Temperature Effects on Seedling Development of Perennial Warm‐Season Forage Grasses1

Abstract

Field establishment of warm‐season perennial forage grasses tends to be difficult due to slow growth and low competitiveness of seedlings. Understanding environmental influences, especially temperature, on seedling development will be helpful in developing and interpreting management practices. We conducted growth chamber studies to evaluate seedling development of Caucasian bluestem (CB) [Bothriochloa caucasica (Trin.) C.E. Hubb.], a native strain of big bluestem (BB) [Andropogon gerardi Vitman), strain IG‐2C‐F1 of indiangrass (IG) [Sorghastrum nutans (L.) Nash], and ‘Cave‐in‐rock’ switchgrass (SG) (Panicum virgatum L.). Crabgrass (CG) [Digitaria sanguinalis (L.) Scop.], an annual weed, was used as a comparison species. Photosynthetic photon flux density was 550 μmol m−2s−1 for 14 h day−1. Relative humidity was near 70%. Seedling growth of all species at 20°C was reduced dramatically when compared with that at 25 and 30°C. Crabgrass developed faster than perennial species, exhibiting the shortest phyllochron (time interval between successive collared leaves) and fastest tillering rate index, leading to the highest leaf number and leaf area. Further, CG initiated permanent roots earlier and faster than did perennial species. Among perennials, SG had the highest leaf elongation rate (LER) and fastest development of permanent roots. Caucasian bluestem had a low LER, but had the fastest phyllochron and the highest tillering rate index, thus developing the largest number of leaves and the fastest leaf area development index among perennials. Switchgrass and CB developed more leaf area and accumulated more dry matter than other perennials over the 28‐day period. Indiangrass emerged rapidly, developed primary and permanent roots earlier than did other perennials, but developed leaf area slowly. Based on a relative index of BB, IG had higher relative total dry matter at early stages than did other perennials. Indiangrass and BB partitioned a greater percentage of dry matter to roots than did SG and CG at early stages. Growth of permanent roots and leaves were both associated closely with total dry matter accumulation. Generally, averaged across temperatures, seedling weight at 28 days was ranked from highest to lowest as CG, SG, CB, IG, and BB, but growth patterns associated with seedling development were markedly different among species. Management practices based on growth responses need to be considered.