NITROGEN AVAILABILITY AND FRUITING INFLUENCE NITROGEN CYCLING IN STRAWBERRY.

Authors: ARCHBOLD, DOUGLAS - UNIVERSITY OF KENTUCKY; MACKOWN, CHARLES

Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/29/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Nitrogen use and redistribution in the strawberry plant probably determines plant vigor and productivity. Experiments were conducted to determine if the availability of N and the presence of fruit alters N use in strawberry and the role of the root system in the use of N. Plants maintained on continuous N were larger and more productive than those with an interrupted dsupply of N. These differences occurred at the expense of the N status of leaves as N redistribution from the leaves to other plant organs occurred. Regardless of the treatments, N in plant tissues was predominantly present as proteins. Fruiting initially decreased growth of roots and N accumulation. The use of N stable isotope revealed that N cycling occurred through all tissues and classes of N compounds, particularly the soluble reduced N compounds composed of amino acids, the building blocks of protein. The root system was not an important temporary storage site of N even though N through the root to other tissues was evident. Leaf N was the most important site of N storage and more readily met the demands for N by other plant organs when N supply was interrupted or fruiting occurred. These results will be useful to crop physiologists and agronomists seeking information on N use by economically important perennial species.

Technical Abstract: Nitrogen (N) allocation and cycling within the strawberry plant may play an important role in plant vigor and productivity. This work determined 1) if N availability and fruit production affects N and fertilizer N (FN) partitioning among and within the vegetative tissues of 'Tribute' strawberry (Fragaria X ananassa Duch.), and 2) if the root N pool is a temporary storage N site. Plants were fed 15N-depleted NH4NO3 for 8 weeks then were grown for 12 weeks with or without N and maintained vegetative or allowed to fruit, sampling the vegetative tissues at 6 and 12 weeks. Plants receiving continuous N showed increased dry weight (DWT) and total N, insoluble reduced N (IRN), and soluble reduced N (SRN) content at 6 and 12 weeks. In plants not receiving N, leaf DWT, N, IRN, and SRN content declined at 6 weeks while values for other tissues increased at 12 weeks. IRN was the dominant N form. Fruiting inhibited root growth and N accumulation through 6 weeks but had little effect from 6 to 12 weeks. Th roots were a strong DWT and N sink from 6 to 12 weeks. The FN pools exhibited changes similar to those for total N in plants not receiving N. In plants receiving N, total leaf and petiole N content increased and FN content declined (26%). The decline was not affected by N availability or fruiting. Increasing atom % 15N values indicated that N cycling occurred through all tissues and N pools, proportionally more for SRN but quantitatively more for IRN. The root N pool was not a 'temporary' N storage site although N cycling through it was evident. Rather leaf N was more accessible for remobilization.