IDENTIFICATION OF SOME ROOTSTOCKS FOR WATERMELON CULTURES FROM ROMANIA

Among the grafting aims are (1) to enhance plant growth, fruit yield and quality; (2) to control wilt caused by pathogens; (3) to reduce viral, fungal and bacterial infection; (4) to strengthen tolerance to thermal or saline stress; (5) to increase nutrient and mineral uptake to the shoot. The cultivars used to obtain of grafted seedlings were from the Baronesa F1 (Citrullus lanatus) hybrid scion and the Pelops F1 (Lagenaria siceraria), Kiwano (Cucumis metuliferus) and Zefir (Benicasa hispida) rootstocks. The rootstock has influenced the number of fruits per plant, weight/fruit and production/plant; the Pelops rootstock has had a positive influence and the Kiwano and Zefir rootstocks have had a negative influence compared to the non-grafted variant. The Pelops rootstock (105.84 t/ha) has had a positive influence and the Kiwano rootstock (53.45 t/ha) and Zefir rootstock (51.38 t/ha) have had have a negative influence compared to the non-grafted variant (95.5 t/ha). The biometric measurements on watermelon fruit yield were made in 2020 year. The experience aimed the identification of some rootstocks for the watermelon cultures from Romania. The research shows that the rootstocks has influenced fruit yield and some grafting combinations researched may be recommended for cropping in Romania.

Salinity stress effects on the growth, morphological, physiological, and biochemical properties of Melia (Melia dubia Cav.) plant

Salinity stress severely affects the growth, physiological and developmental processes in plant species. Melia dubia is an ecologically and economically important tree species of the Indian subcontinent. However, systematic information with respect to the species salt tolerance potential is completely lacking. Under salt stress conditions, determining suitable soil EC range is required for the better survival, growth and productivity of the tree species. In present study, we investigated the effects of different soil salinity (EC 4, 8, and 12) levels on the ion homeostasis, physio-biochemistry, morphology, and growth of M. dubia plant. Results revealed that increase in soil salinity causes higher Na+ content and Na+/K+ ratio, while lower K+ content, in the leaf tissues of M. dubia. The physiological processes such as the photosynthetic rate, stomatal conductance, internal CO2 concentration, and transpiration rate were adversely affected with the increased salt stress levels. Morphological parameters, such as internodal length, petiole length, leaf length, and leaf width also decreased (P<0.05) under saline stress conditions. Results further indicated that salinity levels significantly (P<0.05) affected the M. dubia growth, and the growth rate was found optimum upto 8 EC, thereafter it slightly decreased with the increased salt stress to 12 EC. Our findings showed that increased salinity stress causes significant changes in the physiological, morphological, and growth pattern of M. dubia. Therefore, based on present experiment, we found M. dubia suitable for the salt affected soils of EC 8 with optimum growth rate and at EC 12 with the moderate (20–25%) growth reduction.

Photosynthesis of Physalis peruviana under different densities of photons and saline stress

Physalis peruviana L. is a solanacea that has been gaining prominence due to its fruits presenting good acceptance in the national and international market. However, several abiotic factors, such as salinity, can cause physiological disturbances in plants, and these changes may be of greater or lesser intent according to species. Therefore, the objective of the present work was to evaluate the physiological behavior of P. peruviana submitted to different fluxes of photosynthetically active photons (PPFD) and saline stress. The experimental design was a randomized block design with three saline levels (ECw) (0.5, 2.75 and 5.00 dS m-1) with four replications. Gas exchange measurements were performed with a portable infrared gas analyzer. Liquid CO2 assimilation, stomatal conductance, internal CO2 concentration, water use efficiency and instantaneous carboxylation efficiency were measured. Data were subjected to analysis of variance by F test and in cases of significance applied to regression analysis. The increase in PPFD provided reductions in stomatal conductance up to the density of approximately 400 μmol m-2s-1, being more pronounced in ECw of 2.75 and 5.0 dS m-1. The maximum CO2 assimilation rates in the three salinities are different according to the PPFD. The salinity of irrigation water reduced the quantum efficiency of photosynthesis in P. peruviana plants.

Plant substrate as a vehicle for trituration: a pilot study

Motivation: Lactose and hydroalcoholic solutions are not the proper substances to study the High Dilution (HD) effects using plant models. Plant substrate can not be considered an inert vehicle, but it is not harmful to plants. Aim: In this pilot study we verify the possibility to use plant substrate as a trituration vehicle to prepare substances to be used in plants. Methods: We used a partially dried commercial plant substrate (12% humidity) as the vehicle to prepare a set of trituration, having NaCl as the initial active substance. Triturations were performed using a ball mill, with a mass dilution rate of 1:18 (set A) and 1:100 (set B), up to the 7th trituration, that is, each set contained 8 groups: A0 to A7 and B0 to B7. For each group, the triturated substrate was mixed with a fresh one in a mass ratio of 1:1. After homogenization, 18 seeds of radish (Raphanus sativus) were sown in plastic trays (31 ml cell), for each group and kept in a green house exposed to natural thermal and light variations. After 4 weeks we determine the germination rate and number of mature cotyledon. Then 5 plants from each group were selected at random to determine the following parameters: averaged leaf area, length, fresh and dry mass and pigments amount (chlorophyll a and b, carotenes). Results: Groups A0 and B0 (higher saline concentration) showed those typical effects of saline stress: lower germination ratio, immature cotyledons, smaller and shorter leaves, higher water content and less pigments. All the others groups showed similar results, for all parameters, except pigments amount. The chlorophyll to carotene ratio (CCr) showed an unexpected but interesting behavior (figure 1).Both sets showed an initial CCr growing (as expected due the saline ratio decrease), but followed by an unexpected decrement. Set B (the higher mass dilution rate, 1:100) showed a slower change, compared to set A. When we sort the results in order of saline amount we observe two peaks (figure 2), indicating that this behavior can not be explained by the saline stress.Conclusions: Trituration using plant substrate as vehicle can be suitable to assess HD effects in plant models. In this pilot study we observed unusual results regarding to the expected saline stress due the saline concentration.

PGPB Improve Photosynthetic Activity and Tolerance to Oxidative Stress in Brassica napus Grown on Salinized Soils

Soil salinization, one of the most common causes of soil degradation, negatively affects plant growth, reproduction, and yield in plants. Saline conditions elicit some physiological changes to cope with the imposed osmotic and oxidative stresses. Inoculation of plants with some bacterial species that stimulate their growth, i.e., plant growth-promoting bacteria (PGPB), may help plants to counteract saline stress, thus improving the plant’s fitness. This manuscript reports the effects of the inoculation of a salt-sensitive cultivar of Brassica napus (canola) with five different PGPB species (separately), i.e., Azospirillum brasilense, Arthrobacter globiformis, Burkholderia ambifaria, Herbaspirillum seropedicae, and Pseudomonas sp. on plant salt stress physiological responses. The seeds were sown in saline soil (8 dS/m) and inoculated with bacterial suspensions. Seedlings were grown to the phenological stage of rosetta, when morphological and physiological features were determined. In the presence of the above-mentioned PGPB, salt exposed canola plants grew better than non-inoculated controls. The water loss was reduced in inoculated plants under saline conditions, due to a low level of membrane damage and the enhanced synthesis of the osmolyte proline, the latter depending on the bacterial strain inoculated. The reduction in membrane damage was also due to the increased antioxidant activity (i.e., higher amount of phenolic compounds, enhanced superoxide dismutase, and ascorbate peroxidase activities) in salt-stressed and inoculated Brassica napus. Furthermore, the salt-stressed and inoculated plants did not show detrimental effects to their photosynthetic apparatus, i.e., higher efficiency of PSII and low energy dissipation by heat for photosynthesis were detected. The improvement of the response to salt stress provided by PGPB paves the way to further use of PGPB as inoculants of plants grown in saline soils.

Effective Categorization of Tolerance to Salt Stress through Clustering Prunus Rootstocks According to Their Physiological Performances

The effects of climate change on traditional stone fruit producing areas, together with the generation of new varieties with lower chilling requirements that allow the cultivation of previously unexplored areas, are setting up a challenging scenario for the establishment of productive orchards that must be more efficient in their capacity to adapt to new edaphoclimatic conditions. In this context, the rootstock breeding programs are a key piece in the agronomic strategy to achieve this adaptation through the development of rootstocks compatible with the new varieties and capable of transferring their tolerance to stress. An effective categorization of phenotypes within the germplasm involved in a plant breeding program is of utmost importance. Through the measurement of physiological parameters in both roots and leaves, tolerance to saline stress (120 mM NaCl) was evaluated in seven Prunus rootstocks whose genetic background included representatives of the subgenera Prunus, Cerasus, and Amygdalus. To group the genotypes according to their physiological performance under salt stress, an agglomerative hierarchical clustering was applied. The genotypes were grouped into three clusters containing rootstocks very sensitive (‘Mazzard F12/1’), moderately tolerant (‘Maxma 60’, ‘Cab6P’ and ‘AGAF 0204-09’), and tolerant (‘Mariana 2624’, ‘Garnem’ and ‘Colt’) to salt stress. ‘Mariana 2624’, a plum-based rootstock, was identified as the most tolerant Prunus rootstock. The information reported is valuable both in the productive context, for the selection of the most appropriate rootstocks to establish an orchard, and in the context of plant breeding programs, when choosing parents with outstanding traits to obtain progenies tolerant to salt stress.