This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Web of Science (28) Citing Articles via Google Scholar Google Scholar Articles by Kalt-Torres, W. Articles by Huber, S. C. Search for Related Content PubMed PubMed Citation Articles by Kalt-Torres, W. Articles by Huber, S. C. Agricola Articles by Kalt-Torres, W. Articles by Huber, S. C.

Metabolism and Enzymology

Diurnal Changes in Maize Leaf Photosynthesis ¹

III. Leaf Elongation Rate in Relation to Carbohydrates and Activities of Sucrose Metabolizing Enzymes in Elongating Leaf Tissue

United States Department of Agriculture, Agricultural Research Service, North Carolina State University Raleigh, North Carolina 27695-7631, Department of Botany, North Carolina State University Raleigh, North Carolina 27695-7631, Department of Crop Science North Carolina State University Raleigh, North Carolina 27695-7631

Maize (Zea mays L. cv. Pioneer 3184) leaf elongation rate was measured diurnally and was related to diurnal changes in the activities of sucrose metabolizing enzymes and carbohydrate content in the elongating portion of the leaf. The rate of leaf elongation was greatest at midday (1300 hours) and was coincident with the maximum assimilate export rate from the distal portion of the leaf. Leaf elongation during the light period accounted for 70% of the total observed increase in leaf length per 24 hour period. Pronounced diurnal fluctuations were observed in the activities of acid and neutral invertase and sucrose phosphate synthase. Maximum activities of sucrose phosphate synthase and acid invertase were observed at 0900 hours, after which activity declined rapidly. The activity of sucrose phosphate synthase was substantially lower than that observed in maize leaf source tissue. Neutral invertase activity was greatest at midday (1200 hours) and was correlated positively with diurnal changes in leaf elongation rate. There was no significant change in the activity of sucrose synthase over the light/dark cycle. Sucrose accumulation rate increased during a period when leaf elongation rate was maximal and beginning to decline. Maximum sucrose concentration was observed at 1500 hours, when the activities of sucrose metabolizing enzymes were low. At no time was there a significant accumulation of hexose sugars. The rate of starch accumulation increased after the maximum sucrose concentration was observed, continuing until the end of the light period. There was no delay in the onset of starch mobilization at the beginning of the dark period, and essentially all of the starch was depleted by the end of the night. Mobilization of starch in the elongating tissue at night could account for a significant proportion of the calculated increase in the tissue dry weight due to growth. Collectively, the results suggested that leaf growth may be controlled by the activities of certain sucrose metabolizing enzymes and may be coordinated with assimilate export from the distal, source portion of the leaf. Results are discussed with reference to diurnal photoassimilation and export in the distal, source portion of the leaf.

This article has been cited by other articles:

				K. A. Duncan and S. C. Huber Sucrose Synthase Oligomerization and F-actin Association are Regulated by Sucrose Concentration and Phosphorylation Plant Cell Physiol., November 1, 2007; 48(11): 1612 - 1623. [Abstract] [Full Text] [PDF]