International Water & Irrigation

35 According to previous research, combinations of low temperatures and luminosity coupled with high humidity are liable to prolong the crop cycle, delaying flowering and physiological maturation. The average plant height (PH) of the varieties formed two groups, the first with heights of 1.0 to 1.1 m and the second with heights from 1.2 to 1.4 m. These values are within limits indicated for commercial varieties of sunflower (0.7 to 4.0 m) the photosynthetic process, whose product will be translocated to vegetative organs during the plant growth and reproductive organs. The adaptation of the cultivar to high temperatures, such as those in the Brazilian semiarid, may result in different in number of leaves, since according to previous research the total number of leaves in high-temperature environments is determined by the balance between two conditions. The first condition is the increase in number of leaves due to a high production rate, while the second is the decrease in number of leaves due to the shortleaf production period. The stem diameter (SD) is the parameter that defines the capacity of the plant to bear the capitulum and the resistance to lodging found in the present work for the same cultivars. The number of lodged plants (NLP) of the varieties showed significant differences. The varieties V2, V3, V4, VS, V6, Vl2, Vl3, Vl4 and V2 l showed the highest NLP, which may be related to the stem diameter, since cultivars V2, V4, VS, Vl3, Vl4 and V21 also had small stem diameters, which decrease lodging resistance. According to previous research, the reduction of water availability for a short period is not liable to damage the plant’s cells. Conclusions The conclusion of the trials showed that the V7 and V8 sunflower varieties performed best in all of the tests reaching yields of around 3,000 kilos per hectare while maintaining a consistently low level of lodged and broken plants, making them the most attractive option for sunflower growers in the semiarid conditions found in the particular region. ■ Map of Brazil Table two: Days from sowing to flowering (DSF), plant height (PH), number of live leaves (NLL), stem diameter (SD), capitulum diameter (CD of the 21 sunflower varieties under evaluation Variety DSF PH(m) NLL SD (mm) CD (cm) V1 1.3 29.1 15.8 19.3 1.3 V2 1.0 24.9 11.4 17.1 7.0 V3 1.2 26.8 18.2 17.5 2.8 V4 1.1 24.5 15.2 15.4 4.5 V5 1.0 22.8 13.3 17.3 3.3 V6 1.2 25.6 17.8 18.3 3.0 V7 1.3 27.9 16.4 18.5 0.3 V8 1.3 26.5 19.0 21.3 0.5 V9 1.4 25.0 17.0 22.1 0.3 V10 1.1 22.9 15.3 17.8 0.8 V11 1.3 27.0 17.6 19.1 2.3 V12 1.2 27.0 17.8 18.7 2.8 V13 1.3 27.1 14.9 19.0 4.5 V14 1.0 23.9 13.0 17.9 4.5 V15 1.1 27.0 18.0 21.8 0.0 V16 1.0 23.2 17.5 19.3 1.5 V17 1.1 26.1 22.6 21.6 0.8 V18 1.3 31.1 21.8 19.9 1.0 V19 1.0 24.4 17.0 20.3 2.0 V20 1.1 23.6 16.9 19.9 1.5 V21 1,1 24.4 14.9 20.3 20.3 According to previous research, the reduction of water availability for a short period is not liable to damage the plant’s cells