An anatomical study of tissues involved with carbohydrate import into developing caryopsis endosperm in three cultivars of sorghum [Sorghum bicolor (L.) Moench] was complemented by determination of the assimilate concentration of placental sac fluids to investigate the role of the placental sac. Individual panicles were tagged daily at anthesis. Caryopses were harvested from anthesis to maturity and from 10 to 20 days postanthesis at 5‐day intervals for microscopic examination and placental sac fluid carbohydrate analysis. Formation of endosperm tissue by 5 days postanthesis coincided with differentiation of transfer cells within the outer surface of endosperm tissue adjacent to the placental region. All caryopsis tissues thought to be associated with carbohydrate movement to the endosperm (vascular tissue, chalazal tissue, remnant nucellar tissue, the placental sac, and aleurone transfer cells) were present in the cultivars by 10 days postanthesis. The role of the placental sac as an apoplastic sink for hexose import into the endosperm was supported by anatomical location and high glucose and fructose concentrations relative to sucrose concentrations in placental sac fluids of all cultivars at 10,15, and 20 days postanthesis. A model for hexose import into the endosperm following vascular unloading in sorghum was developed based on prior findings for maize (Zea mays L.). Results indicate that the placental sac provides an intermediate apoplastic sink for assimilate accumulation from placental tissues and subsequent hexose import by transfer cells of the endosperm.

Nonsenescence and sweet culms are being incorporated into cultivars of grain sorghum [Sorghum blcolor (L.) Moench.] for potential improvement in yield. Clarification of carbohydrate production and accumulation patterns within the culm during grain filling is needed for guidance in breeding. Data on culm carbohydrate levels are also needed to evaluate blomass for possible energy uses. A senescent, hybrid, cultivar designated 37 and three non senescent, hybrid, cultlvars designated PS, 65, and 6R were harvested at three stages of maturity: (i) 15 days post anthesls (PA), (il) black layer (BL), and 15 days post black layer (PBL). Panicles on some plants within each replicate were also removed at BL Glucose, fructose, sucrose, and starch concentrations were determined on the culms. Culm and total plant weight, kernel weight, and grain per panicle were also measured. Culm glucose levels at PA were 90.5, 48.1, 39.5, and 12.6 mg/g oven dry weight (ODW), respectively, for PS, 6R, 65, and 37. Glucose levels declined at each successive harvest except in cultivar 65. A similar pattern was obtained for fructose at PA with values of 78.8, 44.2, 43.7, and 21.1 mg/g ODW for the same cultivar sequence. Levels of sucrose decreased from PA to BL by 66.8 and 21.9 mg/g ODW, respectively, for P5 and 65, and then increased to 124.6 and 173.3 mg/g. Sucrose increased in 6R at each maturity stage and a significant increase to 303 mg/g ODW was obtained in PBL. Slight increases of sucrose occurred in 37 during the successive maturing stages. Starch levels increased at all stages in 6R, but declined from PA to BL in PS, 65, and 37, then increased by PBL. Weight/100 kernels was 2.86, 2.80, 2.17, and 1.91g at PBL, and grain weight/panicle was 66.7, 66.5, 55.3, and 48.2g, respectively for PS, 65, 6R, and 37. These results suggest that sweet culms do not reduce grain weights. Culm sugar accumulation patterns differed among cultivars. Patterns exhibited by P5 and 65 appeared to be desirable for grain production and possibly as biomass for energy use since the culms continued to fill with sugar after BL. The nonsenescing cultlvars contained significantly more carbohydrates at all maturity stages than the senescing one. Plants with panicles removed at BL had accumulated more culm carbohydrates at PBL than reported above in most cases.

Several selections of bermudagrass and other turfgrass species were evaluated for turf quality characteristics under different levels of light intensity. Light levels of approximately 35, 60, and 100% and 25, 35, and 100% of incident light, respectively, were used in two independent studies. A variety of bermudagrass, ‘No‐Mow (FB‐137)’, exhibited exceptional tolerance to low light intensity. Turf quality of No‐Mow was better when grown under reduced light than when exposed to full sunlight. No‐Mow also exhibited more shade tolerance than Common St. Augustinegrass. Bermudagrass selection T‐135 showed some tolerance to shading but less than No‐Mow. Other grasses, including Pensacola bahiagrass, Meyer zoysia, and two additional varieties of bermudagrass, generally were unsatisfactory.

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