Biomedical subjects

U Kutschera

Publications and source records attributed to U Kutschera.

22 records · Page 2Linked to original sources

PubMed1987

Rapid auxin-induced stimulation of cell wall synthesis in pea internodes.

The effect of auxin (indole-3-acetic acid; IAA) on growth and incorporation of myo-[2-(3)H(N)]inositol ([(3)H]Ins) into noncellulosic polysaccharides in the cell walls of third internode sections from red light-grown pea seedlings (Pisum sativum L. cv. Alaska) was investigated. Intact sections were incubated on [(3)H]Ins for 4 hr to permit uptake of the tracer and then IAA was added. Growth started after a lag phase of 15 min under these conditions. The sections were removed from the tracer and separated into epidermis and cortical cylinder (cortex plus vascular tissue). In the epidermis, IAA-induced stimulation of [(3)H]Ins incorporation started after a lag of 15 min. The amount of incorporation was 15% higher after 30 min and 24% higher after 2 hr than in the control. In the cortical cylinder, IAA-induced stimulation of [(3)H]Ins incorporation started only approximately 1 hr after adding IAA. The ionophore monensin (20 muM) inhibited the IAA-induced growth by 95%. Under these conditions, the IAA-induced stimulation of [(3)H]Ins incorporation and the IAA-induced increase in in vivo extensibility of the sections was almost completely inhibited, although oxygen uptake was unaffected. We suggest that wall synthesis (as represented by [(3)H]Ins incorporation) and wall loosening (increase in in vivo extensibility) are related processes. The results support the hypothesis that IAA induces growth by rapid stimulation of cell wall synthesis in the growth-limiting epidermal cell layer.

Journal Article↗

PubMed1987

Differential effect of auxin on in vivo extensibility of cortical cylinder and epidermis in pea internodes.

The effect of auxin indole-3-acetic acid (IAA) on growth and in vivo extensibility of third internode sections from red light grown pea seedlings (Pisum sativum L. cv Alaska) and the isolated tissues (cortex plus vascular tissue = cortical cylinder, and epidermis) was investigated. Living tissue was stretched at constant force (creep test) in a custom-built extensiometer. In the intact section, IAA-induced increase in total (E(tot)), elastic (E(el)), and plastic (E(pl)) extensibility is closely related to the growth rate. The extensibility of the cortical cylinder, measured immediately after peeling of intact sections incubated for 4 hours in IAA, is not increased by IAA. Epidermal strips, peeled from growing sections incubated in IAA, show a E(pl) increase, which is correlated to the growth rate of the intact segments. The isolated cortical cylinder expands in water; IAA has only a small growth-promoting effect. The extensibility of the cortical cylinder is not increased by IAA. Epidermal strips contract about 10% on isolation. When incubated in IAA, they do not elongate, but respond with an E(pl) increase. The amount of expansion of the cortical cylinder and contraction of the epidermis (tissue tension), measured immediately following excision and peeling, stays constant during IAA-induced growth of intact sections. The results support the hypothesis that IAA induces growth of the intact section by causing an E(pl) increase of the outer epidermal wall. The driving force comes from the expansion of the cortical cylinder which is under constant compression in the intact section.

Journal Article↗

PubMedDate not supplied

The biophysical basis of cell elongation and organ maturation in coleoptiles of rye seedlings: implications for shoot development.

The relationships between changes in irreversible and reversible organ length, turgor (P), osmotic pressure (pi), and metabolic activity of the cells were investigated in intact coleoptiles of rye seedlings ( Secale cereale L.) that were either grown in darkness or irradiated with continuous white light. Cessation of growth at day 4 after sowing was associated with an apparent mechanical stiffening of the cell walls. Turgor pressure was measured in epidermal and mesophyll cells with a miniaturized pressure probe. No gradient of turgor was found between the peripheral and internal cells. In juvenile (growing) coleoptiles, average turgor was 0.60 MPa and a negative water potential (P - pi) was established in these cells. Upon emergence of the primary leaf, turgor declined, but P was maintained at values of 0.43 and 0.52 MPa in 7-day-old light- and dark-grown coleoptiles, respectively. Water potential in non-growing cells approached zero. The rate of dark respiration and elongation growth were not correlated. Surgical removal of the mature coleoptile revealed that the erect position of the 7-day-old shoot was dependent on the presence of this sturdy, turgid organ sheath. It is concluded that, during the first week of seedling development, the pierced, metabolically active coleoptile fulfills an essential function as an elastic basal tube for the juvenile shoot.

Cell Wall↗

PubMedDate not supplied

Cannibalism in a population of the medicinal leech (Hirudo medicinalis L.).

Medicinal leeches (Hirudo medicinalis L.) were maintained in large ponds in a commercial leech farm at Biebertal, Germany. The feeding of hungry adult leeches was performed on representative individuals that were placed on cloth soaked with mammalian blood obtained from a local butchery (pig, Sus scrofa). In a second set of experiments, cane toads (Bufo marinus) were used as host organisms. The leeches rapidly attached to the toads, explored the body and sucked blood. After feeding, the fully engorged leeches were placed into the pond or an aquarium. In this artificial habitat, the satiated leeches were attacked by hungry conspecifics, sucked off and killed. This observation demonstrates that H. medicinalis must be classified as a cannibalistic annelid.

Animals↗