title: Root-Zone Warming Differently Benefits Mature and Newly Unfolded Leaves of Cucumis sativus L. Seedlings under Sub-Optimal Temperature Stress.
abstract: Sub-optimal temperature extensively suppresses crop growth during cool-season greenhouse production. Root-zone (RZ) warming is considered an economical option to alleviate crop growth reduction. In this study we cultivated cucumber seedlings in nutrient solution under different air-RZ temperature treatments to investigate the effects of RZ warming on seedling growth- and photosynthesis-related parameters in leaves. The air-RZ temperature treatments included sub-optimal RZ temperature 13°C and sub-optimal air temperature 20/12°C (day/night) (S13), RZ warming at 19°C and sub-optimal air temperature (S19), and RZ warming at 19°C and optimal air temperature 26/18°C (day/night) (O19). In addition, for each air-RZ temperature treatment, half of the seedlings were also treated with 2% (m/m) polyethylene glycol (PEG) dissolved in nutrient solution to distinguish the effect of root-sourced water supply from RZ temperature. At the whole-plant level, S19 significantly increased the relative growth rate (RGR) by approximately 18% compared with S13, although the increase was less than in O19 (50%) due to delayed leaf emergence. S19 alleviated both diffusive and metabolic limitation of photosynthesis in mature leaves compared with S13, resulting in a photosynthetic rate similar to that in O19 leaves. In newly unfolded leaves, S19 significantly promoted leaf area expansion and alleviated stomatal limitation of photosynthesis compared with S13. PEG addition had a limited influence on RGR and leaf photosynthesis, but significantly suppressed new leaf expansion. Thus, our results indicate that under sub-optimal temperature conditions, RZ warming promotes cucumber seedling growth by differently benefiting mature and newly unfolded leaves. In addition, RZ warming enhanced root-sourced water supply, mainly promoting new leaf expansion, rather than photosynthesis.
authors.affiliation: Beijing Key Laboratory of Growth and Developmental Regulation for Protected Vegetable Crops, China Agricultural University, Beijing, China.
authors.forename: Xiaozhuo
authors.initials: X
authors.lastname: Wang
authors.affiliation: Beijing Key Laboratory of Growth and Developmental Regulation for Protected Vegetable Crops, China Agricultural University, Beijing, China.
authors.forename: Weihua
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Beijing Key Laboratory of Growth and Developmental Regulation for Protected Vegetable Crops, China Agricultural University, Beijing, China.
authors.forename: Yanxiu
authors.initials: Y
authors.lastname: Miao
authors.affiliation: Beijing Key Laboratory of Growth and Developmental Regulation for Protected Vegetable Crops, China Agricultural University, Beijing, China.
authors.forename: Lihong
authors.initials: L
authors.lastname: Gao
mesh_terms: D002734:Chlorophyll / Q000378:metabolism; D018553:Cucumis sativus / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D005453:Fluorescence; D008027:Light; D010788:Photosynthesis; D018515:Plant Leaves / Q000502:physiology*; D010940:Plant Proteins / Q000378:metabolism; D018517:Plant Roots / Q000502:physiology*; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism; D013312:Stress, Physiological; D013696:Temperature
chemical_list: D010940:Plant Proteins; D002734:Chlorophyll; D012273:Ribulose-Bisphosphate Carboxylase