Revista de Ciencias Agrícolas

Growth-promoting rhizobacteria improve physiological variables in lemon balm, Melissa officinalis L., subjected to water stress

Fri, 30 Aug 2024 00:00:00 +0000

Climate change has caused droughts in regions that previously did not have water issues, affecting the production of medicinal plants grown in small-scale agricultural units. Plants such as lemon balm, Melissa officinalis L., are sensitive to water stress, which reduces their yield. One alternative to mitigate water stress is the use of plant growth-promoting rhizobacteria (PGPR). However, in the high tropics of Colombia, the use of these microorganisms is not common due to a lack of knowledge about how they can improve water absorption and increase the yield of medicinal plants. This study aimed to determine the effect of native PGPR on lemon balm plants subjected to water stress conditions using a completely randomized design with six treatments and four replications. Applications of Bacillus cereus and Bacillus amyloliquefaciens were made, and the plants were subjected to two water levels (field capacity and 50% field capacity). Physiological variables of stomatal conductance, chlorophyll content, and fluorescence were measured at the end of the experiment. Bacillus cereus significantly improved growth parameters such as number of leaves (115.00±34.71), fresh weight of root (5.51±3.07 g) and shoot (8.32±4.27), Bacillus amyloliquefaciens increased stomatal conductance (401.3 μmol H₂O m² s¹) in water-stressed plants. These results suggest that the use of native PGPR considerably improves the growth and development parameters of lemon balm plants and provides a viable alternative for farmers to enhance yield and resistance to water stress conditions.

Effect of fertilization on cacao (Theobroma cacao L) seedlings in the southwest of Colombia.

Tue, 27 Aug 2024 00:00:00 +0000

Inadequate understanding of the meaning of cocoa seedlings fertilization during the nursery stage is a significant problem in the performance and profitability of cacao crops, as it negatively affects cacao yield. Therefore, it is crucial to make adequate fertilization plans and, on the other hand to replenish the nutrients extracted and preserve soil health. This study was conducted to evaluate the effect of different doses of N, P, K, Ca and Mg fertilizers on the growth and development of cocoa (Theobroma cacao L.,) seedlings (FEAR-5), under nursery conditions. A completely randomized design was used, with five treatments and three replications. Treatments were defined according to fertilization recommendations for cocoa seedlings (2 to 6 months old) (i.e., N 2.4g; P 0.6g; K 2.4g; Ca 2.3g; and Mg 1.1g) with this we came up with five treatments based on soil analysis: Treatments: T1= recommended fertilization, T2= based on a soil analysis and the addition of 7 g Ca and 3.2 g Mg; T3= 50% of recommended fertilization; T4= 150% of recommended fertilization; and T5= no fertilizer application. Our results indicate that the plants subjected to T2 showed better performance in the variables plant height, stem diameter, leaf area, number of leaves, leaf area, fresh and dry weight of the stem, fresh and dry weight and total fresh and dry weight of the seedlings. In economic terms, T4 had the highest costs. The highest profitability was recorded by T5, despite the low performance in the physiological variables.

Physiological quality of zucchini seeds is positively affected by postharvest resting periods

Fri, 23 Aug 2024 00:00:00 +0000

In fleshy fruit species such as those of the Cucurbitaceae plant family (e.g., zucchini), the storage or resting after harvest of the fruits enables the seeds to complete their maturation process, reaching maximum levels of germination and vigor. The proper resting period can allow early harvestings, improve the agronomic uses of the area, and reduce seed exposure to weathering and the attack of insects and microorganisms. This study evaluates zucchini seed quality after postharvest resting periods. Zucchini fruits harvested 63 days after transplanting were maintained for 0, 3, 6, 9, or 12 days before seed extraction. The percent of processed seeds (clean and whole seeds), the weight of 100 seeds, germination, first count in germination, germination speed index, electrical conductivity, nitrogen (N), and protein contents were evaluated. Data generally fitted positive linear regression models, increasing the weight of 100 seeds, percent of processed seeds, germination, vigor, seed N, and protein as the resting period after harvest (days) increases. Seed electrical conductivity decreased as days of postharvest rest increased. After the harvest of the zucchini fruits, the resting period positively affected the production of homogeneous and high-quality zucchini seeds.