Emergence of Eight Sorghum Lines Varying in Transpiration Efficiency.

High transpiration efficiency (TE) is important for water conservation in semi-arid regions.  Grain sorghum (Sorghum bicolor L. Moench) is one of the most important crops grown in dry areas.  However, the emergence of sorghum lines selected by breeders for their transpiration efficiency apparently has not been studied.  We germinated eight lines of sorghum (four with low TE and four with high TE) in Petri plates with moistened filter paper.  The four lines with low TE were:  PI257309 (from Argentina), PI295121 (Australia), PI586381 (Cameroons), PI267532 (India).  The four lines with high TE were:  PI567933 (Beijing, China), PI391652 (Shaanxi, China), PI533946 (India), PI584085 (Uganda).  Three days after the seeds were placed on filter paper, radicles had emerged on all seeds.  They then were planted at the 2.5-cm depth, six per pot in 48 pots (23 cm diameter; 25 cm tall) with a commercial potting mix under well watered conditions in a greenhouse.  Emergence was measured on the day the pre-germinated seeds were placed in the pots and Days 1, 2, 5, 9, and 13 after that.  Plants with high TE emerged better than plants with low TE.  By Day 13, an average of four plants with high TE had emerged and an average of three plants with low TE had emerged.  Even though six pre-germinated seeds were placed in each pot, no pot had six seedlings emerge.  The better emergence of high TE plants compared to low TE plants indicated that seeds from high TE plants have a physiological mechanism, as yet unknown, that allows better growth and penetration through the soil than seeds from low TE plants.  More research needs to be done to determine what controls vigor in seeds from high and low TE plants.