Biochemical changes in sugar beet lines in dependence on soil moisture

Nine sugar beet lines were grown in a glasshouse on chernozem soil watered to 35, 50 and 65 % of maximal soil water capacity. After 12 d, plant water potential, net photosynthetic rate, contents of soluble proteins, DNA and RNA, proportion of ribulose-1,5-bisphosphate carboxylase/oxygenase (RUBISCO) protein, and carbonic anhydrase activity were measured. As soil moisture decreased, the leaf water potential and net photosynthetic rate decreased. DNA and RNA content and carbonic anhydrase activity decreased under moderate drought, and increased with severe drought. RUBISCO protein proportion did not change significantly under decreased soil moisture, while the total soluble protein content decreased. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effects of soil density on yield and fertilizer requirement of sugar beet

Three experiments (1971–3) on medium-textured soils of low organic-matter content examined the effects of soil density on seedling emergence and yield of sugar beet, and the interactions between soil density and the requirement for nitrogen (N) and phosphate (P₂O₅) fertilizers. Three soil densities were produced by rolling and harrowing, dutch harrowing twice, and power harrowing once; each was tested with 75, 150 and 225 kg ha^-1 N and 0, 100 and 200 kg ha^-1 P₂O₅. Most seedlings emerged on the medium-density treatment produced by dutch harrowing twice. The crop in the least dense soil treatment, produced by power harrowing once, consistently yielded slightly more sugar than the medium-density treatment, which yielded significantly more than the most dense treatment. In dense soil, created by rolling and harrowing, there was a response to more fertilizer N than the less dense ones; the crop did not respond to phosphate fertilizer. Mechanical impedance, not toxic concentrations of ethylene in the soil atmosphere, appeared to be the cause of reduced yield on the dense soils; these reductions were considerable at dry soil bulk densities in excess of 1·5 g ml^-1.     

Effects of moisture stress on the multiplication and expansion of cells in leaves of sugar beet

Summary Sugar beets were subjected to moisture stress by decreasing the water potential of the culture solution osmotically with polyethylene glycol by a known amount, , and, alternatively by applying matric potential, , at the plant roots. Lowering the water potential at the root surface less than 200 millibars by either method resulted in significant decreases in the rate of cell multiplication. The final number of cells per leaf at = -372 mb the final was 165% of that at = -473 mb ( = –101 mb); similarly at = –15 mb the final cell number was 198% of that at = –196 mb ( = –181 mb). The mean cell volume of leaves was not significantly affected by these levels of moisture stress.     

土层厚度对刺槐旱季水分状况和生长的影响

该研究测定了旱季和雨季刺槐(Robinia pseudoacacia)林不同土层厚度的土壤含水量, 刺槐的树高、胸径、小枝凌晨水势、叶片碳稳定同位素组成(δ¹³C)、叶面积、比叶重和气体交换指标; 分析了刺槐旱季和雨季的水分状况和土层厚度之间的关系; 通过刺槐对季节性干旱胁迫的反应, 估计华北石质山区不同土层厚度土壤水分对刺槐的承载能力; 并求证近年来该地区刺槐衰败和水分因素的关系。结果显示: 随着土层厚度减小, 旱季土壤含水量下降、凌晨小枝水势降低; 气孔导度和最大光合速率都减小, 而瞬时水分利用效率增加, 雨季上述指标无显著性差异, 旱季土壤含水量只有雨季的60%左右。随着土层变薄, 刺槐叶片δ¹³C增高, 叶面积减小, 比叶重增加; 刺槐树高和胸径减小。以上结果表明: 刺槐在不同季节下的水分状况综合反映土壤的供水能力, 土层浅薄导致土壤水分承载力不足, 致使刺槐在旱季受到较严重的水分胁迫, 这可能是刺槐出现衰败的重要原因。     

The effect of decreasing soil moisture on the water relations of sunflower seedlings

Автор исследовал инт енсивность корневог о плача, наличный водн ый дефицит семядолей, конечный водный дефи цит семядолей (после 24-часового пребывания растений в среде, насыщенной во дяным паром), сырой вес растений, сухой вес се мядолей и ход завядания (график ? 1) в з ависимости от постеп енного падения почве нной влаги вследствие транспир ации и испарения. Опыт ы проводились в лабор аторных условиях, на сеянцах подсолнеч ника, выращиваемых в п робирках. Предельная капилляр ная влагоемкость исп ользованной почвы со ставляла 29,5% от сухого веса. Точка д лительного завядани я находилась около 8%, т очка конечного (нулевого) дефицита ок оло 9% и точка нулевого корневого плача окол о 13% влажности использованной почв ы. Из приведенных данны х вытекает, что почти ч етвертая часть из общ его количества почвенной влаги межд у точкой длительного завядания и предельн ой капиллярной влагоемкостью почвы оказывается недосту пной для корневого пл ача сеянцев под-солнечника. Сравнивая разные физ иологические индика торы доступности поч венной влаги для сеянцев подсолнечни ка, автор показывает, ч то корневой плач явля ется чувствительным индикатором, примени мым при почвенной вла жности выше точки нул евого корневого плача, когда различии в водном дефиците явл яются относительно н ебольшими.     

Modelling the effect of soil moisture on germination and emergence of wheat and sugar beet with the minimum number of parameters

Soil moisture and temperature, sowing depth and penetration resistance affect the time and percentage of seedling emergence, which are crucial for the simulation of drought‐limited crop production. The aim of this research was to measure the effect of soil water potential on germination and emergence, shoot and root elongation rates (SER and RER) of two different seed/crop types. Sugar beet and durum wheat seeds were sown into two soils (clay and loam), submitted to five matric potentials (?0.01, ?0.1, ?0.2, ?0.4 and ?0.8 MPa) and incubated at constant temperature (25°C) and humidity. Cumulative count analysis was used to estimate parameters of the distribution of germination or emergence times for each box of beet or wheat seeds and to derive estimates for base potentials (ψ_b), hydrothermal times (H) and numbers of viable units. In a second experiment, NaCl solution was used to mimic the soil matric potentials to estimate potential RER and SER. Germination of sugar beet was slightly more sensitive to matric potential than durum wheat (ψ_b of ?1.13 and ?1.23 MPa, respectively). H_(g) was longer for sugar beet than for durum wheat (67 vs 47 MPa °Cd). For emergence ψ_b was similar for both seed types and soils but hydrothermal times (H_(e)) were 40 MPa °Cd higher for sugar beet than for wheat. Emergence was about 20 MPa °Cd earlier in loam than in clay. SER measured in soils were similar for both crops and for durum wheat it agreed with those determined in NaCl solution. RER and SER fell with decreasing osmotic potential to approximately 20% of their maximum values (1.03 mm h^?1 and 0.57 mm h^?1, respectively). Seedling viability decreased with decreasing matric potential and more in clay than in loam soil and more for sugar beet than durum wheat. Seed and soil aggregate size are discussed with respect to the effects of water diffusion and soil–seed contact on germination and emergence modelling.     

Influence of soil heterogeneity on water regime and yields of lucerne,sugar beet and wheat

Lucerne plants in the first crop year as well as plants of spring wheat from different sites of the respective experimental plots showed differences in sap exudation from detopped roots or from stumps of the main shoots, reflecting differences in properties of the soil profile. The differences in sap exudation were observed at a time when the plants did not show any visible differences in water availability. Differences in the water potential deficit of the leaf blades of lucerne plants in the second crop year and of sugar beet plants, related to differences in soil profile properties, were observed in another series of experiments. Sugar beet plants showed a higher physiological lability than lucerne plants. The sites characterized by unfavourable plant-water-relations usually gave lower yields. The coefficients of variability for the yields of lucerne fresh matter from irrigated plots were three times lower than those for yields from plots without irrigation, influenced by soil heterogeneity.     

Effects of boron on nitrogen metabolism and sugar levels of sugar beet

Summary The effects of deficient and toxic levels of boron on various aspects of nitrogen metabolism in sugar beet are studied. Plant analysis shows a nitrate ion accumulation, a decrease in the activity of the nitrate reductase enzyme and a lower molybdenum absorption.The effect of boron levels on the plant and root sugar concentration has also been studied.     

Photosynthesis in sugar beet depends on root growth

Summary Sugar-beet plants, germinated in growth cabinets at 20°C and transplanted into the field after 3 weeks, developed much larger roots than plants grown from seed drilled directly into the soil. At the end of the season, the roots of transplants were 39% greater than from drilled seed—an increase of 14 m tons per hectare. The increased yield was mainly due to a sustained increase in photosynthesis because of the larger sink for carbohydrates provided by plants from the growth cabinets.     

Effects of soil moisture deficits on the water relations of bambara groundnut (Vigna subterranea L. Verdc.)

The components of leaf water potential (_l) and relative watercontent (RWC) were measured for stands of bambara groundnut(Vigna subterranea) exposed to three soil moisture regimes incontrolled-environment glasshouses at the Tropical Crops ResearchUnit, Sutton Bonington Campus. Treatments ranged from fullyirrigated (wet) to no irrigation from 35 days after sowing (DAS)(dry). RWC values varied between 92–96% for the wet treatment,but declined from 93% to 83% in the dry treatment as the seasonprogressed. _l at midday decreased in both the wet and dry treatments,but the seasonal decline was more pronounced in the latter:seasonal minimum values were –1.19 and –2.08 MPa,respectively. Plants in the wet treatment maintained turgor(_p) at about 0.5 MPa throughout the season, whereas values inthe dry treatment approached zero towards the end of the season.There was a linear relationship between _p and _l9 with _p approachingzero at a _l of –2.0 MPa. Mean daily leaf conductance wasconsistently higher in the wet treatment (0.46–0.79 cm^-1)than in the intermediate and dry treatments (0.13–0.48cm s^-1 Conductances in the intermediate and dry treatments weresimilar, and the lower evapotranspirational water losses inthe latter were attributable to its consistently lower leafarea indices (L): L at final harvest was 3.3, 3.3 and 1.9 forthe wet, intermediate and dry treatments. Bambara groundnutwas apparently able to maintain turgor through a combinationof osmotic adjustment, reductions in leaf area index and effectivestomatal regulation of water loss. Key words: Vigna subterranea, water relations, soil moisture     

Effects of beet cryptic virus infection on sugar beet in field trials

The effects of beet cryptic virus (BCV) infection on sugar beet crops were investigated in field trials in 1990. Two sugar beet breeding stock lines were screened for infection by BCV. Seed lots containing different proportions of seed infected with BCV1 & 2 were obtained by crossing the stock lines and used in field trials at five different sites. Five characteristics of the infected plants were assessed. BCV infection appeared to have no significant effects on the sugar beet crop at four locations which suffered from drought stress but significant effects were found at one site where the crop was grown on grade 1 land with good moisture retention properties. Root yield and sugar yield were reduced by up to 17% and 20%, respectively, by BCV infection.     

Effects of mist irrigation on the physiology of sugar beet

Bacilliform particles characteristic of plant rhabdoviruses were found in negatively-stained leaf sap and in thin sections of Laburnum anagyroides in England showing vein yellowing. The particles were detected principally in the perinuclear space of parenchyma cells. They were not transmitted by sap inoculation to twelve herbaceous species. The affected trees also showed mosaic symptoms but there was no evidence of an association between these and the bacilliform particles.     

Studies on the sensitivity of monogerm sugar beet germination to water

Excessive water in the substratum inhibited germination of monogerm sugar beet seed but it was not lethal, and other crop seeds tested were not as sensitive as beet. The inhibition was not evident in a pure oxygen atmosphere and was lessened when the fruit cap was removed. Although bacterial populations on fruits absorbed appreciable quantities of oxygen, differences between populations in optimum and excessive water were insufficient to account for the inhibition. Anatomical observations revealed the presence of a pore through the sclerified fruit wall at the point of attachment to the mother plant. Evidence indicated that the pore was the route for oxygen and water uptake to the seed, and theoretical calculations of gas flux suggested that oxygen supply would be insufficient to sustain germination when the pore was filled with water.     

The growth and development of the storage root of sugar beet

A study was made of the growth of the storage root of sugar beet as a sugar accumulating organ. The storage root grew by simultaneous cell multiplication and expansion from a series of peripheral secondary meristems laid down during the early stages of development. The weight of water and of non-sugar dry matter per cell increased in proportion to the increase in cell volume. The amount of sugar per cell was proportional to cell volume only during the initial stage of cell expansion up to volumes of about 15 times 10^-8 cm³; thereafter it was less proportional. Thus, average cell size is a major determinant of the sugar concentration of the storage root. The implications of this are discussed.     

Effects of soil pH on rhizoctonia damping-off of sugar beet and disease suppression induced by soil amendment with crop residues

Effects of soil pH on damping-off of sugar beet by R. solani (AG2-2) and soil suppressiveness against the disease were studied by comparing disease incidences in pasteurized versus non-pasteurized, infested soils. Soil pH was correlated neither to disease incidence in five soils ranging from pH 4.5 to 7.2 nor to indigenous disease suppressiveness, the difference in disease incidences between non-treated soil and its pasteurized counterpart. When an alkaline soil was acidified with H₂SO₄, disease suppression markedly declined, increasing disease incidence in the non-pasteurized soil. Inversely, disease suppression was enhanced when an acidic soil was neutralized by adding Ca(OH)₂. Soil amendment with dried peanut plant residue suppressed the disease in two pasteurized, near-neutral soils, lowering the incidence to the levels in the non-pasteurized soils, but was less effective in two pasteurized, acidic soils. In vitro mycelial growth of the pathogen and seedling growth was optimal at pH 4.5–5.5 and 6.0–6.5, respectively, and declined as the pH became higher or lower. (Conclusions) These results suggest that the seedlings were inhibited more than the pathogen at low pH, and that indigenous disease suppressiveness through the activity of antagonistic soil microorganisms operates effectively in near-alkaline soils, but is weakened or nullified in acidic soils.     

Transfer of water from roots into dry soil and the effect on wheat water relations and growth

This investigation was performed to study the effect on plant water relations and growth when some of roots grow into dry soil. Common spring water (Triticum aestivum) plants were grown from seed in soil in 1.2 m long PVC (polyvinyl chloride) tubes. Some of the tubes had a PVC partition along their center so that plants developed a split root system (SPR). Part of the roots grew in fully irrigated soil on one side of the partition while the rest of the roots grew into a very dry (-4.1 MPa) soil on the other side of the partition. Split root plants were compared with plants grown from emergence on stored soil moisture (STOR) and with plants that were fully irrigated as needed (IRR). The experiment was duplicated over two temperature regimes (10°/20°C and 15°/25°C, night/day temperatures) in growth chambers. Data were collected on root dry matter distribution, soil moisture status, midday leaf water potential (LWP), leaf relative water content (RWC) and parameters of plant growth and yield.Some roots were found in the dry side of SPR already at 21 DAE (days after emergence) at a soil depth of 15 to 25 cm. Soil water potential around these roots was -0.7 to -1.0 MPa at midday, as compared with the initial value of -4.1 MPa. Therefore, water apparently flowed from the plant into the dry soil, probably during the night. Despite having most of their roots (around 2/3 of the total) in wet soil, SPR plants developed severe plant water stress, even in comparison with STOR plants. Already at 21 DAE, SPR plants had a LWP of -1.5 to -2.0 MPa, while IRR and STOR had a LWP of -0.5 MPa or higher. As a consequence of their greater plant water stress, SPR as compared with IRR plants were lower in tiller number, ear number, shoot dry matter, root dry matter, total biomass, plant height and grain yield and had more epicuticular wax on their leaves.It was concluded that the exposure of a relatively small part of a plant root system to a dry soil may result in a plant-to-soil water potential gradient which may cause severe plant water stress, leading to reduced plant growth and yield.     

Effect of sodium fertiliser on water status and yield of sugar beet

Effects of sodium fertiliser on growth, water status and yield of sugar beet crops were measured in 1974 and 1975. Sodium increased leaf area index early in the growing period, the water content of the leaves and the final yields of root dry matter and sugar in both years. In 1974, it increased leaf relative water content and diffusive conductance under conditions of moderate soil moisture deficit in August but had no effect in June or September when soil moisture deficits were low. There was also no effect in June 1975 but later, when there was a severe drought, sodium decreased leaf water potential. Further evidence of an interaction between sodium and soil moisture on leaf water status was obtained from a reappraisal of results of field experiments made between 1965 and 1976. Sodium increased sugar yield through at least two different physiological mechanisms; it improved interception of radiation by the crop by increasing leaf area early in the season and it improved the efficiency of leaves under conditions of moderate water stress.     

Modelling partitioning between structure and storage in sugar beet: Effects of drought and soil nitrogen

In the UK sugar beet is grown on contrasting soils that vary both in their nutritional status and water-holding capacities. Water shortage and low nitrogen reduce canopy growth and dry matter production, which is compensated in part by an increase in the fraction of assimilates partitioned to storage. Conversely, high nitrogen and ample water encourage growth of the canopy, increase assimilation of carbon dioxide but reduce the proportion of assimilates stored as sugar. This paper sets out to examine simple relationships between sugar yield, total dry matter and soil nitrogen in rain-fed and irrigated sugar beet crops (Beta vulgaris L.) from 46 field experiments spanning 12 years and a range of soil types, in order to improve prediction of sugar yields. Two partitioning functions were fitted to the data. The first represents a useful alternative formulation of the allometric growth function that overcomes some of the difficulties in the interpretation of the parameters. This model adequately described the seasonal progress of sugar yield (Y) in relation to total dry matter (W), but it was difficult to postulate biological mechanisms as to how the parameters should vary in relation to varying soil nitrogen or to drought. The second partitioning function, given by Y = W − (1/k) log(1 + kW), also described the data well, but had the more useful parameter, k, the decay rate of the fraction of assimilates partitioned to structural matter. This was shown to be greater in crops which had experienced significant drought and was inversely proportional to the amount of nitrogen taken up by the crops. Relationships between k and amounts of nitrogen fertilizer applied and/or amounts of residual nitrogen in the soil at sowing, however, were more variable. These could be improved by additionally taking account of soil type and rainfall following nitrogen fertilizer application in late spring. The models are a useful extension to yield forecasting models because they provide a simple means of estimating sugar yield from total dry matter in relation to factors that affect partitioning of assimilates such as drought and soil nitrogen availability. This revised version was published online in June 2006 with corrections to the Cover Date.     

Modelling the effect of varying soil water on root growth dynamics of annual crops

We present a simple framework for modelling root growth and distribution with depth under varying soil water conditions. The framework considers the lateral growth of roots (proliferation) and the vertical extension of roots (root front velocity). The root front velocity is assumed to be constant when the roots descend into an initially wet soil profile. The lateral growth of roots is governed by two factors: (1) the current root mass or root length density at a given depth, and (2) soil water availability at that depth.Under non-limiting soil water conditions, the increase in root mass at any depth is governed by a logistic equation so that the root length density (R _v) cannot exceed the maximum value. The maximumR _v, is assumed to be the same for all depths. Additional dry matter partitioned to roots is initially distributed according to the current root mass at each depth. As the root mass approaches the maximum value, less dry matter is partitioned to that depth.When soil water is limiting, a water deficit factor is introduced to further modify the distribution of root dry matter. It is assumed that the plant is an energy minimiser so that more root mass is partitioned to the wetter regions of the soil where least energy will be expended for root growth. Hence, the model allows for enhanced root growth in areas where soil water is more easily available.Simulation results show that a variety of root distribution patterns can be reproduced due to varying soil water conditions. It has been demonstrated that broad patterns of root distribution reported in the literature can also be simulated by the model.