Effect of Horizontal Clinorotation on the Root System Development and on Lipid Breakdown in Rapeseed (Brassica napus) Seedlings

Abstract

Seedlings of Brassica napus were cultivated on a slowly rotating clinostat (1 rpm) or in the vertical control for 5 d. The root growth, the cotyledonary reserves and the transport of 14C-labeled sucrose from cotyledons to root system were studied in both cultural conditions. The biomass (fresh weight) of the root system was 35% higher in the horizontally clinorotated seedlings than in the controls. This increase was correlated with a greater degradation of reserve lipids and faster accumulation of sucrose in the cotyledons. The activity of isocitrate lyase, one of the two enzymes necessary to conversion of lipids into glucids, was also greater in the cotyledons of clinorotated seedlings. The labeling distribution of 14C in the cotyledons, the hypocotyl and the root system after 30, 60 and 120 min of application of 14C-labeled sucrose on the cotyledons showed higher translocation of the cotyledonary sucrose to the root system of clinorotated seedlings. In addition, we studied the effects of clinorotation on the biomass of the excised root system (of 10 d old seedlings) cultivated in a medium containing 1% sucrose. The horizontally clinorotated root system grew more than that of the controls. These results showed that the horizontal clinorotation acted on the root system growth and provoked a higher sucrose translocation from source to sink, i.e. from cotyledons to root system.

Plant cell proliferation and growth are altered by microgravity conditions in spaceflight

“…In the two experiments, samples grown in space were enriched in earlier phases with respect to 1g controls, and the authors concluded that the cell cycle was slowed down in microgravity. However, this conclusion does not take into account a possible different effect of microgravity depending on the time of exposure and/or on the phase of development of the plant or seedling (Claassen and Spooner, 1994;Aarrouf et al, 1999). In fact, this time of growth under microgravity conditions was quite different in these experiments (28-29 h) and in the experiment reported in the present paper (4 d).…”

“…In addition, it has been hypothesized that the action of microgravity might depend on the duration of exposure to microgravity and/or on the developmental stage of the plant (Claassen and Spooner, 1994). The hypothesis was confirmed experimentally in clinorotated samples (Aarrouf et al, 1999), but not with real microgravity.…”

Effects of acorn storage duration and parental tree on emergence and physiological status of Cork oak (Quercus suber L.) seedlings

“…If this is true, our seedlings from large seeds could accumulate more carbohydrate reserves because of their rapid growth. It has been showed [1,19,24,27] that the carbohydrate reserves play an important role in lateral root emergence, and that seedling performance depends on the rapidity of emergence of lateral roots [6,16,37].…”

NaCl stress causes changes in photosynthetic pigments, proteins, and other metabolic components in the leaves of a true mangrove,Bruguiera parviflora, in hydroponic cultures

“…The pellet that remained after the soluble sugars were extracted was solubilized in 52% perchloric acid for determination of starch content (McCready et al, 1950). Total soluble sugars and starch were estimated according to the anthrone-sulphuric acid method of McCready et al, (1950), with some modification (Aarrouf et al, 1999). We used 0.2% anthrone in concentrated H2SO4 as the reagent.…”

“…Spectrophotometric readings were taken at 630 nm, and a standard curve was plotted with 0 to 100 pg of pure glucose. The concentration of starch was determined by multiplying the obtained value by 0.9 for converting the glucose value to starch content (Aarrouf et al, 1999). We adapted the alkaline copper methods of Nelson (1944) and Somogyi (1945) for estimating the amount of reducing sugars, using an arsenomolybdate reagent.…”