The Translocation of Sulphonamides in Higher Plants: I. UPTAKE AND TRANSLOCATION IN BROAD BEANS

The uptake and translocation of sulphanilamide, sulphacetamide,sulphaguani-dine, sulphapyridine, sulphadiazine, sulphathiazole,and 4:4-diaminodiphenyl-sulphone by broad bean plants growingin water culture has been studied. After varying times of exposureto the compounds at 100/µg./ml., total sulphonamide presentin the roots, stems, and leaves was determined in acid-hydrolysedmacerates by diazotization and coupling of the primary aminogroup. These compounds were identified in the leaves of treatedplants by paper chromatography. Accumulation of sulphonamide in the roots appears to be relatedsimply to time, and the concentration of sulphonamide may, eventually,be far higher than that in the treating solution. Movement fromthe roots to the stems and leaves depends on transpiration.Sulphanilamide and the sulphone passed rapidly into the leaves;sulphacetamide, sulphapyridine, sulphadiazine, and sulphathiazolemoved less rapidly. There was, however, a marked accumulationof sulphacetamide, sulphapyridine, sulphadiazine, sulphathiazole,and the sulphone in the roots. Sulphaguanidine was poorly absorbedfrom the treating solution.     

THE CONTROL OF CERTAIN PLANT DISEASES WITH SULPHONAMIDES

In in vitro tests, sulphanilamide was more toxic to plant pathogenic fungi than to bacterial plant pathogens, but sulphadiazine and other heterocyclic-ring substituted compounds were more toxic to plant pathogenic bacteria than to fungi. When tested in vivo against a number of facultative plant parasites the sulphonamides were without effect except in providing slight control of Pseudomonas coronafaciens on oats. Against a number of obligate parasites including Uromyces fabae on broad beans and Puccinia triticina on wheat, the sulphonamides gave effective control when applied either through the roots or leaves. The minimal effective concentrations in the leaves of the more active compounds varied between 100–200 μg./g. fresh weight of leaf tissue.
The sulphonamides are also toxic to higher plants and both the fungitoxic and phytotoxic effects could be reversed with p -aminobenzoic acid.
A number of sulphanilamides with acyl substituents on the p -amino-group were tested against P. triticina and were shown to control the disease with very slight phytotoxic damage. Control could be attributed to the release of 'free' sulphanilamide by hydrolysis within the plant.
Two factors appear to control the systemic action of sulphonamides: first, the movement in the plant which results in the accumulation of effective concentrations in the leaves, and secondly, the specificity of a sulphonamide for a particular host-parasite association.     

The Translocation of Sulphonamides in Higher Plants: III. ACETYLATION AND DEACETYLATION OF SULPHANILAMIDE IN BROAD BEANS AND WHEAT

The acetylation of both amino groups on sulphanilaniide hasbeen demon strated by paper chromatography of sap expressedfrom broad beans treated with suiphanilamide through the roots.Deacetylation of N¹- and N⁴ mides occurred in the leaves oftreated plants and the N⁴ compound was also acetylated to yieldthe N¹: N⁴-diacetylsulphanilamide. About 30 per cent. of the suiphanilamide entering broad-beanroots was acetylated in the roots, the maximum proportion ofthe N⁴-acetyl compound being reached after 7 days. Deacetylationis a more limited process but reaches a steady state after thesame time. Low levels of acetylation and deacetylation wererecorded in wheat. The amounts of suiphanilamide and N⁴ entering and accumulatingin the various tissues were calculated on a water-uptake basisarid these data show that the main site of acetylation is inthe roots and that deacetyla tion occurs to a limited extentin the roots but predominates in stems and leaves.     

VIRUS DISEASES OF CACAO IN WEST AFRICAL: II. CROSS-IMMUNITY EXPERIMENTS WITH VIRUSES 1A, 1B AND 1C

Experiments on cross-immunity reactions between three viruses attacking Theobroma cacao L. on the Gold Coast are described. A field trial involving 3 acres of graft-inoculated trees revealed some degree of protection afforded by Theobroma virus 1B against infection with virus 1A. The protection appeared to be more effective against insect inoculation than against graft transmission, being only temporary in the latter. Virus 1C (probably unrelated but not to be called Theobroma virus 2 until more evidence is available) conferred no protection against virus 1A.
The latent periods for these viruses were calculated from this experiment, which also provided data on their effects on yield. Virus 1A reduced yield by 50% in the first year after inoculation and killed the trees in the second. Virus 1B had no appreciable effect on yield; virus 1C reduced yield by 50 % in the third year after inoculation but there was no further decline in the fourth.
The rates of spread of these viruses were compared and significant differences demonstrated.     

OBSERVATIONS ON THE PATHOGENICITY OF CALONECTRIA RIGIDIUSCULA (BERK. & BR.) SACC. ON THEOBROMA CACAO L

Calonectria rigidiuscula has been found associated with an acute and a chronic form of dieback of cacao. It can also infect cankers caused primarily by Phytophthora palmivora , and the lesions following attack by the capsids Sahlbergella singidaris and Distantiella theobroma. The association with the capsid lesions is of great economic importance since it appears that capsids alone are capable of killing only green shoots, and that the severe damage caused to woody shoots follows C. rigidiuscula infection of the capsid lesions. Acute dieback occurs only in certain districts after exceptional drought and may be considered primarily the result of environmental conditions. The main importance of chronic dieback is that it prevents the recovery of cacao which has been seriously weakened from other causes. C. rigidiuscula infection retards the healing of P. palmivora cankers and also produces a lesion in the xylem tissue which may be extensive.
C. rigidiuscula has been established in wounded cacao stems of all ages without difficulty. The spread of the fungus is slow, but is more rapid in the xylem than in the cortical tissues. Spread is greatest in the unlignified tissues.     

STUDIES ON SYSTEMIC FUNGICIDES

A number of mono-, di-and trichloro-β-naphthols and the corresponding naphthyloxy- n -carboxylic acids were prepared. They were tested as systemic fungicides against chocolate spot of broad bean ( Vicia faba ) caused by Botrytis fabae and as fungicides in vitro by their effect on the germination of spores of Sclerotinia laxa and the growth of the mycelium of Botrytis fabae.
The systemic fungicide tests showed no difference in the activity of the compounds associated with different side chains, though there were slight but significant effects associated with different chlorine substitutions in the naphthalene nucleus. The 3:4-dichloro-2-naphthol derivatives were more effective than the other compounds tested.
Fungicide tests with the 1:3-dichloro-2-naphthol derivatives suggested that there was some increase in toxicity to the spores of Sclerotinia laxa with increasing length of side chain. The effectiveness of the various chlorine-substituted compounds in suppressing growth of Botrytis fabae was in the following descending order, 1:3:4-trichloro-, 1:3-dichloro-, 1:4-dichloro-and 3:4-dichloro-compounds. The concentrations required in agar culture to induce reductions of B. fabae growth comparable to those found in the leaf could reasonably be expected to occur in the bean plants treated with the 2-naphthyloxyacetic acids at 10 p.p.m.     

The Translocation of Sulphonamides in Higher Plants: II. ENTRY INTO THE LEAVES OF WHEAT

Uptake of a number of suiphonarnides and p-aminobenzoic andsuiphanilic acids can be represented by equations derived fromPick's Law of diffusion. The diffusion constants so derivedhave a Q¹⁰ of the order of 1.4 or 1.7, indicating that the processis primarily physical. The Fick's Law equations provide a measureof the permeability of the system and of the size of the effectivevolume into which the compound is diffusing. Assuming that thebasic process is diffusion from water outside the tissue intowater inside the tissue, the size of the effective volume isconditioned by the absorption of the compound from the aqueousphase of the free space. With sulphanilaniide the effectivevolume is finite while with p-amino benzoic acid the effectivevolume is infinite within the limits of the experiment and concentrationsup to three times that of the treating solution may be attained.A proportion of the suiphanilamide will diffuse out of shootsimmersed in water but p-aminobenzoic acid is held irreversiblyby the tissue.