Responses of Cassia Cenna (L.) and Cassia Italica (Mill.) to Different Levels of Manganese

The purpose of this investigation was to examine the responses of C. senna (L.) and C. italica (Mill.) to different levels of manganese, and to highlight the significant ecological aspects related to the performance of these two plant species in response to manganese additions. The study site selected for this study was the enclosed reserved area at the northern location of the Faculty of Education, University of Khartoum, Sudan (Lat. 15°30/ N ; Long. 32°33/ E). The study was carried out by soil chemical analysis and a soil - culture experiment. The soil samples for chemical analysis were collected randomly from 25 sampling points at the selected site. Seven levels of Mn were used for the growth experiment, together with control, making total of eight treatments. Three replicates corresponding to each treatment were set up for each of the two investigated species. The soil chemical analysis data showed that the investigated site was slightly alkaline (pH = 7.74 ± 0.65) and characterized with high levels of Ca and adequate quantities of Mg, K, and Na. The levels of Mn were low as expected due to the soil alkalinity. The results of the soil - culture experiment showed that the growth of Cassia senna (L.) increased with an increase of manganese concentration from 3 – 6 mg Mn; whereas, that of Cassia italica (Mill.) continued to increase till 9 mg Mn. Beyond these levels a gradual inhibition occurred. The results also showed that the yield of C. italica (Mill.) at each particular Mn-level (except the control) was significantly higher compared to that of C. senna (L.). The increased growth by the two investigated species to manganese additions between 3 - 6 mg Mn for C. senna and 3 – 9 mg Mn for C. italica indicated that manganese was a limiting factor of growth for the two species in their natural habitats. The greater yield of C. italica (Mill.) at high Mn-levels compared to that of C. senna (L.) indicated that C. italica (Mill.) is more tolerant to high levels of manganese concentrations than C. senna (L.).