Dry matter and nitrogen partitioning and translocation in winter oilseed rape (Brassica napus L.) grown under rainfed Mediterranean conditions

Abstract

For crops grown in Mediterranean environments, translocation of pre-anthesis assimilates to the fruit is of great importance, because hot and dry conditions during fruit ripening diminish net assimilation rate and nitrogen (N) uptake. This field study was conducted to assess the pattern of dry matter and N accumulation and the role of assimilate translocation in pod development of oilseed rape plants in a Mediterranean environment. Four cultivars of winter oilseed rape (Brassica napus L.), i.e. three hybrids (Royal, Exact, Excalibur) and an inbred line (Fortis), were grown for two growing seasons (2005–06 and 2006–07) in northern Greece. On average, 581, 1247, 1609, and 2749 growing degree-days (GDD) were required for six leaves, stem elongation, 50% anthesis in main stem, and physiological maturity in the first year, and 539, 1085, 1601, and 2728 GDD in the second year. The R2 of the modified Richards function indicated that aboveground biomass and N accumulation were described with high approximation efficacy. The across-cultivars genotype mean maximum predicted total aboveground dry matter and N content were 1368.8 and 21.4 g m–2 in 2006 and 1655.1 and 25.4 g m–2 in 2007. In 2007, dry matter and N translocation from vegetative tissues to pods were 464.4 and 21.0 g m–2, and significantly higher than the corresponding values recorded in 2006 (264.4 and 17.0 g m–2). These differences were due to greater amounts of dry matter and N accumulating at anthesis and the greater sink capacity of plants (pod number) in 2007. The fact that pod development occurred in a period when N accumulation by oilseed rape plants had stopped led to high values of contribution of pre-anthesis N accumulation to pod N content in both years (92.8% in 2006 and 96.6% in 2007). Results indicated that hot and dry weather post anthesis reduced dramatically the net assimilation rates; thus, translocation of pre-anthesis assimilates was crucial for pod development. The results demonstrate that variation in weather conditions between growing seasons is one of the main causes of seasonal variation in oilseed rape productivity under Mediterranean conditions.

Different Post-Sowing Nitrogen Management Approaches Required to Improve Nitrogen and Water Use Efficiency of Canola and Mustard

“…Across the two seasons, NHI decreased with increased post-flowering N uptake (r = −0.75; P = 0.0006; n = 11). Nitrogen harvest index values reported here are within the range reported for canola by Papantoniou et al (2013) [0.25-0.47 in the present study vs 0.32-0.66 reported by Papantoniou et al (2013)] and close to the lower range reported by Ma and Herath (2016) (0.41-0.83) but much lower than the findings of Hocking and Stapper (2001a).…”

Effects of paclobutrazol on biomass production in relation to resistance to lodging and pod shattering in Brassica napus L.

“…Although paclobutrazol reduced the relative growth rate for stems and the rate of biomass allocation to stems, it significantly increased both the parameters with respect to roots. Earlier work has shown that reduced biomass allocation to stems results in higher yields (Papantoniou et al 2013). In the present study, reducing the allocation to stems increased the allocation to roots -thereby forming a strong root system -and also increased the translocation of stored substances in stems to roots and pods.…”

Low-Input Herbicide Management: Effects on Rapeseed Production and Profitability

“…However, in typically Mediterranean climate, seasons may be either mild and wet or extremely dry. In our study, in 2008, seed filling fell during a period characterized by high temperatures and drought, affecting yield components, and as consequence seed production, as already stated by other authors [4,56] in their studies in Mediterranean-type climate.…”