Pod Elongation Research Articles

Nitrogen supply alleviates seed yield reduction by improving the morphology and carbon metabolism of pod walls in shaded rapeseed.

Shading significantly affects rapeseed yield, while reasonable nitrogen (N) application has efficiency gains. However, the functions and mechanisms of N are not fully established for shaded rapeseed plants. Therefore, we conducted a 2-year field experiment to study the effect of N on pod wall morphology and carbon metabolism of shaded rapeseed. Two varieties, three N rates (120 [N1], 240 [N2], and 360 [N3] kg hm-2 ) and two light intensities (100 and 70% light transmission) from 10 to 35 days after the end of flowering were set as experimental parameters. Shading decreased the pod wall chlorophyll content, ribulose 1,5-bisphosphate carboxylase (Rubisco) activity and glucose content at 25 and 35 days after flowering (DAF). Decreased sucrose synthase (SuSy) and sucrose phosphate synthase activity caused by shading reduced sucrose and fructose content. They are responsible for the decline in the 1000-seed weight and a 22.1-37.6% decline in seed yield. More N under shading promoted pod elongation and pigment content, improved chloroplast ultrastructure, increased Rubisco and SuSy activity at 35 DAF, thus contributing to pod wall photosynthesis and fructose and glucose levels in shaded rapeseed plants. Similar trends were observed in pod number, pod weight, and seed weight, while the greatest increase in seed/wall ratio was observed under N2 for shaded rapeseed plants. The results indicated that N can reduce the yield difference between different light conditions and balance partitioning and conversion of photoassimilates in pod wall, but avoid applying an excessive amount of nitrogen.

Comparative transcriptomics analysis of developing peanut (Arachis hypogaea L.) pods reveals candidate genes affecting peanut seed size.

Pod size is one of the most important agronomic features of peanuts, which directly affects peanut yield. Studies on the regulation mechanism underpinning pod size in cultivated peanuts remain hitherto limited compared to model plant systems. To better understand the molecular elements that underpin peanut pod development, we conducted a comprehensive analysis of chronological transcriptomics during pod development in four peanut accessions with similar genetic backgrounds, but varying pod sizes. Several plant transcription factors, phytohormones, and the mitogen-activated protein kinase (MAPK) signaling pathways were significantly enriched among differentially expressed genes (DEGs) at five consecutive developmental stages, revealing an eclectic range of candidate genes, including PNC, YUC, and IAA that regulate auxin synthesis and metabolism, CYCD and CYCU that regulate cell differentiation and proliferation, and GASA that regulates seed size and pod elongation via gibberellin pathway. It is plausible that MPK3 promotes integument cell division and regulates mitotic activity through phosphorylation, and the interactions between these genes form a network of molecular pathways that affect peanut pod size. Furthermore, two variant sites, GCP4 and RPPL1, were identified which are stable at the QTL interval for seed size attributes and function in plant cell tissue microtubule nucleation. These findings may facilitate the identification of candidate genes that regulate pod size and impart yield improvement in cultivated peanuts.

Photosynthetic performance and sugar variations during key reproductive stages of soybean under potassium iodide-simulated terminal drought

Importance of utilizing chemical desiccants to simulate terminal drought effects is gradually increasing. In the present study, a potassium iodide (KI)-simulated terminal drought stress was imposed during the full bloom (R2), pod elongation (R4), and seed initiation (R5) stages of soybean; the KI-induced desiccation effects were assessed at 1, 3, and 5 d after spraying (DASP). Plants responded to KI-simulated terminal drought stress within 1 DASP of KI-treatment, in terms of photosynthetic and transpiration rates. Seed initiation stage was found to be comparatively tolerant to KI-induced desiccation, with respect to chlorophyll degradation and PSII efficiency, which correlated well with the high hexose accumulation during this period. The present study provides a basic understanding regarding the stage-specific responses of soybean towards KI-simulated terminal drought, with respect to photosynthetic performance and sugar status and a correlation between the two traits, which could be useful for developing terminal drought-tolerant varieties.

Effects of light quality on pod elongation in soybean (Glycine max (L.) Merr.) and cowpea (Vigna unguiculata (L.) Walp.)

ABSTRACTSoybean pods are located at the nodes, where they are in the shadow, whereas cowpea pods are located outside of the leaves and are exposed to sunlight. To compare the effects of light quality on pod growth in soybean and cowpea, we measured the length of pods treated with white, blue, red or far-red light. In both species, pods elongated faster during the dark period than during the light period in all light treatments except red light treatment in cowpea. Red light significantly suppressed pod elongation in soybean during the dark and light periods. On the other hand, the elongation of cowpea pods treated with red light markedly promoted during the light period. These results suggested that the difference in the pod set sites between soybean and cowpea might account for the difference in their red light responses for pod growth.

Legume shovelomics: High—Throughput phenotyping of common bean (Phaseolus vulgaris L.) and cowpea (Vigna unguiculata subsp, unguiculata) root architecture in the field

Low phosphorus (P) availability and drought are primary constraints to common bean and cowpea production in developing countries. Genetic variation of particular root architectural phenes of common bean is associated with improved acquisition of water and phosphorus. Quantitative evaluation of root architectural phenotypes of mature plants in the field is challenging Nonetheless, in situ phenotyping captures responses to environmental variation and is critical to improving crop performance in the target environment. The objective of this study was to develop flexible high-throughput root architectural phenotyping platforms for bean and cowpea, which have distinct but comparable root architectures. The bean phenotyping platform was specifically designed to scale from the lab to the field. Initial laboratory studies revealed cowpea does not have basal root whorls so the cowpea phenotypic platform was taken directly to field evaluation. Protocol development passed through several stages including comparisons of lab to field quantification systems and comparing manual and image-based phenotyping tools of field grown roots. Comparing lab-grown bean seedlings and field measurements at pod elongation stage resulted in a R2 of 0.66 for basal root whorl number (BRWN) and 0.92 for basal root number (BRN) between lab and field observations. Visual ratings were found to agree well with manual measurements for 12 root parameters of common bean. Heritability for 51 traits ranged from zero to eighty-three, with greatest heritability for BRWN and least for disease and secondary branching traits. Heritability for cowpea traits ranged from 0.01 to 0.80 to with number of large hypocotyl roots (1.5A) being most heritable, nodule score (NS) and tap root diameter at 5cm (TD5) being moderately heritable and tap root diameter 15cm below the soil level (TD15) being least heritable. Two minutes per root crown were required to evaluate 12 root phene descriptors manually and image analysis required 1h to analyze 5000 images for 39 phenes. Manual and image-based platforms can differentiate field-grown genotypes on the basis of these traits. We suggest an integrated protocol combining visual scoring, manual measurements, and image analysis. The integrated phenotyping platform presented here has utility for identifying and selecting useful root architectural phenotypes for bean and cowpea and potentially extends to other annual legume or dicotyledonous crops.

Soybean fruit development and set at the node level under combined photoperiod and radiation conditions.

In soybean, long days during post-flowering increase seed number. This positive photoperiodic effect on seed number has been previously associated with increments in the amount of radiation accumulated during the crop cycle because long days extend the duration of the crop cycle. However, evidence of intra-nodal processes independent of the availability of assimilates suggests that photoperiodic effects at the node level might also contribute to pod set. This work aims to identify the main mechanisms responsible for the increase in pod number per node in response to long days; including the dynamics of flowering, pod development, growth and set at the node level. Long days increased pods per node on the main stems, by increasing pods on lateral racemes (usually dominated positions) at some main stem nodes. Long days lengthened the flowering period and thereby increased the number of opened flowers on lateral racemes. The flowering period was prolonged under long days because effective seed filling was delayed on primary racemes (dominant positions). Long days also delayed the development of flowers into pods with filling seeds, delaying the initiation of pod elongation without modifying pod elongation rate. The embryo development matched the external pod length irrespective of the pod's chronological age. These results suggest that long days during post-flowering enhance pod number per node through a relief of the competition between pods of different hierarchy within the node. The photoperiodic effect on the development of dominant pods, delaying their elongation and therefore postponing their active growth, extends flowering and allows pod set at positions that are usually dominated.

Plant bugs (Hemiptera: Miridae) on field beans and soybeans in Manitoba, Canada: species composition and seasonal occurrence

AbstractIn Manitoba, Canada, commercial soybeans and two types of field beans, navy and pinto, were sampled for plant bugs. At the centre and margins of 36 fields, sweep net and tap tray samples were taken weekly. In all three crops, Lygus lineolaris (Palisot de Beauvois) (Hemiptera: Miridae) comprised >78% and Adelphocoris lineolatus (Goeze) (Hemiptera: Miridae) <10% of adult mirids. Species composition varied among years but not among crops. For Lygus Hahn, nymphs were 46% of the catch in trays and 23% in sweeps, but total Lygus catch in trays was >2% of that in sweeps. Catch/sample effort was similar at field centres and margins for both Lygus adults and nymphs. Lygus lineolaris reproduced and developed in all three crops. In field beans, Lygus adults were first collected in late vegetative and early pod set stages and late instar nymphs and adults were present from pod elongation until maturity – results consistent with immigration of first summer generation reproductive adults and development of the second generation in the crops. There was evidence of late season immigration of Lygus into all crops. There was no loss of seed quantity attributable to mirids in any of the crops; in field beans there was no evidence that mirids reduced seed quality.

Role of the gibberellin receptors GID1 during fruit-set in Arabidopsis.

Gibberellins (GAs) play a critical role in fruit-set and fruit growth. Gibberellin is perceived by its nuclear receptors GA INSENSITIVE DWARF1s (GID1s), which then trigger degradation of downstream repressors DELLAs. To understand the role of the three GA receptor genes (GID1A, GID1B and GID1C) in Arabidopsis during fruit initiation, we have examined their temporal and spatial localization, in combination with analysis of mutant phenotypes. Distinct expression patterns are revealed for each GID1: GID1A is expressed throughout the whole pistil, while GID1B is expressed in ovules, and GID1C is expressed in valves. Functional study of gid1 mutant combinations confirms that GID1A plays a major role during fruit-set and growth, whereas GID1B and GID1C have specific roles in seed development and pod elongation, respectively. Therefore, in ovules, GA perception is mediated by GID1A and GID1B, while GID1A and GID1C are involved in GA perception in valves. To identify tissue-specific interactions between GID1s and DELLAs, we analyzed spatial expression patterns of four DELLA genes that have a role in fruit initiation (GAI, RGA, RGL1 and RGL2). Our data suggest that GID1A can interact with RGA and GAI in all tissues, whereas GID1C-RGL1 and GID1B-RGL2 interactions only occur in valves and ovules, respectively. These results uncover specific functions of each GID1-DELLA in the different GA-dependent processes that occur upon fruit-set. In addition, the distribution of GA receptors in valves along with lack of expression of GA biosynthesis genes in this tissue, strongly suggests transport of GAs from the developing seeds to promote fruit growth.

Antioxidant enzymes regulate reactive oxygen species during pod elongation in Pisum sativum and Brassica chinensis.

Previous research has focused on the involvement of reactive oxygen species (ROS) in cell wall loosening and cell extension in plant vegetative growth, but few studies have investigated ROS functions specifically in plant reproductive organs. In this study, ROS levels and antioxidant enzyme activities were assessed in Pisum sativum and Brassica chinensis pods at five developmental stages. In juvenile pods, the high levels of O2 .− and.OH indicates that they had functions in cell wall loosening and cell elongation. In later developmental stages, high levels of.OH were also related to increases in cell wall thickness in lignified tissues. Throughout pod development, most of the O2 .− was detected on plasma membranes of parenchyma cells and outer epidermis cells of the mesocarp, while most of the H2O2 was detected on plasma membranes of most cells throughout the mesocarp. This suggests that these sites are presumably the locations of ROS generation. The antioxidant enzymes superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) apparently contributed to ROS accumulation in pod wall tissues. Furthermore, specifically SOD and POD were found to be associated with pod growth through the regulation of ROS generation and transformation. Throughout pod development, O2 .− decreases were associated with increased SOD activity, while changes in H2O2 accumulation were associated with changes in CAT and POD activities. Additionally, high POD activity may contribute to the generation of.OH in the early development of pods. It is concluded that the ROS are produced in different sites of plasma membranes with the regulation of antioxidant enzymes, and that substantial ROS generation and accumulation are evident in cell elongation and cell wall loosening in pod wall cells.

From flower to seed: identifying phenological markers and reliable growth functions to model reproductive development in the common bean (Phaseolus vulgarisL.)

The lack of dependable morphological indicators for the onset and end of seed growth has hindered modeling work in the common bean (Phaseolus vulgaris L.). We have addressed this problem through the use of mathematical growth functions to analyse and identify critical developmental stages, which can be linked to existing developmental indices. We performed this study under greenhouse conditions with an Andean and a Mesoamerican genotype of contrasting pod and seed phenotypes, and three selected recombinant inbred lines. Pods from tagged flowers were harvested at regular time intervals for various measurements. Differences in flower production and seed and pod growth trajectories among genotypes were detected via comparisons of parameters of fitted growth functions. Regardless of the genotype, the end of pod elongation marked the beginning of seed growth, which lasted until pods displayed a sharp decline in color, or pod hue angle. These results suggest that the end of pod elongation and the onset of color change are reliable indicators of important developmental transitions in the seed, even for widely differing pod phenotypes. We also provide a set of equations that can be used to model different aspects of reproductive growth and development in the common bean.

The Occurrence of Delayed Stem Senescence in Relation to trans-Zeatin Riboside Level in the Xylem Exudate in Soybeans Grown under Excess-Wet and Drought Soil Conditions

Delayed stem senescence (DSS) after pod maturation in soybean (Glycine max) lowers the quality of products in the mechanized harvest. The effects of drought and excess wet soil conditions on the occurrence of DSS were studied with special reference to remobilization of vegetative nitrogen and supply of cytokinin via xylem. Excess wet soil treatment was applied throughout the reproductive period to field-grown soybean in 2003 (Exp.1) and short-term drought stress treatment was applied during the reproductive period to pot-grown soybean plants in 2004 (Exp.2). The degree of DSS at pod maturing was evaluated by the DSS score from “1” for severe DSS to “5” for completely synchronous senescence of pods and vegetative parts. The DSS score in Exp.1 varied from 2.2 to 2.5 and that in Exp.2 from 2.8 to 3.7. Excess wet soil treatment in Exp.1 promoted the occurrence of DSS, while drought stress treatments during the periods of flowering to pod elongation, later seed-filling and seed maturing decreased it. The soybean plants that showed distinct DSS had lower ratios of seed number to vegetative dry weight at seed maturity and a lower rate of nitrogen remobilization from vegetative organs to seeds during the latter half of the reproductive period. The trans-zeatin riboside (t-ZR) level in xylem exudate tended to be higher in soybeans with severer DSS than in those normally matured in both experiments showing increased t-ZR concentration and/or higher exudation rate. These results suggest that DSS can be caused by a wet soil water condition, which lowers pod/seed number and increases vegetative organs mediated by the increased supply of cytokinin through xylem during seed-filling.

Changes in the activities of carbon metabolizing enzymes with pod development in lentil (Lens culinaris L.)

Activities of some key enzymes of carbon metabolism sucrose synthase, acid and alkaline invertase, phosphoenol pyruvate carboxylase, malic enzyme and isocitrate dehydrogenase were investigated in relation to the carbohydrate status in lentil pods. Sucrose remained the dominant soluble sugar in the pod wall and seed, with hexoses (glucose and fructose) present at significantly lower levels. Sucrose synthase is the predominant sucrolytic enzyme in the developing seeds of lentil (Lens culinaris L.). Acid invertase was associated with pod elongation and showed little activity in seeds. Sucrose breakdown was dominated by alkaline invertase during the development of podwall, while both the sucrose synthase and alkaline invertase were active in the branch of inflorescence. A substantial increase of sucrolytic enzymes was observed at the time of maximum seed filling stage (10–20 DAF) in lentil seed. The pattern of activity of sucrose synthase highly paralleled the phase of rapid seed filling and therefore, can be correlated with seed sink strength. It seems likely that the fruiting structures of lentil utilize phosphoenol pyruvate carboxylase for recapturing respired carbon dioxide. Higher activities of isocitrate dehydrogenase and malic enzyme in the seed at the time of rapid seed filling could be effectively linked to the deposition of protein reserves.

Development of self‐incompatible Brassica napus: (I) introgression of S‐alleles from Brassica oleracea through interspecific hybridization

AbstractCultivars in Brassica napus var. oleifera, a self‐pollinating, self‐compatible species, have traditionally been developed as open‐pollinated lines or populations. Significant yield gains in this species have been realized through the exploitation of heterosis. Commercial hybrid production has been possible as a result of the development of a number of pollination control systems. Self‐incompatibility was transferred from B. oleracea var. italica to B. napus var. oleifera through interspecific hybridization. The response to interspecific pollination, as measured by pod elongation and initial stages of ovule development, was genotype dependent, and two highly responsive B. napus genotypes were identified. Embryo rescue was used to produce the interspecific hybrids. Isoelectric focusing of stigma proteins was used to identify S‐alleles in the interspecific hybrids to facilitate backcrossing. Segregation of the S‐locus through a series of back‐crosses to B. napus was complicated by aneuploidy; however, the S‐locus was found to segregate as a single gene. Usefulness of B. oleracea as a source of S‐alleles for pollination control in B. napus is discussed.

Effects of symbiosis with Rhizobium fredii on transport of fixed nitrogen in the xylem of soybean plants

An experiment was conducted to identify the main nitrogenous compound transported in the xylem sap of soybean plants nodulated with Rhizobium fredii. Soybean (Glycine max L. Merr.) cultivars, wild type Bragg (nod+, fix+) and its nitrate tolerant, hypernodulating mutant ntsll16 (nod++, fix+) were used for this experiment. These soybean plants were inoculated with a slowgrowing rhizobium, Bradyrhizobium japonicum USDAllO or fast-growing rhizobia consisting of a mixture of R. fredii USDA191, USDA193, and USDA-194 and grown in a phytotron under natural light and controlled temperature conditions. Xylem sap was collected from Bragg and ntsll16 plants at the flowering and pod elongation stages. Acetylene reduction activity per plant or per nodule weight was not different between soybean lines and inoculums. The composition of the nitrogenous compounds in the xylem sap was compared between the symbionts, with B. japonicum and R. fredii. At the flowering stage, ureide-N and amide-N accounted for 53 to 70% and 20 to 27% respectively of the total N in the sap collected from the plants inoculated either with B. japonicum or R. fredii. At the pod elongation stage, ureide-N and amide-N accounted for 74 to 85%, and 7 to 19% of total sap N. With the growth of the soybean plants, the ratio of ureide-N in the xylem sap increased. These results suggest that in the case of wild soybean and the hypernodulating mutant line nodulated by R. fredii, ureide is transported as the main nitrogenous compound of fixed nitrogen in the xylem sap in the same way as in plants nodulated with B. japonicum.

Delayed maturity associated with southern green stink bug (Heteroptera: Pentatomidae) injury at various soybean phenological stages.

Delayed maturity in soybean, Glycine max (L.) Merr., occurred in response to infestation by southern green stink bug, Nezara viridula (L.), in 4 yr of field studies. Maturity delays followed stink bug infestation that occurred only during the pod set and filling stages (R3-R5.5), and infestations at R3-4 and R5 resulted in delayed maturity more consistently than did infestation at R5.5. Infestation levels of six stink bugs per 0.3 m of row for 7-14 d generally were required to delay soybean maturity. The greatest impact on seed yield and quality parameters followed stink bug infestations that occurred during R3-R5.5, which corresponded closely with the periods of infestation that resulted in delayed maturity. If both delayed maturity and yield reduction are considered, the pod elongation through late pod filling stages were most critical for protecting soybeans from southern green stink bugs.

Expression of gibberellin mutations in fruits of Pisum sativum L.

The gibberellin (GA) economy of young pea (Pisum sativum L.) fruits was investigated using a range of mutants with altered GA biosynthesis or deactivation. The synthesis mutation lh-2 substantially reduced the content of both GA4 and GA1 in young seeds. Among the other synthesis mutations, ls-1, le-1 and le-3, the largest reduction in seed GA1 content was only 1.7-fold (le-1), while GA4 was not reduced in these mutants, and in fact accumulated in some experiments (compared with the wild type). Mutation sln appeared to block the step GA20 to GA29 in young pods and seeds, but not as strongly as in older seeds. Mutations ls-1, le-1 and le-3 markedly reduced pod GA1 levels, but pod elongation was not affected. After feeds of [13C,3H]GA20 to leaves, the pods contained 13C,3H-labelled GA20, GA1, GA29 and GA81, and the seeds, [13C,3H]GA20 and [13C,3H]GA29. These findings are discussed in relation to recent suggestions regarding the role and origin of GA1 in pea fruits.

Pod Elongation and Seed Growth as Influenced by Nodal Position on Stem and Raceme Order in a Determinate Type of Soybean Cultivar.

Pod elongation and seed growth in a determinate type of soybean were investigated in relation to nodal positions and raceme orders. Pods began to elongate on day 16 after the beginning of flowering, and seed growth was started on day 14 after the beginning of pod elongation(i.e., it took 30 days). The lower the raceme orders, the higher the final pod length and seed dry weight. The floral organs on the 4th and 5th orders of racemes began to flower on day 21 after the flowering of basal buds, but started to elongate on day 10 after the beginning of elogation of basal pods. Furthermore, the increase in seed weight began on day 6 after the beginning of the growth of basal pod seeds. The rate of pod elongation was highest on order 3 raceme and the rate of dry matter accumulation in seeds on order 2 raceme was higher than on the basal order raceme. Flower or pod abortion was observed most frequently just before the period of pod elongation. Although soybean had a long flowering period according to raceme orders, both the pod elongation and the seed growth were synchronous among raceme orders; thus seeds were matured at the same time.

Effect of the Growth Retardant 3,5-Dioxo-4-butyryl-cyclohexane Carboxylic Acid Ethyl Ester, an Acylcyclohexanedione Compound, on Fruit Growth and Gibberellin Content of Pollinated and Unpollinated Ovaries in Pea.

Treatment of pollinated pea (Pisum sativum L. cv Alaska, line V1) ovaries with 3,5-dioxo-4-butyryl-cyclohexane carboxylic acid ethyl ester (LAB), an acylcyclohexanedione derivative that competitively inhibits 2-oxoglutarate-dependent gibberellin (GA) dioxygenases, caused a reduction of pod elongation proportional to the amount of inhibitor applied. The effect of LAB was counteracted by GA1 and GA3, and partially by GA20. The inhibitor decreased the contents of GA1 and GA3 (the purported active GAs) and GA8, increased those of GA19 and GA20, and did not affect that of GA29 in both the pod and the developing seeds. These results provide evidence that GA1 and/or GA3 control pod development in pea and show that GA20 is not active per se. In contrast to its effect on pollinated ovaries, LAB promoted parthenocarpic development of unpollinated ovaries, which is associated with an increase of GA1 and GA8 content. The inhibitor enhanced the response of unpollinated ovaries to GA1 and GA20, but it did not alter the response to GA3. LAB is proposed to promote parthenocarpic development and enhance the response to exogenous GAs by blocking the 2[beta]-hydroxylation of GA1 more efficiently than 3[beta]-hydroxylation of GA20.

Water Sensitive Periods during the Reproductive Growth Phase of Glycine max L. II Establishing Water Stress Sensitivity

AbstractThe water sensitivity of soybeans was determined on a day‐to‐day basis from the onset of flowering to physiological maturity by correlating daily leaf water potential values of 50 different soil water regimes with corresponding grain, vegetative and biomass yields. Days, and consecutive days forming periods, during which significant negative correlations were obtained were regarded as water sensitive periods during the reproductive growth phase of the soybean crop.Water deficits during flowering significantly inhibited vegetative and biomass production but inhibited grain yields only when occurring during early flowering. During pod elongation and seed development the sensitivity of the soybean plant to water stress was present but diminished in time with regard to vegetative and biomass yields. The effect on grain yields was restricted to pod elongation and to later seed development stages. Water stress affected grain yields to a far greater extent than vegetative growth during seed filling and physiological maturity.

Growth, sucrose synthase, and invertase activities of developing Phaseolus vulgaris L. fruits

ABSTRACTActivities of the sucrose‐cleaving enzymes, acid and neutral invertase and sucrose synthase, were measured in pods and seeds of developing snap bean (Phaseolus vulgaris L.) fruits, and compared with 14C‐import, elongation and dry weight accumulation. During the first 10 d post‐anthesis, pods elongated rapidly with pod dry weight increase lagging behind by several days. The temporal patterns of acid invertase activity and import coincided closely during the first part of pod development, consonant with a central role for this enzyme in converting imported sucrose during pod elongation and early dry weight accumulation. Later, sucrose synthase became the predominant enzyme of dry weight accumulation and was possibly associated with the development of phloem in pod walls. Sucrose synthase activity in seeds showed two peaks, corresponding to two phases of rapid import and dry weight accumulation; hence, sucrose synthase was associated with seed sink growth. Acid invertase activities in seeds were low and did not show a noticeable relationship with import or growth. All neutral invertase activities, during pod and seed development, were too low for it to have a dominant role in sucrose cleavage. Changes in activities of certain sucrose‐cleaving enzymes appear to be correlated with certain sink functions, including import, storage of reserves, and biosynthetic activities. The data supports the association of specific sucrose‐cleaving enzymes with the specific processes that occur in the developing pods and seeds of snap bean fruits; for example, acid invertase with pod elongation and sucrose synthase with fruit dry matter accumulation.