Senescence occurs at every stage of plant development. Shriveling of the cotyledons in young plants and the seasonal recurrence of leaf yellowing are obvious examples. Similarly, after pollination, petals have fulfilled their biological role and become senescent. Despite this ubiquity, however, the molecular events that initiate senescence have thus far remained a mystery. Thimann et al. (1977)...

Herbivory alters plant gas exchange but the effects depend on the type of leaf damage. In contrast to ectophagous insects, leaf miners, by living inside the leaf tissues, do not affect the integrity of the leaf surface. Thus, the effect of leaf miners on CO2 uptake and water-use efficiency by leaves remains unclear. We explored the impacts of the leaf-mining moth Phyllonorycter blancardella (Le...

Senescence occurs at every stage of plant development. Shriveling of the cotyledons in young plants and the seasonal recurrence of leaf yellowing are obvious examples. Similarly, after pollination, petals have fulfilled their biological role and become senescent. Despite this ubiquity, however, the molecular events that initiate senescence have thus far remained a mystery. Thimann et al. (1977)...

Leaf hydraulic conductance (k leaf) is a central element in the regulation of leaf water balance but the properties of k leaf remain uncertain. Here, the evidence for the following two models for k leaf in well-hydrated plants is evaluated: (i) k leaf is constant or (ii) k leaf increases as transpiration rate (E) increases. The difference between stem and leaf water potential (ΔΨstem-leaf), sto...

Responses of leaf water relations and photosynthesis to summer drought and autumn rewetting were studied in two evergreen Mediterranean oak species, Quercus ilex spp. rotundifolia and Quercus suber. The predawn leaf water potential (Ψ(lPD)), stomatal conductance (gs) and photosynthetic rate (A) at ambient conditions were measured seasonally over a 3-year period. We also measured the photosynthe...

Light (about 3,000 foot-candles) neither increased nor decreased the sink strength of young, rapidly expanding leaves of Phaseolus vulgaris L. cv. Black Valentine, as measured by the comparative rates of import of (14)C-labeled photosynthates by sink leaves in the light versus dark in short term experiments. Although irradiated sink leaves accumulated more (14)C activity, the difference was ful...

Corn flea beetles, Chaetocnema pulicaria, vector Erwinia stewartii (synamorph Pantoea stewartii), which causes Stewart’s bacterial wilt of corn (Zea mays) (10,11). Flea beetles introduce E. stewartii into plant tissues that are wounded during feeding. Movement of E. stewartii in the vascular system of resistant plants is restricted to within a few centimeters of flea beetle feeding wounds. The ...