Effects Of Root Zone Temperature Research Articles

Effects of Root Zone Temperature and N-K Nutrition on the Growth, Flower and Pod Abscissions, Pod Production and Mineral Contents of Bush Snap Bean.

Bush snap bean cv. Torukatto was used to investigate the effects of root zone temperatures (RZTs) and N-K levels on the growth, abscissions of flowers and pods, pod production and mineral contents. The effects of RZTs were more pronounced than N-K supply on the vegetative as well as reproductive performance in this cultivar. RZTs at 20, 25 and 30°C enhanced plant growth while 35°C RZT reduced it producing plants with less vegetative growth of vine, greener leaves and smaller leaf area. Moreover, photosynthetic activity tended to increase with an increase in RZT up to 30°C in combination with either of the N-K levels. Higher number of pods was obtained from plants grown with 20, 25 and 30°C RZT. Increased total-N, Ca and Mg contents were observed in leaf blades while P was higher in the pods and K was similar in both organs. The results suggest that maintaining the root zone temperature within the range of 20 to 30°C may act more effective for growth performance regardless of N-K supply in the nutrient solution. High RZT of 35°C has an adverse effect on root growth that can lead to the death of root tissues.

Applications in sustainable production

Low root temperature has previously been reported to induce boron (B) deficiency in some species but the mechanism is not entirely clear. Using B‐specific resin to buffer B concentrations in solution, we found that decreasing root zone temperature (RZT) from 27 to 12°C for 6 days depressed sunflower (Helianthus annuus L.) dry matter, root length, root to shoot ratio and B uptake. Boron uptake into the shoots was depressed at 12°C RZT to a greater relative extent than dry matter. Furthermore, B partitioning to young leaves decreased with low RZT, particularly at 12°C RZT. The external B requirement for shoot growth increased with low RZT. Leaf functioning was impaired by low B supply as measured by K+ leakage from the youngest mature leaf blade, whereas it was much less affected by RZT, and there was no effect of RZT on B ‐ adequate plants. By contrast, root function was impaired more by low RZT than low B. Therefore, we predict that higher rates of B application will be required for plant growth when soil temperature is below a critical threshold, which for sunflower was about 17°C. Conversely, practices which increase soil temperature above the threshold may also improve plant B nutrition.

Root water flow and growth of aspen (Populus tremuloides) at low root temperatures.

Effects of root zone temperature on growth, shoot water relations, and root water flow were studied in 1-year-old aspen (Populus tremuloides Michx.) seedlings. Seedlings were grown in solution culture and exposed to day/night air temperatures of 22/16 degrees C and solution culture temperatures of 5, 10, or 20 degrees C for 28 days after bud flush. Compared with root growth at 20 degrees C, root growth was completely inhibited at 5 degrees C and inhibited by 97% at 10 degrees C. The 5 and 10 degrees C treatments severely reduced shoot growth, leaf size, and total leaf area. Root water flow was inhibited by the 5 and 10 degrees C treatments. However, when seedlings were grown for 28 days at 5 degrees C and root water flow was measured at 20 degrees C, there was an increase in flow rate. This increase in root water flow was similar in magnitude to the decrease in root water flow observed when seedlings were grown for 28 days at 20 degrees C and root water flow was measured at 5 degrees C. Reduced root water flow of seedlings grown at 5 and 10 degrees C resulted in decreased stomatal conductance, net assimilation, and shoot water potentials. Root water flow was positively correlated with leaf size, total leaf area, shoot length, and new root growth. Transferring seedlings from 5 to 20 degrees C for 24 h significantly increased root water flow, shoot water potential, and net photosynthesis, whereas transferring seedlings from 10 to 20 degrees C resulted in only a slightly increased shoot water potential. Transferring seedlings from 20 to 5 degrees C greatly reduced root water flow, stomatal conductance, and net photosynthesis, whereas shoot water potential decreased only slightly.

327 High Root-zone Temperature Effects on Floral Initiation in `Allstar' June-bearing Strawberry

Temperature, as a potential environmental stressor, interacts with photoperiod in floral initiation of June-bearing strawberries (Fragaria ×ananassa), such that high-temperature exposure can result in poor floral initiation. Our objectives were to examine the effects of various durations of high root-zone temperature on floral initiation and development and on vegetative growth and development. In a 1998 greenhouse experiment, hydroponically grown `Allstar' June-bearing strawberry plants were subjected day/night temperatures of 31/21 °C in the root zone for one, two, or three continuous periods (of ≈7 days), followed by exposure to 17 °C for the duration of the experiment. Control plants were raised at 17 °C in the root zone throughout the experiment. An additional temperature treatment was exposure to 31/21 °C in the root zone for two periods, each followed by a period at 17 °C. Plants were arranged in a randomized complete-block design with factorial treatments of duration of high root-zone temperature and harvest time. At the end of each period, plants were harvested and the apical meristems dissected for microscopic evaluation of vegetative and floral meristems and the stage of development of the primary flower. We observed floral initiation in all treatments after photoperiodic induction. However, exposure to 31/21 °C in the root zone during key periods of floral initiation in June-bearing strawberry may alter floral development.

Effects of root-zone temperature on nitrogen accumulation by non-bearing apple trees

SummaryNon-bearing, potted, apple plants were subjected to root temperature of 8.6.1(LRT) or 23.6.18C (HRT) and irrigated with 100 ml of water containing 20 mg of N as NH4NO3, in which both ammonium and nitrate-N fractions were enriched in 15N (10 atom%). The root system of each plant was pressurized (325 kPa) at day 1, 2, 4, and 8 after15 N application to evaluate the transport of nitrogen derived from fertilizer (NDFF) through the xylem. This technique was used to investigate N absorption. LRT reduced the rate of N uptake the day after 15N application relative to HRT. Two, 4 and 8.d after fertilization, the rate of exudation and consequently the uptake rate was similar for LRT and HRT. The total amount of N removed by plants after 8.d was not affected by root treatments. Carbon dioxide assimilation, transpiration rate and stomatal conductance were lower for trees subjected to LRT during the time course of the experiment. We suggest that the delay in N absorption was related mostly to the lower activity of root nitrate reductase detected at the lower root temperature, which increased the nitrate xylem sap concentration and diminished the rate of N uptake.

Effect of Root-zone Temperature on Strawberry Growth and Development

Root-zone temperature (RZT) effects were studied to determine physiological changes on whole-plant and microscopic levels of strawberry (Fragaria ×ananassa) growth and development. A greenhouse experiment was conducted in 1997 with `Tristar' day-neutral strawberry using a randomized complete-block design with three RZT treatments (23, 29, and 35 °C) and four replications. The total number of flowers was less in plants subjected to 35 °C. Total weight of fruit yield was highest at 29 °C and least at 23 °C, due possibly to later fruit development. Fresh weight was highest in plants grown at 23 and 29 °C. Dry weight analysis showed that root and leaf growth were inhibited at 35 °C. Throughout the duration of the experiment, transpiration rates were lower in plants subjected to 35 °C. In general, plants grown under RZT of 29 °C had more optimal vegetative and reproductive growth than those grown under 23 and 35 °C.

Responses of Scots pine seedlings to low root zone temperature in spring

The effects of root zone temperature (RZT) on growth, gas exchange, H+‐ATPase (EC 3.6.1.3; PM‐ATPase) activity and fatty acid composition of plasma membrane (PM) phospholipids in the roots of one‐year‐old seedlings of Scots pine (Pinus sylvestris L.) were studied for 10 days during flushing in spring. Nursery‐grown seedlings were transferred to cold storage (−5°C) in mid‐October, thawn in a cold room at 5°C in May, and transferred to hydroponic cultures at an air and root zone temperature of 5°C for a 3‐day adjustment period. The experiment started when the RZT was changed to either 5, 12 or 20°C and the air temperature was increased to 20/15°C (day/night). RZTs of 5 and 12°C were suboptimal for root growth, and also shoot growth was suppressed at 5°C. The degree and rate of phospholipid fatty acid saturation in the PM of roots was highest at RZT of 20°C and intermediate at 12°C, while no change in the degree of saturation occurred at 5°C. PM‐ATPase activities, measured at 5 and 12°C (real activities) were severely temperature‐limited, but the increasing potential activities (measured at 38°C) at these RZTs indicated delayed deacclimation of the root system. At RZT 20°C, the decline of C18:2/C16:0 ratio in combination with decreasing potential and real PM‐ATPase activities indicated, instead, fast deacclimation of the root system. Net photosynthesis of the seedlings was limited by non‐stomatal factors at the beginning of the experiment, but recovered from winter inhibition and later became limited by low stomatal conductance at RZTs of 5 and 12°C. Instead, at 20°C the net photosynthesis increased with increasing stomatal conductance during the experiment. We conclude that low RZT suppresses growth of roots and such changes in the PM as are needed for efficient uptake of water and nutrients. This, in turn, limits net photosynthesis and, thus, the availability of photosynthates for root growth in spring. On the other hand, a rise in RZT can rapidly induce the structural and functional changes in PM of the roots that are needed for the efficient gas exchange and growth of the Scots pine seedlings.

Effect of increasing root‐zone temperature on growth and nutrient uptake by ‘gold star’ muskmelon plants1

Growth response of plants to root‐zone temperature (RZT) varies with species. We studied the effects of RZT on muskmelons (Cucumis melo L. ‘Gold Star') held continuously at 25°, 30°, 35°, 40°, and 45°C in a nutrient solution bath for 12 days. Muskmelon seedling sizes used were the first and fourth leaf growth stages. Large seedling size growth rate was approximately double that of the small size. Plant fresh weight gain for large plants was highest at the 25°C RZT, while for small plants fresh weight gain was similar from 25 to 35°C. But dry weight gain was similar for both plant sizes from 25 to 35°C. Root‐zone temperatures >35°C resulted in a sharp linear decrease in fresh weight, dry weight, and leaf number. Shoot elemental phosphorus (P), zinc (Zn), and manganese (Mn) content and concentration followed the same pattern as growth. Root P and Zn concentration increased linearly with increasing RZT, but Mn concentration reached a maximum at 35°C. The RZT threshold for optimum muskmelon seedling growth seems to be 35 to 36°C.

Root Zone Temperature and Calcium Effects on Phosphorus, Sulfur, and Micronutrients in Winter Wheat Forage

AbstractAn understanding of how environmental factors can alter accumulation of nutrients by plants is needed to anticipate and prevent mineral deficiencies in both plants and grazing animals. To determine the effects of root zone temperature (RZT) and Ca level on mineral concentrations of winter wheat (Triticum aestivum L.), ‘Centurk’ seedlings were grown under three RZT regimes (constant 8°C, constant 16°C, and transferral from 8°C after 23 d to 16°C) and four Ca levels (0.2, 0.6, 2.0, and 5.0 mM) in nutrient solution. Plants grown at 8°C RZT had significantly lower shoot and root concentrations and unit absorption rates of P, S, Cu, Zn, and Mn than did those grown at 16°C. Within 2 wk after transfer from 8°C to 16°C RZT, concentrations of P, S, Cu, Zn, and Mn in shoots and roots increased significantly. Increasing Ca levels in solution significantly increased shoot and root concentrations and unit absorption rates of P and Cu. In contrast, increasing Ca levels significantly decreased concentrations and unit absorption rates of Mn and Zn. Thus, a suboptimal RZT could depress accumulation of P, S, Cu, Zn, and Mn by winter wheat forage, and possibly induce mineral deficiencies in both plants and grazing animals. A high solution Ca level could partially ameliorate this adverse effect on P and Cu accumulation by wheat, but it also could exacerbate the problem of low Mn and Zn concentrations at a cool RZT.

Effects of Root Zone Temperature on the Kinetics of Nitrogen Uptake of Non-bearing Apple Trees

Low root-zone temperature is one of the potential causes of low rate of plant nutrient uptake in spring. In this period, fruit trees are frequently supplied with nitrogen and a delay in root absorption could lead to an increase of nitrate leaching. In this study we assessed the effect of low root temperature on kinetic of nitrogen absorption of apple trees. One-year-old rooted cuttings of `Mark' apple rootstocks were subjected to two root temperature: 8 ± 1°C (LT) and 23 ± 1°C (HT). Four days after treatment imposition, the potted plants were supplied with 20 mg of N as NH4N03, enriched with 10 atom% of 15N. One, 2, 4, and 8 days after fertilization, tree root system was inserted into a Sholander bomb where a 0.325-Mpa pressure was applied to collect the xylem sap from the stem cross section. The sap exudation rate was always depressed by low root temperature. Nitrogen flow through the xylem vessel was highest in HT plants the day after fertilization (10-fold higher than LT), then decreased constantly. In LT plants, N flow was low the first and the second day after fertilization then reached the maximum 4 days after fertilization, when it was significantly higher than in HT plants. The amount of fertilizer-N found in leaves reflected the different movement rate of N observed in the two treatments. In HT trees fertilizer-N reached a plateau 2 days after fertilization, while in LT it linearly increased over time. This results suggest that root zone temperature of 8°C, although causes a delay (2–4 days) in nitrogen uptake, does not represent a serious limiting factor for N nutrition of tested apple trees.

Effects of root zone temperature on aluminium toxicity in two cultivars of spring wheat with different resistance to aluminium

Effects of root zone temperature on aluminium toxicity in two cultivars of spring wheat with different resistance to aluminium

Effects of root zone temperature on aluminium toxicity in two cultivars of spring wheat with different resistance to aluminium

Manifestations of aluminium (Al) toxicity in two cultivars of wheat (Triticum aestivum L. cvs Kadett [relatively Al‐resistant] and WW 20299 [relatively Al‐sensitive]) were investigated at two root zone temperatures (RZT) that may occur in the field. The plants were grown for 9 days at 10 or 25°C RZT. Mineral nutrients other than CaSO4 were supplied daily in exponentially increasing amounts to meet the demand of the plants. Al was added as Al2(SO4)3 at the beginning of the culture period at concentrations ranging from 0 to 100 μM. pH was kept constant at 4.1. Experimental data were analysed for interactions between Al and RZT on a fresh weight basis by the nonlinear Weibull function. Cultivar Kadett, when grown at 25°C RZT, was more resistant to Al than when grown at 10°C RZT. Cultivar WW 20299 was equally sensitive to Al at 10 and 25°C RZT but generally more sensitive to Al than cv. Kadett. It is suggested that cv. Kadett, in contrast to cv. WW 20299, possesses a mechanism for Al resistance that is less effective at 10°C than at 25°C RZT and therefore may be metabolically dependent. In roots, the concentrations of K, P, Mg and Ca were not negatively affected by Al or by RZT. In shoots of both cultivars the concentrations of Ca and Mg became comparatively low when the plants were treated with Al or at low RZT, the effect being larger for Ca than for Mg. At 10°C RZT under Al stress, the Ca concentrations in shoots approached the critical concentration where growth may be inhibited. As no Al was detected in the shoots, it is suggested that Al in the roots inhibits shoot growth by reducing transport of Ca from roots to shoots.

Growth and phosphorus, zinc, and manganese content of tomato, muskmelon, and honey locust at high root‐zone temperatures1

Abstract Horticultural species vary in growth response to root‐zone temperature (RZT) that exceed 30°C, but little is known about the effects of RZT on nutrient absorption. We determined the amount of phosphorus (P), zinc (Zn), and manganese (Mn) in plants of tomato (Lycopersicon esculentum Mill. ‘Jet Star'), muskmelon (Cucumis melo L. ‘Gold Star'), and thornless honey locust (Gleditsia triacanthos L. var. inermis Willd.) grown in an Hoagland No. 1 nutrient solution that was held at 24°, 27°, 30°, 33°, and 36°C RZT. Tomato dry mass and P and Mn contents were highest at 27°C RZT, but tomato Zn content did not show a response to RZT. Muskmelon dry mass and P, Zn, and Mn contents, however, were highest at 36°C. Honey locust dry mass and P and Zn contents did not vary with RZT, but honey locust Mn content decreased linearly with increasing RZT. Growth and P, Zn, and Mn absorption by muskmelon were increased by continuous exposure to RZT > 30°C, whereas honey locust growth and P, Zn, and Mn acquisition were no...

Effect of Root Zone Temperature on the Mineral Composition of Xylem Sap and Plasma Membrane K+–Mg++–ATPase Activity of Grafted Cucumber and Figleaf Gourd Root Systems

Cucumber (Cucumis sativus L.) seedlings were grafted onto cucumber-(CG) or figleaf gourd (FG, Cucurbita ficifolia Bouche) seedlings in order to determine the effect of solution temperature 12, 22, and 32C) on the mineral composition of xylem sap and plasma membrane K+–Mg++–ATPase activities of the roots. Low solution temperature (12C) lowered the concentration and in xylem sap of CG plants, but not of FG plants. Concentrations of K+, Ca++, and Mg++ in xylem sap were less affected than anions by solution temperature. The plasma membrane of FG plants grown in 12C solution temperature showed the highest K+–Mg++–ATPase activity at all ATP concentrations up to 3 mM and at low reaction temperature up to 12C, indicating resistance of figleaf gourd to low root temperature.

Root-zone Temperature Effects Onion Content of Tomato, Muskmelon, and Honey Locust

Horticultural species vary in growth response to high root-zone temperature (RZT), but little is known about the effects of RZT on nutrient uptake. We determined P, K, Ca, Mg, Zn, and Mn total plant content of tomato (Lycopersicon esculentum Mill. cv. Jet Star), muskmelon (Cucumis melo L. cv. Gold Star), and honey locust (Gleditsia triacanthos L. var. inermis Willd.) grown in nutrient solution kept at 24, 27, 30, 33, and 36C. RZT effects on plant dry mass gain and gain in nutrient per plant varied by species. Honey locust and tomato total plant gain in P decreased linearly with increasing RZT, while melon P content increased linearly to 36C. Trends in total Mg and Mn content will be presented, as well as results from further research on correlations between supraoptimal RZT, root respiration, and shoot and root P content of tomato.

Antagonistic effects of root zone temperature and iron on phosphorus uptake by bush bean

Abstract Radiophosphorus (32P) and hydroponically‐grown bush bean were used to study P absorption kinetics as affected by root zone temperature (RZT) and iron (Fe). Phosphorus uptake increased significantly (p < 0.05) at each successive 10°C rise in RZT from 15 to 35°C, and quadratic regression equations were highly correlated (R2 = 0.98) between the uptake amount and exposure time. An estimated Q10 value of 1.5, and the corresponding Arrhenius constant μ of 31 kJ/mol for P uptake were within range for a diffusion process in an aqueous solution. A concentration of 5 μmol/L Fe significantly (p < 0.05) reduced P uptake from 6 h on at the RZTs studied, and Q10 and μ values were estimated at 1.2 and 14 kJ/mol, respectively.

PRELIMINARY STUDY ON THE EFFECT OF ROOT ZONE TEMPERATURES ON VEGETATIVE GROWTH AND LEAF MINERAL NUTRIENTS OF `GULF COAST' BLUEBERRY PLANTS

The effect of root zone temperature (temp.) on 18-month-old plants of `Gulf Coast' blueberries (predominantly Vaccinium corymbosum L.) grown in temperature-controlled water tanks during Summer 1993 were determined for plant growth and leaf nutrient status. Soil medium (1 sand: 1 peat, v/v) was maintained at or above –20 k Pa. Six singleplant replicates were placed in either a 24 or 31C tank. After 60 days, plants grown at 24C had more leaves, greater total leaf area, and higher leaf and stem fresh weight. Leaf moisture (P &lt; 0.09) and stem dry wt (P &lt; 0.07) were greater at the lower root temp. Root: shoot ratio and total root dry weight were not affected by root temp. Leaf S and Cu levels were higher and NO3 levels lower in plants grown at the 24C root temp. compared to those grown in the 31C root temp. Nitrogen, K, Na, Ca, Mg, P, Fe, Mn, and Zn (order of decreasing concentration) were not affected by root temp. The total N: NO3-N ratio was higher at the lower root zone temp.

Effect of Root Zone Temperature and Shoot Demand on Uptake and Xylem Transport of Macronutrients in Maize (Zea maysL.)

Effect of Root Zone Temperature and Shoot Demand on Uptake and Xylem Transport of Macronutrients in Maize (<i>Zea mays</i>L.)

Fluctuations in Leaf Carbon Assimilation as Affected by Root-zone Temperature and Growth Environment

Short-term effects of root-zone temperatures (RZT) of 28, 33, 38, and 43C for 6 hours daily on container-grown Musa spp. (AAA) `Grande Naine' and Ixora chinensis L. `Maui' were determined under greenhouse and growth room conditions. Diurnal fluctuation of leaf carbon assimilation (LCA) was altered by treatments. In the growth room at 43C, the maximum LCA occurred about midday for banana, but not until afternoon in ixora. LCA was highest (0.53 mg CO2/m2 per sec) in banana with a 33C RZT under greenhouse conditions, while it was equally high (0.74 mg CO2/m2 per sec) at 33 and 38C in a growth room. In ixora, 33C induced the highest LCA (0.40 mg CO2/m2 per sec) in the greenhouse at 1200 hr, but there were no apparent differences in midday LCA between plants with RZT of 28, 33, and 38C in the growth room. Effects of RZT and environment on the daily fluctuations of gaseous exchange processes raise questions about using measurements at only one time during the day to separate treatment effects.

Phytophthora cryptogea root rot of tomato in rock woo] nutrient culture. II. Effect of root zone temperature on infection, sporulation and symptom development

SummaryThe effect of root‐zone temperature on Phytophthora cryptogea root rot was studied in tomato cv. Counter grown under winter and summer conditions in rockwool culture. A nutrient temperature of 25°C resulted in increased root initiation and growth, higher in winter‐grown than in summer‐grown plants. Rhizosphere zoospore populations were greatly reduced at 25°C and above.Growth of P. cryptogea in vitro was optimal between 20°C and 25°C and completely suppressed at 30°C. Encystment was enhanced by increased temperatures above 20°C. Zoospore release in vitro occurred in cultures maintained at constant temperatures in the absence of the normal chilling stimulus. Optimal release was at 10°C; no zoospores were released at 30°C.Inoculated, winter‐grown tomato plants maintained at 15°C developed acute aerial symptoms and died after 21 days. Comparable plants grown at a root‐zone temperature of 25°C remained symptomless for the 3‐months duration of the experiment. Summer‐grown infected plants at the higher root temperature wilted but did not die. Enhanced temperature was ineffective as a curative treatment in summer‐grown plants with established infection.Aerial symptoms of Phytophthora infection are seen as a function of the net amount of available healthy root. With high root zone temperatures this is determined by new root production and decreased inoculum and infection.