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Vetiver is widespread in saline areas. Only a few studies have reported that they are sufficiently tolerant of salt. The primary mechanism of salt tolerance in vetiver is still not known with certainty. This study aims to determine salinity's effect on early growth of vetiver (Vetiveria zizanioides L.) seedlings. This research was conducted in a greenhouse, Faculty of Agriculture, Universitas Sumatera Utara, Medan. This study used a non-factorial randomized block design (RBD), namely the salinity stress (S) which consisted of 3 levels: EC salinity levels of 0 (distilled water), 4 dsm-1 and 8 dsm-1. The salinity stress treatment showed a significant effect of reducing the growth parameters of plant height, leaf area, chlorophyll a and chlorophyll b. Salinity stress treatment gave significantly better effect in conditions without salinity stress.

Vetiver root is a commodity that is tolerant enough to be planted in salty soils with a certain level of salinity. One approach to increase oxidative stress tolerance that will increase the enzyme substrate at the cellular level is ascorbic acid. The purpose of this study was to increase students' knowledge about how the response of vetiver seed (Vetiveria zizanioides) growth in salt soils to ascorbic acid through practical field learning in plant physiology courses. This research was conducted using a factorial randomized block design (RBD), the first factor was the salinity (S), namely S0: 0 dsm-1 and S1: 4 dsm-1. The second factor was ascorbic acid (A), namely A0: without treatment, A1: 50 ppm, A2: 100 ppm and A3: 150 ppm. There were 8 treatment combinations that were repeated 3 times resulting in 24 experimental units. The parameters observed were plant height, number of leaves and number of stomata. In this study, ascorbic acid had a significant effect on plant height, number of leaves and number of stomata. Saline soil had a significant effect on the number of stomata parameters. No interactions for all parameters were observed.

In order to alleviate the deleterious effects of salinity, different types of phytohormones have been used. Among them, GA3 has been the main focus of some plant scientists. This study aimed to evaluate the effect of gibberellic acid and salinity on growth and production of roselle (Hibiscus sabdariffa L). This research was conducted in a greenhouse of Agriculture Faculty, University of Sumatera Utara, Medan. The study used utterly randomized design with two factors. The first factor was gibberellic acids. They were gibberellic acid (5 mg L-1) and no gibberellic acid. The second factor was salinity. They were 0 dsm-1 and 4-5 dsm-1. The interaction between gibberellic acid and salinity acid indicated a significant effect on the percentage of germination, chlorophyll a and b and beta-carotene. The application of giberellic acid helped in the tolerance of plants to salinity. Thus, application of GA3 become essential to improve overall productivity in salinity.

This experiment has an object to study the response of four potato cultivars to paclobutrazol and paranet shade application in medium plain. Land height is about 700 m about sea level and experimental design in use is Split-Split Plot Design. Three factors used as treatment in this experiment are paranet shade of without shade (0%), shade of 30%, and 50%, four cultivars potato (Granola, Atlantic, Spunta, dan Raja) and regulator, Paclobutrazol (0 ppm, 50 ppm, and 100 ppm). The result shows interaction between paranet shade, cultivar, and paclobutrazol are affecting to height of plants. Interaction between paranet shade and paclobutrazol is affecting to tuber amount. Cultivar Atlantic with 50% paranet shade without application paclobutrazol shows tallest plants that is 69,33 cm and the shortest is 33,83 cm at cultivar raja without paranet shade and application paclobutrazol 100 ppm. The results of this research proved that the growth of potato affects by cultivar, paranet shade, and paclobutrazol application. The best observed plant height of potato was Atlantic cultivar attempted with 50% density of shade without paclobutrazol application. Moreover, Atlantic cultivar showed higher Leaf Surface Area Index (LAI) and Net Assimilation Rate (NAR) value. Otherwise, the best yield was showed by Granola cultivar, so Granola can be counted as adaptable cultivar in medium plain.