayed leaf senescence for the inbred line CB59G and the hybrid CB59G x LH38 show that the contrasting responses to ear removal, rapid versus delayed senescence, can be transmitted as dominant traits to F(1) hybrids. The intermediate response by some genotypes, and the dominance of contrasting senescence traits, suggested a relatively complex inheritance for expression of the ear removal response.

Journal Article↗

PubMed1974

Sterol Accumulation and Composition in Developing Zea mays L. Kernels.

Kernels were collected from three maize (Zea mays L.) inbreds from 10 days after pollination until kernel maturity. Sitosterol, campesterol, and stigmasterol were the major sterols at all stages of kernel development. Cholesterol was less than 1% of the dry weight. The three major sterols accumulated during kernel development, but at a rate slower than dry weight. The ratio of the sterols did not vary greatly among the inbreds. At maturity, the three inbreds, Wf9, Oh43, and Ky226, had sterol levels of 325, 228, and 173 micrograms per kernel, respectively. Sitosterol accounted for 75 to 85% of the sterol. The relative amount of stigmasterol decreased during the linear phase of development, while sitosterol increased in the free fraction and campesterol increased in the steryl ester fraction.Free sterols and steryl esters were the major sterol fractions and steryl glycosides and acylated steryl glycosides were only minor components during kernel development. Free sterol content decreased rapidly in two maize inbreds between 10 and 26 days after pollination, but partially recovered in one of the inbreds during final stages of development. In the same two inbreds the steryl ester content reached a maximum during the late stages of linear kernel growth.

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