Doctoral Dissertations

Date of Award

12-1973

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Plant, Soil and Environmental Sciences

Major Professor

Lloyd Seatz, William Krueger

Abstract

Morphological, physiological, and biochemical parameters were measured to determine the site of action of alachlor [2-chloro-2',6’ diethyl-N-(methoxymethyl) acetanilide] and the protective effect of 1,8-naphthalic anhydride (hereafter referred to as NA) in grain sorghum (Sorghum bicolor (L.) Moench, 'AKS 614’) and com (Zea mays L. 'Tn 5009') seedlings. Time of coleorhiza emergence through the pericarp of grain sorghum was not affected by 1, 5, or 25 ppmw alachlor, by 2 percent w/w NA, or their combinations. Coleoptile emergence was delayed slightly by NA alone and in combination with alachlor, but not by alachlor alone. Emergence of the primary leaf from the coleoptile was inhibited by alachlor treatments in the presence of NA and even more so in its absence. Various degrees of leaf distortion resulted when grain sorghum seedlings not exhibiting leaf emergence were placed in light. Severity of distortion was less with 1 ppmw alachlor than with 5 ppmw and the alachlor-induced distortion was less when in combination with 150 ppmw NA. After four weeks, the primary leaves were still distorted but subsequent emerging leaves were normal in all treatments. More complete emergence and unrolling of the primary leaf was observed when terminal segments (3.5 cm long, including the coleoptile and part of the first internode) of grain sorghum grown in the presence of 150 ppmw NA were vacuum infiltrated with 15, 25, and 50 ppmw alachlor than in the controls. Fifty ppmw gibberellic acid (GA) was as effective as 150 ppmw NA in counteracting alachlor-induced leaf retention in the coleoptiles of com. The GA was also effective in nullifying the height reduction observed in com coleoptiles grown in the presence of 25 ppmw alachlor and ISO ppmw NA, while 150 ppmw NA applied in combination with the alachlor further reduced coleoptile length. One-cm coleoptile segments from com grown in the presence of 25 ppmw alachlor, 150 ppmw NA and their combination responded more to indoleacetic acid (lAA)- induced elongation than did the controls. More force was required to induce leaf slippage in coleoptiles from com grown in the presence of 25 ppmw alachlor than in the controls, or in coleoptiles from plants grown in the presence of 25 ppmw alachlor in combination with 150 ppmw NA. The NA alone reduced the force required to induce leaf slippage below that of all treatments compared. Incubation for 16 hours in 10 ppmw lAA did not lower the amount of force required to induce leaf slippage in coleoptiles from com grown in the presence of 25 ppmw alachlor even though the length of the coleoptiles increased 30 percent more than coleoptiles not receiving lAA treatment. Percent dry matter, dry matter per 100 plants, and percent protein increased in coleoptiles from alachlor treated com, while percent cellulose and lignin decreased. The extent of variation in these parameters was reduced when NA was applied in combination with alachlor, with the exception of percent lignin which was further decreased by the combination treatment. Percent hemicellulose was not affected by alachlor, NA, or their combinations. The RNA-DNA ratio of corn coleoptiles was decreased by the alachlor-NA combination treatment, but not by either chemical alone.

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