Biomass repartitioning, tiller regeneration and salt secretion through leaf microhairs for salinity tolerance in guinea grass (Megathyrsus maximus Jacq.)

Abstract

In this study, guinea grass (Megathyrsus maximus Jacq.) genotypes were evaluated in artificially created saline soils for forage yield and to understand the salinity tolerance mechanism in tolerant genotypes. Varieties BG-1, BG-2, DGG¬1, BG-4, CO-1 and Riversdale were planted in control and artificially created 4 ECe, 8 ECe and 12 ECe soils containing NaCI, Na2SO4, MgCl2 and CaSO4 in the ratio of 13:7:1:2, respectively. Varieties CO-1 and Riversdale failed to survive beyond 4 ECe and 8 ECe soils, respectively. DGG-1 followed by BG-4 and BG-2, recorded highest fresh biomass yield among all the genotypes at 12 ECe. Leaf to stem ratio, senescence index and mean productivity index were also highest in DGG-1. Senescence of the older leaves improved regeneration and tiller number in tolerant genotypes. The correlation of senescence index with fresh biomass, regeneration index and tiller number indicated biomass repartitioning influence. Micro hairs present on the leaves secreted salts in BG-4 and DGG-1. An efficient dry matter partitioning, recycling of dry matter from older leaves to photosynthetically active leaves was observed as growth strategy in tolerant genotypes. The tolerance mechanism also included investment in thin roots, salt secretion through micro hairs, storing salts away from photosynthetic organs, replacing Na+ with K+ and secure osmotic adjustment systems.