Gordon V. Hoad

Kaurenoids and gibberellins, including the newly characterized gibberellin A88, in developing apple seeds

The ethyl acetate-soluble acids from extracts of immature apple seeds (Malus domestica cvs Coxs Orange Pippin, Dabinett, Sunset and Tremletts Bitter) were analysed by combined gas chromatography-mass spectrometry. The following previously characterized gibberellins were identified by comparison of their mass spectra and Kovats retention indices with those of standards: GA1, GA3, GA4, GA7, GA9, GA12, GA15, GA17, GA19, GA20, GA25, GA34, GA35, GA44, GA45, GA53, GA54, GA61, GA62, GA63, GA68, GA80, GA84, and 3-epiGA54. In addition, a number of kaurenoid and gibberellin-like compounds were detected. The identity of one of the gibberellins with ent-3α,10β-dihydroxy-20-norgibberella-9(11),16-diene-7,19-dioic acid 19,10-lactone (9,11-didehydro GA4) was confirmed by partial synthesis from GA7 and is accorded the trivial name GA88.

The biological activity of sixteen gibberellin A4 and gibberellin A9 derivatives using seven bioassays

Abstract C 2 - and C 3 -derivatives of GA 4 and GA 9 were tested for biological activity in a range of plant assays. The activity of most of these derivatives was equal to, or less than, that of the parent GAs. However, 2β-methylGA 4 and 2,2-dimethylGA 4 had a higher activity than GA 4 in some assays and the latter derivative was shown to be the most active GA known to date in the Forward oat first leaf, Tan-ginbozu dwarf rice and d 5 -maize assays. Two other derivatives, 12,16-cycloGA 9 and 19-desoxyGA 9 had less activity than GA 9 .

The biological activities of some new gibberellins (GAs) in six plant bioassays

The biological activities of GA40, GA43, GA46, GA47, GA51 and GA4 20,4-lactone were tested over a wide range of concentrations in six plant bioassays. GA4 20,4-lactone showed the highest activity. Of the two 2α-hydroxylated compounds GA47 showed moderately high activity, and GA40 was slightly active. The 2β-hydroxylated compunds GA43, GA46 and GA51 were virtually inactive.

Leaf stomatal resistance, ethylene evolution and ABA levels as influenced by (2-chloroethyl) phosphonic acid

Abstract The effect on stomatal resistance of ethylene released from ethephon sprays has been studied in 8 species of plants. Ethephon always increased stomatal resistance, but in some species only slightly. In olive and peach, increased stomatal resistance in treated plants was associated with more abscisic acid in the leaf tissues.

Abscisic acid and related compounds in phloem exudate of Yucca flaccida haw. and coconut (Cocos nucifera L.).

Phloem sap collected from Yucca and coconut inflorescence stalks was shown to contain abscisic acid (ABA) and trace amounts of 2-trans ABA. In coconut sap, two compounds probably derived from ABA with mass spectra consistent with their being dihydrophaseic acid and either hydroxyphaseic acid or oxo-dihydrophaseic acid were also found to be present.

Gibberellins A82 and A83 in seed of Lupinus albus

Abstract Extracts from seeds of Lupinus albus at 14, 22, 35 and 52 days after anthesis were separated into free gibberellins, ester conjugates and ether conjugates. Capillary GC-MS of the methylated and trimethylsilylated free gibberellin fractions showed the presence of the known gibberellins A 1 , A 3 , A 4 , A 17 , A 18 , A 23 and A 43 . In addition six new gibberellin-like compounds were detected that corresponded to the addition of the elements of water to gibberellins A 3 , A 4 , A 7 , A 14 , A 18 , and A 34 . Two of these components were identified by chemical syntheses as ent -3α,10β,17-trihydroxy-20-nor-16αHgibberellane-7,19-dioic acid 19,10-lactone and ent -3α,17-dihydroxy- 16αHgibberellane-7,19-dioic acid, which are accorded the gibberellin numbers A 82 , and A 83 , respectively. ent -3α,10β,16β,17-Tetrahydroxy-20-nor-16βHgibberellane-7,19-dioic acid 19,10-lactone was also identified by synthesis of the methyl ester. Similar analyses of the hydrolysed ether conjugate fractions showed the presence of the known gibberellins A 1 , A 3 , A 13 , A 18 and A 43 , the new gibberellin A 82 and the ‘hydrated’ gibberellins A 18 and A 34 ; the 15-ene isomers of gibberellins A 13 and A 43 and the 16ξ17-epoxide of gibberellin A 18 were also identified as probable artefacts. In the hydrolysed ester conjugate fractions the new gibberellin A 82 and the ‘hydrated’ gibberellin A 34 were detected. Gibberellin A 18 was by far the most abundant GA but quantitation of the GAs was not carried out.

A simple system for determining the phloem mobility of compounds using excised pods of lupin (Lupinus albus L.).

Lupin pods were isolated from the plant and the pedicels placed in solutions of either radiolabeled sucrose, glucose, abscisic acid, or gibberellin A9 (GA9). Phloem exudate was collected from the cut stylar ends of the pods and both quantitative and qualitative data were obtained on the activity in the sap. Fed sucrose, abscisic acid, and GA9 were found in phloem exudate, but labeled glucose was immobile as the monosaccharide and activity in exudate appeared in sucrose.

Effects of succinic acid 2,2-dimethylhydrazide (SADH) on the gibberellin and abscisic acid levels in stem tips of M26 apple rootstocks

Abstract Spraying M26 apple rootstocks with 4000 p.p.m. SADH leads to a rapid build up in the level of ABA in the stem tips and a reduction in the level of gibberellin-like substances. These changes in the hormonal balance of the stem tips are probably the first link in the chain conducive to decreased translocation of assimilates to the tips and the transient retardation of growth.

Ethylene production by healthy and Sclerotinia fructigena-infected apple peel

Abstract Production of ethylene by infected preclimacteric apple peel is much more sensitive to inhibition by acetate and potassium nitrate than is that from healthy climacteric peel. The opposite is true of the efrect of rhizobitoxine. It is suggested that the ethylene produced from the infected tissues originates from the hosts metabolism rather than from that of the fungus, but by a pathway different from that operative in healthy climacteric peel.