The vegetative development of the maize shoot can be divided into juvenile and adult phases based on the types of leaves produced at different times in shoot development. Models for the regulation of phase change make explicit predictions about when the identity of these types of leaves is determined. To test these models, we examined the timing of leaf type determination in maize. Clones induc...

Hormones which inhibit senescence in Rumex leaf tissue in the dark include gibberellic acid and the cytokinin zeatin. Abscisic acid accelerates senescence in this tissue. Other workers have proposed that cytokinins, but not gibberellins, interact with abscisic acid in senescing Rumex leaf tissue. The present study reinvestigates the question of interaction using measurements of chlorophyll degr...

A sequential extraction technique for compartmentalizing mercury (Hg) in leaves was developed based on a water extraction of Hg from the leaf surface followed by a solvent extraction of the cuticle. The bulk of leaf Hg was found in the tissue compartment (90-96%) with lesser amounts in the surface and cuticle compartments. Total leaf concentrations of Hg varied among species and was most closel...

Leaf senescence, the final stage of leaf development, is a complex and highly regulated process that involves a series of coordinated actions at the cellular, tissue, organ, and organism levels under the control of a highly regulated genetic program. In the last decade, the use of mutants with different levels of leaf senescence phenotypes has led to the cloning and functional characterizations...

Tomanage insect resistance to transgenic crops that express insecticidal proteins from Bacillus thuringiensis (Bt) Berliner, the U.S. Environmental Protection Agency recommends a refugebased insect resistance management strategy where a percentage of non-Bt (refuge) crop is grown in proximity to a Bt-expressing crop. An important requirement for this strategy is that the toxin exists at a high ...

In vascular plants the shoot apical meristem consists of three tissue layers, L1, L2 and the L3, that are kept separate during organ formation and give rise to the epidermis (L1) and the subepidermal tissues (L2, L3). For proper organ development these different tissue layers must interact with each other, though their relative contributions are a matter of debate. Here we use ANGUSTIFOLIA (AN)...

Analyses were made of chlorophyll a and b and fatty acids (18:3, 18:2, 18:1, 18:0, 16:2, 16:1, and 16:0) of greening and senescing leaf tissue. Those dark-grown tissues given a prior treatment of red, far red, or red followed by far red light showed similar increases in chlorophylls and linolenate (18:3) when exposed to continuous white light. In contrast, green barley (Hordeum vulgare L.) leav...

The effect of exogenous auxin and cytokinin on cell proliferation and differentiation varies with the tissue system, and depends on the endogenous levels of the two hormones in the tissue. In this report, cytokinin (N-benzyladenine, BA) and auxin (indole-3-acetic acid, IAA) were used to treat young seedlings, leaf explants, and genetic tumors of a Nicotiana hybrid. Exogenous BA markedly acceler...