The effects of straw-returning and inorganic K fertilizer on the carbon–nitrogen balance and reproductive growth of cotton

Background Many studies have indicated that straw-returning could meet part or even all of the potassium (K) demand for crop growth in the field, but few have compared the effects of crop straw as K source and inorganic K fertilizer on carbon–nitrogen (C–N) balance of cotton and the reproductive growth. To address this, field experiments were conducted using the cotton cultivar, Siza 3, under there treatments (CK as control group one, no crop straw and inorganic K fertilizer were applied; K150 as control group two, 150 kg·ha−1 of K2O was applied; and W9000, 9 000 kg·ha−1 wheat straw, which could provide K2O about 150 kg·ha−1, was incorporated into soil). Results Although the final reproductive organ biomass did not differ between W9000 and K150, W9000 had a higher ratio of reproductive organ biomass to total biomass (RRT), suggesting that straw-returning was more conducive to the allocation of biomass to reproductive organs. The theoretical maximum biomass of reproductive organ was higher, but the average and maximum accumulation rates of reproductive organ biomass were 2.8%∼8.3% and 2.5%∼8.2% lower under W9000 than K150. Also, the duration of rapid-accumulation period for reproductive organ biomass (T) was 2.0∼2.8 d longer under W9000 than K150, which was a reason for the higher RRT under W9000. Straw-returning altered the dynamics of leaf K with the growth period, so that W9000 had a more drastic effect on leaf C metabolism than K150. Consequently, lower soluble sugar/free amino acid and C/N ratios were measured under W9000 than K150 at boll-setting (BSS) and boll-opening (BOS) stages. Higher leaf net photosynthetic rate, sucrose phosphate synthase and sucrose synthase activities, and lower acid invertase activity were observed under W9000 than K150 at BSS and BOS and these were more conducive to sucrose accumulation. However, less sucrose was measured under W9000 than K150 at these stages. This should be because straw-returning promoted the assimilate transport capacity when compared with inorganic K fertilizer application, which also explained the higher RRT under W9000 than K150. The lower acid invertase activity under W9000 inhibited the conversion of sucrose to other sugars, hence lower contents of soluble sugar and starch were measured under W9000 than K150. Conclusion Under low K condition, crop straw as K source can increase the assimilate transport from source to sink, leading to lower C/N ratio in leaf and higher allocation of biomass to reproductive organs than inorganic K fertilizer.

High temperature disturbs ovule development in field pea (Pisum sativum L.)

High temperatures affect reproductive growth and lead to yield loss in many crops. Field pea is heat sensitive, but little is known about the effect of high temperature on ovules. We investigated heat impact on ovules of flowers at various reproductive nodes of field pea using growth chambers. Six cultivars exhibiting diverse heat tolerance were exposed to four days of heat (35°C day/18°C night) during early flowering. Post-treatment ovules and embryo sacs were assessed employing clearing by light, and fluorescence, microscopy. Results indicated that greater ovule and embryo sac development occurred on some nodes, but poor ovule and embryo sac expansion resulted on other nodes of the same heat-treated plants. While advanced ovule and embryo sac development were identified on heat-tolerant cultivars, a combination of advanced and less advanced ovule and embryo sac development occurred in intermediate and heat-sensitive cultivars. More than 90% of the affected ovules displayed embryos at various stages of development, which indicated disruption around fertilization or shortly thereafter. Callose accumulation around the vascular bundle within ovules suggested disruption of assimilate transport to the embryo sac. The contrasting pattern of ovule development at different nodes implied a conflict between early aging and maternal supply of heat-treated plants.

Comparison of ecophysiological and leaf anatomical traits of native and invasive plant species

Background To address the lack of evidence supporting invasion by three invasive plant species (Imperata cylindrica, Lantana camara, and Chromolaena odorata) in tropical ecosystems, we compared the ecophysiological and leaf anatomical traits of these three invasive alien species with those of species native to Sempu Island, Indonesia. Data on four plant traits were obtained from the TRY Plant Trait Database, and leaf anatomical traits were measured using transverse leaf sections. Results Two ecophysiological traits including specific leaf area (SLA) and seed dry weight showed significant association with plant invasion in the Sempu Island Nature Reserve. Invasive species showed higher SLA and lower seed dry weight than non-invasive species. Moreover, invasive species showed superior leaf anatomical traits including sclerenchymatous tissue thickness, vascular bundle area, chlorophyll content, and bundle sheath area. Principal component analysis (PCA) showed that leaf anatomical traits strongly influenced with cumulative variances (100% in grass and 88.92% in shrubs), where I. cylindrica and C. odorata outperformed non-invasive species in these traits. Conclusions These data suggest that the traits studied are important for plant invasiveness since ecophysiological traits influence of light capture, plant growth, and reproduction while leaf anatomical traits affect herbivory, photosynthetic assimilate transport, and photosynthetic activity.

Plasticity of seasonal xylem and phloem production of Norway spruce along an elevational gradient

Key message Phloem cell production was less influenced by environmental factors than xylem cell production. The moment of maximum number of conducting phloem cells occurred at the end of the growing season. Abstract The understanding of the seasonality of phloem production, its dependence on climatic factors and potential trade-offs with xylem cell production is still limited. This study determined key tree-ring phenological events and examined the dynamics of phloem and xylem cell production of Norway Spruce (Picea abies (L.) Karst) by sampling microcores during the growing seasons 2014 and 2015 along an elevational gradient (450 m, 750 m, 1250 m a.s.l.) in south-western Germany. The onset of phloem formation preceded xylem formation at each elevation by approximately 2 weeks, while cessation showed no clear differences between the stands. Maximum rates of xylem and phloem cell production were observed around the summer solstice, independent of elevation. No linear pattern was found in the occurrence of phenological events along the elevational gradient. Phloem formation appeared to be less sensitive to environmental conditions since no difference was found in the number of produced sieve cells between the 2 years of study, whereas the ratio of xylem to phloem cells was significantly smaller in the year 2015 with summer drought. The total number of conducting, non-collapsed phloem cells did not culminate as expected at the time of the potential maximum assimilate production, but at the end of the growing season. Thus, interpretation of phloem formation should not be limited to the function of assimilate transport but should follow a more holistic view of structural–functional relationships of conductive tissues and tree physiological processes.

Symplasmic phloem unloading and post-phloem transport during bamboo internode elongation

In traditional opinions, no radial transportation was considered to occur in the bamboo internodes but was usually considered to occur in the nodes. Few studies have involved the phloem unloading and post-phloem transport pathways in the rapid elongating bamboo shoots. Our observations indicated a symplastic pathway in phloem unloading and post-unloading pathways in the culms of Fargesiayunnanensis Hsueh et Yi, based on a 5,6-carboxyfluorescein diacetate tracing experiment. Significant lignification and suberinization in fiber and parenchyma cell walls in maturing internodes blocked the apoplastic transport. Assimilates were transported out of the vascular bundles in four directions in the inner zones but in two directions in the outer zones via the continuum of parenchyma cells. In transverse sections, assimilates were outward transported from the inner zones to the outer zones. Assimilates transport velocities varied with time, with the highest values at 0):00 h, which were affected by water transport. The assimilate transport from the adult culms to the young shoots also varied with the developmental degree of bamboo shoots, with the highest transport velocities in the rapidly elongating internodes. The localization of sucrose, glucose, starch grains and the related enzymes reconfirmed that the parenchyma cells in and around the vascular bundles constituted a symplastic pathway for the radial transport of sugars and were the main sites for sugar metabolism. The parenchyma cells functioned as the ‘rays’ for the radial transport in and between vascular bundles in bamboo internodes. These results systematically revealed the transport mechanism of assimilate and water in the elongating bamboo shoots.

Morphological and physiological responses of the potato stem transport tissues to dehydration stress

Main conclusion Adaptation of the xylem under dehydration to smaller sized vessels and the increase in xylem density per stem area facilitate water transport during water-limiting conditions, and this has implications for assimilate transport during drought. Abstract The potato stem is the communication and transport channel between the assimilate-exporting source leaves and the terminal sink tissues of the plant. During environmental stress conditions like water scarcity, which adversely affect the performance (canopy growth and tuber yield) of the potato plant, the response of stem tissues is essential, however, still understudied. In this study, we investigated the response of the stem tissues of cultivated potato grown in the greenhouse to dehydration using a multidisciplinary approach including physiological, biochemical, morphological, microscopic, and magnetic resonance imaging techniques. We observed the most significant effects of water limitation in the lower stem regions of plants. The light microscopy analysis of the potato stem sections revealed that plants exposed to this particular dehydration stress have higher total xylem density per unit area than control plants. This increase in the total xylem density was accompanied by an increase in the number of narrow-diameter xylem vessels and a decrease in the number of large-diameter xylem vessels. Our MRI approach revealed a diurnal rhythm of xylem flux between day and night, with a reduction in xylem flux that is linked to dehydration sensitivity. We also observed that sink strength was the main driver of assimilate transport through the stem in our data set. These findings may present potential breeding targets for drought tolerance in potato.

Physiological, biochemical activities of cherelle wilt on three cocoa clones (Theobroma cacao) under two levels of soil fertilities

Dewi HS ES, Ydono P, Putra ETS, Purwanto BH. 2020. Physiological, biochemical activities of cherelle wilt on three cocoa clones (Theobroma cacao) under two levels of soil fertilities. Biodiversitas 21: 187-194. Cherelle wilt is one of the diseases caused by physiological disorders. It results in loss of young pods by 70-90%. This study aims to reveal the correlation of physiological, biochemical activities of several cocoa clones with two soil fertility status. The study was conducted using a nested design with two blocks as replications. The soil fertility status was classified based on soil chemical status. This obtained two clusters of soil fertility, namely low soil fertility, high soil fertility. The second factor was cocoa clone, consisting of three clones, namely RCC 70, RCC 71, KKM 22. Variables measured were soil character, biochemistry of fresh, wilting cherelles, physiological activities, cherelle wilt, biochemical activities including sucrose content, reducing sugar, invertase activity. The data obtained were analyzed for their variance (ANOVA) with a 95% confidence level, tested using Tukey’s HSD there were significant differences between treatments. The results showed that high soil fertility status could increase contents of N, P, K, boron in leaves, increase nitrate reductase activity, chlorophyll contents, increase photosynthesis rate, suppress transpiration rate, increase assimilate transport from leaves to cherelle, increase enzyme invertase activity. RCC 70 clone indicated better physiological, biochemical activity, had the smallest percentage of cherelle wilt. Soil fertility status can suppress cherelle wilt by up to 60% through increasing physiological, biochemical activity. The RCC 70 clone shows the lowest cherelle wilt values ​​compared to RCC 71, KKM 22 clones.

Delineation of post-phloem assimilate transport pathway into developing caryopsis of Brachypodium distachyon

Assimilates stored in mature cereal grains are mobilized from source tissues and transported towards developing grains through the vascular bundle. Due to the lack of direct vascular connection between maternal grain vascular bundle and filial tissues, post-phloem transportation of assimilates into grain endosperm relies on transfer cells that lie between the grain vascular bundle and the endosperm. Here, we propose Caryopsis Endosperm Assimilate Acquisition Route (CEAAR) models that describes the exact path of assimilate import into caryopsis endosperms. Using fluorescent tracer dyes we also delineated the route of assimilate delivery into Brachypodium distachyon endosperm and classified it as ventral circuitous (vc-CEAAR), an assimilate import model also found in rice. Furthermore, we report a detailed anatomical study of post-phloem assimilate transport pathway in developing grains of Brachypodium distachyon. Our results highlight major anatomical similarities and differences between the grain post-phloem transfer cells of Brachypodium and those of crop species such as rice, wheat, and barley relevant to post-phloem assimilate transport.HighlightsBased on existing work, we propose Caryopsis Endosperm Assimilate Acquisition Route (CEAAR) models, that describes the exact path of assimilate import into caryopsis endosperms.The structure of the post-phloem transfer cells of Brachypodium distachyon mirrors temperate and tropical cereals.Assimilate delivery into Brachypodium distachyon endosperm is identical to assimilate import into rice endosperm.