Matter Accumulation Rate Research Articles

Response of nutrient management on growth, yield and nutrient uptake of hybrid rice in Gangetic plains of West Bengal

A field experiment was conducted at Regional Research Sub-Station (RRS), under Bidhan Chandra Krishi Viswavidyalaya, Chakdaha, Nadia, West Bengal during rainy seasons of 2017 and 2018 to study the effect of different nutrient management on growth, yield and nutrient uptake of hybrid rice. The experiment was laid out in factorial randomized block design with 20 treatment combinations having 4 varieties (3 hybrid varieties and 1 high yielding variety) and 5 combinations of nutrient management in three replications. The treatment combination of Ajay variety with 50% recommended dose of nitrogen (RDN) + 50% RDN from mustard cake + full recommended dose of phosphorus (RDP) and potassium (RDK) recorded the highest plant height but significantly greater values of leaf area index at 75 days after transplanting (DAT), leaf area duration at 30-90 DAT, dry matter accumulation and crop growth rate at 60-75 DAT were recorded in the treatment combination of Arize 6444 with 75% RDN + 25% nitrogen through mustard cake + 20 kg ZnSO4 /ha. In terms of yield attributes and yield treatment combination of hybrid variety Arize 6444 when combined with either of the fertilizer treatment i.e., 50% RDN + 50% RDN from mustard cake + full (RDP) and (RDK) or 75% RDN + 25% RDN from mustard cake + RDP and RDK + 20 kg ZnSO4 ha-1 recorded significantly (p= 0.05) best results. Hence, this combination could be more effective in augmenting growth, yield and nutrient uptake in the Gangetic plains of West Bengal.

Abandonment and rapid infilling of a tide-dominated distributary channel at 0.7 ka in the Mekong River Delta

The Ba Lai distributary channel of the Mekong River Delta was abandoned and infilled with sediment during the Late Holocene, providing a unique opportunity to investigate the sediment fill, timing and mechanisms of channel abandonment in tide-dominated deltaic systems. Based on analysis and age dating of four sediment cores, we show that the channel was active since 2.6 ka and was abandoned at 0.7 ka as marked by the abrupt disappearance of the sand fraction and increase in organic matter and sediment accumulation rate. We estimate that the channel might have been filled in a time range of 45–263 years after detachment from the deltaic network, with sediment accumulation rates of centimetres to decimetres per year, rapidly storing approximately 600 Mt of organic-rich mud. We suggest that the channel was abandoned due to a sediment buildup favoured by an increase in regional sediment supply to the delta. This study highlights that mechanisms for abandonment and infilling of tide-dominated deltaic channels do not entirely fit widely used models developed for fluvial-dominated environments. Their abandonment might be driven by autogenic factors related to the river-tidal and deltaic dynamics and favoured by allogenic factors (e.g., human impact and/or climate change).

Effect of Foliar Application of Micronutrients on Growth and Yield of Greengram (Vigna radiata L.)

Background: Greengram (Vigna radiata L.) is one of the most important pulse crops in India. It is a protein rich staple food which contains about 25 percent protein; It belongs to family leguminaceae so it has the capacity to fix atmospheric nitrogen. Soil application of nutrients is often not enough to meet the growing crop demand particularly in short duration crop like greengram. Therefore, it is hypothesized that foliar nutrition in addition to soil application in commensuration with prevailing weather particularly rainfall will go a long way in meeting crop nutrient need and thereby may help in enhancing poductivity. Foliar application of nutrients using water soluble fertilizer is on the possible ways to enhance the productivity of pulses like greengram. The importance of foliar application of micronutrients i.e., Zinc is essential for enzymes that are involved in many metabolic reactions, necessary for chlorophyll production and for starch formation aids in seed formation. Iron is essential for maintainance of chlorophyll and also an essential component of haemoglobin molecule. Manganese has a role of formation of plants naturally occurring antifungal compounds helping to fight disease infection. It is involved in the enzyme the growth may have biological reactions in plant tissue. Methods: A field experiment was conducted during Zaid season 2019-2020 at Crop Research Farm, Department of Agronomy, Sam Higginbottom University of Agriculture Technology and Sciences, Prayagraj, (U.P.) India. To study the “Effect of foliar applied micronutrient on growth and yield of Greengram (Vigna radiata L.)”. The present investigation was laid out in randomized block design (RBD) consisted of 9 treatments replicated thrice.Result: The results revealed that the maximum growth attributes such as plant height (42.42 cm), dry matter accumulation (113.39 g/m2) and crop growth rate (1.69 g/m2/day) was recorded with RDF + Fe 0.5% + Zn 0.5% + Mn 0.5% at 30 DAS, whereas maximum number of nodules/plant (11) was recorded with RDF+ Fe 0.5% at 30 DAS. However, higher yield and yield attributes i.e. Number of pods/plant (58.40), Number of grains/pod (9.73), 1000 grain weight (38.38 g), seed yield (1384.33) kg/ha, stover yield (2253.33) kg/ha and harvest index (42.44 %) was recorded with RDF + Fe 0.5% + Zn 0.5% + Mn 0.5% at 30 DAS. Similarly, higher Net returns (Rs 59912/ha) and benefit cost ratio (1.51) was also recorded with RDF + Fe 0.5% + Zn 0.5% + Mn 0.5% at 30 DAS as compared to control (RDF + water spray).

Growth and physiological quality in clonal seedlings of Robusta coffee

The intrinsic characteristics of the vegetative propagule may influence the rooting speed and shoot growth, as well as the final physiological quality of clonal seedlings of Coffea canephora. The aim of this study was to evaluate the growth and physiological quality of ‘Robusta’ coffee seedlings produced from propagules (stem cuttings) with different cutting ages. The study was conducted in a greenhouse, in the district of Ouro Preto do Oeste, in Rondonia, Brazil (10˚45’43” S and 62˚15’10” W). The ages of the cuttings were 30, 60, 90, 120 and 150 days, corresponding to five positions on the secondary orthotropic stem (sprout), from the apex to the base. Dry matter accumulation, and relative and absolute growth rates were evaluated for 188 days after cutting, as well as the vegetative characteristics of the seedlings at 125 days after cutting. It appears that growth can be divided into three phases: 1) Initial: slow growth, lasting approximately 83 days; 2) Intermediate: fast growth, lasting approximately 40 days; and 3) Final: slow growth, starting approximately 125 days after cutting. With physiological quality, although all the cuttings showed similar growth curves, those of 60, 90 and 120 days produced, 125 days after cutting, the best vegetative performance in the seedlings.

ПРОДУКЦИОННЫЙ ПРОЦЕСС СОРТОВ FRAGÁRIA X ANANÁSSA В УСЛОВИЯХ ОРЛОВСКОЙ ОБЛАСТИ*

The purpose of the study was to study the characteristics of the main components of the production process of Fragaria x ananassa varieties of different ecological and geographical origin in the conditions of the Oryol region. It has been shown that the varieties “Alba”, “Sonata”, “Solovushka” and “Tzaritsa”, in comparison with Korona, Sara, Marmolada and Kokinskaya rannyaya, demonstrated more efficient photosynthetic activity, high rates of dry matter accumulation, effective outflow, and accumulation of assimilates into ripening fruits, which ultimately affected their high yields.

Measuring urban ecosystem functions through ‘Technomass’—A novel indicator to assess urban metabolism

Cities are complex systems of accumulated matter. The continuous process of matter accumulation in urban systems differs in intensity across the globe according to specific urban features, such as location and age of the urban tissue, and as a physical manifestation of metabolic lineaments, material accumulation should differ amongst cities. In this paper, a new indicator to measure this process of material accumulation is proposed, namely, the Technomass. Emulating ecology, which measures biomass in natural ecosystems, a sample of different urban tissues in a given city – Bogotá – was measured in terms of volume and rates of matter accumulation. Technomass is able to indicate overall asymptotic behaviour, specific spatial profiles and intensification of rates in time. In metabolic terms, the indicator looks into the black box, providing the possibility to link metabolic behaviours with urban form and attempting to fill the gap between urban planning, urban metabolism (UM) and Material Flow Analysis (MFA). This new indicator offers a broad scope of applications. Further possibilities and links to urban research and policy making are explored in the discussion section.

Climate-driven changes in water level: a decadal scale multi-proxy study recording the 8.2-ka event and ecosystem responses in Lake Sarup (Denmark)

A two-stage change in lake level during the 8.2-ka event was identified in Lake Sarup, Denmark (55°N), using a multiproxy approach on precise radiocarbon wiggle-matched annually laminated sediments deposited 8740–8060 cal. yr BP. Changes in δ13C and δ18O indicated closed lake hydrology driven by precipitation. The isotopic, sedimentary and plant macrofossil records suggested that the lake level started to decrease around 8400 cal. yr BP, the decrease accelerating during 8350–8260 before an abrupt increase during 8260–8210. This pattern shows that the climate anomaly started ~150 years before the onset of the 8.2-ka cooling event registered in Greenland ice cores, but was synchronous with hydrologic change in the North American Lake Agassiz drainage. The lake level decrease was accompanied by a higher accumulation rate of inorganic matter and lower accumulation rates of cladoceran subfossils and algal pigments, possibly due to increased turbidity and reduced nutrient input during this drier period. Pigment analysis also showed added importance of diatoms and cryptophytes during this climate anomaly, while cyanobacteria became more important when the water level rose. Moreover, Nymphaeaceae trichosclereids were abundant during the period of algal enrichment. Cladoceran taxa associated with floating leaved plants or benthic habitats responded in a complex way to changes in water level, but the cladoceran assemblages generally reflected deep lake conditions throughout the period. The lake did not return to its pre-8.2-ka event status during the period of analysis, but remained more productive for centuries after the climatic anomaly as judged from the pigment accumulation and assemblage composition. The change to more eutrophic conditions may have been triggered by erosion of marginal deposits. Together, these data confirm the chronology of hydrologic changes and suggest, for the first time, that lake levels exhibited both a decline and an increase in rapid succession in response to the 8.2-ka event in southern Scandinavia.

Productivity, utilization efficiency and sward targets for mixed pastures of marandugrass, forage peanut and tropical kudzu

This study was carried out to evaluate the productivity and utilization efficiency of a mixed marandugrass (Brachiaria brizantha cv. Marandu), forage peanut (Arachis pintoi cv. Mandobi) and tropical kudzu (Pueraria phaseoloides) pasture, rotationally stocked at four daily forage allowance levels (6.6, 10.3, 14.3 and 17.9% of live weight), in order to define sward management targets for these mixtures. In each stocking cycle, dry matter (DM) accumulation rates, defoliation intensity (%), grazing depth (%) and grazed horizon (cm) were evaluated. Sward targets were defined according to the sward condition that best conciliated the grass-legume balance and the equilibrium between forage production and utilization. Pastures submitted to higher forage allowance levels showed higher productivity, but were less efficiently utilized. It was not possible to establish sward management targets for marandugrass-tropical kudzu pastures. For marandugrass-forage peanut pastures the best sward state was set with forage allowance of 10.3% of live weight. Under rotational stocking, the following sward targets were suggested for these pastures in the Western Amazon: pre-grazing height of 30-35 cm (June to September) or 45-50 cm (October to May) and post-grazing sward height of 20-25 cm (June to September) or 25-30 cm (October to May).

Nutrient extraction and exportation by castor bean hybrid lyra

Information about nutrient extraction and exportation by crops, as well as the periods of highest nutrient demand is important for an adequate fertilization management. However, there are no studies on the nutrient uptake of short-stature hybrid castor bean. Therefore, the purpose of this study was to evaluate nutrient extraction and exportation by short-stature castor bean hybrid Lyra, in the spring-summer and fall-winter growing seasons. The experiments were conducted in the 2005/2006 spring-summer and 2006 fall-winter growing seasons on an Oxisol, in Botucatu, SP, in a randomized block design, with four replications. The plots consisted of plant samplings, which occurred 17, 31, 45, 59, 73, 97 and 120 days after emergence (DAE) in the spring-summer and 17, 31, 45, 59, 80, 100 and 120 DAE in fall-winter growing season. The growth of hybrid Lyra was slow and nutrient uptake lowest between emergence and the beginning of flowering. The period of highest dry matter (DM) accumulation rates and highest nutrient demand were observed 40 to 80 DAE, in both growing seasons. The order of nutrient extraction by the plants in the spring-summer growing season was: N>K>Ca>Mg>S>P>Fe>Mn>Zn>B>Cu>Mo. In fall-winter, S was more absorbed than Mg. Seed yield was higher in the spring-summer (2.995 kg ha-1), but nutrient extraction and exportation per ton of seed were similar in both growing seasons. Around 58 % of N and 84 % of P, and approximately half of the S and B absorbed throughout the cycle were exported with the seeds. However, most of the other nutrients accumulated in the plants returned to the soil in plant residues.

BIOMASS ACCUMULATION IN OPUNTIA FICUS-INDICA (L.) MILL PLANTS GROWN IN A CLOSED HYDROPONIC SYSTEM

The research was carried out at the Hydroponic Station of the Agronomy School of the Universidad Autonoma de Nuevo Leon, in Marin, NL Mexico. Tender pad cactus (Opuntia ficus-indica L. Mill.) cultivar 'Villanueva' was planted at a density of 16 plants m -2 . The aims of this study were: a) to estimate the tender pad cactus yield and, b) to determinate the increment of the fresh weight, dry matter, and nitrogen accumulation rate as a function of the air temperature (degree-days). Total cactus yield at 56 days after plantation, based on the fresh weight and dry matter production was 4.265 kg m -2 and 0.2252 kg m -2 , respectively, while the total nitrogen uptake in the same period was 4.36 kg m -2 . The relationship of fresh weight, dry matter and nitrogen uptake to degree-days was a first degree polynomial with R 2 0.9924, 0.9948, and 0.9887 (p<0.001) determination coefficient per research parameter, respectively. The increased production rate of fresh tender pad cactus and dry matter content was 0.004 and 0.0002 kg m -2 (degree-days) -1 , respectively while the nitrogen accumulation rate was estimated to be 0.0228 g m -2 (degree-days) -1 .

Effect of enhanced water exchange on ecosystem functions in backwaters of an urban floodplain

This study evaluated the effects of a controlled surface water connectivity scheme on several backwaters in an urban floodplain within the city limits of Vienna, the Upper Lobau. A phosphorus budget and ecosystem metabolism measurements were used to assess the reaction of two trophically distinct floodplain backwater sections on changed connectivity conditions. The surface water connection led to a reduction of the retention times in the backwater system. The water column nutrient concentrations in the individual backwater sections approached those of the source water body. The significance of these effects, however, depends on the historical and current trophic situation of the respective water bodies. Generally, the surface water connectivity introduced particulate phosphorus export up to 30% increase over the influent loading and dissolved phosphorus up to 14% increase over the influent loading. However, in sections with submersed macrophyte development, which provided enhanced filtering capacities for particulate matter, sediment and phosphorus accumulation rates were increased. At the same time, water transparency increased resulting in a positive feedback supporting further macrophyte development. Based on these findings, the evaluation of restoration measures in urban floodplains needs to consider the spatial and temporal dynamics of nutrients and ecosystem processes such as gross primary production and community respiration to predict long-term development.

Seasonal patterns in permeable sediment and water-column biogeochemical properties on the inner shelf of the Middle Atlantic Bight

Abstract This study examines the responsiveness of permeable shelf sediments to seasonal factors affecting cycles of organic matter deposition and erosion. At a site on the inner continental shelf within the Middle Atlantic Bight (39°27′N, 74°14′W; water depth 13 m), sediment inventories of chlorophyll, phaeopigments, and fine particles enriched in organic matter are reported from SCUBA diver-collected cores retrieved during six cruises conducted over 2 years. These measurements provide little evidence for substantial seasonal variation in rates of organic matter accumulation, in spite of the potential for the sinking of large phytoplankton blooms associated with summer upwelling/downwelling events, or for wave orbital motion to cause both phytodetritus and benthic algae to be trapped in sand ripples. Sediment permeability, porosity, grain size, and extracellular proteolytic activity in both coarse and fine fractions showed little seasonality. Instead, a negative correlation between chlorophyll in surface sediments and bottom-water pools ( r 2 =0.56) was observed. Furthermore, overlays of other water-column properties with results of a principal component analysis of sediment variables suggest benthic–pelagic biogeochemical cycling is forced primarily by sediment resuspension events. Wave and current observations made during this study and during previous long-term experiments in the study area show that sediment resuspension stems from bottom stresses produced by both persistent irregular wind-waves and by very intense storm waves that occur in all seasons.

Relationship between gibberellic acid and water amount in the cotton seed

The role of endogenous GA3 and its application to seed development in two cotton genotypes Hybrid-6 (H-6) (big seeds) and Gujarat cotton 13 (G. Cot) (small seeds) was studied. Kernel and seed coat were subjected to growth analysis in terms of dry weight, water amount, and rates of dry matter accumulation and water uptake. H-6 kernel had manifold higher dry weight and water amount than G. Cot. Seed coat of both genotypes had similar dry weight at maturity, but the maximum rates of dry matter accumulation and water uptake were distinctly higher in H-6. According to growth analysis, development of seed kernel and coat was subdivided into four phases, i.e., cell division, cell elongation, dry matter accumulation and maturation. Endogenous GA3 level was estimated in kernel and seed coat by indirect ELISA using antibodies raised against GA3. GA3 amount per seed components was higher in the seed kernel of H-6 than of G. Cot, except 33 and 36 days after anthesis in kernel. H-6 seed coat had the higher amount of GA3 during cell division phase than that of G. Cot. Close correlation between in vivo GA3 level and water amount was recorded in both seed components. With GA3 or GA3 + NAA treatments in ovule culture, higher promotion in dry weight, water amount and seed size was noted in G. Cot than in H-6 suggesting that G. Cot is more deficient in endogenous GA3. The greatest stimulation of parameters studied was obtained in ovule culture with GA3 + NAA. When GA3 or GA3 + NAA was applied, initial significant difference in water amount and seed size was nullified. Data presented in this study indicated that GA3 regulates cell expansion through the water uptake by cotton seed.

Potassium Efficiency of 10 Potato Cultivars as Related to Their Capability to Use Nonexchangeable Soil Potassium by Chemical Mobilization

Ten potato cultivars were grown in low potassium soil with and without potassium (K) in a pot experiment to test their K efficiency. Two harvests (29 and 83 days after planting) were taken to obtain final dry matter (shoot+tubers) accumulation (DMA) rates of shoot and root growth and K uptake rate per unit root (K influx). Under K deficiency, DMA of different cultivars varied by a factor of more than 2. Based on absolute DMA without K, the cultivars, Linda, Oktan, Ponto, and Maas were more K efficient than Quarta and Belana. Results show that with the same root length, more K efficient cv. Oktan had higher relative shoot growth rate and produced more DMA than less K efficient cv. Quarta in the absence of K by taking up more K per plant from soil and maintaining higher shoot K concentration. The more K efficient cv. Oktan could take up more K per plant due to its higher K influx, and its higher influx was because of its capacity to use higher nonexchangeable soil K. The DMA, K uptake, and K influx in 10 cultivars were more correlated to the quantity of nonexchangeable K depleted (r=0.850, 0.981, and 0.608) than to that of exchangeable K (r=0.284, 0.363, and 0.315, respectively). Stepwise regression analysis indicated that capacity to use nonexchangeable K is the main factor controlling K efficiency of different cultivars followed by root length to DMA ratio and K influx.

A multi-proxy analysis of climate impacts on the recent development of subarctic Lake Saanajärvi in Finnish Lapland

Responses to recent climatic changes in the sediment of subarctic Lake Saanajarvi in northwestern Finnish Lapland are studied by comparison of various biological and sedimentological proxies with the 200-year long climate record, specifically reconstructed for the site using a data-set of European-wide meteorological data. The multi-proxy evidence of simultaneously changing diatom, Cladocera, and chrysophyte assemblages along with the increased rates of organic matter accumulation and pigment concentrations suggest that the lake has undergone a distinct typological change starting from the turn of the 20th century. This change, indicating an increase in lake productivity, parallels a pronounced rise in the meteorologically reconstructed mean annual and summer temperatures in the region between ca. 1850 and 1930's. We postulate that, during the Little Ice Age, the lake was not, or was only weakly, thermally stratified during summer, whereas the subsequent increase in air and hence epilimnetic water temperatures resulted in the development of the present summer stratification. The increased thermal stability of the lake created more suitable conditions for the growth of phyto- and zooplankton and changed the overall primary production from benthos to plankton. Mineral magnetic and carbonaceous particle records suggest long-distance pollution, particularly since the 1920's, yet the observed changes in lake biota and productivity can hardly be explained by this very minor background pollution; the 20th century species configurations are typical of neutral waters and do not indicate any response to pollution.

Oferta de forragem de capim-elefante anão 'Mott' e o rendimento animal

A pesquisa foi realizada durante as estações de crescimento de 1994/95 e 1995/96 (out./abr.), na Estação Experimental de Ituporanga/EPAGRI - SC, objetivando determinar o potencial de produção animal e as respostas em termos de taxa de acúmulo de matéria seca (MS) e qualidade de forragem e estrutura do perfil de uma pastagem de capim-elefante anão `Mott' (CEAM) submetida a quatro níveis de oferta de forragem (OF). Os níveis reais de FO foram 3,8; 7,5; 10,2 e 14,0 kg de MS de lâminas verdes (MSLV)/100 kg de PV/dia, num delineamento em blocos casualizados completos com duas repetições e três novilhos (8 a 10 meses) por potreiro, sob pastejo contínuo e uso da técnica "put-and-take". As OF determinaram resíduos médios de MSLV (RMSLV) de 722; 1537; 2332; e 2542 kg/ha, respectivamente. Ofertas de forragem crescentes condicionaram acréscimos na taxa de acúmulo de MSLV/ha/dia e na densidade da forragem. A OF de 11,3 kg de MSLV/100 kg de PV/dia (RMSLV de 2200 kg/ha) maximiza o desempenho animal com 1,06 kg/dia de ganho médio diário e assegura ganho/ha de 5,6 kg/dia, em condição de sustentabilidade da pastagem de CEAM, em pastejo contínuo.

Organic matter accumulation, peat chemistry, and permafrost melting in peatlands of boreal Alberta

In the discontinuous permafrost zone of boreal western continental Canada, permafrost is limited almost exclusively to ombrotrophic peatlands. Permafrost in peatlands recently has been degrading and continues to degrade at its southern limit across western Canada, with no evidence of regeneration. The melting of permafrost could have dramatic effects on organic matter accumulation, organochemical properties, and nutrient status in peatlands. Our objectives are to quantify differences in peat chemistry (i.e., concentrations of organic fractions, N, P, and S) and rates of organic matter accumulation over the past 200 years between a site with permafrost, a site with degraded permafrost (internal lawn), and three sites with no evidence of permafrost since the last glaciation (continental peatlands: two bogs and one poor fen). Results indicate that peat chemistry may differ according to the presence, absence, or degradation of permafrost. Recent rates of organic matter accumulation follow similar trends over the past 100-200 years in the permafrost and continental bogs; however, net rates of organic matter accumulation are accelerated by 60% in the internal lawn. As decomposition in peatlands is influenced by nutrient limitations and organic matter quality, peat chemistry is likely to be a critical factor in the carbon balance response of boreal peatlands to climate change.

Development and Testing of Cultivar-Specific Tillering Coefficients for Sorghum

Tillering is an important yield component of grain sorghum [Sorghum bicolor (L.) Moench]. Temperature greatly influences tillering, and variability occurs among cultivars. Growth rate has been used to describe mathematically cultivar tillering abilities for a range of environments. Our objectives were to develop tillering coefficients for a range of temperate and tropical grain sorghum cultivars and to test the accuracy of these coefficients in predicting productive tiller numbers using independent field data. Eight grain sorghum cultivars of temperate (DK 39Y, DK 46, RS 610, and Pioneer 8500) and tropical adaptation (AT x 623 x RT x 430, DK E57, Segaolane, and CSM 63) were grown in a growth chamber at Manhattan under three day/night temperature regimes (20/150C, 25/200C, and 30/250C) to determine the relationship between dry matter required per tiller and daily minimum air temperature. Field experiments at St. John and Manhattan were used to determine the effects of dates and rates of planting on tillering of the same cultivars. The results were used to evaluate the accuracy of the tiller dry matter requirements. Growth chamber results showed that the number of tillers was related linearly to daily rates of dry matter accumulation per plant. These dry matter requirements per tiller were related linearly to daily minimum air temperature, with differences among cultivars. Predicted number of productive tillers per plant was approximately 7 to 12 times actual tiller numbers in the field experiments. This was accounted for by low cultivar-specific tillering coefficients, which were not representative of the dry matter requirement of productive tillers.

Temperature response of dry matter accumulation, leaf photosynthesis, and chlorophyll fluorescence in an old and a new maize hybrid during early development

Studies were conducted to investigate whether genetic improvement in dry matter accumulation of maize (Zea mays L.) hybrids recommended in Ontario from the late 1950s to the late 1980s is associated with cold-temperature tolerance during early phases of development. The maize hybrids Pride 5 (released in 1959) and Pioneer 3902 (released in 1988) were compared at 16/7, 23/14, and 33/24 °C under a 16-h photoperiod with a photosynthetic photon flux density of 650 μmol m−2 s−1 in long-term and short-term temperature experiments conducted in controlled-environment cabinets. In the long-term temperature experiment, plants were grown at the three temperature regimes from the 4- to the 12-leaf stage. Total and plant component dry matter was determined at the 8-, 10-, and 12-leaf stage, and leaf photosynthesis and chlorophyll fluorescence were measured at the 10-leaf stage. In the short-term temperature experiment, plants were exposed to the three temperature regimes during a 3-d period after the 9-leaf stage, followed by 2 d at 23/14 °C. Dry matter accumulation during the 5-d period was measured and leaf photosynthesis and chlorophyll fluorescence were measured during each of the last 3 d of the 5-d period. Results showed a highly significant temperature effect on all measured parameters. Dry matter of Pride 5 at the 10-leaf stage was higher than that of Pioneer 3902, but rates of dry matter accumulation and leaf photosynthesis did not differ among hybrids, and hybrid × temperature interactions were not significant for these parameters. Hybrid × temperature interactions were significant for dry matter partitioning and the fluorescence parameter Fv/Fm, suggesting better low-temperature tolerance for Pride 5. Results of the short-term temperature study showed a significant hybrid × temperature interaction for dry matter accumulation, with Pride 5 higher than Pioneer 3902 at the low temperature regime and Pride 5 lower than Pioneer 3902 at the high temperature regime. Results of these experiments suggest that improvement over the past 30 yr of Ontario maize hybrids is not associated with improved low-temperature tolerance during early development. Key words: Maize, low-temperature tolerance, dry matter accumulation, dry matter partitioning, photosynthesis, chlorophyll fluorescence

Effects of transpiration rate on boron uptake by roots and translocation to shoots of table beets (Beta vulgarisL.)1

Abstract The effects of transpiration rate on B uptake by roots and translocation to shoots of table beet (Beta vulgaris L. cv. Red Ace) plants were studied under conditions of environmental control. Plants grown under high or low relative humidities (RH) had low or high rates of transpiration, respectively. Dry weights and B contents of shoots and roots were higher among plants grown at 80% RH and B concentrations of roots were lower compared to plants grown at 30% RH. Shoot B concentrations were not affected by RH. Rates of growth and B accumulation in shoots were closely correlated for plants grown in 30% or 80% RH. These parameters were not closely correlated in roots. The rate of B uptake per g root dry weight was greater in plants having higher transpiration rates; whereas the rate of B translocation to shoots per g dry weight was independent of transpiration rate. Thus we propose that B translocation to shoots is controlled mechanistically by rates of dry matter accumulation during stages of rapid ...