Radicle control

Radicle elongation was quite linear with time (r = 0.98, minimum). Pretreating the seed with DCM reduced early radicle growth, but by 96 h the sterol/DCM treated seed achieved radicle lengths equal to that of the H2O control and 30% more than those of DCM controls. The experiment was terminated at 96 h when space limitations in the petri dishes and near-anaerobic conditions during incubation began to interfere with seedling development. There were no secondary roots visible after 96 h. 

Germination and radicle length expressed as percentage of germination and radicle length of controls. 

Table III. Effect of culture broth (2 ml/petri dish) and dichloromethane extract of culture broth (0.2 mg/petri dish) on cress radicle growth, as related to presence of cyclohex-imide. Data are for all isolates tested in liquid culture whose broth inhibited cress radicle growth to 50% of controls...

Bioassays are performed under sterile conditions in a laminar flow hood. Tomato seeds are previously washed and disinfected with 1% sodium hypochlorite. Seeds are germinated in the Petri dishes containing the S. deppei aqueous leachate. For control, seeds are germinated in 1% agar. Twelve seeds are placed on each Petri dish and kept in the dark at 27°C in a growth chamber. For enzyme activities, 40-50 Petri dishes are used per treatment. Primary roots (radicles) are excised after 72 h, frozen in liquid nitrogen and kept at -70 °C until use. For root growth response, experiments... 

Observations Germination and radicle growth can be determined at 12, 24, 48 and 72 h and the inhibitory effect of the aqueous leachate can be calculated comparing root length of treated seedlings vs. data from control ones. In this case, we only used the 72 h treatment (Figure 1). 

Compounds 58 and 59 showed phytotoxic effects when tested against seedlings of A. hypochondriacus using a Petri dish bioassay. Compounds 58 [IC50 = 6.57 xM] and 59 [IC50 = 3.86 xM] inhibited radicle growth of this species with a similar potency to 2,2—dichlorophenoxyacetic acid [2,4-D IC50 = 18 xM], which was used as a positive control. 

Table I. Change Caused by Nicotine in Seed Germination, Radicle Length and Plumule Length over Control in Two Crops Plants...

Table HI. Amaranthus spinosus Reduction of Seed Germination, Radicle Length, and Plumule Length over Control by Geraniol...

Extracts (12 mL each) were added to Petri dishes 10 cm in diameter containing 50 g of 30-mesh washed sand covered with filter paper circle (7-cm diameter, Whatman 1). Controls were moistened with doubly distilled water. Ten indicator seeds were placed on the filter paper in each dish with the embryo down and the hypocotyl pointed to the center of the Petri dish. Each indicator/extract combination had 3 replicates. The Petri dishes were kept in a dark growth chamber for approximately 72 hr at 25°C. The radicle length of each germinated seedling was measured at 72 hr. 

Light microscopy of radish radicles from a control seed after 16 h imbibition (a, c) and from a seed treated with 1 14-diluted reverse osmosis fraction, 46 h after imbibition. The root from the treated seed (b) is much shorter and coarser than the control (a). Cell expansion is strongly inhibited in the treated root (d) relative to the control (c). 

Electron microscopy of radish radicle, a) and b) Details of cortical cells from radicles of 2 h-imbibed control seeds, (a) Note the abundance of protein reserves in protein bodies (PB) and lipid reserves in the peripheral cytoplasm (arrows), (b) Numerous mitochondria (M) are visible among lipid bodies (L). (c-e) Details of cells from radicles of 16 h-imbibed control seeds, (c) Cortical parenchyma cells. The protein bodies have converted into normal vacuoles (V) and lipid reserves have been partially depleted, (d) Detail of epidermal cell showing a plastid (P) containing starch deposits (S). (e) Detail of cortical cell, showing several mitochondria (M) and a microbody (Mb). 

Electron microscopy of radish radicle. Details of columella cells from 16 h-control seed (a) and seed treated with 1/14-diluted reverse osmosis fraction (b-d). (a) Columella cells in the control are distinctly polarized and contain large amyloplasts (arrows). Nucleus (N). (b) Columella cells in treated roots are not polarized and contain no amyloplasts. The numerous electron-transparent vesicles are swollen mitochondria (M). (c) Detail showing swollen mitochondria (M) and starch-less plastids (P). (d) High magnification of swollen mitochondria showing the two-membrane envelope (arrows). 

Striga seeds were initially surface sterilized with 1% aqueous NaOCl, followed by two deionized water rinses and then were pre-incubated in lOmL of deionized water in the dark at 28°C for 10 days. Samples of pre-incubated seeds were collected on 5 /hn Metricel filters (Gelman Type GA-1) and floated in lOmL test solution or control solution (either 0.1% dimethyl sulfoxide or deionized water). For the germination incubations, seeds and test solution were transferred to 96 well plastic culture dishes (0.4 mL/well and 4 replicates of 8 wells each for a given assay). The Striga seeds were then incubated in the dark for 3 days at 28°C before evaluation of germination (radicle protrusion) under 40X magnification. Each experiment was repeated at least twice. Where necessary, test solution pH was adjusted to 6.8 with 0.IN KOH. 

Lansalot, M., Farcet, C., Charleux, B., Vaison, J.-P., and Piri, R. (1999). Controlled free-radicle miniemulsion pol5mierization of styrene using degenerative transfer. Macromolecules, 32 7354-7360. 

Isolated axes of peas are not dependent on the reserve material of the cotyledons during the initial stages of radicle elongation [17]. Reserves of carbohydrate, protein and fat in the radicle itself must be sufficient for these early events, and sucrose, raffmose and stachyose probably serve as sources of respirable substrate. But after these early events have passed, the further development of the root and shoot systems depends upon the contributions from the cotyledons. Their stored carbohydrate (and the other reserves) are hydrolysed and transported into the axis. It is not yet clear if the initiation of mobilization is actually controlled by the embryonic axis this is discussed fully in Chapter 7. We can say, however, that the subcellular changes in the cotyledons that precede and accompany reserve mobilization do need the presence of axis, at least over the first 48 h after the start of imbibition. 

Soils were collected from underneath bracken stands following the first rain of the season. The wetted upper 2 to 3-cm layer was screened and placed in storage dishes. Grassland soils similarly collected served as controls. Seeds were planted in these soils, watered with distilled water, and the dishes sealed with parafilm and stored. All species tested, except for Bromus rigidus, were inhibited in radicle growth. 

Radicle elongation was a more sensitive measure than germination. Phytotoxicity decreased as the distance from rye shoot material to assay seeds increased. Generally, cress and lettuce were more sensitive indicators than the grass species tested. Phytotoxic compounds from shoots were water extractable. To evaluate the effect of plant part and quantity of residue, roots, shoots, or both were assayed at 0.0, 0.25, 0.5, 1.0, and 2.0 g/dish and placed 5 mm away from the assay seed. Similar amounts of paper towels were used as controls. Shoot tissue was about twice as toxic as root tissue. The data suggested that under field conditions, a... 

Great Lakes 366 ) was used as a test plant. For the control treatment, mushrooms were not added. The lengths of die radicle and hypocotyl of lettuce seedlings were measured after incubation at 20 C in the dark for 3 days. Efficacy of lettuce seedling growth was calculated from the following formula ... 

---