Versuche zur somatischen Beeinflussung der Organbildung pflanzlicher Embryonen
Experiments on influencing cotyledon formation in embryos ofEranthis hiemalis are reported. By treating the seeds with 100–2000 ppm solutions of 2,4-dichlorophenoxyacetic acid, 2,4,5-trichlorophenoxyacetic acid, 2-methyl-4-chlorophenoxyacetic acid, α-naphthylacetic acid and even isopropyl N-phenyl carbamate one can obtain significant increases in twinning and in cotyledon anomalies (syncotyly and pleiocotyly of all degrees). Embryos can be successfully treated until approximately 2 weeks after initial opening of the follicles. X-radiations achieve the same effect, with doses of 2000–4000r corresponding to the treatments with 1000–2000 ppm 2,4-D-solutions. By using weaker concentrations and with sudden temperature changes one can likewise raise the percentage of syn-, tri- and tetracotyls, but pleiocotyls of the higher degrees (5 and more cotyledons) appear only when more intensive methods of treatment are employed. These forms which exceed the normal range of variability arise as bud-like embryo regenerates on the as yet undifferentiated original embryo.
Über die Regenerationsfähigkeit junger Embryonen vonEranthis hiemalis nach Colchicin-Behandlung
Melilotus-Mutanten s ind also als a u s g e s p r o c h e n bitterstoffarm, n i ch t j edoch als bitterstoff[rei zu beze iehnen. Gallz offellk u n d i g l iegt hier also eine Pa ra l l e l e r sche inung zu den bere i t s b e k a n l l t e n Fgl len bei Lupinus u n d Nicotiana vor. Bei den U n t e r s u c h u n g e l l an lu f t t rockel len Bl i i t te rn konl l t e i m fibrigen eine erhebl iche Z u l l a h m e des G e s a m t b i t t e r s t o f f g e h a l t e s festges te l l t werden , die wah r sche i n l ich au f e n z y m a t i s c h e Vorggnge beim Trockn l lngsprozeg zurfickzuff ihren ist. Die W e r t e s chwanken h ier in der T r o c k e n s u b s t a n z zwischen 0,009 u n d 0,25% bei dell M u t a n t e n u n d zwischell 0,3t bis 0 ,60% bei den unbe hande l t en IZontrollpflanzen. Die I n d i v i d u e n 56 t /11 ,561 /1 ,559 / t , 560/17, 560/16 u n d 577/10 s ind p r a k t i s c h als b i t te rs tof f f re i anzusprechen . Auffal lel ld is t das h~uf ige A u f t r e t e n b i t t e r s t o f f a r m e r Pf lanzel l in C 2 n a e h B e h a n d l ung m i t A1C1 a bei m / t 000 . Die Fami l ien , in dene n sich diese P f l anzen fal lden, ze ig ten gegenfiber der u n b e h a n d e l t e n Fami l ie einell gallz andere l l W u c h s t y p . Bezeichllel lderweise war ein groger Tell dieser b i t t e r s to f f a r m e n Pf la l lzen in u n s e r e n Vers u c h s g g r t e n y o n H a s e n angef ressen; eine chemische Ana lyse war dahe r n i ch t bei allen I l ld iv iduen dieser F ami l i en m6gl ich. Die U l l t e r s u c h u n g e n werdell fo r tgese tz t . Die E x i s t e n z der verm u t e t e n b i t t e r s to f fa rme l l Melilotus-Mutanten muB noch d u r c h die B a s t a r d a n a l y s e s icherges te l l t werden . Die U n t e r s u c h u n g e n wurdel l dankenswer t e rwe i se du rch die D e u t s c h e F o r s c h u n g s g e m e i n s e h a f t e rm6gl ich t .
SUGAR MOVEMENT TO ROOTS, MINERAL UPTAKE, AND THE GROWTH CYCLE OF THE COTTON PLANT.
Comparative data .are reported in this paper oni the sugar concentrationls in the fibrous roots (and other parts) of defruited and control cotton plants and the uptake by these plants of bromine, nitrogen, and potassium. The measurements were made 22 days after defruiting (21 days after the addition of bromine to the nutrient solution). The data are discussed in terms of the relation of sugar concentrations in fibrous roots to mineral uptake and the relation of mineral uptake to the growth eyele of the cotton plant. The uptake of soil nutrients by the cotton plant, as shown by WHITE (27), CROWTHER (8, 9), DASTUR (10), OLsoN and BLEDSOE (23), and others, proceeds at an inereasing rate through the period of early growth and flowering but subsequently, as the niumber of bolls carried by the plants inereases, the rate of uptake deelilies anid actual losses of mineral elements from the above-ground portions of the plants mayoccur. It was suggested a niumber of vears ag,o (8) that the observed reduction in nitrogen uptake during the fruiting period of cotton might be due to depressed root growth. The dominance of fruiting activity over vegetative development and root growth has been well established in cotton (12, 13, 19, 20) and it seems certain that the extension of roots into new soil zones and the development of new root surfaces would be important factors in solute uptake. The foregoing explanation, however, insufficielntly accounts for all of the known facts. If, on the other hand, fruiting substantially reduces the concentration of sugars in the fibrous roots, the observed reduction in mineral uptake with fruiting can be more fully comprehended. The necessity for an expeniditure of energy for the accumulation of solutes against concentration differenitials has been outlined by HOAGLAND (17) and more recent work with barley seedlings (5) adds assurance that sugars situated in the roots provide the primary respiratory fuel for mineral uptake. It has been shown (18, 20) that the developing cotton boll tends to have first call on labile carbohydrates. Irrespective of probabilities, however, it has not been established that the sugar concentrations in fibrous roots vary enough with fruiting to constitute a critical intermediate link between fruiting and the rate of mineral uptake. The responses of soybeans (3) and of tomatoes (2) to defloration indicate that fruiting may alter the carbohydrate relations in the above-ground portions of plants without affecting imaterially the rate of mineral uptake. Two additional papers (24, 25) also pertain to the foregoing considerations. In soybeaiis, AUSTIN (3) founid the accumulation of some elements was depressed by defloration; his data show, however, that defloration had little