Diurnal variation in carbohydrate content of plant parts has been recognized for many years. Such variation in the peanut (Arachis hypogaea L.) plant has received little attention. In order to better understand the dynamics of carbohydrate accumulation and utilization in peanut, a greenhouse study was undertaken to examine the effects of shading on diurnal patterns of carbohydrate distribution in this crop. The cultivar, NC 4, was grown under unaltered greenhouse conditions (control) or under shade cloth (37% of photosynthetic photon flux of control). Plants were harvested 40 and 64 days after planting, at beginning bloom and full-pod. At each harvest date plants were sampled every three hours during a 24-h cycle. The concentrations of reducing and nonreducing sugars and starch were analyzed in leaf, stem, and root plus nodule tissues for all samples. Control plants accumulated about twice the dry matter, nodule mass, and fixed N2 as shaded. The carbohydrate concentration was greater in tissues of controls than in those of shaded plants. Growth stage affected both carbohydrate concentration in tissues and the diurnal variation within tissues. All plants harvested at the bloom stage showed significant but individual diurnal effects on concentrations of reducing and nonreducing sugars and starch in leaves, and significant and comparable patterns of nonreducing sugars and starch in roots. Plants harvested at the pod stage exhibited few significant diurnal effects; there was substantial plant-to-plant variability at this stage. Results from this study emphasize the importance of considering the time of day and developmental stage when analyzing nonstructural carbohydrates in peanut tissues.

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Author notes

1Paper No. 10004 of the Journal Series of the North Carolina Agricultural Res. Service, Raleigh, NC 27695–7601.

3Mention of a trademark of proprietary product does not constitue a guarantee or warranty of the product by the North Carolina Agricultural Research Service or imply its approval to the exclusion of other products that may also be suitable.