Soluble Acid Invertase Activity Research Articles

Physiological and biochemical processes underlying the differential sucrose yield and biomass production in sugarcane varieties

Summary Sucrose yield in sugarcane is a complex process regulated by both environmental and endogenous factors. However, the metabolic balance driving vegetative growth and sucrose accumulation remains poorly understood. Herein, we carried out a comprehensive assessment of carbohydrate dynamics throughout the crop cycle in two sugarcane varieties varying in biomass production, evaluating the carbon metabolism in both leaves and stalks. Our data revealed that the decline in photosynthetic rates during sugarcane maturation is associated not only to accumulation of sugars in leaves but also due to stomatal and non-stomatal limitations. We found that metabolic processes in leaves and stalks were intrinsically linked. While IACSP94-2094 had higher stalk sucrose concentration than IACSP95-5000, this latter produced more biomass. Compared to IACSP95-5000, IACSP94-2094 showed higher sucrose phosphate synthase (SPS) activity in leaves and stalks, along with lower soluble acid invertase (SAI) activity in leaves during the maximum growth stage. Interestingly, IACSP94-2094 also exhibited higher stalk SPS activity and lower stalk SAI activity than IACSP95-5000 during maturation. High biomass production by IACSP95-5000 was associated with higher sucrose synthase (SuSy) and SAI activity in leaves and higher SuSy and soluble neutral invertase (SNI) activity in stalks when compared to IACSP94-2094 during the maximum growth. Despite the contrasting strategies, both varieties displayed similar total sucrose yield, a balance between sucrose concentration and biomass production. This phenomenon implies the presence of a compensatory mechanism in sugarcane, with high biomass production compensating low sucrose accumulation and vice versa.

MWCNTs Alleviated saline-alkali stress by optimizing photosynthesis and sucrose metabolism in rice seedling

ABSTRACTSaline and alkali stress affects the growth and development, survival rate, and final yield of rice, while new nano materials can have a positive effect on rice growth. In order to investing the effects of carboxymethyl multi walled carbon nanotubes (MWCNTs) on the growth and development of rice seedlings under salt alkali stress, rice seedlings were cultured using rice variety “Songjing 3” using nutrient solution water culture method. The effects of MWCNTs on water absorption capacity, leaf photosynthesis, and sucrose metabolism of rice seedlings under 50 mmol/L saline-alkali stress (1NaCl: 9Na2SO4: 9NaHCO3: 1Na2CO3) conditions were investigated. The results showed that MWCNTs can improve the water use ability of roots and leaves, especially the water absorption ability of roots, which provides a guarantee for the improvement of rice biomass and the enhancement of leaf photosynthetic capacity under adverse conditions. After treatment with MWCNTs, the photosynthetic rate (Pn), stomatal conductance (gs), and transpiration rate (Tr) of leaves increased significantly, and the photochemical quenching value (qP), photochemical quantum efficiency value (Fv/Fm), and electron transfer rate value (ETR) of chlorophyll fluorescence parameters increased significantly, which is beneficial to the improvement of the PSII photosynthetic system. MWCNTs treatment promoted the increase of photosynthetic pigment content in leaves under salt and alkali stress, improved the ratio of Chla and Chlb parameters, increased the activities of key photosynthetic enzymes (RUBPCase and PEPCase) in leaves, increased the value of total lutein cycle pool (VAZ), and significantly enhanced the deepoxidation effect of lutein cycle (DEPS), which can effectively alleviate the stomatal and non stomatal constraints on leaf photosynthesis caused by salt and alkali stress. MWCNTs treatment significantly enhanced the activities of sucrose phosphate synthase (SPS) and sucrose synthase (SS) under salt and alkali stress, and decreased the activities of soluble acid invertase (SAInv) and alkaline/neutral invertase (A/N-Inv), indicating that MWCNTs promoted sucrose synthesis while inhibiting sucrose decomposition, thereby promoting sucrose accumulation in rice leaves. This study can provide theoretical and experimental basis for the application of MWCNTs to the production of rice under salt and alkali stress, and can find a new way for rice production in saline and alkaline lands.

Transcriptomic and metabolomic analysis of grain weight potential induced by water stress in wheat

The sink strength of developing ovary in wheat determines the grain weight potential. The period from booting to grain setting stage is critical for the growth and development of ovary and potential sink capacity determination. However, the underlying regulation mechanism during this period by which wheat plant balance and coordinate the florets number and ovary/grain weight under water stress has not been clarified. Therefore, we designed two irrigation treatments W0 (no seasonal irrigation) and W1 (additional 75 mm irrigation at jointing stage), and analyzed the responses of the ovary/grain weight to water stress covering the phenotypic, metabolomic, and transcriptomic levels. Results showed that W0 irrigation treatment decreased soil water content, plant height, and green area of flag leaf, thus reduced grain number, especially the inferior grain, but improved the grain weight of superior grain and inferior grain as well as average grain weight at maturity, meanwhile the average ovary/grain weight and volume during -3 to 10 days after anthesis (DAA) also increased. Transcriptomic analysis indicated that the genes involved in both the sucrose metabolism and phytohormone signal transduction were prominently accelerated by W0 treatment, accompanied by increased enzyme activities of soluble acid invertase (SAI) and sucrose synthase (Sus) and elevated abscisic acid (ABA) and indole-3-acetic acid (IAA) levels. The sucrose content was thus decreased, while glucose and fructose content were increased. In addition, several TaTPP genes (especially TaTPP-6) were downregulated and the IAA biosynthesis genes TaTAR1 and TaTAR2 genes were upregulated under W0 treatment before anthesis, which improved IAA level further. Collectively, water stress reduced vegetative organs growth and eliminated most of the inferior grains, but improved the ABA and IAA levels of the surviving ovaries/grains, promoting enzyme activity of Sus and degrading sucrose into glucose and fructose; as a result, the strong sucrose utilization ability, the enhanced enzyme activity of SAI and the ABA- and IAA-mediated signaling jointly improved the weight and volume of surviving ovaries/grains, and finally achieved the trade-off between ovary/grain weight and number in wheat under water stress.

Increasing the Activity of Sugarcane Sucrose Phosphate Synthase Enhanced Growth and Grain Yields in Transgenic Indica Rice

Sucrose is the primary form of mobile photoassimilates, and its level is regulated by sucrose-phosphate synthase (SPS) in plants. Increasing in the SPS activity was accompanied by an increase in sucrose accumulation. This study was designed to examine the effect of the overexpression sugarcane SoSPS1 gene on sucrose metabolizing enzymes, growth, and grain yield of indica rice. The SoSPS1 gene was constructed in a binary vector under the control of a rice ubiquitin promoter and transformed into indica rice using an Agrobacterium vector. Five lines of transgenic rice were selected to develop homozygous transgenic lines and used for analysis. The overexpression of the SoSPS1 gene significantly increased the transcript and protein levels, followed by increasing in SPS activity and sucrose content in the leaves of the transgenic rice lines. Moreover, the activity of soluble acid invertase (SAI) was elevated rather than sucrose synthase (SuSy) in the transgenic lines. The increase in the sucrose-degrading enzymes leads to an increase in plant growth and development. The plant height and number of tillers were significantly higher in the transgenic line compared to non-transgenic (NT) rice. In addition, the amylose content, the number of seeds per panicle, and the weight of 1000 grains of seed, including dry biomass weight, were increased in the transgenic lines. The results indicated that enhancement of SPS activity, as well as sucrose content, provides a higher carbon partitioning for higher growth and productivity of the transgenic rice lines.

Enhancing boll protein synthesis and carbohydrate conversion by the application of exogenous amino acids at the peak flowering stage increased the boll Bt toxin concentration and lint yield in cotton

In Bacillus thuringenesis (Bt) transgenic cotton, the cotton boll has the lowest insecticidal protein content when compared to the other organs. The present study investigated the effects of amino acid spray application at the peak flowering stage on the cotton boll Bt toxin concentration and yield formation. Boll protein synthesis and carbohydrate conversion were also studied to reveal the fundamental mechanism. Three treatments (i.e., CK, the untreated control; LA1, five amino acids; LA2, 21 amino acids) were applied to two Bt cultivars of G. hirsutum (i.e., the hybrid Sikang 3 and the conventional Sikang 1) in the cotton-growing seasons during 2017 and 2018. Amino acid spray application at the peak flowering stage resulted in an increase of 5.2–16.4% in the boll Bt protein concentration and an increase of 5.5–11.3% in the seed cotton yield, but there was no difference between the two amino acid treatments. In addition, amino acid applications led to increases in the amino acid content, soluble protein content, glutamate pyruvate transaminase (GPT) activity, glutamate oxaloacetate transaminase (GOT) activity, glucose content, fructose content and soluble acid invertase (SAI) activity. This study also found that Bt protein content, enhanced boll number and the weight of opened bolls were closely related to carbon and nitrogen metabolism. The Bt protein content had significant linear positive correlations with amino acid and soluble protein contents. Enhanced boll number had significant linear positive correlations with the GPT and GOT activities from 15–25 days after flowering (DAF). The weight of opened bolls from 55–65 DAF had a significant linear positive correlation with the SAI activity. These results indicate that the enhancement of boll protein synthesis and carbohydrate conversion by amino acid application resulted in a simultaneous increase in the boll Bt protein concentration and cotton lint yield.

A positive correlation between seed cotton yield and high-efficiency leaf area index in directly seeded short-season cotton after wheat

Leaf area index (LAI) during the growth process is one of the most important indexes for monitoring high-yield cotton production, but the present use of LAI is limited due to the varying photosynthetic capacity of cotton leaves at different plant positions and growth periods. Thus, a more accurate leaf area-related index that includes both leaf area and photosynthetic capacity was explored herein based on the contribution to final yield and photosynthetic efficiency in directly seeded short-season cotton following wheat cropping in the Yangtze River region of China. Pinhead-squares were labeled to investigate the critical timing of pinhead-square appearance during yield formation from 2015 to 2019, and the photosynthetic characteristics of the corresponding subtending leaves were measured in 2017 and 2018. The results showed that the pinhead-squares that appeared after 64 days before frost (DBF) did not contribute to yield (the bolls failed to open at harvest). Furthermore, the sucrose phosphate synthase (SPS) and soluble acid invertase (SAI) activities, carbon assimilation rate (Pn), and 14 C photosynthate exportation of the corresponding subtending leaves also declined markedly after 20 DBF. Therefore, the subtending leaves of the pinhead-squares that were formed before 64 DBF were defined as effective leaves based on their contribution to final yield, and their leaf areas were correspondingly defined as effective leaf areas. To further explore the contribution to yield, high-efficiency and low-efficiency leaves would exist among the effective leaves according to the load capacity of the reproductive organs (the presence or absence of corresponding subtending reproductive organs. Among the effective leaves, the subtending leaves with loaded bolls exhibited higher Pn, SPS and SAI activities, and 14 C assimilate exportation and were defined as high-efficiency leaves, and their leaf areas were defined as high-efficiency leaf areas. Different effective LAI and high-efficiency LAI cotton populations were constructed using five sowing dates and five nitrogen application rates to assess the relationship between effective LAI, high-efficiency LAI, and seed cotton yield in both 2018 and 2019. With increased effective LAI and high-efficiency LAI, higher seed cotton yields were detected. These results suggested that enhancing effective and high-efficiency leaf area, especially for high-efficiency leaf area, benefits seed cotton yield in cotton production. • The leaves that contributed to final yield could be called as effective leaves. • The photosynthetic efficiency reduced gradually for the effective leaves. • The subtending leaves with bolls loaded could be called as high-efficiency leaves. • The high-efficiency leaves exhibited higher photosynthetic efficiency. • Enhanced effective and high-efficiency LAI increased seed cotton yield.

Effect of Saline–Alkali Stress on Sugar Metabolism of Jujube Fruit

Sugar, an osmoregulatory substance used by plants to adapt to abiotic stresses such as drought and salinity, is one of the most important indexes of fruit quality. In this study, 0–150 mM saline–alkali solutions (NaCl:NaHCO3 = 3:1) were used to irrigate the roots of 10-year-old “Junzao” fruit trees during the growth period to explore the regulation mechanism of different concentrations of saline–alkali stress on sugar and reactive oxygen metabolism in jujube fruit at maturity. The results showed that under low stress (0~90 mM), the contents of sucrose, glucose, and fructose in the jujube fruit and the activities of sucrose phosphate synthase (SPS), sucrose synthase decomposition direction (SS-I), and sucrose synthase synthesis direction (SS-II) increased with increases in stress concentration, results that were consistent with the relative expression trends of the SPS and SS genes; however, the results were reversed under high concentrations (120 and 150 mM). The soluble acid invertase (S-AI) activity decreased with increases in stress concentration under low stress, and the results were reversed with high stress, which was consistent with the relative expression trends of the ZjcINV3, ZjnINV1, and ZjnINV3. Research regarding the response of antioxidant enzymes in fruits under saline–alkali stress showed that only the differences in peroxidase (POD) activity under saline–alkali stress were consistent with sugar accumulation; the proline (PRO), catalase (CAT) decreased and the malondialdehyde (MDA) superoxide dismutase (SOD) increased with increases in saline–alkali stress. These results indicate that the sugar metabolism and antioxidase jointly promote and regulate sugar accumulation in jujube fruits in a low saline–alkali environment.

Characterization of Source–Sink Traits and Carbon Translocation in Maize Hybrids under High Plant Density

Both compact planting and selecting superior maize (Zea mays L.) hybrids can greatly optimize the source–sink relationship and enhance maize productivity. However, the underlying physiological mechanism for regulating carbon (C) assimilate transport and influencing grain yield between maize cultivars has remained unclear under contrasting plant densities. A two-year field experiment was conducted to investigate grain yield, vascular bundle character, grain filling, C allocation in grains and other tissues, and hormone level and enzyme activity in grains under 60,000 (ND) and 90,000 plants ha−1 (HD) densities using Xianyu 335 (XY335) and Zhengdan958 (ZD958) hybrids. Compared to the ZD958, XY335 increased grain yield, kernel number per plant (KNP), and sink capacity by 11.4%, 15.7%, and 7.4%, respectively. Moreover, XY335 performed higher net photosynthetic rate and sucrose synthase activities in grains than those in ZD958, and higher levels of sucrose phosphate synthase and soluble acid invertase activity were mainly exhibited in the middle of the grain filling stage, which contributed to increasing the proportion of grain in total dry matter, grain C content and leaf C transport efficiency by 4.3%, 12.2%, and 52.9%, respectively, under HD conditions. Additionally, a greater area and number of small vascular bundle in ear of XY335 resulted in 21.3% higher matter transport efficiency and 4.8% higher maximum grain filling rate than ZD958 under HD conditions. In addition, grains of XY335 exhibited generally higher levels of indole acetic acid (IAA) and abscisic acid (ABA), as well as ABA/GA3 ratio after maize pollination relative to those from ZD958, conducive to regulating C translocation from leaves to grains. Overall, our study illustrates that stronger source activity, sink characteristics, and matter transport channels for maize hybrids are significant for C assimilate transport to grain for achieving high grain yield under higher plant density.

Role of alkaline/neutral invertases in postharvest storage of potato

Potatoes stored at cold temperatures undergo undesirable sweetening due to the cleavage of sucrose into reducing sugars by invertases. Although significant research has focused on vacuolar invertase (StVAC) during cold storage of potatoes, little is known about the role of alkaline/neutral invertases (StNI). We identified eight members in the NI family from the potato genome, and phylogenetic analysis suggested their probable subcellular location as plastid/mitochondria (group α) or cytosol (group β). Using three commercially important potato cultivars with known differences in cold storage responses (‘Russet Burbank’, ‘Bintje’, and ‘Shepody’), we compared the expression of the eight StNI genes to StVAC and vacuolar invertase inhibitor (StINH2) genes during harvest, and after one and five months of storage at 4 °C or 22 °C. The activity of neutral invertase (NI), soluble acid invertase activity (SAI), and the levels of reducing sugars were also determined. Tubers of ‘Russet Burbank’ displayed high transcript abundance of StNI5, high reducing sugar content and more NI activity than SAI activity. This was associated with a high level of StINH2 transcripts and low StVAC transcript levels suggesting the susceptibility of these tubers to cold-induced sweetening could be due to cytoplasmic cleavage of sucrose by NI. In ‘Bintje’, the induction of StNI5 and StVAC transcripts and NI and SAI activities indicate that sucrose degradation is carried out by both NI and SAI. In ‘Shepody’, a higher abundance of the StNI4 and StNI6 transcripts indicates different isoforms of NI are required for sucrose degradation. This study reveals significant contribution of NI in the regulation of reducing sugars and the process of cold-induced sweetening. Additional studies are needed to determine the in vivo function of NI in cold-stored potato tubers.

Multi-omics analysis revealed room temperature storage affected the quality of litchi by altering carbohydrate metabolism

Litchi (Litchi chinensis Sonn.) fruit easily deteriorates and has a short storage life. Room temperature storage is widely used during short-distance transportation and sale of litchi fruits. This study explored the changes in the quality of litchi pulp at room temperature storage using transcriptomics, proteomics, and metabolomics analyses. The results illustrated significant changes in carbohydrate metabolism pathways. Increases in d-ribose-5-phosphate, d-ribose, d-mannose-6-phosphate, d-mannose, d-mannitol, D-sorbitol, and d-fructose-1-phosphate indicated that fructose and mannose metabolism, the pentose phosphate pathway, and amino sugar and nucleotide sugar metabolism competed with glycolysis for α-d-glucose, α-d-glucose-6-phosphate, and β-d-fructose-6-phosphate. Citrate and l-malic acid from the tricarboxylic acid cycle (TCA cycle) might be consumed via the biosynthesis of amino acids and lipids. Most of the differentially expressed genes and proteins related to glycolysis and the TCA cycle were downregulated, which verified that these two pathways were impeded. Flow direction changes in glycolysis and the TCA cycle might lead to energy deficiency. Upregulated activities of α-amylase and soluble acid invertase cleaved starch and sucrose into glucose and fructose, which replenished deficient energy metabolism substrates. During these processes, the changes in the content and composition of sugar and acid result in a decrease in flavor. Additionally, the polysaccharide degradation softened the texture and reduced the nutritional value. By systematically exploring the regulation of physiological changes in the pulp of litchi fruit stored at room temperature, we provid a basis for optimizing the preservation of litchi fruit and a reference for studying fruit carbohydrate metabolism.

Ratoon Stunting Disease (Leifsonia xyli subsp. xyli) affects source-sink relationship in sugarcane by decreasing sugar partitioning to tillers

Ratoon Stunting Disease, caused by the bacterium Leifsonia xyli subsp. xyli (Lxx), decreases sugarcane yield by reducing culm growth and tillering, especially in plants with high Lxx titers when the symptoms are more severe. The role of Lxx titers in affecting sugar partitioning and sugarcane growing is still unclear. We hypothesized that high Lxx titers affect source-sink relationship by causing physiological changes in the sugarcane that reduces sugar partitioning to tillers. The study was carried out with susceptible sugarcane genotype CB49260, evaluating physiological traits and biomass production in plants with low (158 ± 28 Lxx cells per 100 ng of plant DNA) and high Lxx titers (2090 ± 385 Lxx cells per 100 ng of plant DNA). Overall, the level of bacterial titers affected sugarcane growth through changes in ethylene level, sugar and biomass partitioning. Plants with high Lxx titers presented a lower number and biomass allocation to tillers than low Lxx titers. Additionally, plants with high Lxx titers had higher biomass allocation to the main culm than low Lxx titers plants due to greater sucrose and starch contents in the main culm caused by the higher number of cell parenchyma, decreased soluble acid invertase activity, and low number of tillers. Changes in sugar and biomass partitioning in plants with high Lxx titers were associated with low release of ethylene in the leaf and culm. Sugarcane with high Lxx titers presented physiological changes that restricted sugar supply for tillering, resulting in a decrease in the number and biomass allocation to the tillers.

Effects of Seaweed Extracts on the Growth, Physiological Activity, Cane Yield and Sucrose Content of Sugarcane in China.

Seaweed extracts (SEs) have been widely used as biostimulants in crop management due to their growth-promoting and stress-resistant effects. To date, there are few reports of the effect of SEs on sucrose content and cane yield. Here, we conducted field experiments for three consecutive growth seasons (2017∼2019) in two areas (Suixi and Wengyuan) of China, to investigate the yield and sugar content of sugarcane in response to SE treatment at different growth stages. The results showed that spraying SEs once at seedling (S), early elongation (E), and early mature (M) stages, respectively, once at S and E stages, respectively, or once at the S stage increased the cane yield by 9.23, 9.01, and 3.33%, respectively, implying that SEs application at the early elongation stage played a vital role in promoting sugarcane growth. Photosynthetic parameters and nutrient efficiency analysis showed that spraying SEs at S and E stages enhanced the net photosynthetic rate, transpiration rate, and water use efficiency, and increased N, P, or K utilization efficiency, compared with those of the control. Notably, cane yield increasing rate of SEs in 2017 and 2018 were higher than those in 2019 in Wengyuan but lower than those in 2019 in Suixi. Interestingly, the total rainfall and monthly average rainfall in 2017 and 2018 were lower than those in 2019 in Wengyuan but higher than those in 2019 in Suixi. The results suggested that the yield increasing rate of SEs on sugarcane was better in less rainfall years. The sucrose content of sugarcane showed no difference between spraying SEs at the M stage alone or at the three growth stages but was higher than those of SE treatments at S and/or E stages. Enzyme activity analysis showed that spraying SEs at the M stage increased the activity of sucrose phosphate synthase activity by 9.14% in leaves and 15.16% in stems, and decreased soluble acid invertase activity in stems by 16.52%, which contributed to the sucrose increase of 5.00%. The above results suggested that SEs could increase cane yield and promote sucrose accumulation in sugarcane. The yield increasing effect was more obvious under conditions of drought stress.

Overexpression of Sucrose Phosphate Synthase Enhanced Sucrose Content and Biomass Production in Transgenic Sugarcane.

Sucrose phosphate synthase (SPS) is a key enzyme in sucrose synthesis, which controls sucrose content in plants. This study was designed to examine the efficacy of the overexpression of SoSPS1 gene on sucrose accumulation and carbon partitioning in transgenic sugarcane. The overexpression of SoSPS1 gene increased SPS activity and sucrose content in transgenic sugarcane leaves. More importantly, the overexpression enhanced soluble acid invertase (SAI) activity concomitant with the increase of glucose and fructose levels in the leaves, whereas sucrose synthase activity exhibited almost no change. In the stalk, a similar correlation was observed, but a higher correlation was noted between SPS activity and sugar content. These results suggest that SPS overexpression has both direct and indirect effects on sugar concentration and SAI activity in sugarcane. In addition, SPS overexpression resulted in a significant increase in plant height and stalk number in some transgenic lines compared to those in non-transgenic control. Taken together, these results strongly suggest that enhancing SPS activity is a useful strategy for improving sugarcane yield.

Single and combined effects of heat and water stress and recovery on cotton (Gossypium hirsutum L.) leaf physiology and sucrose metabolism

High temperatures and water-deficit stress limit cotton production around the world. Their individual effects on plant physiology and metabolism have been extensively studied, however, their combination has received considerably less attention. To that end, growth chamber experiments were conducted using cotton (Gossypium hirsutum L.) cultivar ST5288B2F and the objectives were to discern physiological and metabolic alterations after heat and water stress application (single or combined) and recovery, during cotton's vegetative stage. Under water stress conditions, leaf physiological parameters were suppressed and changes in carbohydrate levels, due to alterations in sucrose-metabolizing enzymes activities, were observed. Heat stress alone increased carbohydrate content, and activities of sucrose-degrading enzymes, while leaf physiology remained unaffected. The combined stress did exacerbate decreases in leaf water potential and soluble acid invertase activity, but the rest of the responses were similar to those of water stress. After stress alleviation, leaf physiological parameters of water-stressed plants did not manage to recover and substantial decreases were observed in leaf starch levels and activities of sucrose-cleaving enzymes, while the majority of parameters of heat-shocked plants returned to control levels. Recovery of the plants subjected to the combined stress was comparable to that of water-stressed plants, but significant differences were observed in carbohydrate levels and sucrose synthase activity. Our study demonstrated that under combined stress and post-stress conditions, water stress was the dominant factor affecting cotton leaf physiology and sucrose metabolism, highlighting however, the unique responses of some traits that could not be deduced from the additive effects of the single stresses.

Sucrose and starch metabolism during Fargesia yunnanensis shoot growth.

Bamboo is one of the fastest growing plants in the world, but their shoot buds develop very slowly. Information about the sugar storage and metabolism during the shoot growth is lacking. In the present study, we determined the activity of sucrose and starch metabolizing enzymes during the developmental period of Fargesia yunnanensis from shoot buds to the young culms that have achieved their full height. The soluble sugars and starch contents were also determined and analyzed in shoot buds and shoots at different developmental stages. The results showed that there were higher sucrose contents in shoot buds than shoots, which coincides with the sweeter taste of shoot buds. As the shoot buds sprouted out of the ground, the starch and sucrose were depleted sharply. Coupled with this, the activity of soluble acid invertase (SAI), cell wall-bound invertase (CWI), sucrose synthase at cleavage direction (SUSYC) and starch phosphorylase (STP) increased significantly in the rapidly elongating internodes. These enzymes dominated the rapid elongation of internodes. The activities of SAI, CWI, SUSYC and STP and adenosine diphosphate-glucose pyrophosphorylase were higher as compared to other enzymes in the shoot buds, but were far lower than those in the developing shoots. The slow growth of shoot buds was correlated with the low activity of these enzymes. These results complement our understanding of the physiological differences between shoot buds and elongating shoots and ascertain the physiological mechanism for the rapid growth of bamboo shoots.

Sucrose metabolism in cotton subtending leaves influenced by potassium-to-nitrogen ratios

Nutrient management is important for enhancing crop productivity economically, as well as for environmental protection. The present study explored the best relative ratio of potassium (K) to nitrogen (N) under a new short-season, high-density planting model, based on the sucrose metabolism in the subtending leaves of cotton in relation to yield. A 2-year (2016–2017) field experiment was conducted in a randomized complete block design along with four replicates. The treatments were three K relative ratios to N [K08 {K (K2O): N = 0.8:1 (168:210 kg ha−1)}, K10 {K (K2O): N = 1:1 (210:210 kg ha−1)}, and K12 {K (K2O): N = 1.2:1 (252:210 kg ha−1)}]. The plot size was 36.48 m2 comprised of four rows. Plants were sown on raised beds. Row spacing was managed to 0.76 m with a plant-to-plant distance of 0.14 m to maintain a planting density of 9 plants m−2. The results indicated that increased K application ratios substantially favored sucrose metabolism in the subtending leaves to attain higher cotton yields. K10 and K12 upregulated the photosynthetic rate (Pn) of subtending leaves by 17–32% and 33–59%, sucrose phosphate synthase activities by 4–17% and 14–28%, and sucrose synthase activities by 12–25% and 21–36%, respectively. Glucose-6-phosphate dehydrogenase and soluble acid invertase activities were significantly downregulated. K10 improved seed and lint yield by 10–24% with no differences between K10 and K12, suggesting K10 (K2O: N; 1:1) to be the best ratio for cost-effective cotton production under the new planting model in the Yangtze River Valley, China.

Berry thinning to reduce bunch compactness improves fruit quality of Cabernet Sauvignon (Vitis vinifera L.)

The effects of berry thinning on bunch compactness, grape sugar accumulation and subsequent wine quality were studied in Vitis vinifera L. Cabernet Sauvignon. The experiment was carried out during two consecutive seasons in a commercial vineyard. Berries of pea size were evenly removed manually to reduce berry density in bunches. Based on the decreasing proportion of berries in one bunch, the treatment was designated as C0 (control), C¼ (a 25% decrease) and C½ (a 50% decrease). The results showed that the different berry thinning treatment lowered bunch compactness accordingly. And the content of sugar, anthocyanins, total phenols, and mass of mature berries were all significantly enhanced with decreasing compactness on the same harvested time. However, the content of titratable acidity showed an inverse change. Compared with control, the sugar and anthocyanins of berry accelerated accumulation in loose bunches during grape ripening. Furthermore, the cell wall invertase (CWI) and soluble acid invertase (SAI) of berries had higher activity during grape ripening under treatments, which was associated with upregulated transcription level of VvCWI and VvGIN2. In addition, wines obtained from treatments had a higher total phenolic index, greater anthocyanins, and lower titratable acidity than the control wine. These results suggested that berry thinning with reducing bunch compactness might control accumulation of berry sugar by upregulating activities of CWIs and SAIs in berry and change berry main chemical component influencing the wine composition.

Potassium relative ratio to nitrogen considerably favors carbon metabolism in late-planted cotton at high planting density

A new planting model characterized with late sowing, high planting density, low N and single fertilizer application is much competitive to combat the present high cost cotton production. However, what is the optimal relative ratio of K to N under this model? as we understand it certainly plays a critical role in cotton production through a series of physiological processes. A two year (2016–2017) field experiment was conducted in a randomized complete block design with three K ratios relative to N [0.8 (K1), 1.0 (K2), and 1.2 (K3)] with four replications. Results showed that relative increase in K ratio had significant effect on functional leaf biomass, specific leaf weight, carbon metabolism as well as cotton yield in both growing seasons. K3 and K2 produced the similar seed cotton yield but higher than K1 in both years. Similarly, K3 and K2 prominently up-regulated the activity of ribulose 1, 5-bisphosphate carboxylase oxygenase (Rubisco), sucrose phosphate synthase (SPS) and sucrose synthase (SS) but down-regulated the activity of soluble acid invertase (SAI), glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH). Moreover, the balance of carbohydrates (sucrose, starch, glucose and fructose) and ATP was more efficient under higher K ratio (K3 and K2) as compared with K1. These findings might suggest that K rate should be equal to N as for promising yield and profitable return are concerned under newly proposed cotton planting model in the Yangtze River Valley of China.

Inactivation kinetics, structural, and morphological modification of mango soluble acid invertase by high pressure processing combined with mild temperatures

The activity, structure and morphology of mango soluble acid invertase (SAI) were investigated after high pressure processing (HPP) combined with mild temperature at 50–600MPa and 40–50°C. The activity of mango SAI was efficiently reduced by HPP at 50MPa/45 and 50°C, or 600MPa/40, 45 and 50°C, while it was increased by 10–30% after HPP at 50–200MPa/40°C. Significant antagonistic effect of pressure and temperature on the activity of SAI was observed at 50–400MPa/50°C. The secondary structure of SAI was not influenced by HPP. However, its tertiary structure was modified by HPP, and severer modification occurred with higher pressure, higher temperature, and longer treatment time. Results of atomic force microscope suggested that HPP at 400MPa/50°C for 2.5min induced dissociation of SAI, and HPP at 600MPa/50°C for 30min resulted aggregation of SAI.

Regulation of maize kernel weight and carbohydrate metabolism by abscisic acid applied at the early and middle post-pollination stages in vitro

Abscisic acid (ABA) accumulates in plants under drought stress, but views on the role of ABA in kernel formation and abortion are not unified. The response of the developing maize kernel to exogenous ABA was investigated by excising kernels from cob sections at four days after pollination and culturing in vitro with different concentrations of ABA (0, 5, 10, 100μM). When ABA was applied at the early post-pollination stage (EPPS), significant weight loss was observed at high ABA concentration (100μM), which could be attributed to jointly affected sink capacity and activity. Endosperm cells and starch granules were decreased significantly with high concentration, and ABA inhibited the activities of soluble acid invertase and acid cell wall invertase, together with earlier attainment of peak values. When ABA was applied at the middle post-pollination stage (MPPS), kernel weight was observably reduced with high concentration and mildly increased with low concentration, which was regulated due to sink activity. The inhibitory effect of high concentration and the mild stimulatory effect of low concentration on sucrose synthase and starch synthase activities were noted, but a peak level of ADP-glucose pyrophosphorylase (AGPase) was stimulated in all ABA treatments. Interestingly, AGPase peak values were advanced by low concentration and postponed by high concentration. In addition, compared with the control, the weight of low ABA concentration treatments were not statistically significant at the two stages, whereas weight loss from high concentration applied at EPPS was considerably obvious compared with that of the MPPS, but neither led to kernel abortion. The temporal- and dose-dependent impacts of ABA reveal a complex process of maize kernel growth and development.