Physiological assessment of apetalous flowers and erectophile pods in oilseed rape (Brassica napus)

Abstract

S U M M A R YThe transmission of solar radiation within the crop canopies of oilseed rape is decreased both by the plant's yellow petals during flowering, and by the horizontal posture of the pods once they are formed. The significance of each of these morphologies was assessed, in the 1991/92 and 1992/93 growing seasons, by comparing the performances of an apetalous breeding line (N-o-112) and one with erectophile pods (N-5-130) with two conventional commercial genotypes (Falcon and Tapidor).The apetalous floral layer of line N-o-112 reflected and absorbed significantly less radiation than those of the conventional, petalled genotypes. This resulted in a greater transmission of photosynthetically active radiation (PAR) to the leaf and bract canopy situated below. At peak flowering, 70% more PAR was transmitted through the apetalous floral layer.The erectophile pods of line N-5-130 were angled 20-25° further from the horizontal than the conventional genotypes. The extinction coefficient (K) of its pod layer during late pod growth ranged from 035 to 0-44 as compared to 045 to 055 in the commercial varieties. Line N-5-130 carried a greater proportion of its total fertile pod number in the lower regions of the pod canopy compared to the two conventional genotypes. It also had a greater overall mean number of seeds per pod, and the number decreased proportionately less with depth in the canopy. The line was thus better able to maintain a higher photosynthetic area and to sustain pod and seed growth at the lower levels of the crop canopy than the conventional, commercial varieties. The potential physiological effects of apetalous flowers and erectophile pods are considered to be sufficiently beneficial for their introgression into near-isogenic lines to be pursued.i M T P o n i i r n n M termine the effect of the apetalous morphology on i N i K U U U C i i u w s e e d y i e , d T h e y c o n c l u d e d t h a t t h e character would Yield potential in oilseed rape (Brassica napus L.) be of most benefit in European winter varieties, which is determined by pre-anthesis dry matter (DM) flower more profusely. accumulation (Mendham et al. 1981), whilst the Chapman et al. (1984) reported that a dense pod realisation of this potential is dependent upon post-canopy greatly restricted radiation penetration during anthesis photosynthesis, and the translocation of pod filling, with only 6% of incident PAR reaching assimilates to the seed (Evans 1984). Radiation the base of the pod layer. Shading of the lower pods transmission to the leaf canopy during flowering is by the upper pods reduced their photosynthetic rate, reduced by the highly reflective and absorptive yellow induced higher pod and seed abortion and contributed floral layer. Chapman et al. (1984) found that this to low seed yields in the basal layer of the pod canopy resulted in only 24 and 7% of incident PAR reaching (Mendham et al. 1981). Poor radiation transmission the base of the floral layer at early and late flowering through the pod canopy may be caused by th...

Ground cover and leaf area index relationship in a grass, legume and crucifer crop

“…The results obtained for k were 0.44, 0.56, and 0.57 for barley, vetch and rape, respectively (Figure 1). These values are within the ranges reported in the literature (Fray et al 1996, Thomson and Siddique 1997, Kemanian et al 2004.…”

Maternal control of seed oil content in Brassica napus: the role of silique wall photosynthesis

“…This study suggests an alternative method for traditional breeding and transgenic research to obtain higher oil contents. The photosynthetic activity in the silique may be a useful trait for the selection of varieties with high oil contents, such as the apetalous and erectophile pods lines that attract more photosynthetically active radiation (Fray et al. , 1996).…”

Inheritance of Apetalous Flowers in a Mutant of Oilseed Rape

“…In Brassica species, mutants have been observed which show increased petals, reduced petals, or complete absence of petals (apetalous) (Singh, 1961a,b; Cours and Williams, 1977; Buzza, 1983; Lü and Fu, 1990; Fray et al, 1997). Apetalous genotypes may be more efficient in photosynthesis and reallocation of assimilates because the yellow petal layer of Brassica oilseed crops reflects a large part of the photosynthetically active radiation (Chapman et al, 1984; Yates and Steven, 1987; Mendham et al, 1991; Fray et al, 1996; Jiang and Becker, 2001a). Moreover, apetalous types may avoid some diseases, especially stem rot caused by Sclerotinia sclerotiorum (Lib.)…”