ISSN:
1573-5036
Keywords:
Helianthus annuus L.
;
15N
;
nitrogen supply
;
redistribution
;
remobilization
;
seed N
;
sunflower
;
total N
;
vegetative organs
Source:
Springer Online Journal Archives 1860-2000
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
Abstract A glasshouse study was made of the distribution of 15N among vegetative organs of sunflower and its later remobilization and redistribution to seeds, as influenced by the developmental stage at which 15N was provided, and by the N status of the plants. Plants of Hysun 30 sunflower were grown in sand culture and provided with K15NO3 for a 3-day period at: (a) 3 days before the end of floret initiation; (b) 3 days before anthesis; (c) the start of anthesis; (d) full anthesis; and (e) 8 days after full anthesis. The plants were grown on a range of N supply rates, from severely deficient to more than adequate for maximum growth. Nitrogen-15 was distributed to all parts of the plant at the end of the 15N uptake periods. With the exception of the most N-stressed plants, subsequent remobilization of 15N from roots, stems and leaves occurred irrespective of the time the 15N was taken up. However, the percentage redistribution to seeds of 15N taken up at the end of floret initiation was less than for 15N taken up at anthesis. Remobilization of 15N from leaves and roots was higher (70%) for 15N taken up during and after anthesis than for 15N taken up at the end of floret initiation (45%), except for plants grown on the lowest N supply. By contrast, remobilization of 15N from the stem was lower for 15N taken up after full anthesis (40%) than before or during anthesis (〉70%). The proportion of 15N remobilized from the top third of the stem was less than that from the bottom third, and decreased with increasing plant N status. Nitrogen-15 taken up over the 3-day supply periods during anthesis contributed from 2 to 11% of the total seed N at maturity; the contribution to seeds was greatest for plants grown on the highest N supply. Nitrogen taken up just before and during anthesis contributed most of the N accumulated in mature seeds of plants grown on an adequate N supply, but N taken up between the end of floret initiation and just before anthesis, or after full anthesis seemed to make an equally important contribution to mature seeds as N taken up during anthesis for plants grown on a very low N supply. It was concluded that the development of florets and seeds of sunflower is supported by N taken up by the plant between the end of floret initiation and anthesis, and by N redistributed from vegetative organs. Unless soil N is so low as to impair early growth, split applications of N fertilizer would be best made just before the end of floret initiation (‘star stage’) and just before anthesis.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00010490
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