Physiological Studies on Nodule Formation. The Characteristics and Inheritance of Abnormal Nodulation of Trifolium pratense by Rhizobium leguminosarum

Five to 7 per cent of plants of Trifolium repens L. and T.pratenseL. and 100 per cent of plants of T. subterraneum L. were nodulatedby Rhizobium leguminosarum but none of T. hybridum L., T. glomeratumL. or T parvifirum Ehrh. The frequency of nodulation of T. pratenseby R. leguminosarum was much increased by breeding from susceptibleplants. Such plants were not nodulated by bacteria isolatedfrom any other cross-inoculation group, but remained fully susceptibleto R. trifolii. The nodules formed by R. leguminosarum are generallyassociated with lateral roots and are ineffective.     

Silica and Ash in Tissues of Some Plants Growing in the Coastal Area of Mississippi, USA

Ash and silica contents and their depositional patterns in differenttissues of 27 plants growing in the Ocean Springs area of Mississippi(many grow elsewhere), were determined. Silica content of driedplant parts varied from no more than 0 per cent in Borrichiafrutescens (L.) D.C. stems to 18.76 per cent in Arundinariagigantea (Walt.) Muhl. leaves. Ash content varied from 0·73per cent in Cliftonia monophylla (Lam.) Britt. ex Sarg. stemsto 44·02 per cent in Batis maritima L. leaves. Plantssuch as Batis maritima L., Borrichia frutescens (L.) D.C., Salicorniabigelovii Torr. and Salicornia virginica L. which grew in salinemarshes had high ash contents due NaCl in their tissues. Morusrubra L. leaves had a high silica content for a dicotyledonousplant (3·12 per cent). Energy-dispersive X-ray analysisshows that the distribution of the element silicon is clearlyrelated to certain epidermal structures such as ridges, cellwalls, rows of irregular shaped structures lengthwise of theleaf, dumb-bell shaped ones and especially in trichomes. Therewas a high concentration of silica containing trichomes alongthe veins on the underside of Morus rubra L. leaves and thiswould protect them from insects. The outer parts of the inflorescencesof Ctenium aromaticum (Walt.) Wood, Elymus virginicus L., Juncuspolycephalus Michx. and phragmites communis Trin. were highlysilicified. This should give the seed some protection from insects.The sharp particles would be irritating to oesophageal tissuesand might be implicated in such a cancer.     

Some Effects of Sucrose Concentration on Primordium Development in Excised Primary Roots

The effects of varying the amount of sucrose used to supplementthe culture medium maintaining the growth of excised roots ofPisum sativum L., Vicia faba L., Zea mays L. and Phaseolus vulgarisL., on the rates of primordium initiation and subsequent emergenceas lateral roots and on the duration of the interval betweenprimordium inception and emergence as a secondary root throughthe tissues of the primary have been investigated. Variation in the exogenous concentration of sucrose from 0.5to 8 per cent had little effect on the rate of primordium inceptionin Pisum and Vicia and the rates never reached the values obtainedfor the roots of the corresponding intact plants. Moreover,over the 6 day culture period lateral root emergence did notoccur in any of the excised roots of these two species. In contrast,each of the aspects of primordium development examined in theexcised roots of Zea and Phaseolus was markedly affected bythe amount of sucrose used to supplement the culture medium.In addition, in the presence of about 6 per cent sucrose, primordiumdevelopment in these cultured roots was very similar to thatin roots of the corresponding intact plants. The results indicate either that some factor necessary for primordiumdevelopment is present in adequate amounts in excised rootsof Zea and Phaseolus, but not in those of Pisum and Vicia, orthat the factors controlling such development are differentin the former and latter two species. Vicia faba L., Pisum sativum L., Zea mays L., Phaseolus vulgaris L., broad bean, garden pea, maize, dwarf bean, primordium development, sucrose concentration, cultured roots     

An Examination of the Factors affecting Variability in the Growth of the Mesocotyl and Coleoptile of Etiolated Avena Seedlings

Experiments were carried out on the effect of rate of air-flowand of humidity on the growth of Avena seedlings. The experimentalmethods used are described in some detail. The effect of air-flow on mesocoryl growth was considerablewhen unsaturated air was used, but with saturated air growthwas independent of air-flow. The effect must therefore be dueto variation in transpiration rate. A 10 per cent, variationin relative humidity, at a constant rate of flow, caused a 30per cent, variation in mesocotyl length. The coleoptiles showedless pronounced effects, but even in saturated air variabilitywas not eliminated. Under the conditions used a difference of 2·3 mm. inmesocotyl length (per 50 plants), i.e. 8 per cent., was significantat P = 0·05; for the coleoptiles a difference of 1 mm.(8 per cent.) was significant at this level.     

Silica and Ash in Tissues of Some Coastal Plants

Ash and silica contents and their depositional patterns in differenttissues of 44 Mississippi coastal plants were determined. Silicacontent of dried plants varied from no more than a trace inChenopodium album L. leaves to 7.37 per cent in Zizanopsis miliacea(Michx) Doell & Aschers leaves. Ash content varied from2.50 per cent in Lythrum lineare L. stems to 28.24 per centin Borrichia frutescens (L.) DC leaves. Plants in the same familytend to be alike in their ability to absorb or not absorb silica.Poaceae and Cyperaceae had consistently high concentrationsof silica. In contrast, the Asteraceae studied had very lowsilica contents but often had high contents of other minerals.Dicotyledonous plants studied had consistently lower silicacontents than the monocotyledons. Plants growing in salt watercontained considerable sodium chloride. Spectra were obtainedfor major elements in four different plants. Energy-dispersiveX-ray analysis shows that distribution of the element siliconis clearly related to certain epidermal structures such as guardcells, ridges, dumb-bells and balls that appear in electronmicrographs. Silica was deposited differently in each type ofplant studied. In many of the plants silica was deposited inrows of irregular-shaped particles running lengthwise of theleaf and in guard cells. In others, like Zizanopsis miliacea(Michx) Doell & Aschers, the deposit was sheet-like. Zizaniaaquatica L. not only had a sheet-like deposit, but the depositwas ridged and there were rows of dumb-bell-shaped silica cells.Related plants had similar structures. Euchlaena mexicana Schrad.,Tripsacum dactyloides (L.) L and Manisuris rugosa (Nutt.) Kuntzeall had irregular phytoliths similar to those in Zea mays L. coastal plants, marsh plants, ash content, silica deposition, scanning electron microscopy, energy-dispersive X-ray analysis, silicon distribution, X-ray diffraction patterns, spectra of elements in plants     

The Influence of Genes ar and n on Senescence in Pisum sativum L.

The effect of genes ar (violet flowers, small hilum) and n (thick,fleshy pod wall) on whole plant in senescence peas was examinedby comparing Ar- with arar and N- with nn plants in segregatingprogenies. Homozygosity for ar or n significantly delayed the time whenthe plants were ready for harvest of their entire seed crop.These genes did not delay either the onset of reproduction orthe onset of apical arrest in the first instance. However, whereasAr- N- plants almost invariably senesced and died as the firstseed crop matured, the majority of arar and/or nn plants entereda period of secondary growth and a further fruiting cycle. Comparedwith Ar- plants, arar plants had over twice as many pods andseeds but individual seeds were 58 per cent lighter and totalseed yield (wt) was 19 per cent less. Pod length was unaffected.Compared with N-plants, nn plants had shorter pods (16 per cent),fewer seeds per pod (21 per cent), smaller seeds (20 per cent)and a lower total seed yield (wt 14 per cent less). It appearsthat ar and n impose a lower metabolic drain per reproductivenode as a consequence of their effects on hilum anatomy andpod morphology, respectively. These mutants disrupt the normalpattern of monocarpic senescence by breaking the coordinationbetween apical arrest and subsequent events. The developingseed crop delimited by the first arrest fails to cause plantdeath, possibly because sink size is less than in normal counterparts. Pisum sativum L, garden pea, senescence, hilum, pod, seed size, genetics     

Shoot Formation from Explant Cultures of Fourteen Potato Cultivars and Studies of the Cytology and Morphology of Regenerated Plants

Plants were regenerated in quantity from cultured excised stem,rachis or leaf pieces of 13 potato (Solarium tuberosum L.) cultivarsusing modifications of a two-step procedure. Pronounced differenceswere observed in the response of different cultivars and explantsources to medium formulations containing different auxins orcytokinins. A few plants were recovered from tuber pieces ofseven cultivars by a different two-step procedure. Morphologicaldifferences from control plants were observed in some of theprimary regenerants. Anthocyanin pigmentation of tubers wasscored and stable changes to red-splashed white or white tuberswere found in some plants regenerated from cv. Desiree. Regenerantsfrom the particoloured cultivars Cara and King Edward oftenlost this trait but it returned to varying extents in subsequentgenerations. Most of the regenerated plants (87 per cent) containedthe euploid number of chromosomes (2n = 4x = 48). The methodsare suitable for production of plants for assessment of somaclonalvariation in a range of genotypes. Potato breeding, somaclonal variation, chromosome variation, skin colour, explant culture, plant regeneration, solanum tuberosum L. potato     

Sulphate Transport into Plants and Excised Roots of Soybean (Glycine max L.)

The rates of sulphate transport into intact and excised rootsof soybean (Glycine max L.) were not significantly differentin the first hour and were maximal at pH 7. However, intactroots accumulated four times as much sulphate as excised rootsin 24 h, because of a marked reduction in the rate of transportby excised roots. The continued high rates of transport intointact roots were observed in plants kept in the light, andobserved in darkened plants growing in 1 per cent sucrose. Similarly,sulphate accumulation by excised roots was stimulated 2-foldby 1 per cent sucrose. The characteristics of sulphate accumulation by roots were notuseful in predicting sulphate translocation to the leaves. Transportto the leaves was maximal at pH 2–3, was almost totallylight-dependent and was not enhanced by growing plants in sucrose. Sulphate transport, Glycine max L., soybean, excised roots     

Effects of Drought on Partitioning of Nitrogen in Two Wheat Varieties Differing in Drought-tolerance

A model was constructed to describe the translocation and partitioningof nitrogen on the seventh day after anthesis for well-wateredand droughted plants of two wheat varieties (Triticum aestivumL. cv. Warigal and Condor). The glasshouse-grown plants weredetillered so that a simplified model could be derived for themain stem. A 9-d drought treatment was imposed just after anthesisand this coincided with the period of endosperm cell divisionin the grains. Warigal, which had a higher grain yield thanCondor under drought, absorbed up to 15-times more nitrogenand translocated 1.5-fold more nitrogen to the shoot via thexylem. In both varieties, nitrogen redistributed from vegetativeorgans accounted for more than 60 per cent in control and 70per cent in droughted plants of the nitrogen needed for eargrowth. The net loss of nitrogen increased by 4-3 per cent inthe leaves, but decreased by 60 per cent in the stem under drought.Stem and roots appeared to play an important role in the nitrogeneconomy of droughted plants: less nitrogen was translocateddirectly to the grains from the senescing leaves and 40–60per cent more nitrogen was translocated to the roots. Nearlyall the nitrogen reaching the roots in the phloem was reloadedinto the xylem stream and translocated back to the shoot. Thetransfer of nitrogen through the stem was reduced under droughtand this resulted in a constant C:N ratio of the grains whichmay be important in the regulation of endosperm cell division. Triticum aestivum L., wheat, drought, nitrogen, senescence, translocation     

A Comparison of the Rate of Maintenance Respiration in Some Crop Legumes and Tobacco Determined by Three Methods

Carbon exchange was measured on whole plants of field bean,lucerne, chick pea, kidney bean, pea and tobacco. The maintenance respiration rate was measured in three ways:(i) by allowing the CO₂ efflux to decay in prolonged darknessto an asymptotic value which was then taken to be the maintenancevalue (the dark decay method); (ii) by plotting the dark CO₂efflux as a function of the net CO₂ uptake over a range of irradiancesand taking maintenance as the dark CO₂ efflux when the net CO₂uptake was zero (the dynamic method); and (iii) by plottingthe total CO₂ uptake as a function of the growth rate and takingmaintenance respiration as the CO₂ efflux when the growth ratewas zero (the zero growth rate method). The range of valuesfor the maintenance coefficient over all species was from 1.6to 2.1 per cent of the dry weight per day, 1.8 to 2.1 per centand 2.7 to 2.9 per cent as determined by these three methodsrespectively. There was a linear relationship, common to allspecies, between the maintenance respiration rate (dark decaymethod) and dry weight, total nitrogen and the organic nitrogencontent. The growth coefficient (0.69±0.01) was the samefor field bean, chick pea and lucerne and was unaffected bythe method of estimation. It was concluded that the dark decay method provided the bestestimate of the minimal maintenance requirements in the plantsstudied. Vicia faba L., Medicago sativa L., Cicer arientinum L., Phaseolus vulgaris L., Pisum sativum L., Nicotiana tobacum L., field bean, lucerne, chick pea, kidney bean, pea, tobacco, respiration, maintenance, growth, nitrogen content     

Dynamics of Carbon Photosynthetically Assimilated in Nodulated Soya Bean Plants under Steady-state Conditions 1. Development and Application of 13CO2 Assimilation System at a Constant 13C Abundance

A long-term, steady-state ¹³CO₂ assimilation system at a constantCO₂ concentration with a constant ¹³C abundance was designedand applied to quantitative investigations on the allocationof photoassimilated carbon in nodulated soya bean (Glycine maxL.) plants. The CO₂ concentration in the assimilation chamberand its ¹³C abundance were maintained constant with relativevariances of less than ±0.5 per cent during an 8-h assimilationperiod. At the termination of 8-h ¹³CO₂ assimilation by plantsat early flowering stage, the currently assimilated carbon relativeto total tissue carbon (measured by the degree of isotopic saturation)were for young leaves (including flower buds), 13.9 per cent;mature leaves, 15.7 per cent; stems+petioles, 5.9 per cent;roots, 5.4 per cent and nodules, 6.9 per cent, 48 h after theend of the ¹³CO₂ assimilation period, they were 12.3, 7.5, 7.4,6.8 and 6.1 per cent, respectively. The treatment with a highconcentration of nitrate in the nutrient media significantlydecreased the allocation of ¹³C into nodules. Experiments on¹³CO₂ assimilation by plants at the pod-filling stage were alsoconducted. Labelling by ¹³C was weaker than at the early floweringstage, but an intense accumulation of ¹³C into reproductiveorgans was observed. Glycine max L., nodulated soya bean plants, ¹³CO₂ assimilation, carbon dynamics     

Overcoming Incompatibility in Brassica campestris L. by Carbon Dioxide, and Dark Fixation of the Gas by Self- and Cross-pollinated Pistils

Supplementing pollen suspension cultures with CO₂ (3–5per cent) caused a marked increase in germination and tube growthin vitro in Brassica campestris L. cv. toria. A weakening ofself-incompatibility by increased CO₂ levels from 3–5per cent was observed. The percentage of pollen tubes whichpenetrated the cuticle layer of stigmatic papilla cells in self-pollinatedpistils was high when CO₂ level was 5 per cent. Phosphoenolpyruvate (PEP) carboxylase activity was greater in the pollengerminated in 4 per cent CO₂ as compared to air (0.03 per cent).A possible role of CO₂ for self-recognition and control of pollentube growth is proposed, proposed. Brassica campestris L., carbon dioxide, self-incompatibility, phosphoenol pyruvate carboxylase     

The Response of Phaseolus vulgaris L. to Root-zone Anaerobiosis, Waterlogging and High Sodium Chloride

Phaseolus vulgaris L. grown at a range of external concentrationsof NaCl (0 to 80 mM) responded differently to gaseous anaerobiosis(N₂ gas) in nutrient solution or stagnant waterlogging of theroot-zone. With similar patterns of distribution of Na⁺ andCl^- occurring in the plants with comparable NaCl treatments,and similar final concentrations of Na⁺ and Cl^- in plants grownunder both root-zone conditions, rates of uptake of Na⁺ andCl^- were much higher in plants with the stagnant waterloggedrootzones. After 72 h stagnant waterlogging, plant tops fromplants grown at 40 mM NaCl contained 1.42 per cent Na⁺ and 3.44per cent Cl^- (d. wt basis) while after 9 days exposure to NaClwith gaseous anaerobiosis, leaf tissue contained 1.49 per centNa⁺ and 4.28 per cen Cl^- (d. wt basis). Plants exposed to 40mM external NaCl were severely damaged within 72 h when grownwith stagnant waterlogged root-zones; those grown with N₂ anaerobiosiscontinued growth and development over the 9 d period. Plantsgrown in nutrient solution showed changes in distribution andconcentration of Na⁺ and Cl^- when oxygen concentration was reducedbelow 21 per cent O₂ (full aeration). Phaseolus vulgaris. L., bean, mineral salt distribution, anaerobiosis, salinity, waterlogging     

Effect of Post-anthesis Drought on Cell Division and Starch Accumulation in Developing Wheat Grains

Wheat plants (Triticum aestivum L., cv. Warigal) were subjectedto 20 d of water deficit during the period of endosperm celldivision. Drought accentuated the differences in final grainweight between spikelets and between grains within spikelets.The distal grains of top spikelets were most affected by drought.The maximum number of endosperm cells was, respectively, 30and 40 per cent lower in basal grains and distal grains of draughtedplants. In basal grains of middle spikelets, the number of largestarch granules per cell was unaffected but the number of smallstarch granules per cell was 45 per cent lower in grains ofdraughted plants. The initiation of small starch granules wasmore affected than cell division because severe water deficitoccurred earlier during the former process than the latter.Final dry weight appeared to correlate well with the maximumnumber of endosperm cells, but depended also on the number ofstarch granules per cell. Consequently, the amount of dry matterper cell was not constant in both treatments. The concentration of sucrose per endosperm cell was lower onlyin the droughted distal grains of top spikelets. The supplyof sucrose to endosperm cells did not regulate the initiationof small starch granules. Triticum aestivum L., wheat, drought, grain growth, cell division, starch     

Determination of Nitrate Reductase Activity in Barley Leaves and Roots

The inactivation of nitrate reductase in the leaves and rootsof barley (Hordeum vulgare L. cv. Mazurka) during and afterextracting was investigated. At 0 °C in the absence of casein,25 per cent of ‘total’. i.e. maximal in vitro, nitratereductase activity was lost during the 2 min extraction process,followed by a slower loss of activity while the extract wasstored in ice. Activity was maintained by adding a minimum of1 per cent casein to the extraction medium containing 0·1M phosphate (pH 7·5), 1 mM EDTA and 1 mM dithiothreitol.Nitrate reductase was stable for several hours in these extracts,but declined in a first order manner in the absence of dithiothreitol.Casein also prevented the initial loss while making root extracts,but had less effect during storage. Using casein and thiols, nitrate reductase activity in light,(as product of maximal in vitro rates and wt g^–1) in leaveswas 98 per cent of the total activity in 31-day-old plants grownwith full nutrient in water culture and 60-day-old field-grownplants receiving no fertilizer. Field-grown plants, however,exhibited only 17 per cent of the activity of culture-grownplants. Nitrate reductase in leaves of barley plants grown in waterculture had a diurnal rhythm. During the first 3 h of the lightperiod, activity increased to 1·3 x the ‘dark’value. This was followed by a temporary decrease and then byanother increase to a maximum of 1·7 x the ‘dark’value, occurring about 8 h after illumination. Activity thendecreased during the rest of the light period and in darkness. Hordeum vulgare L., barley, nitrate reductase     

Vegetable Plant Part Relationships. III. Modification of Carrot (Daucus carota L.) Root and Shoot Weights by Gibberellic Acid and Daminozide

Aqueous foliar sprays of N-dimethylaminosuccinamic acid (daminozide)at 2000 p.p.m. and gibberellic acid (GA) at 100 p.p.m. wereapplied 45, 59, 82 and 100 days after sowing to Chantenay carrotswith population densities of 244, 495 and 883 plants m^–2.The plants were harvested on ten approximately weekly occasions;fresh weights were determined and d. wt estimates were obtainedfor the separated shoots (s) and roots (r). Allometric linearregressions of the logarithm of s on that of r at each harvestseparately, clearly showed that GA always increased shoot: rootratio and reduced root yield (by approximately 35 per cent)but could sometimes also increase whole-plant weight. Daminozideincreased root yield (by approximately 7 per cent from 80 tonnesha^–1) and tended to have effects opposite to those ofGA. Daucus carota L., carrot, root weight, shoot weight, N-dimethylaminosuccinamic acid (daminozide), gibberellic acid     

Distribution of Nitrogen during Growth of Sunflower (Helianthus annuus L.)

The accumulation, distribution and redistribution of dry matterand nitrogen is described for Helianthus annuus L. cv. Hysun21 grown on 6 mM urea in glasshouse culture. Seed dry matterand nitrogen were transferred to seedlings with net efficienciesof 40 and 86 per cent respectively. At flowering, the stem hadmost of the plant's dry matter and the leaves most of its nitrogen.About 35 per cent of the plant's nitrogen accumulated afterthree-row anthesis. The amount of protein in vegetative parts,especially leaves, declined after flowering. Concentrationsof free amino compounds also decreased during growth. Matureseeds had 38 per cent of the total plant dry weight and 68 percent of the total nitrogen. Seeds acquired 33 per cent of theirdry matter and nitrogen from redistribution from above-groundplant parts. The stem was most important for storage of carbohydrate,leaves the most important for nitrogen. Over 50 per cent ofthe nitrogen in the stem and leaves was redistributed. Plantsthat received 6 mM nitrate accumulated more dry matter thanurea-grown plants. Seeds from nitrate-grown plants were heavier(58 mg) than those of urea-grown plants (46 mg), and their percentageoil was greater (50 and 41 respectively). The amount of nitrogenper seed was the same. Little or no urea was detected in xylem sap of plants suppliedwith 5 mM urea, but it was detected in sap of plants which received25 mM. Concentrations of urea and amino compounds in the sapdecreased up the stem. Plants supplied with nitrate had mostof the nitrogen in xylem sap as NO₂^–, suggesting littlenitrate reduction in roots. Plants grown on 6 mM nitrate andchanged to high levels of urea-nitrogen for 14 days still hadhigh levels of nitrate; little nitrate remained in plants receivinglow levels of urea. When urea is applied in irrigation waterto field-grown sunflower, the nitrogen is subsequently takenup as nitrate due to rapid nitrogen transformations in the soil. Helianthus annuus L., sunflower, urea, nitrate, nitrogen transport, xylem sap, nitrogen accumulation nitrogen distribution     

Models of the Use of Root-zone CO2 by Selected North American Isoetids

Sediment CO₂, entering via the roots, contributes a significantportion of the total carbon uptake for isoetids (small, evergreen,submersed, vascular plants). Laboratory studies of inorganiccarbon uptake via the roots and shoots by five isoetids wereused to model the use of root-zone CO₂. Simple first-order linearmodels accounted for at least 75 per cent of the variation inthe data for Gratiola aurea, Isoetes macrospora, Littorellauniflora and Lobelia dortmanna. For Eriocaulon septangulare,which relies almost exclusively on root-zone CO₂, models couldaccount for only about 62 per cent of the variation in root-zoneCO₂ use. For each species, we present the best fitting regressionof root-zone CO₂ use as a function of root- and shoot-zone CO₂concentrations. For the species studied, carbon uptake was not saturated atfield concentrations of root and shoot-zone CO₂. Maximum ratesof carbon uptake were lower for species that naturally occurredat greater depths, compared with species more common in shallowwater. At equal external CO₂ concentrations carbon entry perunit root surface area was several times more rapid than entryper unit shoot surface area for L. dortmanna. The entry ratesper unit root and shoot surface area were about equal for G.aurea and E. septangulare. Shoots were equally or more permeablethan the roots of L. uniflora and I. macrospora, a fact thatmay be related to the functioning of crassulacean acid metabolismin these plants. Carbon, CO₂, photosynthesis, isoetid, Eriocaulon septangulare, Gratiola aurea, Isoetes macrospora, Littorella uniflora, Lobelia dortmanna     

Mineral Ion Nutrition of Developing Barley Grains 1. Effect of Magnesium Deficiency on Ion Content of Immature Embryos and Endosperms

The effect on the mineral ion nutrition of developing barleyembryos and endosperms was studied when both Mg and Mn werewithdrawn simultancously from the rooting medium. Both embryosand endosperms had lower Mg levels, on average 40 and 50 percent, respectively, over the developmental period, than thosefrom control plants grown in complete nutrient solution. Comparedto the controls, higher levels of Mn (average 20 per cent) andCa (average 20 per cent) were found in Mg-deficient embryosfrom test plants, but Mn levels were lower (average 30 per cent)and Ca levels unaffected in Mg-deficient endosperms. K levelsin both embryos and endosperms were not changed. The endospermsfrom test plants had lower total N levels than the controls. Hordeum vulgare L., barley, embryo, endosperm, sand culture, magnesium, manganese, calcium, potassium, nitrogen, mineral nutrition     

The Development of Desiccation-tolerance and Maximum Seed Quality During Seed Maturation in Six Grain Legumes

‘Physiological maturity’, i.e. the time when seedsreach their maximum dry weight during development, occurredwhen maturation drying on the parent plant in the field hadreduced seed moisture content to approximately 60 per cent infaba bean (Vicia faba L.), lentil (Lens culinaris Medic.), chickpea(Cicer arietinum L.), white lupin (Lupinus albus L.), soya bean(Glycine max [L.] Merr.) and pea (Pisum sativum L.) The onsetof desiccation-tolerance, i.e. the ability of seeds to germinatefollowing harvest and rapid artificial drying, coincided withphysiological maturity, except in pea where it occurred a littleearlier at about 70 per cent moisture content. Maximum seedquality as determined by maximum viability, minimum seedlingabnormalities and maximum seedling size occurred in pea, chickpeaand lupin when seeds were harvested for rapid drying at physiologicalmaturity; but for maximum seed quality in the other speciesmaturation drying had to proceed further - to about 45 per centmoisture content in soya bean and to about 30 per cent moisturecontent in lentil and faba bean seed crops. Much of this variationamongst the six species, however, was due to differences inthe variation in maturity within each seed crop. Results forindividual pods showed that peak maturity, i.e. maximum seedquality following harvest and rapid artificial drying, was achievedin all six species once maturation drying had reduced the moisturecontent of the seeds to 45–50 per cent. In pea, faba beanand soya bean there was a substantial decline in viability andan increase in seedling abnormalities when harvest was delayedbeyond the optimal moisture content for harvest.