No abstract

No abstract

The development of sorghum [Sorghum bicolor (L.) Moench] is influenced by genes that control sensitivity to photoperiod, and their interaction with photoperiod and temperature. While temperature influences development throughout the life cycle of plants, photoperiod influences the vegetative stage (from seedling emergence to panicle initiation). In order to simulate plant development, it is essential to know when sorghum plants first become sensitive to photoperiod, and how long that photoperiod sensitivity persists. Ten cultivars with different levels of photoperiod sensitivity were grown in pots under natural climatic conditions both in short days (SD: 8 h day-1) and long days (LD: 17 h d-l). Plants were transferred at different times after seedling emergence from SD to LD and vice versa. The time to panicle initiation (PI) for each transfer treatment was detemfined. In cultivars that remained continuously in SD, the time to PI varied from 16 to 27 d, whereas, in continuous LD it varied from 22 to 37 d. The cultivars started reacting to photoperiod 4-9 d after seedling emergence. After sensing photoperiod stimuli, inductive effects among cultivars persisted for 4-14 d in SD, and for 15-33 d in LD depending on their intrinsic photoperiod sensitivity. The sensitivity ended 2-5 d before panicle initiation. This interval, between completion of the photoperiod-inductive phase and the actual observation of PI under the microscope, represents the time required for the photoperiod-inductive stimulus to promote sufficient cell division and growth at the shoot apex for the morphological change to become visible as a shiny globular structure, We conclude that photoperiod sensitivity in these sorghum cultivars ends shortly before or at the PI stage. Our results support the assumptions followed in several crop simulation models that sorghum remains photoperiod-sensitive until the completion of the vegetative stage.

In arcas of thc \cnl~-arid tropics ~h t l r c sorghum 1 5 gro\$n. d l o~~g h l at some \trtge of crop g r o~t h 1s cjl'ten the main f'actol-ciius~ng low y 1eld5. I o address t h~s pruhlcm. the International Crops Kcscarcli In5t1tutc l i~r the Scnii-.Arid Troptcs (1C'RIS.AT) has Initiated a rewarch prograrnnie to s t~i d y the broadcr

No abstract

No abstract

No abstract

No abstract