Avocado rootstock influences scion leaf mineral content

ABSTRACT

To test the influence of avocado rootstocks on the scion leaf ionome, the nutritional status of avocado cultivars Hass and Ettinger grafted onto 15 rootstocks was compared over 3 years. The rootstocks were of different genetic origins (West Indian or Mexican) and were clonally or reproductively propagated. The trees were grown in a high-density orchard, and were continually fertigated as is common in modern avocado orchards. Leaf mineral composition was analysed and found to be correlated with crop load. ‘Hass’ leaves had significantly higher levels of B, Ca, Mg, Na, P and K than ‘Ettinger’ leaves. Rootstocks of Mexican origin produced higher foliar Cl levels, but lower levels of Mg and Mn. Rootstocks grown from seedlings conferred higher foliar K and lower B, Ca and Mg. The results demonstrate that avocado rootstocks affect the nutritional status of the tree, by a differential mineral transport, which is indicated by the scion leaf ionome.     

Heat tolerance and the effects of shade on the behavior of Simmental bulls on pasture

The objectives were to assess the degree of thermolysis capacity as a characteristic of heat tolerance of the Simmental beef cattle and evaluate the effects of shade and shade type (artificial: AS, trees: TS, or no shade: NS) on daily behavior patterns during summer. Black globe temperature (BGT) was different under the two types of shade (P < 0.05) and was lower under the TS (P < 0.01) and under AS (P > 0.01) than average BGT in the sun. Animals when in AS used more intensely the shade (P = 0.002) mostly lying down under it (10.00–14.00 hours), while time standing was similar (P = 0.107) between TS and NS. Bulls without shade (NS) spent significantly more time at the water trough and most part of the day standing idle (72.4%, 10.1 h/14 h). TS bulls spent more time grazing/standing (P < 0.001). The Simmental bulls that were in TS and AS spent more time ruminating than bulls that stay without shade (NS). The availability of shade changes grazing, rumination and idling behavior of cattle in response to environmental conditions. Shade provided by trees can be more efficient than artificial shading as cattle spent more time grazing when tree shade was available. Thermolysis capacity can be used to select heat‐tolerant animals.     

Tree age effect on fine-root and leaf morphology in a silver birch forest chronosequence

The influence of forest ageing on fine-root morphology and relations between fine-root and leaf characteristics is poorly studied. The aim of this study was to analyse age-driven changes in ectomycorrhizal roots (EcM roots) and leaf morphology in a chronosequence of silver birch (Betula pendula Roth.), which would provide a better understanding of adaptation responses and acclimation capacity of tree roots and leaves. The chronosequence included six age classes (3, 6, 14, 32, 45, and 60 years.). All stands had regenerated naturally and grew in a highly productive Oxalis forest site type in Estonia. Most changes in the morphology of EcM roots and leaves of silver birch occur faster at a young age. The functional parameters—mean specific area of EcM root (SRA) and leaf specific area (SLA) as well as leaf N—decreased with age. EcM root SRA and specific root length (SRL) decreased with stand age as a result of increased mean diameter and tissue density. In age classes of 6, 14, and 32 years, the total number of dominating EcM taxa was 34, and the distribution of four different dominating EcM exploration types (contact-, short-, medium-, long-distance) was similar. We conclude that high values of SRA, SLA, and leaf N measured in young silver birch stands indicate high activity of physiological processes necessary for fast-growing young trees. A decrease of SLA and SRA and N in the chronosequence of fertile stands of silver birch is most probably caused by down-regulation of growth, affecting simultaneously leaves and fine roots.     

Effect of plant development on turbulent fluxes of a screenhouse banana plantation

This study focuses on CO₂ and water vapor flux measurements, water use efficiency estimates and evapotranspiration modeling during the course of growth of a young banana crop in a screenhouse in northern Israel. An eddy covariance system was deployed at the center of the screenhouse during two growth periods of the banana crop: small and large plants. Results show that daily whole canopy evapotranspiration increased during the measurement period from 2.2 mm day^?1 for the smaller plants to 3.4 mm day^?1 for the larger plants. The increase in net daily CO₂ consumption doubled during the same period, from about 11 to 21.5 g m^?2 day^?1 per unit ground area. Water vapor and CO₂ fluxes per unit leaf area were independent of plant size and averaged with 51 and 0.29 g m^?2 day^?1, respectively. Consequently, water use efficiency, defined as the ratio between net vertical fluxes of CO₂ and water vapor, was nearly constant during growth of the plants. Evapotranspiration models provided more accurate predictions for larger than for smaller plants. This was due to inadequate treatment of the partial cover of young plants, which could be overcome by the use of a crop coefficient. A modified Penman–Monteith evapotranspiration model adapted to the screenhouse environment, applied here for the first time to a banana screenhouse, was in better agreement with the measurements than an open canopy model.     

Detection of <Emphasis Type="Italic">Potato virus Y</Emphasis> in industrial quantities of seed potatoes by TaqMan Real Time PCR

Potato (Solanum tuberosum) is the largest crop in Israel. Production is based on the import of seed tubers from Europe for the spring crop. Imported tubers are generally free from virus infection. The most important virus infecting potato is Potato virus Y (PVY), which may cause severe damage to marketable yields. In Israel, tubers from the spring harvest are stored over the summer for planting in the autumn. It is important to be able to determine the infection rate of seed tuber lots from the spring harvest prior to storage. Commonly, infection is measured by sprouting tubers and measuring virus titre in the leaves using ELISA (the “Growing-On test”), which takes at least 6 weeks to give results. There is a need for a faster method to produce results, such as Taqman Real Time PCR (qPCR), for direct analysis of viral infection in tubers at harvest. To use qPCR as a diagnostic tool, it is necessary to demonstrate that both techniques give comparable results on batches of field-grown tubers. Such a comparison was performed on potential seed tuber lots of 14 different cultivars over three Israeli spring harvests (2013–2015). The agreement between the results of the two techniques was not of high statistical significance. However, the qPCR technique can distinguish well, by binary classification, between tuber lots with a low PVY infection rate (<5% by Growing On test; suitable for seed) and those unsuitable for seed (≥5% by Growing On test). Therefore, qPCR is an appropriate technique for determination of the PVY infection rate of seed tuber lots in Israel.     

The dynamics of biomass production in relation to foliar and root traits in a grey alder (Alnus incana (L.) Moench) plantation on abandoned agricultural land

The dynamics of the above-ground biomass production of a greyalder plantation on abandoned farmland was investigated during11 years after establishment. In the 12-year-old stand, thetotal biomass of the above-ground part of the stand was 68.8t dry matter (DM) ha^–1 and the current annual production(CAP) was 14.0 t DM ha^–1 year^–1. The predicted meanannual increment (MAI) reached is maximum at the age of 16 years,which indicates bulk maturity (the stand age when CAI = MAI)and appropriate rotation time for obtaining maximum biomassproduction. In the case of short-rotation forestry, initialstand density should not be higher than 6500–6000 treesper hectare. Below-ground biomass accounted for 18 and 16 percent of total stand biomass at a stand age of 5 and 10 years,respectively. The biomass of the nodules was estimated at 155± 63 kg DM ha^–1 and the biomass of the fine rootswas estimated at 870 ± 130 kg DM ha^–1 in the 10-year-oldgrey alder stand. Of the fine roots, 80 per cent and almostall nodules were located in the upper 0–20 cm soil layerin both the 5-year-old and the 10-year-old stand. The valueof leaf area index increased with stand age, ranging between1.38 and 5.43 m² m^–2 during the development of the stand.Specific leaf area varied in different years from 11.1 to 13.5m² kg^–1.     

Evaluating water stress in irrigated olives: correlation of soil water status,tree water status,and thermal imagery

Irrigation of olive orchards is challenged to optimize both yields and oil quality. Best management practices for olive irrigation will likely depend on the ability to maintain mild to moderate levels of water stress during at least some parts of the growing season. We examined a number of soil, plant and remote sensing parameters for evaluating water stress in bearing olive (var. Barnea) trees in Israel. The trees were irrigated with five water application treatments (30, 50, 75, 100 and 125% of potential evapotranspiration) and the measurements of soil water content and potential, mid-day stem water potential, and stomatal resistance were taken. Remote thermal images of individual trees were used to alternatively measure average canopy temperature and to calculate the tree’s crop water stress index (CWSI), testing empirical and analytical approaches. A strong non-linear response showing similar trends and behavior was evident in soil and plant water status measurements as well as in the CWSI, with decreasing rates of change at the higher irrigation application levels. No statistically significant difference was found between the analytical and the empirical CWSI, suggesting that the relative simplicity of the analytical method would make it preferable in practical applications.     

Effect of leaching events on the fate of polyhalite nutrient minerals used for crop fertilization

Abstract

Polyhalite is a natural mineral containing potassium (K), calcium (Ca), magnesium (Mg) and sulfur (S) and is proposed as a fertilizer source for these essential nutrients. Application of polyhalite is expected to be most relevant in soils where the availability of these nutrients is low: in sandy soils, in highly leached soils, or in areas where crops are irrigated by water with low content of these nutrients or are rain-fed. A controlled lysimeter experiment investigated the efficacy of surface applied polyhalite as a fertilizer supplying K, Ca, Mg and S compared to soluble sulfate salts in two soils (sandy and loamy) with or without simulated rain leaching events through two cycles of cropping. In the first cycle, carrot response and nutrient uptake, transport, and loss through leaching were studied, while in the second cycle the residual effect of the fertilizer was considered on maize without additional fertilizer application or leaching. Polyhalite plus rain led to increased carrot yield due to augmented Ca uptake in sandy soil. In both soils, polyhalite behaved as a prolonged availability fertilizer with more nutrients retained in the top soil layer and not leached below the root zone. The treatments did not affect maize growth or nutrient uptake except for lower K and S uptake in soils where rain had been simulated for the previous crop. We conclude that polyhalite shows potential as a commercial fertilizer to supply K, Ca, Mg, and S nutrients under conditions of dryland agriculture where occasionally leaching by rainfall occurs.