Influence of water deficit and canopy senescence pattern on Helianthus annuus [L.] root functionality during the grain - filling phase

Root system size and functionality during the grain-filling phase are critical for water uptake and grain yield realization. In spite of its potential importance, root system functionality during this phase has received little attention. The study reported here aimed at documenting root system functionality dynamics between anthesis and physiological maturity, and its responses to water deficit, in two sunflower [Helianthus annuus L.] hybrids of contrasting intrinsic patterns of canopy senescence. In experiments repeated in two separate years, crops of the hybrids Aguará 6 [stay green [SG]] and CF 101 [fast dry down [FDD]] were exposed to two levels of soil water availability [irrigation and drought] during grain filling, and the temporal dynamics of root and crop system variables [live root length density [LRLD], root respiration, sap flow rate, green leaf area index [GLAI] and the percentage of live roots [LR percent ]] were followed. The highest values for all variables were observed close to anthesis, and these differed little or not at all between hybrids within water regimes; but decreased thereafter at rates that differed between hybrids, water supply treatment and response variable. Drought hastened the beginning of root and leaf senescence in of both hybrids. The start of the decline in GLAI in the SG hybrid was significantly [p less than 0.05] delayed with respect to that of the FDD hybrid under both water regimes, so that the SG hybrid maintained a significantly [p less than 0.05] greater canopy area for the duration of the experiments under both water regimes. The SG hybrid also exhibited significantly [p less than 0.05] higher values of LRLD, and root respiration, as well as significantly [p less than 0.05] lower rates of LR percent decrease under both water treatments. On days of high evaporative demand the SG hybrid showed significantly [p less than 0.05] greater rates of sap flow under both water regimes. These response patterns were consistent across the 2 years of experimentation. Importantly, when the dynamics of all measured variables were contrasted, it was found that root senescence preceded canopy senescence. We conclude that the SG syndrome in sunflower is associated with improved root functionality during grain filling under both irrigation and drought conditions.

Bibliographic Details

Main Authors:	Lisanti, Sebastián, Hall, Antonio Juan, Chimenti, Claudio Alejandro
Format:	Texto biblioteca
Language:	eng
Subjects:	CANOPY SENESCENCE, DROUGHT, ROOT FUNCTIONALITY, SUNFLOWER, GROWTH RESPONSE, MATURATION, ROOT SYSTEM, SENESCENCE, WATER SUPPLY, WATER TREATMENT, WATER UPTAKE,
Online Access:	http://ceiba.agro.uba.ar/cgi-bin/koha/opac-detail.pl?biblionumber=46878
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