C and N Mobilization from Stalk and Leaves during Kernel Filling by ¹³C and ¹⁵N Tracing in Zea mays L.

Abstract

The sink capacity of the stalk in Zea mays L. (cv DEA) during the elongation period was previously investigated with 13C and 15N tracing. The chase experiment described here demonstrates the different behavior of intermediary reserves for C and N remobilization until full maturity of the kernels. Carbon incorporated during stalk elongation participated mainly in cellulose formation in vegetative organs appearing after the labeling period; the remobilization to kernels was low (0.5%). Soluble carbohydrates and proteins were the main intermediary sink compounds, starch being little remobilized. N first incorporated in roots, sheaths, stalk, blades was translocated to the kernel; 42% of the labeled N were recovered in kernels where they represented 8% of the total N. Cob, husk, and shank acted first as N sinks and then as N sources during ear development. It appeared that aminoacids used for synthesis of kemel proteins have a common origin, except for glutelin G3.vegetative parts for the development of the ear and to point out use of intermediary reserves of the stalk for kernel filling. MATERIALS AND METHODS Plant Culture and Labeling ExperimentMaize plants (Zea mays L., cv Dea) were grown in a greenhouse for 45 d. Control plants were maintained in the greenhouse while 15 other plants were put in a climatic chamber to assimilate '3C02 (1.2889 13C atom %) at 450 ppm in a controlled atmosphere and '5N-nitrates (1.9643 '5N atom %) in the nutrient solution (4), for an 8-d exposure. After the labeling, 3 plants were harvested and the 12 remaining plants continued their development in the greenhouse under previous conditions. The whole experimental procedure is detailed further in a previous paper (4). The use of stable isotope labeling at the natural abundance range and its use for estimation ofthe long-term partitioning was described previously (8, 9).The contribution of C and N reserves accumulated in the shoot to the ear growth is an important factor in crop yield (12,22). In maize, redistribution of carbon and nitrogen reserves from the senescent leaves to the kernel has already been reported (6,10

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Carbon autonomy of reproductive shoots of Siberian alder ( Alnus hirsuta var. sibirica )

“…Our specific questions are: (1) whether flowers obtain photosynthates assimilated in the leaves on the current-year shoots to which they are attached, (2) whether the fruits obtain photosynthates assimilated in the leaves on the current-year shoots developed on the fruiting 1-year-old shoot, and (3) which current-year shoots on a fruiting 1-year-old shoot are effective for fruit maturation. To answer these questions, we conducted a tracing experiment using isotope-labelled CO 2 , a popular technique with which to examine the movement of photosynthate in a plant body (Rabideau and Burr 1945;Hartt et al 1963;Geiger and Swanson 1965;Hartt 1965;Hansen 1967Hansen , 1969Davis and Sparks 1974;Steer and Pearson 1976;Takeda et al 1980;Cliquet et al 1989Cliquet et al , 1990Deléens et al 1994). …”

Do trees use reserve or newly assimilated carbon for their defense reactions? A 13C labeling approach with young Scots pines inoculated with a bark-beetle-associated fungus (Ophiostoma brunneo ciliatum)

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