Higher Total Dry Mass Research Articles

Evaluation of Buffel Grass Forage Production, Soil Microbial Biomass, and Enzymatic Activity in Silvopastoral Systems

The adoption of silvopastoral systems enables the achievement of sustainable intensification using multiple arrangements and species in the same area. This study aimed to evaluate the forage production of buffel grass and determine soil microbial biomass and enzymatic activity in two arrangements of a silvopastoral system. The study design was a randomized block with four replicates using a 2 x 4 factorial arrangement. The factors were two arrangements of the silvopastoral systems (buffel + Eucalyptus urograndis = SPS1 and buffel + pigeon pea + E. urograndis = SPS2) and four distances from the E. urograndis trees (2, 4, 6, and 8 m). Soil sampling was carried out at 0–5, 5–10, and 10–20 cm depths to evaluate microbial nitrogen (Nmic) and carbon (Cmic), while the activity of β-glucosidase and urease enzymes was evaluated at 0–5 and 5–10 cm. Buffel grass in the SPS1 showed higher canopy height, total dry mass, and root mass values. In SPS1, the highest total dry mass (3290.7 kg·ha−1) was observed at 8 m from the trees. At a 5–10 cm depth, Cmic was higher at 2 m than 8 m from the trees. The highest value of Nmic was found at 5–10 cm, at a distance of 2 m. The SPS2 showed a higher Nmic than the SPS1 at the 10–20 cm depth. The β-glucosidase activity was higher at a distance of 2 m in SPS1 at 0–5 and 5–10 depths. Urease activity was lower at 8 m at both depths. Thus, we observed the highest values of root-and-shoot biomass of buffel grass in SPS1 system at 8 m from the E. urograndis trees. However, the soil microbial response indicated that the intensification using tree, legume and grass in silvopastoral systems increased soil microbial activity.

Exploring the coupling mode of irrigation method and fertilization rate for improving growth and water-fertilizer use efficiency of young mango tree

Unsuitable irrigation and soil nutrient deficiency affect the normal physiology and growth of mango (Mangifera indica L.) of tropical fruit tree in Southwest China. To obtain optimal fertigation mode for mango, the effects of three micro-irrigation methods (i.e., micro-sprinkler irrigation (SI), drip irrigation (DI) and micro-moistening irrigation (MM)) on photosynthetic characteristics, hydraulic conductivity, growth and water-fertilizer use efficiency of young mango tree were investigated under four fertilization rates (i.e., 0 g plant−1 (FN), 9.3 g plant−1 (FL), 18.6 g plant−1 (FM) and 27.9 g plant−1 (FH), a compound water-soluble fertilizer) using a randomized block design experiment. The results indicated that DI and MM increased net photosynthetic rate (Pn) by 17.50 and 28.95%, root hydraulic conductivity (Kr) by 39.65 and 52.69%, shoot hydraulic conductivity (Ksh) by 48.63 and 82.38%, total dry mass (DM) by 27.44 and 47.13%, water use efficiency (WUEET) by 43.27 and 73.17%, fertilizer agronomic efficiency (FAE) by 45.92 and 95.41%, and partial factor productivity of fertilizer (PFP) by 33.96 and 54.44%, but reduced transpiration rate (Tr) by 6.61 and 16.38%, leaf with petiole hydraulic conductivity (Kl+p) by 13.11 and 30.32%, and water consumption (ET) by 10.38 and 14.85% when compared with SI. Compared with FN, enhancing fertilization rate significantly increased Pn, Tr, total hydraulic conductivity (root to leaf), total DM, healthy index (Hi) and WUEET, and their maximum values appeared in the FM. FAE firstly increased and then decreased, while PFP gradually reduced with the increase of fertilization rate. MMFM had the highest total DM and WUEET, 2.32 and 2.58 times of SIFN (CK), and the largest FAE of 4.95 kg−1. Thus, MMFM (micro-moistening irrigation with moderate fertilization rate of 18.6 g plant−1) significantly promoted growth and improved water-fertilizer use efficiency of young mango tree, which was the best coupling mode of irrigation method and fertilization rate.

Weed Interference on Growth and Leaf Nutrient Accumulation in Two Cassava Varieties

The development of cassava varieties with more efficient nutrient absorption can prevent losses caused by weed competition. The objective of this study was to evaluate dry matter accumulation and leaf nutrient content in traditional and improved cassava varieties, with and without coexistence with weeds throughout the cycle. A randomized complete block design was used in a 2 x 2 x 11 factorial scheme with four replications. The first factor consisted of two varieties (Baianinha and Clone 56-03); the second factor was composed of the conditions with and without coexistence with weeds, and the third factor was 11 harvest periods. Coexistence with weeds reduced leaf contents of N (20.8% and 24.8%), P (26.7% and 4.6%) and K (27.1% and 12.6%) for 'Baianinha' and 'Clone 56-03', respectively. For coexistence with 'Baianinha', the period up to the maximum daily nutrient accumulation rate (N, P and K) ranged from 82 to 99 days after planting (DAP), while for 'Clone 56-03', coexistence in this period ranged from 80 to 88 DAP. The plants from the variety 'Clone 56-03' presented higher total dry mass and root dry mass accumulation, as well as higher leaf contents of N, P and K than the traditional cassava variety 'Baianinha', especially when in coexistence with weeds during the whole cycle.

Plant morphological traits and competition index comparisons of three invasive and native submerged plants

The submerged species Carolina fanwort (Cabomba caroliniana) has attracted considerable attention in Lake Taihu Basin (LTB), China. This species was widely used as a garden plant until 2016, when it was identified as invasive. In this study, we conducted a mesocosm experiment to compare the morphological traits, includingtotal dry mass, shoot/root (S/R) ratio, relative growth rate (RGR) and competition index log response ratio (ln RR), of C. caroliniana and two frequently co-occurring native submerged plants, water thyme (Hydrilla verticillata) and Eurasian watermilfoil (Myriophyllum spicatum). The results demonstrated that C. caroliniana did not show more advantageous traits (higher total dry mass, S/R ratio and RGR) or have a lower ln RR than H. verticillata or M. spicatum. We provide a counterexample to commonly accepted thought in which the successful invasion of invasive species may not be explained by outcompeting native plants. Other biotic or abiotic factors that determine the successful invasion of C. caroliniana must be studied further.

Evaluation of yield, chemical composition and yield of essential oil of four cultivars of sweet basil (Ocimum basilicum L.) affected by different levels of nitrogen

A field experiment was conducted to evaluate yield and some qualitative characteristics of four cultivars of sweet basil treated with different levels of nitrogen fertilizer. The experiments were located on the Agricultural Research Station of Khorramabad, Iran, during the 2016-2017 growing season. Treatments were arranged in factorial split-plot-in time in randomized complete block design with three replications. Experimental treatments were four cultivars of sweet basil (Ocimum basilicum ‘Italian Large Leaf’, O. basilicum ‘Mobarakeh’, O. basilicum ‘Cinnamon’ and O. basilicum ‘Thai’), three levels of nitrogen fertilizer (0, 100 and 200 kg ha-1 urea) and three harvests. The highest total dry mass (3482.4 kg ha-1) was related to ‘Italian Large Leaf’ with the application of 200 kg ha-1 urea at the second harvest. The maximum (26.79 kg ha-1) essential oil yield belonged to 100 kg ha-1 urea. The highest concentrations of main constituents of essential oil, except methyl chavicol, 1,8-cineole and methyl cinnamate were obtained by control (without nitrogen fertilizer). Italian Large Leaf cultivar and application of 100 kg ha-1 urea are recommended to access an acceptable agricultural yield and essential oil yield in sweet basil under the environmental condition similar to Khorramabad

The response of the sugar beet (Beta vulgaris L.ssp. vulgaris var. altissima Döll) genotypes to heat stress in initial growth stage

The continuous trend of global warming and increasing interest toward cultivating sugar beet (Beta vulgaris L. ssp. vulgaris var. altissima Döll) in tropical regions led us to conduct this study to investigate the effect of high temperature on sugar beet at initial growth stages. Thirty one genotypes were incubated at two temperatures (20 °C and 30 °C) in laboratory for germination test. The same genotypes were assessed for physiological parameters at 30 °C in greenhouse, too. Increasing temperature decreased germination indices with a high variability among the genotypes. Seed vigor index and seminal root length were decreased higher than other indices. The genotypes with higher greenness index had higher total dry mass, leaf area and leaf temperature depression (LTD), and those with higher seed vigor index indicated great quantum efficiency of PSII (Fv/Fm) values. ‘S1-92521’ produced high records in both laboratory and greenhouse experiments. Although ‘S1-92521’ showed good tolerance in both laboratory and greenhouse experiments, totally, sugar beet genotypes had different performance at two experiments. According to the results, seed vigor index could be used as a screening tool in laboratory, and LTD and Fv/Fm were considered as good criteria for screening heat-tolerant genotypes in greenhouse.

Evaluation of the growth and quality of lettuce (Lactuca sativa L.) in a closed recirculating hydroponic system

The production of lettuce in hydroponic systems with a recirculating nutrient solution has been growing, so it is necessary to evaluate the growth and quality of production under this system. Two harvest cycles were evaluated, comparing the behavior of physiological variables and growth rates on lettuce plants in a hydroponic system with a plastic cover. Lettuce plants were planted at 30 days after germination in an NFT hydroponic system. Nutrient solutions were prepared with sources of potassium nitrate, calcium nitrate, urea phosphate, magnesium sulfate and a source of minor nutrifeed. The second cycle had the highest total dry mass and leaf area index (LAI) at 43 days after transplant (dat). The relative growth rate (RGR) declined over time. The absolute growth rate (AGR) presented a sigmoid behavior as a gaussian bell shape; the leaf area index (LAI) increased until 43 dat, with the second cycle presenting the highest value; the net assimilation rate (NAR) decreased over time, with the second cycle having the highest value at 22 dat. The chlorophyll content for this variety was low, with a yellow pigmentation in the plant. The stomatal conductance (SC) in the two cycles at transplant time presented low values caused by the stress leaded by an imbalance in the pH of the solution, when the plants adapted to the system, this value increased.

Response of plant functional traits to species origin and adaptive reproduction in weeds

Exotic species and clonal species are more competitive than co-occurring species, and several plant traits have already been identified to contribute to their superior competitiveness. In this study, 13 functional traits of 36 weed species were analyzed to determine if there was generalizable difference among these species. The results indicated that species origin significantly affected fluctuating asymmetry of width (FAW), specific leaf area (SLA), and total dry mass (TDM), with exotic species showing a higher FAW and TDM but a lower SLA. Adaptive reproduction had a significant effect so that FAW and FAA tended to be higher for non-clonal species, but RMF and R/S ratio tended to be higher for clonal species. Meanwhile, the response of these traits to species origin and reproduction was altered by their interactive effect. Detrended correspondence analysis (DCA) ordination indicated an extremely positive relationship with all leaf traits and TDM, in exotic species, but a similar relationship with SLA, TDM, and Slw in clonal species. Clonal invasive species tended to have higher TDM, while non-clonal invasive species tended to have higher FA.

Growth and Physiological Responses of Rangpur Lime Seedlings Irrigated by a Prototype Subirrigation Tray

Citrus rootstock production in Brazil commonly uses manual overhead irrigation systems to water plants. Manual irrigation systems present low efficiency, apply more water than needed, and result in release of nutrients and pesticides into the soil with a potential to contaminate groundwater. Closed irrigation systems that avoid the disposal of nutrient solutions like subirrigation can be used to increase production efficiency and reduce the environmental contamination. Our objective was to evaluate the effect of subirrigation applied by a prototype tray on plant growth and morphological and physiological responses of Rangpur lime (Citrus limonia Osbeck ‘Limeira’) seedlings subjected to different water levels in conic containers filled with pine bark substrate. We tested three treatments: T1) subirrigation with water reaching two-thirds of the container height (8 cm); T2) subirrigation with water reaching one-third of the container height (4 cm); and T3) control with manual overhead irrigation. Subirrigation resulted in higher plant growth of Rangpur lime seedlings. At 90 days after sowing (DAS), we observed significant effects of T1 over the other treatments on plant growth, as indicated by higher total dry mass (P = 0.0057), shoot/root ratio (P = 0.0089), shoot height (P = 0.0004), leaf area (P = 0.0005), and root length (P = 0.0333). The number of bifurcations was 400% higher in T3 than at the subirrigated treatments, which can lead to an increase in the labor costs for pruning. Seedlings grown under T1 presented leaf water potential 13% higher compared with T3 at predawn, which was the time of highest stomatal efficiency, presenting the lowest water loss, maximum stomatal closure, and higher transpiration at lower stomatal resistance. T2 plants displayed intermediate water status with a water potential 5% higher than T3. T3 plants showed a higher transpiration rate under maximum stomatal closure, reducing leaf water potential. The subirrigated treatment with water level of two-thirds of container height (8 cm) induced higher plant growth and shortened the crop cycle, anticipating the transplanting to the next phase (grafting) with the possibility of reducing production costs in the nursery.

Calcium Ameliorates the Tolerance of Lisianthus [Eustoma grandiflorum (Raf.) Shinn.] to Alkalinity in Irrigation Water

Irrigation water high in alkalinity can severely compromise the growth and marketability of ornamental plants. In the present study we investigated the response of lisianthus to increased calcium (Ca) when irrigated with solutions containing high levels of bicarbonate (HCO3−)-induced alkalinity. Alkalinity in irrigation water reduced the growth of lisianthus; however, plants supplemented with an increased concentration of Ca at alkalinity levels from 4 to 7 meq·L−1 of HCO3– exhibited improved growth and dry mass (DM) accumulation or were not detrimentally affected, demonstrating that Ca contributes to the increase of the tolerance of lisianthus to alkalinity. Supplementary Ca did maintain a high stomatal conductance (gS) and transpiration rate when alkalinity was at 4 meq·L−1, which explained the lower water potential in young leaves. Plants irrigated with solutions containing supplementary Ca had higher total DM, which was associated with a higher gS; however, when conductance was higher than 0.280 cm·s−1, like in plants with no supplementary Ca, DM tended to decrease. At a typical Ca concentration, there was a disruption on stomata functioning as gS and transpiration rate increased, which was associated with a reduction in shoot potassium (K). Calcium ameliorated the uptake of K when alkalinity was 4 meq·L−1 by allowing a less marked reduction in shoot K concentration. Chlorophyll was reduced by increasing alkalinity as a result of a decrease in shoot iron (Fe); however, supplementary Ca also contributed in increasing plant tolerance to alkalinity at 4 meq·L−1 by sustaining a high shoot Fe concentration. Supplementary Ca increased catalase and peroxidase activities, indicating that lisianthus responded to the stress by enhancing the activity of these enzymes to reduce oxidative damage.

Carbohydrate changes in Cymbidium ‘Red Fire’ in response to night interruption

The effects of night interruption (NI) on growth and soluble carbohydrate contents were investigated in Cymbidium ‘Red Fire’. Plants were vegetatively propagated and grown under different light conditions for 2 years. NI was employed twice during experimental period, 16 weeks for each year: 9/15h ambient light/dark (control), 9h ambient light plus NI (22:00–02:00h) with low light intensity at 3–7μmolm−2s−1 (LNI) and 9h ambient light plus NI with high light intensity at 120μmolm−2s−1 (HNI). The light intensities of LNI and HNI at plant canopy were adjusted by placing pots at 4 and 1m from the high-pressure sodium lamps. The pseudobulb diameter was larger under both LNI and HNI conditions than under control condition. Plants grown under LNI and HNI conditions had higher total dry mass than those grown under control condition. Soluble sugar contents were higher in the plants grown under LNI and HNI conditions than in those grown under control condition. Glucose was the most abundant soluble sugar in the pseudobulbs with flower initiation in the plants grown under LNI and HNI conditions. Sucrose contents were much higher in the leaves than in the pseudobulbs and roots after NI treatments. Starch contents in the leaves and roots were higher during vegetative growth, while those in the pseudobulbs were higher during reproductive growth. The pseudobulbs and roots of the plants acted as a strong sink during flowering, preferentially metabolizing carbohydrates, rather than storing them. These results suggest that the increases of starch in leaves during vegetative growth and soluble sugars in pseudobulbs and roots during reproductive growth of Cymbidium ‘Red Fire’ under NI are crucial for increasing plant size and thereby promoting flowering.

Traits fonctionnels et plasticité en relation avec les performances de semis de ligneux méditerranéens sous ombrage et en situation de sécheresse

Interspecific differences in morphology, biomass allocation and phenotypic plasticity along an experimental irradiance gradient and two contrasting water regimes were studied for eight Mediterranean woody species at the seedling stage; a critical demographic stage in Mediterranean plant communities. We tested whether species variation in these traits can explain previously reported interspecific differences in performance under shade and drought. Four irradiance levels (1%, 6%, 20% and 100% of full sunlight) and two water regimes (well watered and water-stressed conditions) in 6% and 100% irradiance levels were established. Quercus species exhibited the largest seeds, the highest total dry mass and also the highest root-shoot ratio, but their leaf mass fraction (LMF) and leaf area ratio (LAR) were low. Pistacia terebinthus, and Arbutus unedo exhibited the opposite traits. From those traits that correlated with seed size only LAR resulted significantly linked to survival in deep shade. None of the traits studied correlated with survival under water-stressed conditions. Overall phenotypic plasticity was negatively correlated with survival in deep shade but no correlation was found with survival under water-stressed conditions. Our results highlight the importance of low LAR and low phenotypic plasticity as potential determinants of enhanced performance under shade during the very early seedling stages of Mediterranean woody species. Low LAR was also positively correlated with seed size and consequently, its relationship with enhanced performance under shade might change at later life stages of the plant when seed reserves are no longer available.