When abraded oat (Avena sativa L. cv Victory) leaf segments are floated on KCl solution, white light causes acidification of the solution external to leaf tissue. The presence of mannitol amplifies the light-induced proton secretion. Mature leaves as well as young ones acidify the medium in light, while senescing leaves (after 3 to 4 days incubated in water in the dark) lose the ability to prod...

Accelerated leaf senescence is one of the harmful effects of elevated tropospheric ozone concentrations ([O(3)]) on plants. The number of studies dealing with mature forest trees is scarce however. Therefore, five 66-year-old beech trees (Fagus sylvatica L.) have been exposed to twice-ambient (2xambient) [O(3)] levels by means of a free-air canopy O(3) exposure system. During the sixth year of ...

The plastid-nucleus located protein WHIRLY1 has been described as an upstream regulator of leaf senescence, binding to the promoter of senescence-associated genes like HvS40. To investigate the impact of WHIRLY1 on drought stress-induced, premature senescence, transgenic barley plants with an RNAi-mediated knockdown of the HvWHIRLY1 gene were grown under normal and drought stress conditions. Th...

Changes in the number and composition of chloroplasts of mesophyll cells were followed during senescence of the primary leaf of wheat (Triticum aestivum L.). Senescence was due to the natural pattern of leaf ontogeny or was either induced by leaf detachment and incubation in darkness, or incubation of attached leaves in the dark. In each case discrete sections (1 centimeter) of the leaf, repres...

We investigated the effects of ozone and leaf senescence on steady-state stomatal conductance and stomatal response to light variation. Measurements were carried out in a free-air ozone exposure experiment on a representative deciduous broadleaved tree species in Japan (Fagus crenata). Both steady-state and dynamic stomatal response to light variation varied intrinsically with season due to lea...

The Arabidopsis thaliana genome encodes three RNA-binding proteins (RBPs), UBP1-associated protein 2a (UBA2a), UBA2b, and UBA2c, that contain two RNA-recognition motif (RRM) domains. They play important roles in wounding response and leaf senescence, and are homologs of Vicia faba abscisic-acid-activated protein kinase-interacting protein 1 (VfAKIP1). The potato (Solanum tuberosum) genome encod...

In pea (Pisum sativum L.) leaves, manganese superoxide dismutase (Mn-SOD) is mainly localized in mitochondria as well as in peroxisomes. In this work, the effect of leaf senescence on the peroxisomal and mitochondrial Mn-SOD was studied in detached leaves from pea plants which were incubated in the dark at 25 degrees C for 3-11 d. Northern blots hybridized with a cDNA encoding mitochondrial Mn-...

Fruit yield decreases gradually after several years of cultivation in Amomum villosum, an important Chinese medicinal herb, which is generally attributed to plant senescence. However, the reasons for plant senescence are still not clear until now. In this study, we investigated the effects of micronutrient deficiencies on leaf senescence. We hypothesized that micronutrient deficiencies may caus...

In the present study, we evaluate the protective effect of nitric oxide (NO) against the senescence of rice leaves promoted by hydrogen peroxide (H 2 O 2 ). Senescence of rice leaves was determined by decreases in protein content. H 2 O 2 treatment resulted in (1) increases in leaf H 2 O 2 content, (2) induction of leaf senescence, (3) increases in lipid peroxidation, (4) decreases in ascorbic ...