Abstract
Seven sugarcane (Saccharum sp.) commercial cultivars, viz., UT-94-2-483, LK92-11, K84-200, K97-32, K95-84, K88-92 and K 92-80, originally derived from meristem cuttings were subjected to simulated osmotic stress (as 200 mM mannitol) under controlled environmental conditions. Proline content in the leaf tissues of all cultivars except K92-80, increased in plants subjected to mannitol-induced osmotic stress. Chlorophyll a (Chl(a)), chlorophyll b (Chl(b)), total chlorophyll (TC), maximum quantum yield of PSII (F-v/F-m), and photon yield of PSII (Phi(PSII)) of all seven cultivars decreased under osmotic stress resulting in a reduction in net-photosynthetic rate (P-n). A positive correlation was found between F-v/F-m and Phi(PSII), proline content and non-photochemical quenching (NPQ), Phi(PSII) and P-n, and P-n and plant dry weight in the sugarcane cultivars. Based upon Ward's multivariate cluster analyses of data for proline content, photosynthetic capacity, chlorophyll fluorescence, and growth inhibition, three cultivars (K88-92, K92-80 and UT-94-2-483) were identified as water deficit sensitive, whereas four (K84-200, K95-84, K97-32 and LK92-11) as water deficit tolerant. These observations on different cultivar's sensitivity/tolerance were confirmed by growth and yield attributes measured in a field trial. The plant dry weight (in vitro) correlated positively with total stalk weight of sugarcane cultivars
