Optical and anatomical characteristics of bracts from the Chinese "glasshouse" plant, Rheum alexandrae Batalin (Polygonaceae), in Yunnan, China.

Bracts that lacked chlorophyll were compared with rosette leaves on the Chinese glasshouse plant Rheum alexandrae Batalin. The structures were analyzed anatomically and with photospectrometry. Histological features were significantly different between the bracts and the rosette leaves.

Thermal insulation and accumulation of heat in the downy inflorescences of Saussurea medusa (Asteraceae) at high elevation in Yunnan, China.

Himalayan snowball plants, which are considered to be an extreme form of downy plants, have very dense trichomes on well-developed bracts that surround the inflorescences. It has been postulated that the downy inflorescences of these plants might serve to keep the interior of inflorescences warmer than the outside and, thus, to protect reproductive cells from low temperatures in their Himalayan habitat. In the present study, we examined the downy inflorescences of Saussurea medusaMaxim.

Leaf anatomy of a rheophyte, Dendranthema yoshinaganthum (Asteraceae), and of hybrids between D. yoshinaganthumand a closely related non-rheophyte, D. indicum.

The rheophyte Dendranthema yoshinaganthum(Makino ex Kitam.) Kitam. is endemic to a region along the Naka River in Shikoku, Japan.

Organ shape and size: a lesson from studies of leaf morphogenesis.

Control of the shape and size of indeterminate organs, such as roots and stems, is directly related to the control of the shape and size of the cells in these organs, as predicted by orthodox cell theory. For example, the polarity-dependent growth of leaf cells directly affects the polar expansion of leaves. Thus, the control of leaf shape is related to the control of the shape of cells within the leaf, as suggested by cell theory.

Interpretation of mutants in leaf morphology: genetic evidence for a compensatory system in leaf morphogenesis that provides a new link between cell and organismal theories.

On the basis of "cell theory," we tend to think that some changes in cellular behavior must be responsible for mutant morphology. According to the cell theory, the unit of morphogenesis of a multicellular organism is the cell. Another interpretation of morphogenesis of plants is the "organismal theory," which postulates that the individual cell is not the basic unit of morphogenesis.

Leaf development.

The shoot system is the basic unit of development of seed plants and is composed of a leaf, a stem, and a lateral bud that differentiates into a lateral shoot. The most specialized organ in angiosperms, the flower, can be considered to be part of the same shoot system since floral organs, such as the sepal, petal, stamen, and carpel, are all modified leaves. Scales, bracts, and certain kinds of needle are also derived from leaves.

Source analysis of magnetic field responses from the human auditory cortex elicited by short speech sounds.

We made a detailed source analysis of the magnetic field responses that were elicited in the human brain by different monosyllabic speech sounds, including vowel, plosive, fricative, and nasal speech. Recordings of the magnetic field responses from a lateral area of the left hemisphere of human subjects were made using a multichannel SQUID magnetometer, having 37 field-sensing coils. A single source of the equivalent current dipole of the field was estimated from the spatial distribution of the evoked responses.