Effect of the Matric Potential on Growth and Water, Nitrate and Potassium Absorption of Vegetables under Soilless Culture

To exploit the full potential of plants, it is essential to provide an adequate water balance during critical growth stages. With knowledge of the substrate’s matric potential, it is possible to realistically measure the amount of water available to the plant. The objective of this research is to study the effect of the matric potential of the substrate on the growth of beans, lettuce, sweet peppers, watermelon, and cauliflower plants. The research goal was to evaluate the effect of the matric potential on the main fertigation parameters of horticultural plants. The plants were cultivated at the University of Almería (Spain) in a controlled chamber in a pot with 250 mL of coconut fiber substrate from block propagation. For treatments T15, T30, T45, and T60, new irrigation was applied when easily available water (EAW) depletion levels of 15, 30, 45, and 60% were reached, respectively. The efficiency of the use of water (WUE), nitrate (NUE), and potassium (KUE) was measured. From T15 to T60, a significant effect was found for the absorption of water, nitrate and potassium, WUE, NUE, and KUE. T60 reduced the plant growth by half. The largest growth was between 15 and 30% of the level of use of EAW. Two different models were constructed according to each plant. It is possible to have a small depletion in the available water and still have plant growth, if there is a balance between the air and water needs of the substrate.

HARA STATUS OF POTASSIUM Absorption IN PRODUCING PALM OIL PLANT IN PERLABIAN VILLAGE, KAMPUNG RAKYAT DISTRICT, LABUHANBATU SELATAN DISTRICT

Potassium is a macro nutrient that can affect the quality and quantity of oil palm bunches as well as resistance to disease and drought stress. So far, testing the status of potassium nutrient uptake in people's plantations in Perlabian Village, Kampung Rakyat Labuhanbatu Selatan District has never been carried out. Fertilization and maintenance are carried out through knowledge from generation to generation, so it is important to have a study on the nutrient uptake status of potassium in oil palm leaves. This research was conducted using a free grid survey method at the semi-detailed survey level with a density of 100 meters. A total of 6 leaf samples were taken on the 17th leaf midrib and then rubbed with 70% alcohol and then put into the plastic sample for further testing in the laboratory of PT. Socfindo. The results showed that the potassium in leaf samples 1, 3 and 4 experienced deficiency and leaf samples 2, 5 and 6 were at the optimum. In oil palm plantations in smallholder plantations in Perlabian Village, Kampung Rakyat Subdistrict, it shows that the total K content of leaves is included in the optimum category.

Effects of potassium fertilizer on dry matter accumulation and potassium absorption characteristics of maize (Zea mays L.) inbred lines with different yield types

In this experiment, 20 different maize inbred lines were used as basic materials, which were divided into high-yield type, middle-yield type and low-yield type by yield cluster analysis. A 3-year long-term positioning field experiment (2016–2018) was carried out to assess the effects of potassium fertilizer on dry matter, potassium absorption and potassium absorption efficiency of maize inbred lines with different yield types. The results showed that the dry matter, potassium absorption and potassium absorption efficiency of leaf, stem, bract, rachis and grain of maize inbred lines have been significantly increased with potassium application in comparison with no potassium application. Potassium fertilizer could improve the dry matter accumulation capacity and potassium absorption characteristics of maize, promote the potassium absorption by maize plants, influence the growth and development of maize, and then improve the maize yield. The decrease of dry matter, potassium absorption and potassium absorption efficiency of high-yield maize inbred lines was smaller under low potassium stress. The high-yield maize inbred lines had stronger ability to maintain higher dry matter accumulation and potassium absorption characteristics under low potassium stress. The study provided a theoretical basis for the breeding of potassium-efficient maize materials.

LBT transmission spectroscopy of HAT-P-12b

The hot sub-Saturn-mass exoplanet HAT-P-12b is an ideal target for transmission spectroscopy because of its inflated radius. We observed one transit of the planet with the multi-object double spectrograph (MODS) on the Large Binocular Telescope (LBT) with the binocular mode and obtained an atmosphere transmission spectrum with a wavelength coverage of ~0.4–0.9 μm. The spectrum is relatively flat and does not show any significant sodium or potassium absorption features. Our result is consistent with the revised Hubble Space Telescope (HST) transmission spectrum of a previous work, except that the HST result indicates a tentative detection of potassium. The potassium discrepancy could be the result of statistical fluctuation of the HST dataset. We fit the planetary transmission spectrum with an extensive grid of cloudy models and confirm the presence of high-altitude clouds in the planetary atmosphere. The fit was performed on the combined LBT and HST spectrum, which has an overall wavelength range of 0.4–1.6 μm. The LBT/MODS spectrograph has unique advantages in transmission spectroscopy observations because it can cover a wide wavelength range with a single exposure and acquire two sets of independent spectra simultaneously.

The potassium absorption on HD189733b and HD209458b

ABSTRACT In this work, we investigate the potassium excess absorption around 7699 Å of the exoplanets HD189733b and HD209458b. For this purpose, we used high-spectral resolution transit observations acquired with the 2 × 8.4 m Large Binocular Telescope (LBT) and the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI). For a bandwidth of 0.8 Å, we present a detection >7σ with an absorption level of 0.18 per cent for HD189733b. Applying the same analysis to HD209458b, we can set 3σ upper limit of 0.09 per cent, even though we do not detect a K-excess absorption. The investigation suggests that the K feature is less present in the atmosphere of HD209458b than in the one of HD189733b. This comparison confirms previous claims that the atmospheres of these two planets must have fundamentally different properties.

Deciphering the atmosphere of HAT-P-12b: solving discrepant results

Context. Two independent investigations of the atmosphere of the hot Jupiter HAT-P-12b by two different groups resulted in discrepant solutions. Using broad-band photometry from the ground, one study found a flat and featureless transmission spectrum that was interpreted as gray absorption by dense cloud coverage. The second study made use of Hubble Space Telescope (HST) observations and found Rayleigh scattering at optical wavelengths caused by haze. Aims. The main purpose of this work is to determine the source of this inconsistency and provide feedback to prevent similar discrepancies in future analyses of other exoplanetary atmospheres. Methods. We studied the observed discrepancy via two methods. With further broad-band observations in the optical wavelength regions, we strengthened the previous measurements in precision, and with a homogeneous reanalysis of the published data, we were able to assess the systematic errors and the independent analyses of the two different groups. Results. Repeating the analysis steps of both works, we found that deviating values for the orbital parameters are the reason for the aforementioned discrepancy. Our work showed a degeneracy of the planetary spectral slope with these parameters. In a homogeneous reanalysis of all data, the two literature data sets and the new observations converge to a consistent transmission spectrum, showing a low-amplitude spectral slope and a tentative detection of potassium absorption.