Subtending Leaf Research Articles

Pollen-cones of Pinus bungeana Zucc. ex Endl. (Pinaceae, Coniferales): Do they indicate a pseudanthial origin?

Even today, the evolutionary origin of coniferous pollen-cones is still controversial and conflicting theories about the identity of their microsporangiophores exist. Previous studies strongly suggest that the simple pollen-cone structure of some Taxaceae s.l. is most likely derived from a compound structure and each microsporangiophore represents a lateral, however markedly reduced flower. To test if a similar evolutionary pathway remembering the pseudathium concept sensu Wettstein applies also for Pinaceae, normal shaped and abnormal pollen-cones of Pinus bungeana (Pinaceae) are investigated with SEM and paraffin microtome technique. Pinus sylvestris, which is the type species of the genus, is used as another example. The early development of bisporangiate microsporangiophores starts with two distinct primordia. They fuse in basal parts and form a common stalk. The distal parts remain free and each develops a stalk, a distinct phyllom-like scutellum and one abaxial microsporangium. In some bisporangiate microsporangiophores two monosporangiate microsporangiophores are inserted laterally at the common stalk, which forms a distinct terminal apex. Other microsporangiophores bear a subunit in form of a second, however, aborted microsporangiophore in a lateral position at the base of the common stalk. It is suggested that the bisporangiate microsporangiophore is not a staminate leaf in the sense of a microsporophyll, but a dorsiventral synangium consisting at least of two fused microsporangiophores. In this case each microsporangiophore corresponds to a markedly reduced cone (= flower) which however has lost its pherophyll (= subtending leaf). Similar as shown for Torreya the simple pollen-cone structure in Pinaceae is thus derived from a pseudanthial (= compound) origin.

Thaigardenia (Rubiaceae: Gardenieae), a new genus distributed from Thailand to South China

Identified as Gardenia over a century ago, three known species from Thailand to south China differ considerably from typical members of that genus, from which growth habits, aspects of branch architecture and corolla shape set them apart. They form a new genus, here named Thaigardenia, the species of which are scrambling to thicket-forming shrubs to sometimes treelets or small trees. They have typically unequal (asymmetric) development of each internode that offsets what began as opposite pairs of axillary buds (and potential axillary branches) from subtending leaf axils at the same level, and small infundibular corollas with insignificant tubular bases. In contrast, typical Gardenia are non-scrambling shrubs or trees, often have extra-axillary buds or branches that consistently continue to develop at the same level (i.e., remaining opposite); and showy hypocrateriform (salverform) corollas with elongate tubular bases. The unequal development of different sides of an internode that brings an initially opposite pair of axillary buds (branches) to different levels, so that they do not appear paired subsequently, is, as far as is known, unique and unknown in other Rubiaceae or opposite-leaved plants; this shared feature is a key synapomorphic character for species of the newly recognised genus.

Phosphorus-induced greater enhancement in carbon supply and storage for oil synthesis during the crucial period made cottonseed kernel oil yield have a higher increment than protein

Cottonseed has a high utilization value due to its luxuriant oil and protein, but low phosphorus (P) in cropland reduces its yield and quality. A limited understanding of the physiological mechanism underlying these results restricted the exploration of P efficient management in cotton cultivation. A 3-year experiment was performed with Lu 54 (low-P sensitive) and Yuzaomian 9110 (low-P tolerant) under 0 (deficient-P), 100 (critical-P), and 200 (excessive-P) kg P2O5 ha−1 in a field having 16.9 mg kg−1 available P to explore the key pathway for P to regulate cottonseed oil and protein formation. P application markedly increased cottonseed oil and protein yields, with the enhanced acetyl-CoA and oxaloacetate contents during 20–26 days post anthesis being a vital reason. Notably, during the crucial period, decreased phosphoenolpyruvate carboxylase activity weakened the carbon allocation to protein, making malonyl-CoA content increase greater than free amino acid; Meanwhile, P application accelerated the carbon storage in oil but retarded that in protein. Consequently, cottonseed oil yield increased more than protein. Oil and protein synthesis in Lu 54 was more susceptible to P, resulting in greater increments in oil and protein yields than Yuzaomian 9110. Based on acetyl-CoA and oxaloacetate contents (the key substrates), the critical P content in the subtending leaf to cotton boll needed by oil and protein synthesis in Lu 54 (0.35%) was higher than Yuzaomian 9110 (0.31%). This study provided a new perception of the regulation of P on cottonseed oil and protein formation, contributing to the efficient P management in cotton cultivation.

Relationship between the Growth of Current Shoot and the Development of Inflorescence and Vegetative Buds in Oncidesa Gower Ramsey ‘Honey Angel’ Leaf Axils

The flowering control of Oncidesa Gower Ramsey ‘Honey Angel’ is important and in-demand by the industry. Therefore, an understanding of the development of inflorescence and vegetative shoot from the leaf axils on the current shoot is required. The internode of a young Oncidesa current shoot between the 0th (at the base of the pseudobulb) and 1st (immediately above the pseudobulb) nodes can enlarge to form a pseudobulb, and the axillary bud on the 0th or -1st (immediately below the 0th node) node can differentiate into an inflorescence bud. The axillary buds on the lower nodes (-2nd to -4th nodes) can remain vegetative. In this study, we investigated the growth and anatomical features of axillary buds at various stages during the growth of the current shoot. We sampled the axillary buds on the 0th to -4th nodes from the current shoots when they were 10, 15, 20, 25, and 30 cm in length for sectioning and anatomical observations. Vegetative buds on the -2nd to -4th nodes grew faster and had more nodes than the inflorescence bud when the current shoot grew from 10 to 25 cm. However, when the current shoot elongated from 25 to 30 cm, the length and node number in the inflorescence bud on the 0th node increased and the inflorescence branch primordia were observable. The length and node number of the inflorescence bud became the same as that of the vegetative buds, which had no further growth, whereas the current shoot grew from 25 to 30 cm. The pseudobulb began to emerge from the leaf sheath (unsheathing) when the current shoot had reached 30 cm in length. Therefore, the time when the pseudobulb started to unsheathe from its subtending leaf was critical for the reproductive growth of Oncidesa Gower Ramsey ‘Honey Angel’ when growth acceleration of the inflorescence bud occurred. Evaluating the current shoot length can be a nondestructive method of estimating the developmental stage of the inflorescence bud.

Genotypic variation in carbon and nitrogen metabolism in the cotton subtending leaves and seed cotton yield under various nitrogen levels.

Nitrogen (N) is the key nutrient required for high cotton production; however, its excessive use can increase the cost of production and environmental problems. Reducing the application of N while sustaining the yield is an important issue to be solved. Therefore, this study was designed to investigate the genotypic variations in subtending leaf physiology and its contribution to seed cotton yield of contrasting N-efficient cotton genotypes under various N levels in pot and field conditions. The results showed that the application of N increased the enzymatic activities related to carbon (C) and N metabolisms. Under the same N level, the C/N metabolisms of the N-efficient genotypes were significantly higher than N-inefficient genotypes, indicating a strong N assimilation and photoassimilation ability in N-efficient genotypes, especially under low N level. Moreover, the antioxidant enzymatic activities were significantly higher, whereas malondialdehyde content was lower in N-efficient cotton genotypes than in N-inefficient ones. Therefore, N-efficient cotton genotypes showed strong resistance, higher C/N metabolisms, and provided sufficient dry matter for boll development. As a result, the yield, N use efficiency, and value cost ratio of the N-efficient cotton genotypes were higher than in the N-inefficient genotypes. It was confirmed that the higher C/N metabolisms in the cotton subtending leaves of N-efficient cotton genotypes could support higher seed cotton yield under relatively low N application. © 2022 Society of Chemical Industry.

Effects of phosphorus application on carbohydrate metabolism in cottonseed kernel during the key development period provided a new insight for phosphorus management in cotton production

Cottonseed provides abundant and high-quality raw materials for biodiesel, fine chemical, and other industries due to its rich oil, but phosphorus-deficient farmland and finite phosphate resource hinder its production. Cottonseed development is based on its carbohydrate, and exploring the response of cottonseed carbohydrate metabolism to phosphorus could contribute to optimizing phosphorus management in cotton production and continuously obtaining high-quality cottonseed. Here, the experiment on phosphorus rates [0 (phosphorus deficient), 100 (phosphorus critical), and 200 (phosphorus excess) kg P2O5 ha−1] was conducted using Lu 54 (low-phosphorus sensitive) and Yuzaomian 9110 (low-phosphorus tolerant) in a field containing 16.9 mg kg−1 available phosphorus to assess the effects of phosphorus on cottonseed yield, cottonseed total phosphorus, ash, and oil contents, carbohydrate metabolism related carbohydrate contents, and enzymes activities. The results showed that phosphorus application increased cottonseed yield and oil content by 32.4%−54.2% and 14.8%−20.1% on average, respectively, which could be attributed to the improvements in sucrose transport and hydrolysis in cottonseed kernel during 18–26 days post anthesis induced by higher total phosphorus content (17.1%−26.7%). During the key development period of cottonseed kernel, phosphorus application increased sucrose content (13.0%−19.4%) by increasing the expression of sucrose transporter genes, and promoted sucrose hydrolysis by elevating enzymes activities, especially sucrose synthase (11.2%−19.1%) in cottonseed kernel. Consequently, phosphorus application increased hexose levels in cottonseed kernel and thus provided more substrates for its development, which promoted the formation of cottonseed kernel biomass (6.2%−10.6%), cottonseed and oil yields. Additionally, carbohydrate metabolism in Lu 54 was more sensitive to phosphorus than Yuzaomian 9110 during the key development period, resulting in greater increases in cottonseed kernel biomass, cottonseed yield, and oil content for Lu 54. Notably, the increments generated by unit phosphate fertilizer on the above indicators attenuated markedly with phosphorus application. Based on sucrose content, the key substance, the critical phosphorus concentration in the subtending leaf to cotton boll (LPC) needed by the efficient operation of the key carbohydrate metabolic pathway was 0.38% for Lu 54 versus 0.34% for Yuzaomian 9110. This report first unveiled the key carbohydrate metabolic pathway regulated by phosphorus for cottonseed and oil yield formation and its demand for LPC during the key development period, providing a new insight for diagnosing and regulating phosphorus in cotton production.

Carbon assimilation and distribution in cotton photosynthetic organs is a limiting factor affecting boll weight formation under drought.

Previous studies have documented cotton boll weight reductions under drought, but the relative importance of the subtending leaf, bracts and capsule wall in driving drought-induced reductions in boll mass has received limited attention. To investigate the role of carbon metabolism in driving organ-specific differences in contribution to boll weight formation, under drought conditions. Controlled experiments were carried out under soil relative water content (SRWC) (75 ± 5)% (well-watered conditions, control), (60 ± 5)% (moderate drought) and (45 ± 5)% (severe drought) in 2018 and 2019 with two cultivars Yuzaomian 9110 and Dexiamian 1. Under severe drought, the decreases of photosynthetic rate (Pn) and carbon isotope composition (δ13C) were observed in the subtending leaf, bract and capsule wall, suggesting that carbon assimilation of three organs was restricted and the limitation was most pronounced in the subtending leaf. Changes in the activities of sucrose phosphate synthase (SPS), sucrose synthase (SuSy), invertases as well as the reduction in expression of sucrose transporter (GhSUT1) led to variabilities in the sucrose content of three organs. Moreover, photosynthate distribution from subtending leaf to seeds plus fibers (the components of boll weight) was significantly restricted and the photosynthetic contribution rate of subtending leaf to boll weight was decreased, while contributions of bracts and capsule wall were increased by drought. This, in conjunction with the observed decreases in boll weight, indicated that the subtending leaf was the most sensitive photosynthetic organ to drought and was a dominant driver of boll weight loss under drought. Therefore, the subtending leaf governs boll weight loss under drought due to limitations in carbon assimilation, perturbations in sucrose metabolism and inhibition of sucrose transport.

Leaf anatomical alterations reduce cotton's mesophyll conductance under dynamic drought stress conditions.

Drought stress significantly affects cotton's net photosynthetic rate (A) by restraining stomatal (gs ) and mesophyll conductance (gm ) as well as perturbing its biochemical process, resulting in yield reductions. Despite the significant progress in dissecting effects of drought on photosynthesis, the variability observed in cotton's gm , and the mechanisms contributing to that variability under dynamic drought stress conditions are poorly understood. For that reason, a controlled-environment experiment with two cotton genotypes (Dexiamian 1, Yuzaomian 9110), three water levels (soil relative water content: control [75 ± 5]%, moderate drought [60 ± 5]%, severe drought [45 ± 5]%), and two drought durations (10 and 31 days) were conducted. The results indicated that the cotton boll biomass was significantly decreased under 10-day severe drought and 31-day moderate and severe drought. Decreases in gs were later accompanied by decreases in gm and further combined with reductions in electron transport rate, as drought stress progressed in duration and severity, ultimately resulting in significant reductions in A of subtending leaf. Stomatal and mesophyll conductance constraints were the primary factors limiting photosynthesis, while biochemical constraints decreased, as drought stress progressed. Considering gm , its decline was ascribed to increases in the diffusion resistance of CO2 through cytoplasm (rcyt ), under short- or long-term drought, as well as to increases in leaf dry mass (LMA), and decreases in the chloroplast surface area exposed to intercellular air space (Sc /S), under long-term drought. It was concluded that A could be enhanced, under dynamic drought stress conditions, by increasing gm through increasing Sc /S and reducing LMA and rcyt .

Soil drought duration and severity affect cotton boll biomass by altering recovery times and carbon dynamics of subtending leaf

AbstractDrought appears at flowering and boll formation for cotton frequently. However, reports on the impact of carbon dynamics in the subtending leaf on boll biomass under periodic droughts are limited. To investigate this, experiments were carried out with two cultivars (drought‐tolerant: Dexiamian 1; drought‐sensitive: Yuzaomian 9110), three water levels [soil relative water content (SRWC): control (75 ± 5)%, moderate drought (60 ± 5)%, severe drought (45 ± 5)%] and five drought durations (10, 17, 24, 31 and 38 days). A 38‐day drought declined the net photosynthetic rate of subtending leaf, which could be collectively attributed to the reduction in carboxylation with reduced ribulose‐1,5‐bisphosphate carboxylase activity, and stomal limitation with decreased stomatal conductance, along with the damage of photosynthetic apparatus with depressed maximum and actual photochemical quantum yield, leading to lower starch content. A 38‐day drought also increased the activities of sucrose phosphate synthase (SPS), sucrose synthase (Susy) and expressions of genes (GhSPS1, GhSPS2, GhSusA and GhSusB) associated with these enzymes, causing the accumulation of sucrose content, finally resulting in lower boll biomass. Some of the above parameters fully recovered under more than 17‐day moderate drought or over 10‐day severe drought, but boll biomass still decreased after re‐watering. Under 10‐day moderate drought, all aforementioned indices and boll biomass were completely recovered within 7 days of re‐watering, and the recovery capacity of Yuzaomian 9110 was lower than that of Dexiamian 1. Therefore, rapid recovery of photosynthesis and decline in the subtending leaf sucrose content to pre‐stress levels are important factors in lessening the impacts of drought on boll biomass and are indicative of cultivar tolerance to short‐term moderate water deficit.

Physiological Characteristics of Cotton Subtending Leaf Are Associated With Yield in Contrasting Nitrogen-Efficient Cotton Genotypes.

Nitrogen (N) plays an important role in various plant physiological processes, but studies on the photosynthetic efficiency and enzymatic activities in the cotton subtending leaves and their contribution to yield are still lacking. This study explored the influence of low, moderate, and high N levels on the growth, photosynthesis, carbon (C) and N metabolizing enzymes, and their contribution to yield in CCRI-69 (N-efficient) and XLZ-30 (N-inefficient). The results showed that moderate to high N levels had significantly improved growth, photosynthesis, and sucrose content of CCRI-69 as compared to XLZ-30. The seed cotton yield and lint yield of CCRI-69 were similar under moderate and high N levels but higher than XLZ-30. Similarly, moderate to high N levels improved the C/N metabolizing enzymatic activities in the subtending leaf of CCRI-69 than XLZ-30. A strong correlation was found between subtending leaf N concentration with C/N metabolizing enzymes, photosynthesis, sucrose contents, boll weight, and seed cotton yield of N-efficient cotton genotype. These findings suggest that subtending leaf N concentration regulates the enzymatic activities and has a key role in improving the yield. These parameters may be considered for breeding N-efficient cotton genotypes, which might help to reduce fertilizer loss and improve crop productivity.

Genotypic variation in root morphology, cotton subtending leaf physiology and fiber quality against nitrogen

BackgroundNitrogen (N) is important for improving various morphological and physiological processes of cotton but their contribution to fiber quality is still lacking.AimsThe current study aimed to explore the relationship between root morphology, subtending leaf physiology, and fiber quality of contrasting N-efficient cotton genotypes in response to N.MethodsWe analyzed the above parameters of CCRI 69 (N-efficient) and Xinluzao-30 (XLZ-30, N-inefficient) under control (2.5 mmol·L−1) and high N (5 mmol·L−1) conditions.ResultsThe results showed that root morphological traits were increased in CCRI-69 under control conditions than high N. Subtending leaf morphology, chlorophyll and carotenoid contents, free amino acids, and soluble proteins were higher under high N as compared with the control. However, soluble sugars, fructose, sucrose contents, and sucrose phosphate synthase were higher under control conditions than high N across the growth stages. Irrespective of the N conditions, all morphological and physiological traits of cotton subtending leaf were higher in CCRI-69 than XLZ-30. Except for fiber uniformity, fiber quality traits like fiber length, strength, micronaire, and elongation were improved under control conditions than high N. Between the genotypes, CCRI-69 had significantly higher fiber length, strength, micronaire, and elongation as compared with XLZ-30. Strong positive correlations were found between root morphology, soluble sugars, sucrose content, and sucrose phosphate synthase activity with fiber quality traits, respectively.ConclusionsThese findings suggest that CCRI-69 performed better in terms of growth and fiber quality under relatively low N condition, which will help to reduce fertilizer use, the cost of production, and environmental pollution.

The reproductive biology of glossopterid gymnosperms—A review

We review recent advances on glossopterid reproductive biology and their implications for seed plant phylogeny and the ecology of this widespread Permian Gondwanan group. Microsporangiate organs are interpreted to have been arranged in loose compound cones—an organization that evokes comparisons with Ginkgoales, Cordaitales and early conifers. The pollen was typically taeniate, bisaccate, and primarily adapted to wind dispersal. The diverse ovuliferous organs generally incorporated some form of marginal flange or wing. In most cases, the wing was probably protective, wrapping around the ovules during early development. However, we postulate that some conspicuous flanges were potentially analogous to angiosperm petals, functioning as corolla-like guides to attract insect pollinators. The arrangement of seed-bearing polysperms adnate to the subtending leaf to form a fertiliger in glossopterids represented another means of protecting the ovules. In some cases, highlighting the polysperm against the attached leaf might have increased the showiness of the ovule-bearing part for pollinators. In other cases, detachment of the fertiliger may have aided anemochory by retarding seed fall through rotation analogous to dispersal in extant Tilia. The microgametophyte in glossopterids is characterized by a short, weakly branched, haustorial tube, and the release of motile sperm cells. At least some seeds of glossopterids express polyembryony. Mature seeds possessed various micropylar modifications for the entrapment of pollen, and winged or bulbous expansions of the outer integument to aid anemochory or possibly hydrochory. Vegetative regeneration as a response to damage occurred via epicormic buds and possibly by the development of lignotubers.

Dissecting Source-Sink Relationship of Subtending Leaf for Yield and Fiber Quality Attributes in Upland Cotton (Gossypium hirsutum L.).

Photosynthesis as a source is a significant contributor to the reproductive sink affecting cotton yield and fiber quality. Moreover, carbon assimilation from subtending leaves adds up a significant proportion to the reproductive sink. Therefore, this study aimed to address the source-sink relationship of boll subtending leaf with fiber quality and yield related traits in upland cotton. A core collection of 355 upland cotton accessions was subjected to subtending leaf removal treatment effects across 2 years. The analysis of variance suggested a significant effect range in the source-sink relationship under subtending leaf removal effects at different growth stages. Further insight into the variation was provided by the correlation analysis and principal component analysis. A significant positive correlation between different traits was observed and the multivariate analysis including hierarchical clustering and principal component analysis (PCA) categorised germplasm accessions into three groups on the basis of four subtending leaf removal treatment effects across 2 years. A set of genotypes with the lowest and highest treatment effects has been identified. Selected accessions and the outcome of the current study may provide a basis for a further study to explore the molecular mechanism of source-sink relationship of boll subtending leaf and utilization of breeding programs focused on cotton improvement.

Improving boll capsule wall, subtending leaves anatomy and photosynthetic capacity can increase seed cotton yield under limited drip irrigation systems

Drought stress is considered to be the main source of yield reduction around the world. Improving plant performance under stressful environments by understanding growth and physio-biochemical responses are important. However, the detail mechanism of how boll capsule wall and subtending leaves anatomy, physio-biochemical characteristics and key enzymes i.e. Ribulose-1,5-bisphosphate carboxylase (RUBPC) and phosphoenolpyruvate carboxylase (PEPC) affect cotton (Gossypium hirsutum L.) yield have not yet been reported. To cover this knowledge gap, a two-year field experiment evaluated three drip irrigation rates [W1 (4800 m³ ha−1), W2 (3840 m³ ha−1) and W3 (2880 m³ ha−1)] effects on cotton main stem leaves, boll subtending leaves, capsule wall anatomy, biomass accumulation, RUBPC and PEPC activity. Compared with W1, W2 had 10.4–15.7 %, 8.3–24.6 %, 4.4–22.7 % and 5.0–15.3 % higher boll subtending leaf net photosynthetic rate, chlorophyll content, RUBP and PEPC activity at 21–42 days after anthesis. The palisade tissue thickness at 35 DAA (days after anthesis) and the ratio of palisade tissue to sponge tissue (p/s) of boll subtending leaf during 21–49 DAA were 7.7 % and 3.6–10.2 % higher for W2 over W1. Under W2treatment,improvements in these attributes significantly prolonged biomass accumulation rate (T, 6.9 d and 22.1 d) of main stem leaves and boll subtending leaf resulted in the maximum growth rate of seed cotton weight (Vx, 0.195 g d-1). Conclusively, higher photosynthetic capacity of the boll subtending leaves during 21–42 DAA and thicker capsule wall are the main drivers for achieving higher seed cotton weight under limited drip irrigation systems in arid region.

Two new species of Harpalyce (Leguminosae, Papilionoideae) from the Cerrado hotspot of biodiversity in Brazil

Two new Brazilian species of Harpalyce (Leguminosae, Papilionoideae, Brongniartieae) are described and illustrated from the Cerrado hotspot of biodiversity. Harpalyce correntina occurs in western Bahia state, while Harpalyce tombadorensis is apparently endemic to the Serra do Tombador in northern Goias state. Harpalyce correntina is morphologically similar to H. hilariana but it differs mainly by the ferruginous-tomentose indumentum on the branches and leaf rachis, persistent stipules, narrower leaflets, and an inflorescence that is usually shorter than the subtending leaf. Harpalyce tombadorensis is related to H. robusta but it differs by its shorter stipules, leaflets with brochidodromous venation, glabrous upper surface and attenuate-apiculate apex, smaller linear-triangular bracteoles and larger legumes with valves slightly reticulate-veined externally. The taxonomy, geographic distribution, conservation status, and phenology of the newly described species are also provided.

Influence of drought stress on pistil physiology and reproductive success of two Gossypium hirsutum cultivars differing in drought tolerance.

The causes of reproductive failure under drought stress (DS) are poorly understood. We hypothesized that reproductive failure was related to drought-induced changes in pistil biochemistry. To address this hypothesis, a water deficit-induced experiment was conducted with two cotton cultivars (Dexiamian 1, drought tolerant; Yuzaomian 9110, drought sensitive). Results showed that DS decreased the photosynthesis of subtending leaf and downregulated sucrose transporter gene (GhSUT-1) expression in pistil for both cultivars, resulting in lower pistil carbon accumulation which was reflected in the decreased starch accumulation. Lower starch, as potential energy, and adenosine triphosphate (ATP), as direct energy, in droughted pistils suggested less energy for pollen tube entrance into ovules, reducing the fertilized ovule number and fertilization efficiency. Further, although pistil peroxidase activity increased under DS, a higher hydrogen peroxide (H2 O2 ) level still was measured in droughted pistils than well-watered pistils, damaging reproductive activities. Moreover, larger decreases in photosynthesis, pistil GhSUT-1 expression, carbon accumulation, starch and ATP contents caused by DS for Yuzaomian 9110 than Dexiamian 1, and different responses of superoxide dismutase and catalase activities, and ascorbic acid and H2 O2 contents to DS between the two cultivars might be the reasons causing a greater decrease in fertilization efficiency for Yuzaomian 9110 than Dexiamian 1 under DS. Thus, we suggest that decreased ovule fertilization under DS was related to the disorganized carbohydrate metabolism and inefficient antioxidant defense in droughted pistils, and the effects of DS on pistil carbohydrate metabolism and antioxidant defense were more significant for drought-sensitive cultivars than drought-tolerant cultivars.

Sorghum tiller bud growth is repressed by contact with the overlying leaf.

Basal branching in grasses, or tillering, is an important trait determining both form and function of crops. Although similarities exist between eudicot and grass branching programs, one notable difference is that the tiller buds of grasses are covered by the subtending leaf, whereas eudicot buds are typically unconstrained. The current study shows that contact with the leaf sheath represses sorghum bud growth by providing a mechanical signal that cues the bud to refrain from rapid growth. Leaf removal resulted in massive reprogramming of the bud transcriptome that included signatures of epigenetic modifications and also implicated several hormones in the response. Bud abscisic acid transiently increased, then decreased following leaf removal relative to controls, and abscisic acid was necessary to repress bud growth in the presence of the leaf. Jasmonic acid (JA) levels and signalling increased in buds following leaf removal. Remarkably, application of JA to buds in situ promoted growth. The repression of bud growth by leaf contact shares characteristics of thigmomorphogenic responses in other systems, including the involvement of JA, though the JA effect is opposite. The repression of bud growth by leaf contact may represent a mechanism to time tillering to an appropriate developmental stage of the plant.

Short-term soil-waterlogging contributes to cotton cross tolerance to chronic elevated temperature by regulating ROS metabolism in the subtending leaf

Chronic elevated temperature and soil-waterlogging events often occur concomitantly in the Yangtze River Valley; however, a clear understanding of the effects of aforementioned co-occurring stresses on antioxidant defense in cotton has not been attained. To address this, two temperature conditions during the whole flowering and boll development periods, and three soil-waterlogging levels (0, 3, 6 d) starting on the day of anthesis were established. In the current study, no siginificant difference was observed on plant performance for 3 d soil-waterlogging, whereas 6 d soil-waterlogging event and elevated temperature in isolation negatively affected plant performance (i.e. leaf area declined by 33.3% and 14.7% in AW6 (soil waterlogging for 6 d under ambient temperature regime) and EC (soil well-watered (SRWC(75 ± 5) %) under elevated temperature for 2–3 °C) relative to AC (soil well-watered (SRWC(75 ± 5) %) under ambient temperature regime)) and induced ROS (reactive oxygen species) production and scavenging mechanisms in the subtending leaf of cotton. SOD (superoxide dismutase), CAT (catalase), and POX (peroxidase) activities were increased, and ASA (ascorbic acid) concentration was enhanced due to higher H2O2 (hydrogen peroxide) and O2− accumulations. Whereas, APX (ascorbate peroxidase), DHAR (dehydroascorbate reductase) and GR (glutathione reductase) activities were inhibited under elevated temperature regime or waterlogging event, especially in the treatment of EW6 (soil waterlogging for 6 d under elevated temperature for 2–3 °C), which resulted in increasing H2O2 concentration and higher O2− generation rate. However, plants acclimated to a short-term waterlogging stress (3 d) performed a cross tolerance to chronic elevated temperature regime (leaf number increased by 11.4%, whereas the abscission rate decreased by 4.6% in EW3 (soil waterlogging for 3 d under elevated temperature for 2–3 °C) compared with EC (soil well-watered (SRWC(75 ± 5) %) under elevated temperature for 2–3 °C)). Moreover, plants undergone a brief soil-waterlogging (3 d) induced higher GR activity and increased ASA concentration, along with enhanced SOD, CAT, POX activities, limiting H2O2 and O2− accumulation and reducing oxidative damage to membrane lipids as evidenced by reduced MDA (malondialdehyde) concentration when cotton was subsequently exposed to chronic elevated temperature regime.

Foliar and seed application of plant growth regulators affects cotton yield by altering leaf physiology and floral bud carbohydrate accumulation

The development of cotton (Gossypium hirsutum L.) floral bud prior to flowering is fundamental for yield formation since it is the initial step in the fruiting cycle. However, little information is available on the early reproductive stage of cotton subjected to plant growth regulators (PGRs). A 2-year experiment was conducted to investigate the effects of gibberellic acid (GA3), N6-benzyladenine (6-BA) and N, N-dimethyl piperidinium chloride (DPC) with two application methods [(A) seed soaking and (B) foliar spraying at squaring stage] on cotton floral bud development, yield and yield components compared with the control (water application). The results showed that seedcotton yield increased by 6.3%–7.5% and 12.1%–13.3% respectively in GA3 and 6-BA seed soaking treatments, and by 7.7%–8.5% and 8.2%–11.0% after foliar application compared to control due to increased boll numbers, which were associated with higher floral bud numbers. However, there was no response to yield for DPC treatment. Additionally, GA3 and 6-BA significantly increased photosynthesis rate (Pn) accordingly affecting the subtending leaf carbohydrate content and translocation, resulting in higher sucrose and starch contents in floral buds, which substantially enhanced dry matter of floral buds and reduced abscission rate. Those responses in floral buds are conductive to favorable boll development, which was evidenced by higher boll retention and boll opening rate for GA3 and 6-BA application relative to control. Specially, 6-BA showed equal effects to GA3 on yield and yield components with application method B, whereas induced a greater promotion than GA3 with application method A in the following aspects: (1) square numbers, boll numbers and seedcotton yield increased more obviously under 6-BA than GA3; (2) the increases in boll retention and boll opening rate were larger under 6-BA than GA3; (3) 6-BA induced higher carbohydrate content in floral buds than GA3.

The interplay between ovule number, pollination and resources as determinants of seed set in a modular plant.

BackgroundA classical dichotomous perspective proposes that either pollination or plant resources limit seed production. However, ovule number could also be limiting when pollination results in complete ovule fertilization and there are more plant resources available than needed to develop seeds. Moreover, this dichotomous view assumes that all flowers of a plant have equal access to a shared pool of resources, although these are frequently compartmentalized within plant modules, for example, inflorescences. How ovule number, pollination and resources affect seed production in physiologically-compartmentalized rather than physiologically-integrated plants has yet to be explored. We used raspberry (Rubus idaeus) to address this question.MethodsWe first assessed if ovule number affected the fraction of ovules that develop into seed (i.e., seed set) and whether this effect related to the extent of physiological integration among flowers within plants. This was achieved by statistically testing predictions on the sign and level of plant organization (i.e., among flowers within inflorescences, among inflorescences within ramets, and among ramets) of the relation between ovule number and seed set given different degrees of physiological integration. We then explored whether the relation between ovule number and seed set was affected by plant age (used here as a surrogate of resource availability) and pollination intensity (open-pollination vs. exclusion).ResultsWithin inflorescences, flowers with more ovules set a larger fraction of seeds. On the other hand, seed set at the inflorescence level was negatively related to the average number of ovules per flower. Seed set increased with ovule number and open-pollination, and decreased with ramet age. However, ovule number explained more variation in seed set than ramet age and pollination treatment. Ramet age affected the strength of the relation of seed set to ovule number, which was stronger in old than young ramets. Pollination did not alter the strength of this relation to any significant extent.DiscussionResults reveal the importance of ovule number as an overriding factor affecting seed set. Within inflorescences, resources appear to be differentially allocated to developing fruits from flowers with many ovules. This is consistent with the fact that in the raspberry a large proportion of the carbon invested in fruit development is fixed by the inflorescence subtending leaf. Differential resource allocation to flowers with many ovules is not affected by pollinator exclusion, being stronger in resource-exhausted ramets. This suggests that the effects of pollen limitation and resource allocation are compartmentalized at the inflorescence level. Consequently, modular plants can be viewed as reproductive mosaics where either ovule number, pollination or resources limit the number of seeds set by different flowers, so that improvements in any of them could increase plant seed production.