Tiyung cultivar, the consumer preferences of hot pepper in Magelang Regency, is still low in productivity (7 ton.ha-1). This research aimed to determine the growth and yield of hot pepper planted in relay intercropping as affected by biological agent application as a technology to increase productivity. This research was arranged in a Factorial Randomized Complete Block Design with an intercropping pattern of hot pepper (two and three rows model). The second factor was the application of biological agents, consisting of Trichoderma asperellum, Bacillus velezensis B-27 and Arbuscular Mycorrhizal Fungi (with and without biological agents). The control was the monoculture of hot pepper without biological agent application. The data observed were analyzed using Analysis of Variance and followed by the Duncan's Multiple Range Test at α= 5 %. The results showed that the relay intercropping of hot pepper produced less numbers of branches and leaves.  It indicated more efficiency in the use of assimilates for the development of generative organs, thereby resulting in the high values fruits weight per plant, which were as high as those in monoculture. The productivity observed in relay intercropping was 12.93 ton.ha-1, which was 15.8 % higher than in monoculture. The application of biological agents significantly increased the stomatal density, the size of stomatal opening, the number of leaves, weight of fruits per plant and productivity of hot pepper. The productivity of plant applied with biological agents was 16.84 ton.ha-1, which was 86.50 % higher than that without biological agents application.

High temperature in tropical countries is a significant constraint for potato plant development. It is important to identify the accumulation of excess air temperature between the region with low-temperature and high-temperature during one growing season, as a basis for determining the suitable area for potato plants in a tropical region. Two series of experiments have conducted, the first had carried out in two locations, (1) in the high-temperature area (380 masl) and (2) in the low-temperature area (1360 masl). The second experiment had carried out in a high-temperature area (600 masl). The potato cultivars tested were sensitive to high temperatures. The results of the first experiment showed that the difference between the minimum/maximum air temperature accumulation of one growing season between 1360 masl and 380 masl was 179.49/330.42°C and the decrease in tuber yield reached -76%, resulting in unmarketable potato tuber. The results of the second experiment showed that the difference in the accumulation of minimum/maximum air temperature between 1360 masl and 600 masl was 18.8/188.4°C, which decreasing in tuber yield about -15.2%. This study indicates, the temperature at 600 masl still exceeds the optimum temperature; nonetheless, the quantity and quality of the potato tubers produced were marketable.