Hui-lian Xu

Effects of fertigation management on growth and photosynthesis of tomato plants grown in peat, rockwool and NFT

A greenhouse experiment was conducted to determine the effects of substrate, irrigation scheduling and nutrient solution electrical conductivity (EC) on plant growth and photosynthesis of tomato plants. The plants grown in peat-bags were irrigated by a potential evapotranspiration (PET) dependent irrigation system. The first peat-bag treatment (control) was irrigated when the soil water potential reached −5 kPa. EC was fixed at 2.5 dS m−1. EC of other two peat-bag treatments was varied between 1 and 4 dS m−1 with a soil water potential setpoint (SWPS) of either −5 or −9 kPa. Plants grown in rockwool and by the nutrient film technique (NFT) were treated with EC levels of 2.5, 4.0 and 5.5 dS m−1. EC variation resulted in higher photosynthetic capacity (Pc), quantum use efficiency (QUE) and dry matter production (DMP) under high SWPS compared with the control. The increase in DMP resulted mainly from fruit yield increase. In the treatment of EC variation with low SWPS, Pc and DMP were lower than in treatment of EC variation with high SWPS, but not different from that in the treatment of fixed EC. The high EC treatment of 4.0 dS m−1 decreased DMP in NFT, but did not in rockwool. EC of 5.5 dS m−1 decreased fruit yield but did not affect shoot DMP. However, high EC treatments, especially EC of 4 dS m−1, increased Pc as well as QUE in rockwool and in NFT. DMP and Pc was not positively correlated with each other for EC treatment. However, it is concluded that PET-dependent EC variation increases photosynthetic capacity, plant growth and fruit yield of greenhouse tomato plants.

Photosynthetic potential of Thymus vulgaris selections under two light regimes and three soil water levels

Abstract A greenhouse experiment was conducted to measure the effects of two light regimes (LR) (supplemental, SL of 200 μmol m −2 s −1 and natural, NL) and three different soil water levels (SWL) (50, 70 and 90% field capacity) on biomass production, relative growth rate (RGR), net CO 2 assimilation ( Pn ), stomatal ( g s ) and mesophyll ( g m ) conductance, chlorophyll a and b (chl a and chl b ) content and leaf water potential (LWP) on two Thymus vulgaris L. clonal selections. There was a significant increase in total dry matter (DM) production and RGR due to SL and increased SWL. The highest Pn , 24.6 μmol CO 2 m −2 s −1 , was obtained from Selection 1, grown under SL at 70% SWL. The lowest Pn , 6.3 μmol CO 2 m −2 s −1 , was obtained from Selection 2, grown under NL at 50% SWL. Selection 1 had higher Pn , g s and g m than Selection 2 under all growing conditions. Thymus vulgaris leaves developed under SL were more quantum-use efficient than those grown under NL. Total leaf chlorophyll concentration per leaf area basis was significantly ( P ⩽ 0.01) higher in plants grown under SL than NL. The lowest LWP was recorded for Selection 2 grown under SL at 50% SWL.