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Dormancy release and germination in recalcitrant Aesculus hippocastanum seeds

100%

Obroucheva N. V. , Lityagina S. V.

Dendrobiology

2007

tom 57

27-33

The investigation of dormancy release in Aesculus hippocastanum seeds was aimed at estimating the proportion of coat-imposed to embryo dormancy, and studying the growth initiation providing embryo dormancy release. During winter, horse chestnut seeds exhibited 16–17 week-lasting deep dormancy, which predominantly was determined by coat-imposed dormancy. Embryo dormancy lasted for 11–12 weeks of wet cold stratification. Embryo dormancy was weak, even the embryo axes excised from deeply dormant seeds were capable of extending to the size exceeding the axis length in intact seeds at radicle protrusion. Embryo dormancy release manifested itself in gradually increasing growth capacity of both embryo axes and cotyledonary petioles. The growth initiation in horse chestnut seeds occurs only by cell elongation. During growth initiation, a more rapid fresh weight gain was observed in comparison with length increment, thus indicating that accumulation of osmotically active substances and active water uptake by embryo axis cells were ahead of their increasing longitudinal cell wall extensibility. Cell wall loosening appeared to be directly related to embryo dormancy release. The hormonal regulation of embryo dormancy release in horse chestnut seeds is discussed.

Nickel and zinc effects, accumulation and distribution in ruderal plants Lepidium ruderale and Capsella bursa -pastoris

51%

Kozhevnikova A. D. , Erlikh N. T. , Zhukovskaya N. V. , Obroucheva N. V. , Ivanov V. B. , Belinskaya A. A. , Khutoryanskaya M. Y. , Seregin I. V.

Acta Physiologiae Plantarum

2014

tom 36

nr 12

Ruderal plants can grow in polluted areas, but little is known about heavy metal accumulation and distribution in them. Here Ni and Zn accumulation, distribution and effects were investigated in Lepidium ruderale and Capsella bursa-pastoris grown at 5–30 µM Ni(NO₃)₂ or 10–80 µM Zn(NO₃)₂. Metal contents were measured by flame atomic absorption spectrophotometry and tissue distribution of metals was studied histochemically. Ni was more toxic than Zn for both plants. When metal-induced growth-inhibiting effects were compared at various metal concentrations in solution, L. ruderale was more tolerant to Ni, whereas C. bursa-pastoris to Zn. However, when compared at similar Zn or Ni contents in roots, root growth of C. bursa-pastoris was more tolerant than that of L. ruderale. On the contrary, at similar Zn or Ni contents in shoots, shoot growth of L. ruderale was more tolerant. Both plants are excluders maintaining low metal levels in shoots. In roots, Ni located in protoplasts while Zn was also detected in cell walls. Metal accumulation in root apices resulted in growth inhibition. Ni accumulation in root cortex constrained metal translocation into central cylinder and then to shoots, where it located only in conductive tissues and epidermis, particularly in leaf trichomes of C. bursa-pastoris. Zn was translocated to shoots more actively and distributed in all shoot tissues, being accumulated in leaf vascular bundles and epidermis. To conclude, these patterns of Ni and Zn distribution are aimed at metal sequestration in roots and leaf epidermis, thus keeping mesophyll from metal penetration and pigment degradation.