Impact of phloem girdling on water status in desert plants Alhagi sparsifolia Shap. (Fabaceae) and Karelinia Caspica (Pall.) Less. (Asteraceae)
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Girdling
Stomatal Conductance
Leaf photosynthesis and related traits at 4 growth stages of 8 peanut varieties difference in yield potential were studied using Li-6400 portable photosynthesis system.No significant difference in photosynthesis rate(Pn)was found among the 7 varieties with high yield potential,although their yield difference may be more than 10%,while one variety,Isgv-9,an Indian origin,had lower yield potential and significantly lower leaf Pn.The highest Pn occurred at the last second or third fully expended leaf and at pod enlarging stage(52 days after planting,DAP).Leaf stomata conductance(Cond)and intercellular CO 2 concentration(Ci)were found to be higly correlated with Pn,and low night temperature and decrease of Cond and Ci is responsible for the low Pn in late growth stage(88 DAP).Leaf petiole girdling by hot water resulted in immediate dropdown of Pn,Cond and transpiration rate(Trmmol)but sharp increase of Ci,indicating a stimulated respiration.It is concluded that,for the peanut varieties with high yield potential,leaf Pn coordinates well with the growth conditions and Pn is not a limiting factor for further increase of yield.
Petiole (insect anatomy)
Stomatal Conductance
Girdling
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In order to study the effects of altered source-sink correlation on leaf photosynthetic characteristics at fruit fast development stages in Shatangju tangerine,fruit thinning and retaining fruit were carried out on one-year-old shoot,and through preventing exportation of the assimilates to the non experimental parts of the tree by girdling one-year-old shoot and keeping the sane leaves between fruit thinning and retaining fruit,and the photosynthetic characteristic was analyzed.The results showed that: Fruit thinning significantly decreased net photosynthetic rate(Pn),stomatal conductance(Gs) and transpiration rate(Tr),while no significant different of substomatal CO2(Ci),Ls and WUE.The alter of source-sink correlation did not impact the curve of the diurnal change in the Pn,they were all showed a typical bimodal curve,the first and the second peak occurredat 8:00 and 14:00 respectively,and no midday depression phenomenon of photosynthesis occurred.
Thinning
Sink (geography)
Stomatal Conductance
Girdling
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The presence of strong sinks of photoassimilates is thought to stimulate photosynthesis by minimizing photosynthetic end product accumulation in leaves. This hypothesis was examined in soybeans (Glycine max [L] Merr.) with treatments designed to alter the phloem translocation of photoassimilates out of source leaves. Pod removal and petiole girdling resulted in 70 and 90% reductions, respectively, in leaf CO(2) exchange rate. Reductions of similar magnitude also were observed in stomatal diffusive conductivity.Time course data showed that CO(2) exchange rates as well as stomatal conductivities were significantly reduced 0.5 hour after girdling and 5 hours after pod removal, thus suggesting that stomatal closure was the cause of the reduced rates of photosynthesis.Mesophyll conductivities to CO(2), calculated from gas exchange data, were not affected by the treatments. Radiocarbon assimilation rates by leaf slices floated in KH(14)CO(3) solutions were not reduced by pod removal and were reduced only 10% by girdling. It was concluded that treatments which block or slow translocation from source leaves reduce their photosynthetic rate by inducing stomatal closure.
Girdling
Petiole (insect anatomy)
Closure (psychology)
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Effects of 0(CK),150,300 and 450 mg·L-1 nano-SiO2 on daily change(from 7:00 to 16:00) of photosynthetic characteristic parameters including net photosynthetic rate,stomatal conductance,transpiration rate,intercellular CO2 concentration,stomatal limitation value and water use efficiency of Indocalamus barbatus McClure leaves were researched by foliar spraying method.The results show that all daily change curves of net photosynthetic rate,stomatal conductance,transpiration rate and stomatal limitation value are double type and have obvious midday depression phenomenon,while those of intercellular CO2 concentration and water use efficiency are W type and U type,respectively.Compared to the control,spraying 150,300 and 450 mg·L-1 nano-SiO2 can increase net photosynthetic rate,stomatal conductance and transpiration rate with different degrees,decrease change range of stomatal limitation value and intercellular CO2 concentration,improve water use efficiency at midday depression and relieve midday depression phenomenon of photosynthesis.In which,the effect of 300 mg·L-1 nano-SiO2 treatment group is the best,net photosynthetic rate,stomatal conductance and transpiration rate of this group increase by 13.98%,71.21% and 49.09% respectively to the control at 10:00 of appearing maximum peak value,and all of them have significant differences to the control(P0.05).The comprehensive analysis results show that the improvement of photosynthetic capacity of I.barbatus is caused by interaction of stomatal and non-stomatal limitation factors,while spraying appropriate amount of nano-SiO2 can improve non-stomatal limitation factor to a certain extent,thus can enhance photosynthetic capacity of I.barbatus leaves.: nano-SiO2;Indocalamus barbatus McClure;photosynthetic characteristic parameter;daily change
Stomatal Conductance
Water Use Efficiency
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Abstract Apple ( Pyrus malus L.) seedlings or rooted layers growing in nutrient solution in the greenhouse were used to determine the role of xylem and phloem in the accumulation of Ca in the leaves. 45 calcium accumulation increased with increasing rates of transpiration as measured by water losses. Girdling experiments demonstrated that the phloem was the primary route of translocation. Young leaves accumulated more 45 ca than old leaves even though the water losses for plants bearing only young leaves or only old leaves were similar. 45 calcium accumulation in mature leaves was decreased when the shoot tips were removed. Apparently, in young apple trees Ca moves primarily in the phloem, but leaks into the xylem at increasing reates in the younger stem and near the growing apex.
Girdling
Transpiration stream
Malus
Apex (geometry)
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The studies on parameters of photosynthetic physiology and yield were carried on maize hybrid Shen Dan 16 at different levels of N,P and K fertilizer.It is shown that there was a significantly positive relationship between the net photosynthetic rate(Pn)and transpiration rate(Tr) and stomatal conductance(Gs) of summer maize under N,P and K fertilizer.Especially,It is optimal under treatment of OPT.The rate of increase of net photosynthetic rate(Pn),stomatal conductance(Gs) and transpiration rate(Tr) in treatment of OPT-P/2,OPT+P/2,OPT-K,OPT-N,OPT-P are decreased gradually comapared to CK.However,it is not obvious that phosphate fertilizer impact to net photosynthetic rate(Pn),stomatal conductance(Gs) and transpiration rate(Tr).The highest grain yield of corn,12 777.0 kg/hm2 is obatined in best teatement of OPT fertilization,significant increased 31.6% comapred to CK. Interaction of NPK fertilizers based on treatment OPT were positive on the corn yield.And it is optimal under OPT treatment especially.
Stomatal Conductance
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Girdling
Stomatal Conductance
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Abstract The effects of two liquid modifiers (polyacrylate compound modifier and organic polymer compound modifier) and phloem girdling (stem girdling and branch girdling) on cadmium (Cd) content, Cd transport, and photosynthetic parameters of cotton (Xinluzao 60) in Cd-contaminated soil (40 mg kg −1 ) were studied through barrel experiment. The results showed that the distribution ratios of Cd in stem, leaves, and bolls, leaf net photosynthetic rate ( Pn ), leaf stomatal conductance ( Gs ), leaf transpiration rate ( Tr ), and chlorophyll content were decreased after girdling; and the application of modifiers reduced the Cd content and the Cd transported to the shoot, while alleviating photosynthetic damage caused by girdling. In general, our results indicated that the inhibition of carbohydrate supply caused by girdling reduced the photosynthetic capacity of cotton, while the applications of the two liquid modifiers decrease the influence to cotton photosynthesis. Moreover, Cd and modifiers may be transported to the shoot through both phloem and xylem.
Girdling
Stomatal Conductance
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The gas exchange rates of C3-and C4-grass leaves at low and high vapor pressure difference (VPD) conditions were measured and demonstrated the effects of anatomical and morphological features of the leaves, i.e. stomatal frequency and size and interveinal distance (IVD), on gas exchange characteristics.When the photosynthesis type was ignored, there was a positive correlation between stomatal frequency and stomatal conductance.However, there was less significant correlation between stomatal frequency and transpiration rate when plotted species within the same photosynthetic pathway.There was a negative correlation between stomatal frequency and net photosynthetic rate, suggesting that CO2 diffusion process from ambient to intercellular space was not much affected by the stomatal morphology, instead that a consequence of biochemical differences in photosynthetic characteristics of the mesophyll was more important.An increase in IVD significantly decreased net photosynthetic rate and water use efficiency (WUE).In addition to the regulation of CO2 concentrating mechanism in Kranz cells of the C4 subtypes, a rapid translocation of photosynthate from bundle sheath cells to the phloem in grasses with C4-MS type (NADP-ME) may contribute to maintain their high performances in photosynthesis and WUE through shorter IVD.
Stomatal Conductance
Water Use Efficiency
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The photosynthetic characteristics of one-year-old diploid and tetraploid Paulownia australis leaves were determined by Li-6400 portable photosynthesis system.The results indicated that tetraploid Paulownia australis had the same photosynthetic rule as diploid Paulownia australis;but the net photosynthetic rate(Pn),stomatal conductance(Gs),transpiration rate(Tr) and intracellular CO2 concentration(Ci) of the former were higher than those of the latter in various months.The diurnal variations in the Pn,Gs and Tr of both diploid and tetraploid Paulownia australis showed single-peak curve in May,July,September and October,but those were bimodal in June and August.The change in Ci revealed a single-valley curve.
Paulownia
Stomatal Conductance
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