Circumnutation as an autonomous root movement in plants.

Although publications on circumnutation of the aerial parts of flowering plants are numerous and primarily from the time between Darwin (1880) and the 1950s, reports on circumnutation of roots are scarce. With the introduction of modern molecular biology techniques, many topics in the plant sciences have been revitalized; among these is root circumnutation. The most important research in this area has been done on Arabidopsis thaliana, which has roots that behave differently from those of many other plants; roots grown on inclined agar dishes produce a pattern of half waves slanted to one side.

BVOC emission from Populus × canadensis saplings in response to acute UV-A radiation.

Hybrid poplar (Populus × canadensis) saplings were subjected to acute ultraviolet-A (UV-A) irradiation (30 W m(-2) , ambient treatment, 60, 90 and 120 W m(-2) of UV-A irradiance) to determine the effects on photosynthesis and biogenic volatile organic compound (BVOC) emissions in two different short-term experiments (i.e. sequential increase in UV-A irradiance and UV-A intensity-response relationships).

Neutron irradiation affects the expression of genes involved in the response to auxin, senescence and oxidative stress in Arabidopsis.

We report, in Arabidopsis thaliana plants, the effect of neutron irradiation on the transcription of a set of genes belonging to different physiological groups: auxin action, senescence, oxidative stress, and some aspects of photosynthesis. The results indicated that, in the wild-types, the effect on the ARF1, ARF2, and 19 genes was of down-regulation, whereas of the tested AUX/IAA only AUX/IAA7 showed up-regulation. Different results were obtained as regards the irradiation of the auxin transport mutants aux1 and eir1, because in these cases the ARF genes were up-regulated, whereas AUX/IAA7 was down-regulated in eir1.

Arabidopsis root growth movements and their symmetry: progress and problems arising from recent work.

Over the last fifteen years, an increasing number of plant scientists have become interested in the Arabidopsis root growth pattern, that is produced on the surface of an agar plate, inclined from the vertical. In this situation, the roots wave intensely and slant preferentially towards one side, showing torsions in the epidermal cell files alternately right-and left handed. In addition, the pattern switches to the formation of large or strict coils when the plate is set horizontally.

Rha1, a new mutant of Arabidopsis disturbed in root slanting, gravitropism and auxin physiology.

A new Arabidopsis mutant is characterized (rha1) that shows, in the roots, reduced right-handed slanting, reduced gravitropism and resistance to 2,4-D, TIBA, NPA and ethylene. It also shows reduced length in the shoot and root, reduced number of lateral roots and shorter siliques. The gene was cloned through TAIL-PCR and resulted in a HSF.

Isoprene emission is not temperature-dependent during and after severe drought-stress: a physiological and biochemical analysis.

Black poplar (Populus nigra L.) plants grown at 25 and 35 degrees C were subjected to drought stress to assess the combined impact of two consequences of global climate change--rising temperature and drought--on isoprene biosynthesis and emission. At both temperatures, photosynthesis was inhibited by moderate drought, but isoprene emission only decreased when drought was prolonged.

Response of isoprene emission and carbon metabolism to drought in white poplar (Populus alba) saplings.

The mechanism uncoupling isoprene emission and photosynthesis under drought was investigated in Populus alba saplings. Isoprene emission, incorporation of 13C into the isoprene molecule, isoprene synthase (ISPS) activity, concentration and gene expression, and photosynthesis were measured as a function of the fraction of transpirable soil water (FTSW) and in plants recovering from drought. Photosynthesis sharply declined below FTSW30 (a FTSW of 30%) and its inhibition was not caused by metabolic factors.