Effects of water stress on growth and photosynthetic system characters of Lycopersicon esculentum L.

The experiment was conducted under two water levels: no stress(75%-80% of field capacity),stress(30%-40% of field capacity).The changes of growth and photosynthetic system characters of tomato were investigated.The results showed that,under the water stress condition,the growth of the plants was inhibited,leaf water potential and leaf relative water content decreased.The total plant dry weight declined significantly and the reduction was 59.36% for Meifen-2 and 51.17% for Hongsheng,respectively.The root/shoot ratio increased 37.93% for Meifen-2 and 29.17% for Hongsheng.The net photosynthesis rate(Pn),stomata conductance(Gs),transpiration rate(Tr),intercellular CO2 concentration(Ci),the actual photosynthesis efficiency of PSⅡ in the light(ΦPSⅡ),the electron transport rate(ETR) and photochemical quenching(qP) decreased whereas the non-photochemical quenching(NPQ) and water use efficiency(WUE) increased.The stomata became smaller and the density decreased,most of them closed.The chloroplasts became round in shape,the lamellae arranged disorderly and the number of starch grain decreased or disappeared.