Periods of Shoot Chilling Sensitivity in Soybean Flower Development, and Compensation in Yield after Chilling

Soybeans [Glycine max (L.) Merr. cv. Ransom] grown at a constant25 °C were placed in a 12-h inductive photoperiod at twoweeks of age. Subgroups were shoot-chilled for one week at aconstant 10 °C during each of the first four weeks of floralinduction. Controls were photoinduced but not chilled. Chillingduring the first week of photoinduction inhibited productionof floral primordia, but did not increase the abscission rateof flowers and pods. Chilling during the second week did notaffect primordium production or abscission rate, but did causea significant increase in numbers of fused and malformed pods.Chilling during the third week caused loss of 77 per cent ofearly flowers and pods by abscission, while fourth week chillingcaused less severe losses by abscission. Inhibition of vegetativegrowth may have been responsible for primordium loss in first-weekplants, while disturbances in the development of flowers wereresponsible for the losses in the other chilling weeks. Althoughchilling during the first and third photoinduction weeks causeda significant reduction in early pod numbers, plants harvestedat 16 weeks of age showed no significant loss in seed yield.Low abscission rates late in pod filling and increased weightof individual seeds compensated for early losses of pods. Thesecompensatory responses to a chilling-induced loss of pods aresimilar to those reported for mechanically depodded soybeans. Glycine max (L.) Merr., soybean, temperature, chilling, floral initiation, anthesis, abscission, yield, compensation     

Comparisons of Earlier- and Later-formed Pods of Chickpeas (Cicer arietinum L.)

In chickpeas (Cicer arietinum L.) flowering and pod developmentproceed acropetally. In plants grown under normal field conditionsat Hyderabad, in peninsular India, and at Hissar in north India,at successively apical nodes of the branches there was a declinein pod number per node, weight per pod, seed number per podand/or weight per seed. The percentage of nitrogen in the seedswas the same in earlier and later-formed pods at Hyderabad;at Hissar the later-formed seeds contained a higher percentage.Earlier- and later-formed flowers contained similar numbersof ovules. The decline in seed number and/or weight per seedin the later-formed pods of 28 out of 29 cultivars indicatedthat pod-filling was limited by the supply of assimilates orother nutrients. By contrast, in one exceptionally small-seededcultivar there was no decline in the number or weight of seedsin later-formed pods, indicating that yield was limited by ‘sink’size. Cicer arietinum L., chickpea, flowering, pod development, seed number, seed weight, nitrogen content     

CHANGES IN THE CONTENT OF GIBBERELLIN-LIKE SUBSTANCES IN RIPENING SEED AND POD OF LUPINUS LUTEUS

The amount of gibberellin-like substances in seed, pod, embryoand "endosperm" of Lupinus luteus in relation to their developmentwas studied by means of the rice seedling test. The amount of gibberellin-like substances per seed increasedremarkably at the first stage of development, when the growthof seed and pod was very slow, and attained its maximum at suchan early stage as the dry weight of seed reached a value ofonly 10 per cent and that of pod 28 per cent of their respectivemaximum levels. Changes in amount of gibberellin-like substancespresent in the pod were very closely related to the changesin growth of pod. Gibberellin-like substances equivalent to0.3 µg gibberellin A₃ per seed and 0.028 µg perpod were found at the 20th day after anthesis, and no activityin mature seed and 0.09 µg per pod at the 50th day. Noactivity was found in the embryo itself at all stages, indicatingthat the gibberellin-like substances in seed occur only in the"endosperm," i.e. in the tissues that will eventually form testain fully ripened stage. (Received December 18, 1962; )     

Influence of Irradiated Pollen on Embryo and Endosperm Development in Kiwifruit

Development of seeds following pollination with irradiated pollenwas studied inActinidia deliciosa(kiwifruit) ‘Hayward’.Pollinations were carried out using two different sources ofpollen (‘Tomuri’ and ‘Matua’) irradiatedwith gamma rays at doses of 700 and 900 Gy. Non-irradiated crosseswere used as controls. Pollen irradiation had little effectonin vitropollen germination. Irradiated pollen affected seedset and seed content, and induced the formation of parthenogeneticembryos. In comparison to the control, the embryo growth ratewas slower and the endosperm contained very low amounts of storageproducts. Seed set was significantly reduced following bothdoses of irradiation. Two types of seeds were observed: (1)seeds with endosperm only; and (2) seeds with both embryo andendosperm. The proportion of seeds containing endosperm onlywas almost ten-fold higher than those containing both embryoand endosperm. Embryo production by gamma-irradiated pollenwas genotype- and dose-dependent. The induction of parthenogenesiswas higher following gamma ray doses of 900 Gy than 700 Gy,which suggests the ‘Hertwig Effect’; the best efficiencywas obtained with ‘Tomuri’ pollen. Ploidy levelof parthenogenetic embryos was evaluated by nuclear size (area)with the use of image analysis. There was a large differencein embryo nuclei size between control and parthenogenetic embryos(mean size 90.8 and 49.1 µm², respectively). It is concludedthat parthenogenetic embryos represent trihaploids.Copyright1998 Annals of Botany Company. Actinidia deliciosa, kiwifruit, pollen irradiation, induced parthenogenesis.     

Dry Matter Partitioning in a Determinate and an Indeterminate Cultivar of Vicia faba L. Under Contrasting Plant Distributions and Densities

Models for root: shoot, vegetative: generative and stem: leafpartitioning are presented to quantify dry matter partitioningof two contrasting genotypes of Vicia faba, an indeterminateand a ‘topless’. A third plant type, a determinateof which two to three inflorescences had been removed, was alsoincluded but behaved similarly to the intact plant. The root:shoot partitioning model predicts linear relationships betweenroot proportion and the product of air vapour pressure deficitand relative growth rate. Data from field experiments were consistentwith model prediction and coefficients estimated were similarfor both genotypes. Partitioning into pods was modelled as proportionalto the number of actively growing pods younger than 1000°Cd. Coefficients estimated were similar in both genotypes butdifferent between densities and years. In the indeterminategenotype, stem: leaf ratio was allometric throughout, whereasleaf growth ceased but stem growth continued in the determinateafter formation of the terminal inflorescence. Relatively moredry matter was allocated to stems than to leaves in high thanin low densities. In conclusion, the main differences in drymatter partitioning between genotypes concern leaf: stem partitioningduring early pod filling and pod partitioning due to pod numberdifferences. Partitioning, root, shoot, leaf, stem, Vicia faba L.     

Effects of Nutrient Supply on Seed Growth of Field Bean (Vicia faba L.). 1. Effects of Different Sulphur and Methionine Regimes on Cotyledon Growth, Protein and Uncombined Amino Acids In vivo

The effects of exogenous methionine on growth of developingVicia faba seeds in vivo was studied. Methionine (51 or 102µmol in total) injected into the base of the pod overa period of 15 d (26–40 d after pollination) decreasedgrowth and protein accumulation in proximal seeds but increasedin distal seeds. Distal seeds of methionine injected pods accumulatedmore d. wt and protein than distal seeds of water-injected pods.However, on a pod basis methionine reduced overall seed growthand protein accumulation. Exogenous methionine caused a relative increase in legumin buta decrease in vicilin. Injected methionine also affected thecomposition of uncombined amino acids, especially those derivedfrom aspartic acid. In contrast, the amino acid compositionof the protein fraction did not change appreciably. The data suggest that seed growth is not limited by methioninebiosynthesis but seed protein composition is regulated by methionine. Vicia faba L., field bean, cotyledon, growth, in vitro culture, uncombined amino acids, protein composition, legumin, vicilin, methionine, sulphur     

Early Endosperm Development in Ovules of Soybean, Glycine max (L) Merr. (Fabaceae)

Endosperm development was studied in normally setting flowersand pods of soybean from anthesis to a pod length of 10–20mm. The free-nuclear stage following double fertilization istypified by loss of starch and increasing vacuolation. The cytoplasmprovides evidence of extensive metabolic activity. Wall ingrowths,already present at the micropylar end of the embryo sac wallprior to fertilization, develop along the lateral wall of thecentral cell as well as at the chalazal endosperm haustorium.Endosperm cellularization begins when the embryo has developeda distinct globular embryo proper and suspensor. Cellularizationstarts at the micropylar end of the embryo sac as a series ofantidinal walls projecting into the endosperm cytoplasm fromthe wall of the central cell. The free, growing ends of thesewalls are associated with vesicles, microtubules, and endoplasrnicreticulum. Pendinal walls that complete the compartmentalizalionof portions of the endosperm cytoplasm are initiated as cellplates formed during continued mitosis of the endosperm nuclei.Endosperm cell walls are traversed by plasmodesmata. This studywill provide a basis for comparison with endosperin from soybeanflowers programmed to abscise. Glycine max, soybean, endosperm, ovules     

Fusarium Wilt of Bananas in Jamaica: II. Some Apsects of Host-parasite Relationships

The incidence of Fusarium wilt in a given variety of bananais determined by numerous interacting factors such as geneticallydetermined resistance, physical and chemical soil conditions,and abundance of Fusarium oxysporum f. cubense. To attain markedresistance to wilt, ‘Gros Michel’ apparently requiresa combination of conditions; thus the soil must be alkaline,of medium to heavy texture, and rich in available potash. Nitrogenfertilizing tends to increase susceptibility to wilt. Some striking effects of weather on wilt incidence are describedand various aspects of crop management are discussed: soil deteriorationunder bananas undoubtedly contributed to development of wiltin the past. In the earliest stages of rootlet infection, the pathogen growsmore slowly in the resistant ‘Cavendish’ than inthe susceptible ‘Gros Michel’, probably owing tomore effective tissue reactions in the former. In the field,infections progressing along the root are often checked at theroot base: with ‘Gros Michel’, however, a smallproportion enter the rhizome and as a result wilt generallydevelops. Ability to check such infections, leading to recovery,is only exhibited on very fertile soils. The possible mode of action of various factors on wilt incidenceis discussed, and the importance of vigorous root growth inpromoting host resistance is emphasized.     

Mobilization and exudation of photo-assimilated14C by developing pods of groundnut (Arachis hypogaea L.)

Summary ‘Pod washings’ were collected from groundnut at three hour intervals for 24 hours after feeding the plants with¹⁴CO₂. Low radioactivity was found in the first four ‘Pod washings’ of 10 day old pods and the radioactivity increased with time. Highest radioactivity was found in washings of 20 and 30 day old pods and was twice the activity found in the washings of 50 day old pods. The radioactivity of both ethanol-soluble and insoluble fractions in pods was determined. The radioactivity mobilized into the pods increased with age and it was highest in 50 day old pods. The influence of the pod exudates on geocarposphere microflora during pod development is discussed.     

Rapid regeneration of <Emphasis Type="Italic">Phaseolus angustissimus</Emphasis> and <Emphasis Type="Italic">P. vulgaris</Emphasis> from very young zygotic embryos

A rapid regeneration protocol for proembryos of Phaseolus angustissimus as young as 1 day after pollination (DAP) involving pod culture for 1 week followed by embryo culture for 2 weeks and embryo germination for 1 or 2 weeks is provided. Optimization of the media was conducted with pods collected 3 DAP. The best pod culture medium was composed of basal medium [(Phillips and Collins 1979) salts with (Geerts et al. 2001) vitamins], 1000 mg l⁻¹ glutamine, 1000 mg l⁻¹ casein hydrolysate, 3% sucrose and 0.5% agar. Embryo culture medium consisted of basal medium with 500 mg l⁻¹ glutamine, 250 mg l⁻¹ casein hydrolysate, 1.9 μM ABA, 3% sucrose and 0.5% bacto-agar. Embryos developed into plantlets on germination medium containing basal medium with 0.25 μM BA, 3% sucrose and 0.7% bacto-agar. Fertile, normal plants were recovered from direct embryogenesis and from micrografted embryo-derived shoots. Embryos obtained from pods collected 3 DAP regenerated plantlets at a rate of 29.3%, while embryos from pods collected 2 DAP and 1 DAP regenerated at rates of 20.2 and 4%, respectively. A second accession of P. angustissimusregenerated at a rate of 26.2%. Using this 5-week protocol for P. vulgaris resulted in a plantlet regeneration rate of 12.5%.     

The role of gibberellins A1 and A3 in fruit growth of Pisum sativum L. and the identification of gibberellins A4 and A7 in young seeds

Gibberellins A₁ and A₃ are the major physiologically active gibberellins (GAs) present in young fruit of pea (Pisum sativum L.). The relative importance of these GAs in controlling fruit growth and their biosynthetic origins were investigated in cv. Alaska. In addition, the non-13-hydroxylated active GAs, GA₄ and GA₇, were identified for the first time in young seeds harvested 4 d after anthesis, although they are minor components and are not expected to play major physiological roles. The GA₁ content is maximal in seeds and pods at 6 d after anthesis, the time of highest growth-rate of the pod (Garcia-Martinez et al. 1991, Planta 184: 53–60), whereas gibberellic acid (GA₃), which is present at high levels in seeds 4–8 d after anthesis, has very low abundance in pods. Gibberellins A₁₉, A₂₀ and A₂₉ are most concentrated in seeds at, or shortly after, anthesis and their abundance declines rapidly with development, concomitant with the sharp increase in GA₁ and GA₃ content. Application of GA₁ or GA₃ to the leaf subtending an emasculated flower stimulated parthenocarpic fruit development. Measurement of the GA content of the pods at 4 d after anthesis indicated that only 0.002–0.5% of the applied GA was transported to the fruit, depending on dose. There was a linear relationship between GA₁ content and pod weight up to about 2 ng · (g FW)⁻¹, whereas no such correlation existed for GA₃ content. The concentration of endogenous GA₁ in pods from pollinated ovaries is just sufficient to give the maximum growth response. It is concluded that GA₁, but not GA₃, controls pod growth in pea; GA₃ may be involved in early seed development. The distribution of GAs within the seeds at 4 d post anthesis was also investigated. Most of the GA₁, GA₈, GA₁₉, GA₂₀ and GA₂₉ was present in the testa, whereas GA₃ was distributed equally between testa and endosperm and GA₄ was localised mainly in the endosperm. Of the GAs analysed, only GA₃ and GA₂₀ were detected in the embryo. Metabolism experiments with intact tissues and cell-free fractions indicated compartmentation of GA biosynthesis within the seed. Using ¹⁴C-labelled GA₁₂, GA₉, 2,3-didehydroGA₉ and GA₂₀ as substrates, the testa was shown to contain 13-hydroxylase and 20-oxidase activities, the endosperm, 3β-hydroxylase and 20-oxidase activities. Both tissues also produced 16,17-dihydrodiols. However, GA₁ and GA₃ were not obtained as products and it is unlikely that they are formed via the early 13-hydroxylation pathway. [¹⁴C]gibberellin A₁₂, applied to the inside surface of pods in situ, was metabolised to GA₁₉, GA₂₀, GA₂₉, GA₂₉-catabolite, GA₈₁ and GA₉₇, but GA₁ was not detected. Gibberellin A₂₀ was metabolised by this tissue to GA₂₉ and GA₂₉-catabolite. Received: 23 July 1996 / Accepted: 2 September 1996     

The Effect of Temperature on the Production and Abscission of Flowers and Pods in Snap Bean (Phaseolus vulgaris L.)

The effect of temperature on production and abscission of flowerbuds, flowers and pods was studied in a determinate snap-beancultivar (cv. Tenderette). Under moderate temperature (e.g.27/17 °C) the onset of pod development was associated withcessation of flower bud production and with enhanced abscissionof flower buds. Raising night temperature from 17 °C to27 °C strongly reduced pod production, mature pod size andseeds per pod, while an increase in day temperature from 22°C to 32 °C had smaller and less consistent effects.Pod production under high night temperature was not constrainedby flower production since 27 °C at night promoted branchingand flower bud appearance. Under 32/27 °C day/night temperaturethe large reduction in pod set was due to enhanced abscissionof flower buds, flowers and young pods (< 3 cm). Flowershad the highest relative abscission followed by young pods andflower buds. Therefore, the onset of anthesis and of pod developmentwere the plant stages most sensitive to night temperature. Podslarger than 3 cm did not abscise but usually aborted and shrivelledunder high night temperature. The effects of 32/27 °C werenot due to transient water stresses and were observed even undercontinuous irrigation and mist-spraying. High temperature, flower production, pod set, seed set, abscission, snap bean, Phaseolus vulgaris L., cv. Tenderette     

Inter-conversion of free sugars and accumulation of galactomannan in response to supplied metabolic mediators during pod filling in guar

Detached inflorescences of guar (Cyamopsis tetragonoloba), each bearing 4 uniformly-developing pods at 42 days post anthesis (DPA), were cultured for 6 days in complete liquid medium manipulated with a fixed concentration of mannose and varying concentration of myo-inositol. Such inflorescences, but with 2 pods, were also maintained in the solutions of (i) glucose(U-14C) containing myo-inositol or phytohormones, and (ii) mannose(U-14C) containing galactose for 36 hr. Effect of such exogenously supplied metabolic mediators on interconversion of free sugars in pod wall, endosperm and cotyledons and galactomannan accumulation in endosperm was studied. Myo-inositol decreased, over control, the relative proportion of invert sugars in pod wall, endosperm and cotyledons and at lower concentration (27.75 mM) it decreased the level of free sugars in pod wall and galactomannan in endosperm. In all pod tissues, 14C from both glucose and mannose got incorporated into myo-inositol as well as various sugars and maximum incorporation occurred in sucrose. High concentration of total free sugars and their 14C activity in pod wall indicated that this pod tissue was a potent accumulator of free sugars. With myoinositol, the relative proportion of 14C from glucose into raffinose sugars of pod wall and endosperm increased with a simultaneous decrease in this incorporation into galactomannan of the latter. Accompanying this, relative proportion of 14C into hexoses and myo-inositol decreased in pod tissues. Galactose increased 14C incorporation from mannose into total free sugars, sucrose and galactomannan with a concomitant decline in the labelling of hexoses. IAA and ABA enhanced 14C incorporation from glucose into total free sugars and this enhancement was much higher with IAA than ABA. The latter inhibited 14C incorporation into galactomannan. Based on these results, it was suggested that myo-inositol at lower concentration was inadequate to mediate the metabolism of sugars and, thereby, galactomannan synthesis. Galactose and mannose exhibited a mutual beneficial effect on their transportation to pods. Phytohormones stimulated the accumulation of sucrose in pod wall for its obligatory unloading into the seed.     

The Effect of Temperature on the Production and Abscission of Flowers and Pods in Snap Bean (Phaseolus vulgaris L.)

The effect of temperature on production and abscission of flowerbuds, flowers and pods was studied in a determinate snap-beancultivar (cv. Tenderette). Under moderate temperature (e.g.27/17°C) the onset of pod development was associated withcessation of flower bud production and with enhanced abscissionof flower buds. Raising night temperature from 17°C to 27°Cstrongly reduced pod production, mature pod size and seeds perpod, while an increase in day temperature from 22°C to 32°Chad smaller and less consistent effects. Pod production underhigh night temperature was not constrained by flower productionsince 27°C at night promoted branching and flower bud appearance.Under 32/27°C day/night temperature the large reductionin pod set was due to enhanced abscission of flower buds, flowersand young pods ( 3 cm). Flowers had the highest relative abscissionfollowed by young pods and flower buds. Therefore, the onsetof anthesis and of pod development were the plant stages mostsensitive to night temperature. Pods larger than 3 cm did notabscise but usually aborted and shrivelled under high nighttemperature. The effects of 32/27°C were not due to transientwater stresses and were observed even under continuous irrigationand mist-spraying. High temperature, flower production, pod set, seed set, abscission, snap bean, Phaseolus vulgaris L, Tenderette     

Phenotypic variation in the agronomic and morphological traits of <Emphasis Type="Italic">Pisum sativum</Emphasis> L. Germplasm obtained from different parts of the world

A total of 286 genotypes were collected from 39 countries of the world and were evaluated to determine the phenotypic diversity for 17 quantitative traits. Higher degree of coefficient of variation were recorded for grain yield⁻⁵ (52.46%), biomass⁻⁵ (45.73%), fresh pod width-10 (47.24%), dry pod weight⁻¹⁰ (40.33%), plant height⁻¹ (35.25%), harvest index (32.70%) and number of branches⁻⁵. Cluster-II clearly reflected that late genotypes were having lightest pods weight, shortest pod width, and pod length; low grain yield, biomass and harvest index. Width, and pod length; low grain yield, biomass and harvest index. While genotypes in Cluster-III were in contrast to Cluster-II having heaviest pods weight, longest pods width and length, highest grain yield, biomass and harvest index. Higher PC₋₁ values have been determined for days to flower initiation which consequently were contributing weighed positive to days to pods picking, days to flower completion, days to dry pod appearance, days to plant harvesting while negatively contributed to yield producing traits, indicating that late flowering pea germplasm emphasizes more on the vegetative growth and was low yielding. However, higher PC₋₂ values have been obtained for number of branches⁻⁵, grain yield and biomass while lower values for days to flowering, days to pods picking, days to flower completion, days to dry pod appearance and days to plant harvesting confirming the fact that early genotypes were high yielding.     

Rate of Increase in Size and Dry Weight of Individual Pods of Field Grown Soya Bean Plants

The dry weight of the whole fruit, the pod wall and an enclosedseed of randomly harvested soya beans is estimated from theexternal dimensions of the attached pod. The relations betweendimensions and dry weight are independent of cultivar and growthcondition and can be used on pods from 1 cm in length untilthe seeds reach their maximum fresh weight. Dimensions of tagged pods of three cultivars of field grownsoya beans differing in time to reach maturity were measuredevery 2–3 days from initial pod elongation until maturation.Dry weights for each pod were estimated from the dimensions,and the dry weight accumulation with time was fitted to thelogistic function to find the growth rate that best characterizedthe data for each pod. The final weight, the specific growthrate and the maximum growth rate of the whole fruit, the podwall and a single seed were subjected to analysis of variance. The most significant difference between pods of these cultivarswas the specific growth rate of individual seeds, which decreasedwith increasing maturity group. There were no differences ingrowth of the pod wall. However, most of the variation was betweenindividual pods within a cultivar, where the rate of dry weightaccumulation of the whole fruit, governed largely by the seedgrowth rate times the number of seeds, was highly correlatedwith the earlier growth of the pod wall. This suggests thatthe growth of individual whole fruit was determined early inpod development and was slightly influenced by factors appliedduring the period of rapid seed growth. Glycine max (L.) Merrill, Soya bean, seed growth analysis, specific growth rate     

The Influence of Temperature and Water Deficits on the Partitioning of Dry Matter in Groundnut (Arachis hypogaea L.)

The partitioning of dry matter to stems, leaves and pods ofgroundnut was examined as a function of mean air temperatureand water stress. Different levels of stress were imposed bygrowing plants on stored moisture at five different mean temperaturesbetween 19 °C and 31 °C and at four levels of saturationvapour pressure deficit. Stands of plants were grown in controlledenvironment glasshouses. The ratio of pod to shoot weight (PWR) was greatest at 22 °Cand decreased from 0.28 to 0.04 as temperature increased to31 °C. PWR was closely related to the number of pods longerthan 5.0 mm but negatively correlated with stem weight ratio.In general, water stress had a minor influence on PWR althoughpeg and pod production were stimulated in five of the nine treatments.Mild water stress promoted peg and pod production because reproductivegrowth was less affected than the growth of leaves and stems,the major sinks early in the reproductive phase. In one treatment,mild water stress increased PWR by a factor of 2.2 indicatingthat when adequate water is supplied to relieve a mild stress,PWR can be greatly increased. Key words: Temperature, Water deficit, Partitioning, Groundnut     

Soya Bean Seed Growth and Maturation by In Vitro Pod Culture

Immature Glycine max (L.) Merr. seeds initially at 50–70mg fresh weight were successfully grown and matured in vitroin detached pods. Surface sterilized pods were floated in aliquid medium containing 5 per cent sucrose, minerals, and glutaminein 125 ml Erlenmeyer flasks and incubated at 25 °C under350–400 µE m^–1 s^–1 white light. Seedswhich were matured in vitro increased tenfold in dry weight,were visually similar to commercial seeds of the same size,were tolerant to desiccation and germinated with normal seedlinggrowth. Excised pods transported dye from the pedicel to thegrowing seed within 120 min. Soya bean pod culture is a usefultechnique to study the influence of single or combinations ofchemical or environmental parameters on regulation of seed growth,seed maturation, and subsequent germination events without theconfounding interactions with the mother plant. Glycine max (L.) Merr., soya bean, pod culture, seed culture, seed growth, seed maturation, germination     

Factors Affecting the Abscission of Reproductive Organs in Yellow Lupins (Lupinus luteus L.): III. ENDOGENOUS GROWTH SUBSTANCES IN VIRUS-INFECTED AND HEALTHY PLANTS AND THEIR EFFECT ON ABSCISSION

Extracts of small and mature-size lupin pods yielded four substancesaffecting the growth of wheat-coleoptile sections: one acidpromotor (A), two acid inhibitors(B and X), and one neutralinhibitor(Y). Inhibitor B was extremely active, however, coleoptile sectionsshowed no signs of toxic effects; they resumed growth at a rapidrate after rinsing them and adding ß-indolylaceticand (IAA) to the medium. 1 µg of IAA was required to counteractthe effect of ‘B’ extracted from 230 mg. Of tissue.On an equal fresh weight basis the inhibiting action of ‘B’in lupin pods was 500–1,500 times more potent than thatof ‘inhibitor ß’ in etiolated pea seedlings. Small pods of plants infected with pea-mosaic virus yielded3 times the amount of ‘A’ of healthy plants (equivalentto 1 µg. IAA 0.3 µg. IAA per 25 g. of tissue respectively),and approximately the amount of ‘B’. Mature podsof virus-infected plants again yielded more‘A’,but also 2? times more ‘B’ than pods of healthyplants. Healthy pods yielded more ‘A’ than virus-infectedpods, and there was no difference in ‘X’. A lupin abscission test was developed and the effects of proximaland distal application of -naphthyl acetic acid (NAA) are presented,and discussed with respect to results of other abscission tests. ‘A’ accelerated abscission when applied proximally,and delayed or prevented it when applied distally. ‘B’strongly accelerated abscission when applied in either way.A possible mechanism explaining the abscission-inducing effectof developing pods on later flowers is discussed in terms ofthe substances ‘A’ and ‘B’. The partlyprevented abscission observed on virus-infected plants was foundto agree well with the proposed mechanism.