Contribution of Nitrogen Uptake and Retranslocation during Reproductive Growth to the Nitrogen Efficiency of Winter Oilseed-Rape Cultivars (Brassica napus L.) Differing in Leaf Senescence

Abstract

Genotypic variation in N efficiency defined as high grain yield under limited nitrogen (N) supply of winter oilseed-rape line-cultivars has been predominantly attributed to N uptake efficiency (NUPT) through maintained N uptake during reproductive growth related to functional stay-green. For investigating the role of stay-green, N retranslocation and N uptake during the reproductive phase for grain yield formation, two line cultivars differing in N starvation-induced leaf senescence were grown in a field experiment without mineral N (N0) and with 160 kg N¨ha´1 (N160). Through frequent harvests from full flowering until maturity N uptake, N utilization and apparent N remobilization from vegetative plant parts to the pods could be calculated. NUPT proved being more important than N utilization efficiency (NUE) for grain yield formation under N-limiting (N0) conditions. For cultivar differences in N efficiency, particularly N uptake during flowering (NUPT) and biomass allocation efficiency (HI) to the grains, were decisive. Both crop traits were related to delayed senescence of the older leaves. Remobilization of N particularly from stems and leaves was more important for pod N accumulation than N uptake after full flowering. Pod walls (high N concentrations) and stems (high biomass) mainly contributed to the crop-residue N at maturity. Decreasing the crop-inherent high N budget surplus of winter oilseed-rape requires increasing the low N remobilization efficiency particularly of pod-wall N to the grains. Addressing this conclusion, multi-year and -location field experiments with an extended range of cultivars including hybrids are desirable.

Natural Variations and Dynamic Changes of Nitrogen Indices throughout Growing Seasons for Twenty Tea Plant (Camellia sinensis) Varieties

“…The characteristics of tea plant variety response to N, how they are regulated by field management practices, and how they contribute to NUE, remain unknown. A promising approach is to breed N-efficient varieties, thereby increasing yield under limited N and potential yield under normal N conditions, which thus allows for decreasing the requirement of N application to achieve optimum yields and maintain quality [ 37 , 38 ]. Plant NUE is a complex trait that is governed by many physiological processes, including N uptake, assimilation, transport, allocation, and remobilization, as well as the environmental factor of soil N availability.…”

Dynamic changes and genotypic variations of nitrogen concentration and remobilization for 20 tea plant (Camellia sinensis) cultivars throughout growing seasons

“…The characteristics of major tea plant cultivars response to N, how they are regulated by field management practices and how it contributes to N use efficiency (NUE) were remain unclear. A promising approach is the breeding and cultivation of N-efficient cultivars, considerable yield under limited N and potential yield under normal N conditions, which allows decreasing the N application necessary to achieve optimum yields and maintain quality [13,35]. Plant NUE is a complex trait that is governed by many physiological processes, including N uptake, assimilation, metabolism, transport, allocation, and remobilization, as well as environmental factors, such as the availability of soil N.…”

“…The N remobilization is highly affected by nutrient condition in plant [11] and it is essential at the whole plant level due to the fact that underlying mechanisms associated with the nutrient budget allow the redistribution of N between source organs and sink organs for growth and adaptation [12]. Mechanisms related with N use efficiency were investigated in many crops, to identify two decisive factors of N uptake during flowering and biomass allocation efficiency to seeds in winter oilseed-rape [13], to reveal canopy N and light profile parameters contribute to yield and NUE in rice [14,15], to announce the UK Genetic Improvement Network project for Wheat [16], to make clear relationship between senescence and yield, quality and NUE in perennial grasses etc [17,18]. N demand is the maximum of the growth activity-driven demand for crops [19].…”

Special Issue: Nitrogen Transport and Assimilation in Plants

“…[8], another model species, are included in two of the four research articles. The importance of N remobilization and recycling in two crops, namely Hordeum vulgare L. and oilseed rape (Brassica napus L.), is presented in the two other research papers, with particular emphasis on the role of senescence and autophagy [9,10].…”