Reproductive Ontogeny Research Articles

Geographic variability in the gonadal development and sexual ontogeny of Hemigymnus, Cheilinus and Oxycheilinus wrasses among Indo-Pacific coral reefs.

Patterns of reproductive ontogeny in four species of coral reef wrasses (F: Labridae) Hemigymnus melapterus, Hemigymnus fasciatus, Cheilinus fasciatus and Oxycheilinus digramma were investigated. Populations of each species were sampled from two island groups of the central Great Barrier Reef (GBR), Australia, and from coral reefs in the central Philippines. These three sampling locations span 30° of latitude. The GBR and Philippine reefs experience biologically significant differences in water temperature, geography and human activity. The studied wrasses are effectively unfished in Australia but heavily fished in the Philippines. Gonad weights, histology and demographic data were obtained across the entire size and age range of H. melapterus, C. fasciatus and O. digramma from all locations. Analysis identified three processes of male recruitment: functional gonochorism and both forms of protogynous hermaphroditism, monandry and diandry. The expression of these distinct sexual ontogenies was locality dependent. Populations of H. melapterus, H. fasciatus, C. fasciatus and O. digramma on the GBR showed consistently uniform patterns of sexual ontogeny, with all species being exclusively monandric. H. melapterus, C. fasciatus and O. digramma in the Philippines displayed complex sexual ontogenies, with all species showing histological evidence of both diandry and functional gonochorism. Reproductive investment in gonadal tissue, and population sex structure, also differed between GBR and Philippine coral reefs. Philippine populations had substantially lower gonado-somatic indices than populations on the GBR. Nonetheless, Philippine populations matured more rapidly and displayed a protracted timing of sex change over a large size and age range. Thus, mature females appeared earlier and persisted later into ontogeny in the Philippines than on GBR reefs. Protracted timing of sex change on Philippine reefs is likely linked to the presence of primary males in the population, which is known to reduce the strength of selection for mature females to undergo sex change and become male. Hypotheses based on social structure of fish populations, environmental factors and evolutionary history were developed to account for the different patterns of sexual ontogeny in the focal wrasses.

Age‐specific sensitivity of sperm length and testes size to developmental temperature in the bruchid beetle

AbstractIn an era of global warming, the negative effects of temperature stress on fertility could intensify predicted losses of biodiversity. Male fertility is particularly sensitive to temperature stress, yet we have an incomplete understanding of when, during reproductive ontogeny, spermatogenesis is most affected. Here, we used a temperature‐switch protocol to identify when during development temperature affects the expression of sperm length and testes size in the bruchid beetle Callosobruchus maculatus. Egg‐to‐adult development took place at 17°C, 27°C or 33°C for either the full duration of pre‐imago development or it was switched at different stages during development. Full development at 17°C or 33°C resulted in significantly shorter sperm than at 27°C. However, when developing larvae were switched to higher or lower temperatures, we observed switch‐specific phenotypic expression of sperm length and testes size. Our key finding was that sperm length was sensitive to high‐temperature stress during the early stages of ontogeny and to low‐temperature stress during the latter stages of ontogeny. Such age‐specific developmental sensitivity suggests that infertility resulting from transient heat stress (i.e. heatwaves) could be mitigated by age‐related developmental heterogeneity within populations. Those individuals able to avoid severe effects of heat stress on fertility, through serendipitously being at less‐sensitive stages of development, could potentially compensate for the loss of fertility experienced by those individuals at more sensitive stages of development.

Genomic Determination of Reproductive Mode in Facultatively Parthenogenetic Opiliones.

Sexual reproduction may pose myriad short-term costs to females. Despite these costs, sexual reproduction is near ubiquitous. Facultative parthenogenesis is theorized to mitigate some of the costs of sex, as individuals can participate in occasional sex to limit costs while obtaining many benefits. However, most theoretical models assume sexual reproduction is fixed following mating, with no possibility of clutches of mixed reproductive ontogeny. Therefore, we asked: if coercive males are present at high frequency in a population of facultative parthenogens, will their clutches be solely sexually produced, or will there be evidence of sexually and asexually-produced offspring? How will their offspring production compare to conspecifics in low-frequency male populations? We addressed our questions by collecting females and egg clutches of the facultatively parthenogenetic Opiliones species Leiobunum manubriatum and L. globosum. In L. manubriatum, females from populations with few males were not significantly more fecund than females from populations with higher male relative frequency, despite the potential release of the former from sexual conflict. We used 3 genotyping methods along with a custom set of DNA capture probes to reveal that offspring of L. manubriatum from these high male populations were primarily produced via asexual reproduction. This is surprising because sex ratios in these southern populations approach equality, increasing the probability for females to encounter mates and produce offspring sexually. We additionally found evidence for reproductive polymorphisms within populations. Rapid and accurate SNP genotyping data will continue to allow us to address broader evolutionary questions regarding the role of facultative reproductive modes in the maintenance of sex.

Reproductive Ontogeny and the Evolution of Morphological Diversity in Conifers and Other Plants.

Biologists often study morphological evolution through form and function relationships. But biological structures can perform multiple functional roles, complicating efforts to understand the evolutionary significance of any one relationship. Plant reproductive organs perform multiple roles in a sequence, however, which provides a unique opportunity to understand how structures evolve to meet multiple functional demands. Using conifers as a study group, we discuss how a shared developmental trajectory links the performance of sequential functional roles. Variation in development among lineages can underlie morphological diversity; pollination-stage seed cones in Pinaceae conifers function similarly but show diverse forms reflecting differences in developmental rate. As cones develop further, the morphologies that they use to perform later functional roles are influenced by the specific developmental patterns used to meet earlier demands, which may ultimately limit morphological diversity. However, we also show how selective pressures relating to the final functional stage (seed dispersal) may influence cone anatomy and morphology over all previous stages, highlighting the complex linkages among form, function, and development. We end by discussing the potential relationships between functional ontogeny and morphological disparity in plant reproductive structures more broadly, suggesting that the complex functional roles associated with seed plant reproduction probably underlie the high disparity in this group.

Host-Parasite Interactions from the Inside: Plant Reproductive Ontogeny Drives Specialization in Parasitic Insects.

Host plant interactions are likely key drivers of evolutionary processes involved in the diversification of phytophagous insects. Granivory has received substantial attention for its crucial role in shaping the interaction between plants and their seed parasites, but fine-scale mechanisms explaining the role of host plant reproductive biology on specialization of seed parasites remain poorly described. In a comparative approach using plant histological techniques, we tested the hypotheses that different seed parasite species synchronize their life cycles to specific stages in seed development, and that the stage they target depends on major differences in seed development programs. In a pinaceous system, seed storage products are initiated before ovule fertilization and the wasps target the ovule’s nucellus during megagametogenesis, a stage at which larvae may benefit from the by-products derived from both secreting cells and dying nucellar cells. In a cupressaceous system, oviposition activity peaks later, during embryogenesis, and the wasps target the ovule’s megagametophyte where larvae may benefit from cell disintegration during embryogenesis. Our cytohistological approach shows for the first time how, despite divergent oviposition targets, different parasite species share a common strategy that consists of first competing for nutrients with developing plant structures, and then consuming these developed structures to complete their development. Our results support the prediction that seed developmental program is an axis for specialization in seed parasites, and that it could be an important parameter in models of their ecological and taxonomic divergence. This study provides the basis for further investigating the possibility of the link between plant ontogeny and pre-dispersal seed parasitism.

Venom Alkaloid and Cuticular Hydrocarbon Profiles Are Associated with Social Organization, Queen Fertility Status, and Queen Genotype in the Fire Ant Solenopsis invicta

Queens in social insect colonies advertise their presence in the colony to: a) attract workers' attention and care; b) gain acceptance by workers as replacement or supplemental reproductives; c) prevent reproductive development in nestmates. We analyzed the chemical content of whole body surface extracts of adult queens of different developmental and reproductive stages, and of adult workers from monogyne (single colony queen) and polygyne (multiple colony queens) forms of the fire ant Solenopsis invicta. We found that the composition of the most abundant components, venom alkaloids, differed between queens and workers, as well as between reproductive and non-reproductive queens. Additionally, workers of the two forms could be distinguished by alkaloid composition. Finally, sexually mature, non-reproductive queens from polygyne colonies differed in their proportions of cis-piperidine alkaloids, depending on their Gp-9 genotype, although the difference disappeared once they became functional reproductives. Among the unsaturated cuticular hydrocarbons characteristic of queens, there were differences in amounts of alkenes/alkadienes between non-reproductive polygyne queens of different Gp-9 genotypes, between non-reproductive and reproductive queens, and between polygyne and monogyne reproductive queens, with the amounts increasing at a relatively higher rate through reproductive ontogeny in queens bearing the Gp-9 b allele. Given that the genotype-specific piperidine differences reflect differences in rates of reproductive maturation between queens, we speculate that these abundant and unique compounds have been co-opted to serve in fertility signaling, while the cuticular hydrocarbons now play a complementary role in regulation of social organization by signaling queen Gp-9 genotype.

Reduced embryonic survival in rainbow trout resulting from paternal exposure to the environmental estrogen 17α-ethynylestradiol during late sexual maturation

Exposure of fishes to environmental estrogens is known to affect sexual development and spawning, but little information exists regarding effects on gametes. This study evaluated embryonic survival of offspring from male rainbow trout (Oncorhynchus mykiss) exposed to 17alpha-ethynylestradiol (EE(2)) using an in vitro fertilization protocol. Males were exposed at either 1800 or 6700 degree days ( degrees d) (i.e. 161 or 587 days post-fertilization (dpf)) to test for effects on testes linked to reproductive ontogeny. At 1800 degrees d, fish were beginning testicular differentiation and were exposed to 109 ng EE(2)/l for 21 days. At 6700 degrees d, fish have testes containing spermatocytes and spermatids and were exposed for 56 days to either 0.8, 8.3, or 65 ng EE(2)/l. Semen was collected at full sexual maturity in each group and used to fertilize eggs pooled from several non-exposed females. Significant decreases in embryonic survival were observed only with the 6700 degrees d exposure. In 0.8 and 8.3 ng EE(2)/l treatments, embryo survival was significantly reduced at 19 dpf when compared with the control. In contrast, an immediate decrease in embryonic survival at 0.5 dpf was observed in the 65 ng EE(2)/l treatment. Blood samples collected at spawning from 6700 degrees d exposed males revealed a significant decrease in 11-ketotestosterone and a significant increase in luteinizing hormone levels for the 65 ng EE(2)/l treatment when compared with the other treatment groups. Results indicate that sexually maturing male rainbow trout are susceptible to EE(2) exposure with these fish exhibiting two possible mechanisms of reduced embryonic survival through sperm varying dependant on EE(2) exposure concentrations experienced.

Induced abnormality in Mir- and earth grown super dwarf wheat

Super-dwarf wheat grown on the Mir space station using the Svet “Greenhouse” exhibited morphological, metabolic and reproductive abnormalities compared with Earth-grown wheat. Of prominent importance were the abnormalities associated with reproductive ontogeny and the total absence of seed formation on Mir. Changes in the apical meristem associated with transition from the vegetative phase to floral initiation and development of the reproductive spike were all typical of ‘Super-Dwarf’ wheat up to the point of anthesis. Observation of ruptured anthers from the Mir-grown plants revealed what appeared to be normally developed pollen. These pollen gains, however, contained only one nuclei, while normal viable pollen is tri-nucleate. A potentially important difference in the flight experiment, compared with ground reference studies, was the presence of a high level of atmospheric ethylene (1,200 ppb). Ground studies conducted by exposing ‘Super-Dwarf’ wheat to ethylene just prior to anthesis resulted in manifestation of the same abnormalities observed in the space flight samples.

Canopy temperature and water stress quantificaiton in rainfed pigeonpea ( Cajanus cajan (L.) Millsp.)

Field studies were conducted at Anand (22°35′N, 72°55′E), India, to investigate utility of remotely sensed canopy temperature to assess crop water status and to quantify terminal water stress in rainfed pigeonpea ( Cajanus cajan (L.) Millsp.) during the southwest monsoon seasons of 1993–1994 and 1994–1995, using different planting dates. Canopy–air temperature differential were measured by thermal IR thermometer. Differences in temporal variation in canopy–air temperature differential clearly described the differential response of pigeonpea to soil water availability. The canopy–air temperature differential ( T c− T a) was significantly ( P≤0.05) related to soil moisture, soil water content in the root zone and evapotranspiration. Significantly negative relationship was also noticed for yield attributes with both T c− T a and stress degree days (SDD) during reproductive ontogeny. Total water use during reproductive phase in pigeonpea decreased with increasing SDD. A close relationship between seed yield per plant and SDD in flowering stage clearly showed the potential utility of canopy temperature to describe water stress effects in rainfed pigeonpea.

Effects of drought on O 2 evolution and stomatal conductance of beans at the pollination stage

The predawn leaf water potential (Ψ l), O 2 evolution (Ac) and stomatal conductance ( g s) of three bean genotypes growing in a greenhouse were evaluated in order to compare the effect of water stress induced at different ages, especially during reproductive ontogeny. There was a peak of Ac for all genotypes 30 days after sowing (DAS) at the pollination stage, and the greatest effects of drought on this parameter occurred at this stage, with a decline in Ac from a higher Ψ l (−0.35 MPa) than at the other stages (below −1.0 MPa). The Ψ l and final yield were also more reduced when drought was imposed at the pollination and flowering stages than at the vegetative or pod filling stages. During water stress, the g s of the genotypes was reduced by drought, but Ouro negro showed a different behavior in its stomatal control under drought. Firstly, with water deficit imposition, it maintained a higher g s level in the morning (9:00 h), when the vapor pressure deficit is the lowest of the day, than at midday (12:00 h) and in the afternoon (15:00 h). Secondly, after rehydration, this genotype had a higher g s than non stressed plants.

Early Reproductive Ontogeny in Interspecific Crosses of Arachis hypogaea and Section Arachis Species

Wild Arachis species have been recognized as sources of resistance to pests and pathogens that infect A. hypogaea L. and cause substantial yield losses. However, utilization of these genetic resources for crop improvement has been difficult. This study was conducted to ( a) understand the processes of early embryo growth and development in four Arachis species, two A. hypogaea cultivars and their hybrids and ( b) identify parental compatibilities in reciprocal crosses of A. hypogaea. The results indicated that delayed fertilization beyond 24 h, coupled with slow proembryo growth, leads to embryo abortion in many interspecific crosses. For example, in female A. cardenasii crosses, lack of or delayed fertilization leads to failure to obtain hybrids. When A. batizocoi was used as a female parent, delayed fertilization and the inability of quiescent proembryos to resume growth after soil penetration caused abortion. Embryos of A. hypogaea × A. glandulifera crosses developed normally during the first 21 d after fertilization, but then aborted at a later time. In this study, A. hypogaea was always a better female parent than the wild Arachis species. Increasing the number of pollinations per cross, using the cultivated species as the female parent, utilizing different A. hypogaea varieties, and embryo rescue techniques are suggested to improve the probability of obtaining interspecific hybrids in Arachis.

Genotypic variation in growth and seed yield of soybean (Glycine max (L.) Merr.) in saturated soil culture

Studies were conducted over several years at field sites in south east Queensland to evaluate the response of diverse soybean genotypes to saturated soil culture (SSC), relative to that in conventional irrigation (CI). In an initial study at Dalby, 56 accessions from 12 countries were tested, and all exhibited the ability to acclimate to, and grow in SSC. The chance occurrence of residual picloram herbicide on the site confounded interpretation of differential genotypic responses, but highlighted the potential vulnerability of the SSC system to chemical residues in the surface soil. In more detailed studies with representative subsets of lines at Lawes, there was large genotypic variation in relative responsiveness (RR, defined as {[Response in SSC-Response in CI]/Response in CI}) of yield to SSC, with seed yields reduced by up to 52%, enhanced by up to 37%, or unchanged, depending on genotype and agronomic management. Genotypic variation in RR was generally consistent across seasons, and was variously associated with genotypic differences in phenology when grown under CI. In general, the most positively responsive genotypes were those that started flowering late enough for the plants to have already acclimated to SSC, and that then flowered for a longer duration. Negatively responsive genotypes were those in which the pre-flowering period was sufficiently short for flowering to have commenced before acclimation was complete, i.e. where the acclimation phase intruded into reproductive ontogeny. Very late genotypes were also less responsive, perhaps because of greater lodging under the very favourable growth conditions provided by SSC. The studies indicated the potential for predicting responsiveness to SSC from knowledge of genotypic responses under conventional irrigation.

Agronomic and Physiological Constraints to the Productivity of Tropical Grain Legumes and Prospects for Improvement

SUMMARYGrowth and development of the tropical grain legumes are generally highly sensitive to photo-thermal regime, so that seasonal and regional effects on phenology and yield potential can be large. Yet failure adequately to recognize and fully exploit the consequences of genotype × latitude/sowing date × density interactions has frequently constrained both agronomic and genetic advance with these species. Thus there is opportunity for short term productivity improvements through agronomic strategies which accept the implications of phenological plasticity, and seek to optimize management practices such as sowing date and sowing density, to exploit more effectively the yield potential and broaden the adaptation of existing cultivars. The greatest physiological potential for genetic improvement in the productivity of the tropical grain legumes lies not with increasing total biomass, but with increasing the proportion of bio-mass partitioned into seed, i.e. with improved harvest index (HI). There are difficulties in selecting for higher HI, including its association with phenology, although the latter provides the most powerful tool for manipulating HI in the short term. As with the cereals, more productive genotypes are likely to be characterized by reduced sensitivity to photothermal conditions, shorter growth duration, a more synchronous reproductive ontogeny, and greater HI, than is typical of traditional cultivars. Accordingly, optimal sowing densities will be higher, and crops will need more inputs, better management and more effective protection, than afforded to them in subsistence systems of production. Moreover, the increases in productivity will be achieved, at least partially, at the expense of the potential for yield homeostasis in adverse environments, and of non-seed components such as forage, fuel or tubers - attributes that are often highly valued in subsistence agriculture where many of the tropical food legumes are presently grown. Improvement programmes will therefore need to adopt strategies in particular situations which reflect local perceptions of the importance of productivity improvement relative to that of minimizing inputs and risk.

Comparisons Among Effective Filling Period, Reproductive Period Duration,and R5 to R7 in Determinate Soybeans1

Visual estimates of seed filling duration are important tools in soybean [Glycine max (L.) Merr.] research. Yet little information exists on the correspondence between visual estimates of seed filling duration and direct measurements of seed mass accumulation. The objectives of our study were a) to compare visual estimates of seed filling duration with those obtained from seed growth data to determine if they could be used interchangeably and b) to determine their comparative stability across environments, to assess which estimates of seed filling duration would be a better selection criterion.Five field experiments were conducted in 2 years at Gainesville, FL. Crop growth analyses were performed on 88 random F7 lines from two crosses and their parents in 1982, and on 20 selected lines combined from both crosses in 1983. Genotypes used had determinate growth habit and were in Maturity Groups VII and VIII. The period R5 to R7 was determined additionally on 56 random genotypes in 1983. Effective filling period (EFP) was determined as the time required to achieve final mature plant seed mass using the calculated linear seed growth rate. Reproductive period duration (RPD), defined as the period of linear harvest index (HI) crease, was estimated disregarding fallen leaves.The beginning of EFP and RPD occurred simultaneously while stage R5 occurred 9 to 17 days earlier. The period R5 to R7 was 8 to 13 days longer than EFP, and 1 to 7 days longer than RPD. Associations among EFP, RPD, and R5 to R7 were always positive, but not consistently significant. Therefore, EFP, RPD, and R5 to R7 estimated different periods in the reproductive ontogeny of determinate soybeans. The usefulness of EFP, RPD, and R5 to R7 as selection criteria appears to be limited by the existence of highly significant genotype by environment interactions that were primarily due to changes in the ranking of genotypes across environments. Low broad sense heritability estimates for R5 to R7 were observed.

Irrigation of Soybean Genotypes During Reproductive Ontogeny. I. Agronomic Responses1

Successful irrigation management for soybeans [Glycine max (L.) Merr.] requires a knowledge of the effect of irrigations applied during specific stages of reproductive ontogeny. Eight soybean cultivars, varying in stem growth habit and maturity, were subjected to a factorial set of eight irrigation treatments involving either no irrigation or one irrigation applied at three reproductive stages: R1 to R2 flowering (F), R3 to R5 pod elongation (P), or R5 to R6 seed enlargement (S). The experiment was conducted for 3 years on a Sharpsburg silty clay loam (Typic Argiudoll). An F irrigation had little effect on ultimate seed yield (+20 kg/ha) and for some cultivars actually depressed yield below that of the nonirrigated check. A P irrigation consistently increased seed yield (+379 kg/ha), irrespective of cultivar or year. An S irrigation also enhanced seed yield (+ 384 kg/ha), but the degree of enhancement was inconsistent across years, being influenced by the amount of natural rainfall occurring during the seed enlargement stage. Although a dual F‐P irrigation treatment enhanced seed yield above that for both the nonirrigated check and single F irrigation treatment, the seed yield increase was significantly smaller (+166 kg/ha) than that achieved with a single P irrigation treatment. Soybean maturity was delayed 2 to 6 days with irrigation but the delay was greatest when irrigation was applied late in reproductive ontogeny. This senescence delay lengthened the seed‐fill period and was responsible in part for the seed yield enhancement effected by irrigation. Increases in soybean plant height and lodging were greatest with an F irrigation, intermediate with a P irrigation, and minimal with an S irrigation. Although irrigation effects on seed quality were variable depending on the cnltivar, there was an overall tendency for a P irrigation to improve and an S irrigation to worsen seed quality. An F irrigation had no effect on seed quality. Of the eight cultlvars evaluated, the determinate ‘Elf’ was the most yield responsive to irrigation and was relatively resistant to changes induced by irrigation in plant height, lodging, and seed quality. Based on these data, optimal yield enhancement in irrigated soybean culture can be achieved with the use of short‐stature or lodging‐resistant cultivars irrigated during pod elongation (R3 to R4) and seed enlargement (R5 to R6).

Irrigation of Soybean Genotypes During Reproductive Ontogeny II. Yield Component Responses1

The magnitude of a seed yield increase that occurs when soybeans [Glycine max (L.) Merr.] are irrigated depends upon the phenologic timing of the irrigation in relation to the temporal sequence with which the components of seed yield are established and fixed. Eight soybean cultivars, varying in stem growth habit and maturity, were irrigated according to a factorial treatment design in which either no irrigation or one irrigation was applied at three reproductive stages: R1 to R2 flowering (F), R3 to R4 pod elongation (P), or R5 to R6 enlargement (S). An F irrigation increased the numbers of pods/plant (+ 2.8) and seeds/plant (+ 5.8), but an offsetting decrease occurred 100‐seed weight (−0.9 g), resulting in little change in seed yield. P irrigation had no effect on 100‐seed weight, but increased the numbers of pods/plant (+3.4) and seeds/plant (+7.9) resulting in a large increase in seed yield. An S irrigation resulted in only slight increases in the numbers of pods/plant (+1.0) and seeds/plant (+3.3), but greatly increased 100‐seed weight (+1.4 g), again leading to a large seed yield increase. These observations suggested that irrigation early in reproductive ontogeny greatly reduced flower and pod abortion, whereas irrigation later in ontogeny reduced ovule abortion within developing pods. The cultivar ‘Harcor’ possessed unusually high numbers of oneand two‐seed pods, while ‘Elf’ had substantially fewer numbers of three‐seed pods, and ‘Woodworth’ possessed larger numbers of fourseed pods. Irrigation timing differentially influenced the frequencies of the various pod classes relative to their contribution to the increase in total pods/plant, primarily because of effects on ovule abortion within developing pods. The effects of irrigation timing on number of seeds/plant and 100‐seed weight were thus consistent with the effects on seed yield reported earlier.

Growth, reproductive development and yield of effectively nodulated cowpea plants in contrasting aerial environments

SUMMARYEffectively nodulated cowpea plants were grown to reproductive maturity in growth cabinets set to simulate factorial combinations of daylength (11 h 40 min or 13 h 20 min), day temperature (27 or 33°C) and night temperature (19 or 24°C) characteristic of humid tropical environments. The experiment was designed specifically to compare and contrast the growth, reproductive ontogeny and seed yield of these plants with data obtained earlier when the same symbiotic combination (cv. K 2809 and Rhizobium CB 756) received large amounts (197 mg/l) of inorganic nitrogen throughout growth. These comparisons have shown that effectively nodulated plants are potentially no less adaptable to the aerial environment than are plants depending on inorganic nitrogen, whilst producing equally as good, or even better, seed yields.

Photomorphogenetic effects on cowpea: A comparison of controlled environment and field-grown plants

Five cowpea cultivars ( Vigna unguiculata (L.) Walp) were grown in controlled environment growth cabinets under each of three fluorescent lamp types, either alone or supplemented with tungsten lamps. For comparison, the same cultivars were grown widely spaced in the field at Ibadan, Nigeria. Several morphological attributes were recorded at first flowering in both situations and, accordingly, photomorphogenetic effects of lamp type were assessed. Providing the correct lamp type is used, plants of cv. TVu 4552 can be grown under artificial light in growth cabinets and closely resemble those grown in the field in the tropics in terms of reproductive ontogeny and overall morphology — stem elongation, branch production and leaf expansion.

Effects of night temperature and photoperiod on the reproductive ontogeny of cultivars of cowpea and of soyabean selected for the wet tropics

Experiments carried out in glasshouse in which daylength and day and night temperatures were controlled, have shown that night temperature differences of the range which would be experienced by tropical legumes in their natural habitat, can have profound effects on reproductive ontegeny; especially when coupled with photoperiodic effects. Data so obtained can help in the interpretation and/or prediction of field performance. They do, as well, form a basis for a more critical assessment of the effects of environment on the components of yield which may well throw light on the major constraints to total seed yield. It is, clearly, of little value to screen tropical grain legumes for photoperiod sensitivity only at a single night temperature.