Peter B. Kaufman

Heavy metal contents in some macrophytes from Saginaw Bay (Lake Huron, U.S.A.)

Abstract During the summer of 1977, a total of 71 plant collections, representing 22 species of macrophytes (one green alga and 21 spermatophytes), was analyzed for heavy metals concentration using neutron activation analysis. The 15 elements analyzed were Ag, As, Ba, Cd, Ce, Co, Cr, Cs, Ni, Rb, Sb, Se, Th, U and Zn. Highest concentrations tended to occur in plants collected near the mouth of the Siginaw River. The alga, Cladophora sp., and cat-tail (Typha angustifolia L.) are noteworthy in their high heavy metal concentrations. Seven species sampled from wilderness areas in Michigans upper peninsula contained higher concentrations of certain metals than any sample from Saginaw Bay.

The role of hormone transport and metabolism in apical dominance in oats

14C-benzyladenine (BA) and 14C-indole-3-acetic acid (IAA) were used to study hormone transport to the tiller bud and hormone catabolism in excised oat stem segments. Acropetal BA transport was greatest from upright stem segments to tiller buds suppressed by apical dominance. IAA, abscisic acid (ABA), and C2H4 inhibited BA transport to the tiller bud. IAA transport to the tiller bud site was inhibited by BA, C2H4, or after gravistimulation, which affected BA transport to a lesser extent than IAA transport. Multiple peaks of radioactivity were observed in 14C-BA- or 14C-IAA-treated stem segments after 9 h of transport. IAA, ABA, and C2H4 promoted BA catabolism. Auxin, ABA, and C2H4 may inhibit tiller bud release by inhibiting cytokinin transport to the tiller bud and by promoting cytokinin catabolism. Gravistimulation may promote tiller release by inhibiting IAA transport to the tiller bud and allowing cytokinins to accumulate there preferentially.

Gravity Perception and Response Mechanism in Graviresponding Cereal Grass Shoots

The gravitropic response involves three components: (1) gravity perception, (2) transduction, and (3) asymmetric growth response. We have already reported recently (in this series edited by S. S. Purohit) on the transduction phase, that is, the stage when hormones (IAA, GAs and their conjugates) become asymmetrically distributed and bring about asymmetric growth in gravistimulated cereal grass leaf-sheath pulvini (Kaufman and Dayanandan, 1984). In this review, we shall focus on the most recent information available on what is known about the first and third components of response, namely, gravity perception and the mechanism of asymmetric growth in upward bending cereal grass leaf-sheath pulvini.

Changes in Endogenous Levels of Free Polyamines during Petiole Elongation in the Semiaquatic Plant Ranunculus sceleratus

We investigated the relationships between polyamines and indole‐3‐acetic acid‐ (IAA) and ethylene‐induced petiole elongation in Ranunculus sceleratus. When applied exogenously, polyamines inhibited IAA‐induced petiole elongation in the presence or absence of ethylene. An inhibitor of arginine decarboxylase, &agr;‐difluoromethylarginine, stimulated IAA‐induced petiole growth. IAA, ethylene, and fusicoccin all caused decreases in levels of endogenous spermine and other polyamine(s) (spermidine or putrescine or both). According to our kinetic studies, IAA and ethylene induced changes in endogenous polyamine contents at late stages of petiole elongation. Based on these results, we conclude that polyamines are involved in the regulation of IAA‐ and ethylene‐induced growth, especially in late stages of petiole elongation in Ranunculus.