Rapeseed (Brassica napus L.) is sensitive to light quality. The factory production of rapeseed seedlings for vegetable use and for transplanting in the field requires an investigation of the responses of rapeseed to light quality. This study evaluated the responses of the leaf of rapeseed (cv. ‘Zhongshuang 11’) to different ratios of red-photonflux (RPF) and blue-photonflux (BPF) from light emitting diodes (LEDs). The treatments were set as monochromatic lights, including 100R:0B% and 0R:100B%, and compound lights (CLs), including 75R:25B%, 50R:50B% and 25R:75B%. The total photonflux in all of the treatments was set as 550 μmolm-2s-1. With an increase of BPF, the rapeseed leaves changed from wrinkled blades and down-rolled margins to flat blades and slightly up-rolled margins, and the compact degree of palisade tissue increased. One layer of the cells of palisade tissue was present under 100R:0B%, whereas two layers were present under the other treatments. Compared to 100R:0B%, 0R:100B% enhanced the indexes of leaf thickness, leaf mass per area (LMA), stomatal density, chlorophyll (Chl) content per weight and photosynthetic capacity (Pmax), and the CLs with high BPF ratios enhanced these indexes. However, the 100R:0B% and CLs with high RPF ratios enhanced the net photosynthetic rate (Pn). The leaves under the CLs showed growth vigor, whereas the leaves under 100R:0B% or 0R:100B% were stressed with a low Fv/Fm (photosynthetic maximum quantum yield) and a high content of O2.- and H2O2. The top second leaves under 100R:0B% or 0R:100B% showed stress resistance responses with a high activity of antioxidase, but the top third leaves showed irreversible damage and inactivity of antioxidase. Our results showed that the rapeseed leaves grown under 0R:100B% or CLs with a high BPF ratio showed higher ability to utilize high photonflux, while the leaves grown under 100R:0B% or CLs with a low BPF ratio showed higher efficiency in utilizing low photonflux. Under different R:B photonflux ratios, red and blue lights may play mutual roles in Pn. When the blue light dominated, the Pn showed a B-preference. When the red light dominated, the Pn showed an R-preference. Furthermore, CLs were suitable for the Pn of rapeseed seedlings.

/pdf/morphological-photosynthetic-and-physiological-responses-of-54c5iysovm.pdf

Morphological, Photosynthetic, and Physiological Responses of Rapeseed Leaf to Different Combinations of Red and Blue Lights at the Rosette Stage

Perennial crops have fewer environmental impacts compared to annual crops, but there are no perennial grains available to replace the annual grains that occupy a majority of U.S. cropland. Here we report grain and biomass yields from an improved breeding population of intermediate wheatgrass (IWG) [Thinopyrum intermedium (Host) Buckworth & Dewey], a perennial grass being domesticated to serve as the first widely grown perennial grain crop. Our objective was to measure grain and biomass yields of this improved grain-type IWG (TLI-C2), a forage variety of IWG (cultivar Rush), and switchgrass (Panicum virgatum L.) in response to N fertilization rates ranging from 0 to 200 kg N ha–¹. TLI-C2 grain yields responded quadratically to increasing N rates in all but one environment, but yields declined at high N rates due to lodging. TLI-C2 grain yields were highest during the first year of fertilization, yielding 961 and 893 kg ha–¹ when fertilized at agronomically optimum nitrogen rates (AONRs) of 61 and 96 kg N ha–¹ for stands seeded in fall of 2011 and spring of 2012, respectively. Grain yields declined with stand age. When fertilized with AONRs for grain, biomass yields of TLI-C2 harvested after grain ranged from 9.2 to 12.3 Mg ha–¹ and had similar forage and bioenergy quality characteristics compared to Rush, which demonstrates the potential to manage TLI-C2 as a dual-use cropping system for both grain and forage.

Intermediate wheatgrass grain and forage yield responses to nitrogen fertilization

The critical period for yield and quality determination in canola ( Brassica napus L.)

Plasticity of seed weight compensates reductions in seed number of oilseed rape in response to shading at flowering

Vegetative plasticity and floral branching compensate low plant density in modern spring rapeseed

Early shade signals promote the shade avoidance syndrome (SAS) which causes, among others, petiole and shoot elongation and upward leaf position. In spite of its relevance, these photomorphogenic responses have not been deeply studied in rapeseed (Brassica napus). In contrast to other crops like maize and wheat, rapeseed has a complex developmental phenotypic pattern as it evolves from an initial rosette to the main stem elongation and an indeterminate growth of floral raceme. In this work, we analyzed (1) morphological and physiological responses at individual level due to low red/far-red (R/FR) ratio during plant development, and (2) changes in biomass allocation, grain yield and composition at crop level in response to high R/FR ratio and low irradiance in two modern spring rapeseed genotypes. We carried out pot and field experiments modifying R/FR ratios and irradiance at vegetative or reproductive stages. In pot experiments, low R/FR ratio increased the petiole and lamina length, upward leaf position and also accelerated leaf senescence. Furthermore, low R/FR ratio reduced main floral raceme and increased floral branching with higher remobilization of soluble carbohydrates from the stems. In field experiments, low irradiance during post-flowering reduced grain yield, harvest index and grain oil content, and high R/FR ratio reaching the crop partially alleviated such effects. We conclude that photomorphogenic signals are integrated early during the vegetative growth, and irradiance has stronger effects than R/FR signals at rapeseed crop level.

Marcos E. Roberts

Papers

Physiological responses of spring rapeseed (Brassica napus) to red/far‐red ratios and irradiance during pre‐ and post‐flowering stages