Uptake and utilization of nutrients by developing kernels of Zea mays L

Thesis/Dissertation · Thu Jan 01 04:00:00 EST 1987

OSTI ID:6029498

Lyznik, L A

The mechanisms involved in amino acid and sugar uptake by developing maize kernels were investigated. In the pedicel region of maize kernel, the site of nutrient unloading from phloem terminals, amino acids are accumulated in considerable amounts and undergo significant interconversion. A wide spectrum of enzymatic activities involved in the metabolism of amino acids is observed in these tissues. Subsequently, amino acids are taken up by the endosperm tissue in processes which require energy and the presence of carrier proteins. Conversely, no evidence was found that energy and carriers are involved in sugar uptake. This process of sugar uptake is not inhibited by metabolic inhibitors and shows nonsaturable kinetics, but the uptake is pH-dependent. L-glucose is taken up at a significantly reduced rate in comparison to D-glucose uptake. Based on analysis of radioactivity distribution among sugar fractions after incubations of kernels with radiolabeled D-glucose, it seems that sucrose is not efficiently resynthesized from D-glucose in the endosperm tissue. Thus, the proposed mechanism of sucrose transport involving sucrose hydrolysis in the pedicel region and subsequent resynthesis in endosperm cells may not be the main pathway. The evidence that transfer cells play an active role in D-glucose transport is presented.

• Research Organization: Purdue Univ., Lafayette, IN (USA)
• OSTI ID: 6029498
• Country of Publication: United States
• Language: English

Related Subjects

550501* -- Metabolism-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ALDEHYDES
AMINO ACIDS
BIOLOGICAL PATHWAYS
BODY
CARBOHYDRATES
CARBOXYLIC ACIDS
CEREALS
DISACCHARIDES
ENZYME ACTIVITY
GLUCOSE
GRASS
HEXOSES
ISOTOPE APPLICATIONS
ISOTOPES
LABELLED COMPOUNDS
LILIOPSIDA
MAGNOLIOPHYTA
MAIZE
MEMBRANE TRANSPORT
METABOLISM
MONOSACCHARIDES
NUTRIENTS
OLIGOSACCHARIDES
ORGANIC ACIDS
ORGANIC COMPOUNDS
PLANT TISSUES
PLANTS
RADIOISOTOPES
SACCHARIDES
SACCHAROSE
TISSUES
TRACER TECHNIQUES
UPTAKE