Tuber sink modifies photosynthetic response in potato under water stress

Citation
Ps. Basu et al., Tuber sink modifies photosynthetic response in potato under water stress, ENVIR EXP B, 42(1), 1999, pp. 25-39
Citations number
28
Categorie Soggetti
Plant Sciences
Journal title
ENVIRONMENTAL AND EXPERIMENTAL BOTANY
ISSN journal
00988472 → ACNP
Volume
42
Issue
1
Year of publication
1999
Pages
25 - 39
Database
ISI
SICI code
0098-8472(199908)42:1<25:TSMPRI>2.0.ZU;2-V
Abstract
Source-sink relations were studied by tuber detachment in potato (Solanum t uberosum cv. Kufri Sindhuri) under irrigated and drought conditions. Within 6 h of tuber detachment from irrigated plants (leaf water potential, psi(w ), -0.2 MPa), light saturated rates of net photosynthesis (P-max) declined from 22 mu mol CO2 m(-2) s(-1) to a value close to zero along with a parall el decline in the stomatal conductance (g(s)). After 5 days of tuber excisi on, P-max partially recovered to 7 mu mol CO2 m(-2) s(-1) whereas g(s) reco vered fully to pre-excision level. At this stage, plants with excised tuber s were subjected to water stress along with plants having tubers. After PO days of stress (psi(w) - 0.8 MPa), P-max declined severely from 7 mu mol CO 2 m(-2) s(-1) to almost zero in plants without tubers, whereas only 30% red uction in P-max was observed in plants with tubers. Irrespective of the pre sence or absence of drought, plants with excised tubers showed a high accum ulation of leaf carbohydrates (sucrose and hexose), increased acid-invertas e activity and low sucrose-phosphate synthase activity compared with plants having tubers. Under low sink activity (tuber removed), high levels of lea f carbohydrates with decreased sink demand caused a down-regulation of P-ma x or complete inhibition under water stress. This could be due to feedback inhibition of photosynthesis. On the other hand, the presence of a strong t uber sink led to a lower level of leaf carbohydrates, thus avoiding feedbac k inhibition of photosynthesis under drought. Stressed plants without tuber s showed an irreversible decrease in the quantum yield of photosystem II (F -v/F-m), indicating photoinhibition when exposed to high irradiance. Intera ction between the presence or absence of tubers and drought stress was high ly significant (P < 0.01). The results suggest a dominant role of the tuber sink in avoiding feedback inhibition of photosynthesis. (C) 1999 Elsevier Science B.V. All rights reserved.