Embryo Drying Rates during the Acquisition of Desiccation Tolerance in Maize Seed

Abstract

germination and vigor as maturation progresses. Maize ears harvested from 400 to 500 g H 2 Okg Ϫ1 fw could be Maize (Zea mays L.) seed quality is often reduced because of safely dried down to 120 g H 2 Ok g Ϫ1 fw with temperadrying injury, although the causes and impairment mechanisms are tures around 40ЊC (Kiesselbach, 1939;Washko, 1949; poorly understood. In this study, we investigated changes in embryo McRostie, 1949;Navratil and Burris, 1984), whereas drying rates and their effect on the acquisition of desiccation tolerance in maize seed. Ears of hybrid maize [B73 ϫ (H99 ϫ H95)] were ears harvested at MC Ͻ 2 5 0gH 2 Ok g Ϫ1 fw could be harvested at about 550, 500, 400, and 320 g H 2 Ok g Ϫ1 fresh weight dried at 50ЊC (Navratil and Burris, 1984). Nevertheless, (fw) and subjected to preconditioning (PC) (ear drying at 35؇C and maize ears harvested as early as 30 d after silking and 0.47 m s Ϫ1 airflow rate) for 0, 12, 24, 36, and 48 h before fluidized dried slowly are able to withstand desiccation (Knittle bed (FB) drying (shelled seed, 35؇C and 5.10 m s Ϫ1 airflow rate)and Burris, 1976;Peterson, 1997). This may illustrate treatments to decrease moisture content (MC) to about 130 g H 2 O the importance of drying rate. kg Ϫ1 fw. Additionally, ears were entirely dried under PC (35C) and Maize seed is composed of different tissues, which unheated-air (NH) conditions. At the four harvests, different drying appear to dry at different rates because of their position. rate phases were evident in embryos of seed dried entirely at PC Under field drying conditions, embryo moisture remains (35C) conditions. A slower drying phase coincided with the PC period, about 150 g H 2 Ok g Ϫ1 fw higher than whole seed as it which increased with increasing maturation. Under FB drying, embryo MC declined at a faster rate down to about 400 g H 2 Ok g Ϫ1 fw, drops from 400 to 300 g H 2 Okg Ϫ1 fw. Then, the embryo followed by an intermediate drying rate down to about 200 g H 2 OMC decreases rapidly to equilibrium with whole seed kg Ϫ1 fw, and a slower drying rate below this point. As embryo MC at about 150 g H 2 Okg Ϫ1 fw (Struve, 1958). This phenomdeclined to 400 g H 2 Okg Ϫ1 fw at slower drying rates, either with PC enon has also been reported under artificial drying and or field drying, the ability to withstand the faster drying rates of the preconditioning (slow drying before fast drying) treat-

Seed quality of high protein corn lines in low input and conventional farming systems

“…The higher the values of electrical conductivity, the greater will be the leakage of solutes from the seeds and thus the lower the seed vigor (Halloin, 1986). Poor vigor seeds leak solutes into the surrounding soil (Cordova-Tellez and Burris, 2002b) at planting which modify the microenvironment around the seed increasing their vulnerability to pathogens. A higher electrical conductivity in the adapted inbred checks and the 20 genotypes indicated that the lower seed vigor in the low input system could be associated with environmental factors such as soil fertility, disease, and weed management.…”

Methods for identifying frost injury in immature maize seed

“…The decrease in vigor in control samples of both hybrids may be associated with premature harvest and drying. Cordova-Tellez and Burris (2002) found that at high moisture content (500-550 g H 2 0 kg" 1 fw) some genotypes were sensitive to premature drying even when proper techniques were used. The current study supports this conclusion, and suggests that both B73xlRF311 and Mo17xlRF311 hybrids may be sensitive to drying when harvested above 500 g H 2 0 kg" 1 fw.…”

“…After the freezing cycle was complete the ears were husked and dried in the experimental, forced air dryer until the seed was dry (140-150 g kg" 1 ). Cordova-Tellez and Burris (2002) showed that drying corn seed with 400-450 g kg" 1 at 35°C did not cause damage and in fact mimicked maturation on the parent plant. Ears were shelled and the seed stored at 10°C and 50% relative humidity until RNA extraction.…”

“…One of these mechanisms is the migration of lipid bodies. Lipid bodies migrate to the perimeter of cells during maturation drying (Cordova-Tellez and Burris, 2002;Perdomo and Burris, 1998). In this study, decreased drying damage was associated with alignment of lipid bodies along the plasma membrane.…”

“…The authors hypothesized that water was lost more slowly and in a more organized fashion (Cordova-Tellez and Burris, 2002). Also, the lipid bodies represent a reserve of membrane materials that can be used upon rehydration when the membrane expands.…”