Leaf Growth Rate Research Articles

Growth and biomass of Vallisneria gigantea’s leaf in Senggarang River flow, Tanjungpinang City, Riau Islands

The objective of this study were to determine the density, the growth rate, and growth of biomass of Vallisneria gigantea. This research was conducted on May-June 2020 in a river in Senggarang, Tanjungpinang City. This research was used random sampling method of 30 points using transect quadrant (50x50 cm). The results showed that V. gigantea had a density value of 148.80 ind/m2. The growth rate of V. gigantea was 0.06 cm/day and biomass growth were 21.71 gr/m2. Light intencity was the principle component of V. gigantea’s leaf growth rate while pH, velocity, and temperatur were principle component for growth biomass leaf.Keywords: Density; Giant Vallisneria; Growth; Macrophyte; Productivity

Quantification of the pluriannual dynamics of grapevine growth responses to nitrogen supply using a Bayesian approach.

The effect of nitrogen (N) nutrition on grapevine carbon (C) dynamics has been well studied at the annual scale, but poorly addressed at a pluriannual timescale. The aim of this study was to quantify, in an integrated conceptual framework, the effect of N nutrition on potted grapevine growth and storage over 2 consecutive years. The consequences of using destructive measurements were investigated using a hierarchical Bayesian model. The rate and duration of leaf growth were both positively impacted by the chlorophyll content of the leaves, but they were negatively impacted by the initial carbohydrate measurements, raising a distortion in the estimation of initial reserves. The C production per unit of global radiation depended on the leaf area dynamics. The allocation of dry matter mainly relied on the phenological stage. The present study highlights the importance of using appropriate statistical methods to overcome uncertainties due to destructive measurements. The genericity of the statistical approach presented may encourage its implementation in other agronomy studies. Based on our results, a simple conceptual framework of grapevine pluriannual growth under various N supplies was built. This provides a relevant basis for a future model of C and N balance and responses to N fertilization in grapevine.

Freshwater wetland plants respond nonlinearly to inundation over a sustained period.

Wetland plants regularly experience physiological stresses resulting from inundation; however, plant responses to the interacting effects of water level and inundation duration are not fully understood. We conducted a mesocosm experiment on two wetland species, sawgrass (Cladium jamaicense) and muhly grass (Muhlenbergia filipes), that co-dominate many freshwater wetlands in the Florida Everglades. We tracked photosynthesis, respiration, and growth at water levels of -10 (control), 10 (shallow), and 35 cm (deep) with reference to soil surface over 6 months. The response of photosynthesis to inundation was nonlinear. Specifically, photosynthetic capacity (Amax ) declined by 25% in sawgrass and by 70% in muhly grass after 1-2 months of inundation. After 4 months, Amax of muhly grass in the deep-water treatment declined to near zero. Inundated sawgrass maintained similar leaf respiration and growth rates as the control, whereas inundated muhly grass suppressed both respiration and growth. At the end of the experiment, sawgrass had similar nonstructural carbohydrate pools in all treatments. By contrast, muhly grass in the deep-water treatment had largely depleted sugar reserves but maintained a similar starch pool as the control, which is critical for post-stress recovery. Overall, the two species exhibited nonlinear and contrasting patterns of carbon uptake and use under inundation stress, which ultimately defines their strategies of surviving regularly flooded habitats. The results suggest that a future scenario with more intensive inundation, due to the water management and climate change, may weaken the dominance of muhly grass in many freshwater wetlands of the Everglades.

Seasonal Acclimation Modulates the Impacts of Simulated Warming and Light Reduction on Temperate Seagrass Productivity and Biochemical Composition

Increases in seawater temperature and reduction in light quality have emerged as some of the most important threats to marine coastal communities including seagrass ecosystems. Temperate seagrasses, including Zostera marina, typically have pronounced seasonal cycles which modulate seagrass growth, physiology and reproductive effort. These marked temporal patterns can affect experimental seagrass responses to climate change effects depending on the seasons of the year in which the experiments are conducted. This study aimed at evaluating how seasonal acclimatization modulates productivity and biochemical responses of Zostera marina to experimental warming and irradiance reduction. Seagrass shoots were exposed to different temperatures (6, 12, 16, 20, and 24°C), combined with high (180 μmol photons m–2 s–1) and low (60 μmol photons m–2 s–1) light conditions across four seasons (spring: April, summer: July, and autumn: November 2015, and winter: January 2016). Plants exhibited similar temperature growth rates between 16 and 20°C; at 24°C, a drastic reduction in growth was observed; this was more accentuated in colder months and under low irradiance conditions. Higher leaf growth rates occurred in winter while the largest rhizomes were reached in experiments conducted in spring and summer. Increases in temperature induced a significant reduction in polyunsaturated fatty acids (PUFA), particularly omega-3 (n-3 PUFA). Our results highlight that temperate seagrass populations currently living under temperature limitation will be favored by future increases in sea surface temperature in terms of leaf and rhizome productivity. Together with results from this study on Z. marina from a temperate region, a wider review of the reported impacts of experimental warming indicates the likely reduction in some compounds of nutritional importance for higher trophic levels in seagrass leaves. Our results further demonstrate that data derived from laboratory-based studies investigating environmental stress on seagrass growth and acclimation, and their subsequent interpretation, are strongly influenced by seasonality and in situ conditions that precede any experimental exposure.

Evaluation of IoT-Based Grow Light Automation on Hydroponic Plant Growth

This research aims to design, create, and evaluate a hydroponic automation system by monitoring the quality of plant growth that uses LED grow lights and natural light conditions on hydroponics. Checking whether the proposed system has a significant effect on the box Choy hydroponic growth is also an important aspect and becomes the contribution of this paper. The contribution of this paper is by discussing in detail the automation of LED grow lights using RTC modules and relays while also discussing the significance of LED light performance in hydroponic growth. On the proposed hydroponic automation systems, light-feeding is done automatically, this can be carried out with the help of a real-time clock (RTC) module and relays. Furthermore, the monitoring function is carried out through temperature and humidity measurement sensors. The data obtained from the sensor will be stored in the database for research on plant quality. The results of a comparison test show that the LED grows lights are superior in terms of fresh weight, the number of leaves, and plant height respectively with an average value of 23.6 grams, 11.2 leaves, and 18.1 cm on the 30th day. Compared to sunlight, respectively with an average value of 20.2 grams, 9.3 leaves, and 17.1 cm on the 30th day. PDF calculation and t-test are used to calculate the growth significance. The results are that the H0 for fresh weight and leaf growth rate is rejected and the H0 for plant growth rate is not rejected. It can be concluded that the LED grow lights give a significant effect on the fresh weight and leaf growth rate of IoT-based box Choy hydroponics if compared to sunlight.

Population structure of a newly recorded (Halodule uninervis) and native seagrass (Halophila ovalis) species from an intertidal creek ecosystem

AbstractThe presence of the seagrass Halodule uninervis was documented for the first time outside the Chilika lagoon at Haripur creek, along with previously documented Halophila ovalis from the same region. The population structure (density; biomass; leaf growth rate; and morphometrics) and environmental parameters was assessed for both seagrass species. The pH levels of the water column above both seagrass meadows were lower than the standard oceanic pH of 8.2, likely attributable to upstream freshwater influences. Halophila ovalis grew on sandy and H. uninervis on silty substrates. High nutrient (nitrate and phosphate) concentrations in the water column of the creek influenced the growth of macroalgae (Ceramium sp. and Gracilaria verrucosa) on the leaves of H. uninervis. Leaf reddening was only observed in H. ovalis leaves. Under similar environmental conditions, the shoot density and biomass (above‐ and below‐ground) of H. ovalis were 2‐fold lower that for H. uninervis. The leaves of H. uninervis were 9‐fold longer than H. ovalis, whereas H. ovalis had 5‐fold wider leaves than H. uninervis. The leaf plastochrone interval of H. ovalis (2.3 days) and H. uninervis (9.6 days) was similar for the Indian Ocean region. Consequently, the H. ovalis leaf growth rate was 2‐fold lower than that for H. uninervis. H. ovalis shoot internodes were 2.6‐fold longer than for H. uninervis, whereas the root lengths of H. uninervis were longer than for H. ovalis. The shorter root length of H. ovalis resulted in a higher branching frequency than for H. uninervis. The total C and N content were higher in the H. ovalis leaves than those of H. uninervis. This study suggest seagrass responses to similar environmental conditions are species‐specific. Regular assessment of the seagrass population structure and water quality monitoring of Haripur creek are essential for better management and conservation of these important seascapes.

Pertumbuhan dan produksi kangkung darat (Ipomoea reptans Poir) pada berbagai dosis pupuk papua nutrient granule di Manokwari

The aim of the study was to determine the apropriate dose of Papua Nutrient Granule fertilizer on the growth and production of kangkong (Ipomea reptans poir). The research was carried out at the screen house of the Faculty of Agriculture, University of Papua, Manokwari for 2 months from July to August 2019. The study was a single factor experiment using a Randomized Block Design. The treatment dose of Papua Nutrient Granule fertilizer consisted of control/Papua Nutrient Fertilizer 0 tons/ha), Papua Nutrient Fertilizer 5 tons/ha, Papua Nutrient Fertilizer 10 tons/ha), Papua Nutrient Fertilizer 15 tons/ha), Papua nutrient fertilizer 20 tons/ha. The results showed that the application of Papua Nutrient significantly affected the growth and yield of kangkong at all ages of observation. Papua Nutrient granule fertilizer with doses of 15 and 20 tons/ha produced height, rate of plant height, number of leaves and leaf growth rate, fresh stover weight and fresh root weight per plant better than other fertilization treatments and control.

Leaf phenology and trunk growth of Avicennia alba (Blume) under a seasonally fluctuating saline environment in the tropical monsoon area of eastern Thailand

AbstractMangrove forests are said to be highly productive ecosystems but it is unclear how they maintain high productivity under the fluctuation of saline environment in the tropical monsoon region. A study of phenological aspects linked with the growth of mangrove trees may be a supportive evidence for this. Here, we studied the seasonal variation in leaf phenology and trunk growth of Avicennia alba trees in a tropical monsoon mangrove forest which has clear rainy and dry seasons at Trat Province, eastern Thailand. For the leaf phenology, the number of new and lost leaves was counted by using demographic techniques, and the monthly rates of leaf emergence and loss were calculated from 45 sample shoots from June 2019 to May 2020. In this period, trunk basal‐area increments were also recorded monthly by using dendrometer bands. The rate of leaf emergence showed a remarkable seasonal pattern that was high during the rainy season and low during the dry season. The monthly rate of leaf emergence and trunk growth showed a positive relationship, indicating that both the leaf and trunk growth of A. alba responded to the changing water salinity in the soil. However, the leaf loss rate fluctuated throughout the study period. It was considered that the cambial activity of trunk growth associated with new leaf formation stimulates tree growth under the low saline environment during the rainy season in the tropics. We discussed a growth strategy that will benefit mangrove trees growing in the intertidal areas under fluctuated saline environment.

The exclosure cage technique revisited: Pasture responses under continuous stocking and their relationship with estimates of forage accumulation in grazing experiments

AbstractForage accumulation (FA) is a key response in grazing experiments, and estimates of FA in continuously stocked pastures are often obtained using exclosure cages. This study evaluated how 14‐, 21‐, and 28‐d exclusion periods using cages affected morphological, physiological, and morphogenetic responses of continuously stocked ‘Mulato II’ hybrid brachiariagrass (Brachiaria spp. syn. Urochloa spp.) pastures maintained at 20‐ and 30‐cm canopy height and how this affected estimates of FA. Grazing exclusion resulted in greater rates of leaf elongation (LER; 1.62 vs. 1.37 cm tiller−1 d−1), stem elongation (SER; 0.16 vs. 0.07 cm tiller−1 d−1), leaf growth (101 vs. 86 kg dry matter [DM] ha−1 d−1), and stem growth (3.4 vs. 1.8 kg DM ha−1 d−1) inside the cages compared with outside. Greater LER resulted in greater final leaf length and leaf area index (LAI) in longer exclusion periods. With greater LAI, photosynthesis was greater within the exclosure cages than on pasture (54.5 vs. 43.9 μmol CO2 m−2 s−1). Greater leaf growth rate, together with same tiller population density and leaf senescence rate (LSR) across exclusion periods, resulted in overestimated FA by 14, 26, and 24% for 14‐, 21‐, and 28‐d exclusions, respectively. There was no effect of canopy height on FA, because greater LER and SER values in 30‐cm canopies were compensated by greater LSR. Choice of sites for cage placement by visual appraisal and reduced number of sampling sites resulted on “negative” values of calculated FA for the 14‐d exclusion, making the choice of sampling sites a major source of error in estimation of actual FA. Increasing the number of sampling sites and using indirect measurements of forage mass (FM) may increase the accuracy of FM and FA estimates.

Growth of Megathyrsus maximus cv. Mombaça as affected by grazing strategies and environmental seasonality. II. Dynamics of herbage accumulation

For tropical forage grasses, leaves are the main morphological component accumulated at the beginning of regrowth, and as leaf area index increases, plants change their growth pattern, allocating more resources to stem elongation as a means of optimising light capture. We hypothesised that, for Mombaça guineagrass, stem elongation and leaf senescence rate play a major role in determining net herbage accumulation rate (NHAR) and that senescence would be the key factor driving the reduction in NHAR when regrowth is interrupted beyond the critical leaf area index, that is, when canopy light interception (LI) exceeds 95%. Treatments corresponded to all combinations of two levels of pre-grazing canopy LI during regrowth (LI95% and LIMax) and two post-grazing heights (30 and 50 cm), and were allocated to experimental units according to a randomised complete block design with four replications. Measurements were performed throughout contrasting climatic conditions during four seasons from January 2001 to February 2002. Overall, spring and the two summers were the seasons when rates of leaf appearance, leaf elongation and leaf growth rate were higher, and leaf lifespan was smaller; the inverse occurred during autumn–winter. Despite the lack of statistically significant differences in NHAR between LI treatments during some seasons of the year, the ratio of leaf growth rate to NHAR was consistently higher for LI95% than LIMax. The pre-grazing target of LI95% was also efficient for decreasing stem elongation and leaf senescence rate. Increased senescence on individual tillers was the key driver generating modifications in the patterns of variation in NHAR beyond the critical leaf area index, suggesting that there is no advantage in extending the regrowth period when the main objective is to maximise leaf growth rate or NHAR.

Automation of leaf counting in maize and sorghum using deep learning

AbstractLeaf number and leaf emergence rate are phenotypes of interest to plant breeders, plant geneticists, and crop modelers. Counting the extant leaves of an individual plant is straightforward even for an untrained individual, but manually tracking changes in leaf numbers for hundreds of individuals across multiple time points is logistically challenging. This study generated a dataset including over 150,000 maize and sorghum images for leaf counting projects. A subset of 17,783 images also includes annotations of the positions of individual leaf tips. With these annotated images, we evaluate two deep learning‐based approaches for automated leaf counting: the first based on counting‐by‐regression from whole image analysis and a second based on counting‐by‐detection. Both approaches can achieve root of mean square error (RMSE) smaller than one leaf, only moderately inferior to the RMSE between human annotators of between 0.57 and 0.73 leaves. The counting‐by‐regression approach based on convolutional neural networks (CNNs) exhibited lower accuracy and increased bias for plants with extreme leaf numbers which are underrepresented in this dataset. The counting‐by‐detection approach based on Faster R‐CNNs (region based convolutional neural networks) object detection models achieve near human performance for plants where all leaf tips are visible. The annotated image data and model performance metrics generated as part of this study provide large scale resources for the comparison and improvement of algorithms for leaf counting from image data in grain crops.

Biomass Enhancement of Stevia rebaudiana Bertoni Shoot Culture in Temporary Immersion System (TIS) RITA® Bioreactor Optimized in Two Different Immersion Periods

Stevia plant contains steviol glycosides, which are estimated to be 300 times sweeter than sucrose. However, conventional (in vivo) propagation of Stevia rebaudiana in Indonesia was not effective due to poor results. Therefore, an alternative method to propagate stevia plants is needed. One of them is by using in vitro method. Multiplication with a large quantity of stevia biomass in a relatively short period can be conducted by using TIS RITA® (Recipient for Automated Temporary Immersion System). This study aimed to evaluate the effect of the immersion period of the medium on growth and the medium bioconversion into the production of shoot biomass. The bioreactors were set up with 15 min and 30 min immersions periods, scheduled every 6 h, and incubated for 21 d. The result indicated that the immersion period affected the biomass and growth rate (µ). Amount of 30 min immersion showed a greater percentage of shoot multiplication, higher biomass, percentage of leaf growth, growth rate, and productivity compared to 15 min immersion. The pattern of sucrose, mineral, and inorganic compounds consumption followed the growth of plant biomass for both systems. In conclusion, 30 min immersion gave a greater efficiency medium bioconversion to plant biomass compared with 15 min immersion.

Canopy Structure and Photosynthetic Performance of Irrigated Cassava Genotypes Growing in Different Seasons in a Tropical Savanna Climate

Growth and photosynthesis performance of cassava during early vegetative growth are important determinants of final biomass. The objective of this work was to investigate canopy structure and photosynthesis performance of four cassava genotypes (Rayong 9, Rayong 11, Kasetsart 50, and CMR38-125-77) growing under irrigation at 3 and 6 months after planting (3MAP and 6MAP). Data for the 3MAP plants were collected from cassava planted on 30 June (Rainy PD), 10 November (Cool PD1), and 15 December (Cool PD2) 2015; and for the 6MAP from those planted on 20 April 2015 (Hot PD), Rainy PD, and Cool PD1. The plants growing in the rainy season had significantly higher leaf area index (LAI) than those growing in the cool and hot seasons. Consequently, they had lower percentage light penetration at the bottom of canopy, and therefore more light interception through the canopy, and hence a higher mean net photosynthesis rate (Pn) across the six canopy levels. At the 3MAP, which is the stage of maximum rate of leaf and stem growth, the Rainy PD and Cool PD2 plants of CMR38-125-77 showed the highest LAI and highest mean Pn. Similarly, the Cool PD1 plants of Kasetsart 50 showed the highest LAI and highest mean Pn. In contrast, at 6MAP during the stage of active starch accumulation in storage roots, the genotypes with the highest mean Pn were the ones having an intermediate (CMR38-125-77 for the Hot PD) or low LAI (Rayong 9 for the Rainy PD, and CMR38-125-77 for the Cool PD1). Data on variations in canopy structure and photosynthesis potentials of different cassava genotypes in response to seasonal variations may be useful for crop growth modeling and may be employed as a criterion for the selection of suitable genotypes for each growing season.

Warming enhances the cadmium toxicity on macrophyte Myriophyllum aquaticum (Vell.) Verd. seedlings.

Due to a close contact with water column, submerged macrophytes are easily disturbed by environment change in freshwater ecosystems, especially at the seedling stage. In recent decades, freshwater ecosystems have been subject to severe cadmium (Cd) pollution, which can cause toxic effects on the growth of submerged macrophytes. Moreover, the temperature rise resulting from climate warming and water level decline may further aggravate such effect, especially in shallow lakes. Here, we investigated the independent and interaction effects of Cd exposure levels (0, 0.5, 1, and 2.5mgL-1) and temperature (15, 25, and 30°C) on morphological and physiological traits of Myriophyllum aquaticum (Vell.) Verd. Seedlings generated from propagules and seeds. The temperature rise and Cd exposure generally resulted in a significant increase of Cd concentrations and antioxidant enzyme activities in leaves, as well as a decrease of chlorophyll a and b concentrations. The number and length of leaves generated from propagules always show a downward trend with the increase of Cd exposure, regardless of the temperature. Moreover, the lowest leaf number and length always occurred at high temperature (i.e. 30°C) when the Cd exposure level increased to 1 and 2.5mgL-1. For the seedlings generated from seeds, the temperature rise caused an increase of leaf emergence rate under low Cd exposure levels, but resulted in a significant decrease with the Cd exposure level. This study indicates the negative effects of Cd exposure and temperature rise on submerged macrophytes at the seedling stage, and highlights that temperature rise would enhance Cd toxicity.

Size dependent associations between tree diameter growth rates and functional traits in an Asian tropical seasonal rainforest.

Many studies focus on the relationships between plant functional traits and tree growth performances. However, little is known about the ontogenetic shifts of the relationships between functional traits and tree growth. This study examined associations between stem and leaf functional traits and growth rates and their ontogenetic shifts across 20 tropical tree species in a tropical seasonal rainforest in Xishuangbanna, south-west China. For each species, physiological active branches of individual trees belonged to three size classes (i.e. small, diameter at breast height (DBH) 5-10 cm; middle, DBH 10-20 cm; big, DBH >20 cm) were sampled respectively. We measured 18 morphological and structural traits, which characterised plant hydraulic properties or leaf economic spectrum. Associations between diameter growth rates and functional traits were analysed across three size classes. Our results revealed that diameter growth rates of big-sized trees were mainly related to traits related to plant hydraulic efficiency (i.e. theoretical hydraulic conductivity (Ktheo) and leaf vein density (Dvein)), which suggests that the growth of large trees is limited mainly by their xylem water transport capacity. For middle-sized trees, growth rates were significantly related to traits representing leaf economic spectrum (i.e. specific leaf area (SLA), individual leaf mass (ILM), palisade thickness (PT) and spongy thickness (SP)). Diameter growth rates of small-sized trees were not correlated with hydraulic or leaf economic traits. Thus, the associations between tree growth rates and functional traits are size dependent. Our results suggest ontogenetic shift of functional traits which could potential contribute to different growth response to climate change.

Previous exposure mediates the response of eelgrass to future warming via clonal transgenerational plasticity.

Mortality and shifts in species distributions are among the most obvious consequences of extreme climatic events. However, the sublethal effects of an extreme event can have persistent impacts throughout an individual's lifetime and into future generations via within-generation and transgenerational phenotypic plasticity. These changes can either confer resilience or increase susceptibility to subsequent stressful events, with impacts on population, community, and potentially ecosystem processes. Here, we show how a simulated extreme warming event causes persistent changes in the morphology and growth of a foundation species (eelgrass, Zostera marina) across multiple clonal generations and multiple years. The effect of previous parental exposure to warming increased aboveground biomass, shoot length, and aboveground-belowground biomass ratios while also greatly decreasing leaf growth rates. Long-term increases in aboveground-belowground biomass ratios could indicate an adaptive clonal transgenerational response to warmer climates that reduces the burden of increased respiration in belowground biomass. These transgenerational responses were likely decoupled from clonal parent provisioning as rhizome size of clonal offspring was standardized at planting and rhizome starch reserves were not impacted by warming treatments. Future investigations into potential epigenetic mechanisms underpinning such clonal transgenerational plasticity will be necessary to understand the resilience of asexual foundation species to repeated extreme climatic events.

Effects of Foliar Application of Liquid Fertilizer on Agronomical and Physiological Traits of Rice (Oryza sativa L.)

Providing rice (<em>Oryza sativa </em>L.) plants with the required nutrients is essential in order to avoid yield reduction. As such, an experiment was performed at the Rice Research Institute of Iran in Amol Township to evaluate the effects of foliar application of nutrients on rice plants. The experiment consisted of a randomized complete block design, with four replications during 2 crop years (2016 and 2017). Experimental treatments included foliar application of nutrients [the chemical composition of liquid fertilizer was as follows: nitrogen (N): 7%, phosphorus (P): 7%, potassium (K): 7%, iron (Fe): 0.05%, boron (B): 0.05%, zinc (Zn): 0.01%, manganese (Mn): 0.01%, and copper (Cu): 0.01%] in the following growth phases: (A) midtillering stage, (B) maximum tillering, (C) panicle initiation, (D) maximum tillering + panicle initiation, (E) all stages, and (F) control treatment (no liquid fertilizer applied). Our results indicate that foliar application of nutrients in different vegetative and generative stages significantly affected plant height, number of tillers per plant, chlorophyll concentration, number of filled grains per panicle, and grain yield. However, our treatments did not significantly affect the 1,000-grain weight. Furthermore, foliar application of nutrients significantly affected physiological traits including leaf area index, growth rate, and total dry weight of plants. Our results indicate that the mean values of the investigated traits were highest in the “maximum tillering + panicle initiation” and “all stages” treatments. In contrast, the lowest mean values of the investigated traits were found in the control treatment. Foliar application of nutrients at the “maximum tillering + panicle initiation” stage resulted in the highest chlorophyll concentrations, leaf area index, and crop growth rate in the flowering stage. Our results indicate that foliar application of nutrients was most effective when applied to Sahel variety rice during two vegetative and reproductive stages.

PENGARUH KONDISI pH TERHADAP RESPONS FISIOLOGIS DAUN LAMUN JENIS Cymodocea rotundata

Meningkatnya konsentrasi karbondioksida (CO2) di atmosfer dapat menyebabkan asidifikasi laut. Asidifikasi menjadi ancaman bagi lamun. Salah satu tantangan yang harus dihadapi saat ini adalah memprediksi dampak jangka panjang dari asidifikasi laut terhadap fisiologi lamun. Tujuan penelitian ini untuk menganalisis respons fisiologis lamun C. rotundata yang meliputi kandungan klorofil a dan b, laju fotosintesis dan laju pertumbuhan daun lamun. Penelitian dilaksanakan pada bulan September – Desember 2017 di Laboratorium Marine Habitat Departemen Ilmu dan Teknologi Kelautan, Institut Pertanian Bogor. Metode yang digunakan adalah rancangan percobaan acak lengkap 5 pengulangan. Perlakuan pH yang digunakan yaitu pada nilai pH rendah (7,55), menengah (7,78) dan kontrol (8,20). Pengaturan nilai pH dengan cara menambahkan unsur CO32-. Kandungan klorofil a dan b, Laju fotosintesis dan Laju pertumbuhan daun C. rotundata perlakuan pH 8,20 lebih tinggi dibandingkan dengan perlakuan pH 7,78 dan pH 7,55. Uji ANOVA menunjukkan hanya klorofil a yang berbeda signifikan. Perbedaan pH mempengaruhi kandungan klorofil a dan b, laju fotosintesis dan laju pertumbuhan daun. Rendahnya pH air laut terbukti menghambat aktivitas fisiologis daun lamun C. rotundata.

Maize plant density affects yield, growth and source-sink relationship of crops in maize/peanut intercropping

Abstract Maize (Zea mays L.)/peanut (Arachishypogaea L.) intercropping has been widely practiced in semi-arid regions to reduce wind erosion and improve resource (e.g. water and light) use efficiencies. Knowledge on optimal maize plant density is lacking from perspective of dry matter accumulation among organs in this intercropping system. We quantified the effect of maize plant density on relative yield total (RYT), maize and peanut yields, and maize dry matter of organs (ears, leaves, and stems) in maize/peanut intercropping. Field experiments were conducted in a semi-arid area of China in 2015 and 2016. Three maize plant densities (6, 9 and 12 plants m−2) were tested in maize/peanut intercropping (per unit growing area designed for maize) and sole systems, whereas the plant density of intercropped peanut and sole peanut was fixed as 24 plants m-2. The beta and logistic growth functions were used to quantitatively characterize the dynamics of dry matter allocation among organs in maize. Increasing maize plant density significantly increased maize yield gain, but not increased peanut yield loss, in maize/peanut intercropping. The greatest yield advantage (RYTs of 1.21 in 2015 and 1.13 in 2016) occured in maize/peanut intercropping with maize planted at 9 plants m−2. Increasing plant density increased leaf growth rate, but reduced leaf longevity and dry matter allocation to ears for maize grown in both intercropping and sole systems. But, greater increases in leaf growth rate and leaf longevity for intercropped maize compared with sole maize resulted in a greater increase in dry matter accumulation for maize grown at 9 and 12 plants m−2. Greater increases in ear dry matter accumulation and yield were found for maize grown at 9 plants m−2 due to greater dry matter allocation to ears. We conclude that the different responses to plant density of the source capacity (leaves) and sink strength (ears) for maize in intercropping and sole systems could help optimize maize plant density (9 plants m-2) for greater maize yield gain and yield advantage in maize/peanut intercropping.

Starch biosynthesis contributes to the maintenance of photosynthesis and leaf growth under drought stress in maize.

To understand the growth response to drought, we performed a proteomics study in the leaf growth zone of maize (Zea mays L.) seedlings and functionally characterized the role of starch biosynthesis in the regulation of growth, photosynthesis and antioxidant capacity, using the shrunken-2 mutant (sh2), defective in ADP-glucose pyrophosphorylase. Drought altered the abundance of 284 proteins overrepresented for photosynthesis, amino acid, sugar and starch metabolism, and redox-regulation. Changes in protein levels correlated with enzyme activities (increased ATP synthase, cysteine synthase, starch synthase, RuBisCo, peroxiredoxin, glutaredoxin, thioredoxin and decreased triosephosphate isomerase, ferredoxin, cellulose synthase activities, respectively) and metabolite concentrations (increased ATP, cysteine, glycine, serine, starch, proline and decreased cellulose levels). The sh2 mutant showed a reduced increase of starch levels under drought conditions, leading to soluble sugar starvation at the end of the night and correlating with an inhibition of leaf growth rates. Increased RuBisCo activity and pigment concentrations observed in WT, in response to drought, were lacking in the mutant, which suffered more oxidative damage and recovered more slowly after re-watering. These results demonstrate that starch biosynthesis contributes to maintaining leaf growth under drought stress and facilitates enhanced carbon acquisition upon recovery.