|Stiller, W - CSIRO-ACRI|
|Constable, G - CSIRO-ACRI|
|Farquhar, G - AUSTRALIAN NATIONAL UNIV|
Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: July 15, 1999
Publication Date: N/A
Technical Abstract: Two cotton (Gossypium hirsutum L.) cultivars, Cascot 014 (early) and Siokra L23 (late), were grown under irrigated and rainfed conditions. Uppermost, fully expanded leaves were sampled for stable C isotope discrimination (CID) and nitrogen concentration (N) about every two weeks, beginning at first square (44 DAP). Because of unusually high rainfall in January, final yield did not differ between water treatments. Leaf CID values declined across the first three sampling dates, then increased and exceeded the initial values. Leaf N and CID were associated negatively across sampling dates in both irrigated (r2=0.47) and rainfed (r2=0.60) plants, suggesting seasonal changes in photosynthetic capacity may influence leaf CID. The cultivar x date interaction was not significant for CID (P>0.07). In four of eight sampling dates, we detected small (0.2-0.5 per mil) but significantly lower CID in Siokra L23 than Cascot 014. The present study found genetic variation for CID in cotton between first square and early bloom, and will present data for leaf water-use efficiency in these two cultivars.