Leaf morphogenesis and site rilling in the establishment period in three Guinea grass (Panicum maximum) cultivars

In two short term experiments, descriptive data for leaf number per main tiller, leaf appearance rate, leaf final length, leaf elongation rate, tiller number and tiller site filling were collected from three cultivars of Guinea grass (Panicum maximum, Jacq.) Aruana, Momba~a. and Tanzania, recently released by research institutions in Brazil. The first experiment (El) was carried out in a growth cabinet, with a constant temperature of 28"C, humidity around 80%, constant light of 350 JJ.m/m?/s and photoperiod of 24 h, and included three levels of defoliation (50 mm, 200 mm and uncut). The second experiment (E2) was carried out in a glasshouse with temperature between 15 and 25"C and natural day light from mid September to mid December. Measurements spanned the establishment period, until plants were four (El) and three months of age (E2). Cv. Momba~a had a faster leaf elongation rate (77 .2 mm leaf tiller/day) and produced longer leaves (752 mm) than cv. Tanzfuria (73.6 mm leaf tiller/day and 519 mm) and Aruana (67.2 mm leaf tiller/day and 426 mm). Aruana had a higher number of leaves on the main stem after 12 weeks growth (18 and 13.9) than cv. Momba~a (14.8 and 11.9) in El and E2, respectively. Severe defoliation depressed leaf elongation rate, mainly in the first week of regrowth in cv. Momba~a and Tanzfuria. All cultivars had more rapid leaf appearance in El than in E2, and more tillers/plant in the second experiment. The site filling ratio was 0.167 in El and 0.227 in E2. The data presented would be suitable for construction of a modular growth simulation for Guinea grass.