| The patterns of TNC accumulation in strawberry ( Fragaria x ananassa Duch.) nursery runner plants, cvs. 'Camarosa' (short-day), 'Ventana' (short-day), and 'Selva' (day-neutral), and the influence of late-season foliar-applied N (80 kg.ha-1) on fruiting patterns of 'Camarosa' and 'Ventana' were studied. The experiments were carried out on plants propagated in high-latitude nurseries in California, and dug in late summer or early autumn. Plant growth and fruit evaluation plots were established in growth chambers and/or under field conditions in Southern California. Plant TNC concentration and content (TNCcc) in roots and crowns were positively correlated with the accumulation of chilling hours (h ≤ 7.2°C) and increased from mid-September to early-October. Plant crown and root biomasses as well as early growth and early-season fruit production were enhanced in October-dug plants. Root TNCcc was more sensitive to chilling-hour accumulation than crown TNCcc. Root TNC concentration increased from ∼4 to 14, ∼6 to 11, and ∼14 to 21% dry mass (DM) in 'Selva', 'Camarosa' and 'Ventana', respectively. Late-season N applications (1) increased early yields as well as the number of early marketable fruits compared to control plants, (2) did not significantly affect total season yields, fruit size, appearance or firmness, (3) resulted in greater N concentration and content in leaves, crowns and roots, and (4) decreased plant starch and TNC concentrations. Plants with leaf N concentration within the sufficiency range (1.9--2.8 DM) at the time of transplanting produced the highest early yields. Plant N-concentration consistently decreased from September to October in control plants but N applications prevented this process. 'Ventana' flowered earlier, had lower dead leaf biomass, dead leaf area, greater leaf number, earlier fruit production, and better fruit appearance than 'Camarosa'. Leaf N-concentration of 'Camarosa' and 'Ventana' ranged from 1.47 to 1.81 and 1.60 to 1.96% DM, respectively. Apparently, the earliness of 'Ventana' was correlated with higher leaf-N concentration, root-TNC content and greater leaf longevity than 'Camarosa'. Late-season N applications in the nursery appeared to stimulate plant growth and reproductive development during the period of flower differentiation as well as enhance N mobilization to crown and root contributing to the advancement of fruit production. |
