Naoya Chishaki

Responses of secondary metabolism in plants to nutrient deficiency

Since levels of some compounds related to secondary metabolism show a sensitive response to nutrient deficiency, we studied the relationship between nutrient deficiency and disorder of secondary metabolism to find a new method of deficiency diagnosis. Deficiencies of N, P and K stimulated phenolic metabolism in rice (Oryza sauva L.) plants. N-deficient plants showed the most sensitive response; levels of some phenolic acids increased in N-deficient plants. In particular, levels of p-coumaric acid and ferulic acid in tops increased noticeably under N deficiency. Addition of Si in the medium decreased sinapic acid level in barley (Hordeum vulgare L.) plants when other nutrient condition were normal. Addition of Si suppressed the increase of phenolic acid levels caused by Mn excess in barley plants. Phenolic acids were analysed in seed coats of (i) field-grown broad been (Vicia Java L.) considered Ca deficient and (ii) plants grown in nutrient solutions containing different Ca concentrations. Sinapic acid and caffeic acid in the seed coats of green seeds increased prior to visual appearance of the browning symptom. Level of p-coumaric acid in the seed coats of the plants grown in 0.5 mM Ca solution was markedly higher than in those grown in 2.0 mM Ca solution. The findings suggest that analysing compounds of secondary metabolism, such as phenolic acids, provides a method for diagnosing nutrient disorders prior to the appearance of visible symptoms.

Incorporation of 13C into carbohydrates and translocation in peanut plant

Abstract To investigate the translocation form of photo assimilates in the peanut (Arachis hypogaea L.) plant, the plants were individually supplied with 13CO2 for 30 min. In the leaves, during the 13CO2 feeding period, fructose was most strongly labeled with 13C, followed by glucose, whereas a small amount of 13C was incorporated into sucrose. Within 1 d after the end of the 13CO2 feeding, the 13C abundances and 13C amounts of fructose and glucose rapidly decreased within 120 min, but increased from 120 to 240 min, and markedly decreased afterwards, while those of sucrose remained constantly low. In the petioles and stems, during the 13C labeling period, the 13C abundances and 13C amounts of fructose and glucose were also remarkably higher than those of other sugars and after the end of the 13CO2 supply, they remained constantly higher than those of sucrose. In the leaves, a large quantity of 13C was incorporated into starch during the 13C labeling period and within 120 min after the end of the 13CO2 supply, and thereafter, rapidly metabolized. Similar results were observed for the petioles and stems. The above results indicate that the carbon currently fixed in the leaves is rapidly exported from the leaves to the petioles and stems and translocated to other parts of the plant in the forms of fructose and glucose but not sucrose, in contrast to other crops in which sucrose is the major translocation form of photoassimilates.

Effect of silicon application on reproductive growth of rice plant

Abstract To analyze the role of silicon at the reproductive stage of rice plant, the plants were grown in a culture solution with 4 silicon levels (0, 5, 15, and 50 mg L−1) from the panicle formation stage. Results obtained were as follows; The delay in heading at the lower silicon levels was due to the shorter length of straw before heading. The brown spots on the hull, whole number increased at the silicon 0 level, appeared until the 10th day after heading. The spikelet number was lower from the day before heading at lower silicon levels than at higher silicon levels. The decrease in the number of unfilled spikelets during growth was delayed when the silicon level in the nutrient solution decreased. The thousand-kernelweight became smaller on the day before heading at lower silicon levels than at higher silicon levels.

Differences in mobility of calcium applied to the aboveground parts of broad bean plants (Vicia faba L.)

Abstract The mobility of 45Ca applied to several of the aboveground parts of the broad bean plant (Vicia faba L.) was investigated to determine the effect of foliar application of calcium (Ca). Calcium applied to the top or the underside surface of a leaf scarcely moved from the leaf. A small amount of Ca applied to a pod moved to the inner seeds, but the majority remained on the pod wall. Calcium applied to the stem was the most mobile. Most of the Ca applied to the axillary side of the stem moved to the leaves and pod on the applied nodes. By contrast, more of the Ca applied to the side opposite the axillary side of the stem moved to the upper nodes. Thus, Ca solution should be sprayed onto the stem rather than the leaves for effective foliar application of Ca.

Effect of Calcium Concentration on the Shape of Sweet Potato (Ipomoea batatas Lam.) Tuberous Root

-1 of watersoluble Ca. The trays were placed above ground at a slope of 15o and covered with sliver sheets for mulching. One plant was planted on each tray. Each plant was supplied weekly with 500ml of nutrient solution containing the following elements (/L); 1.43g NH4NO3, 1.51g KNO3, 3.0g MgSO4, 0.95g KH2PO4, 0.6g Fe-EDTA, 0.07g H3BO3, 0.006g ZnSO4�i 7H2O, 0.002 g CuSO4�i 5H2O, 0.01g MnCl2�i 4H2O and 0.0009g (NH4)6Mo7O24�i 4H2O and 0 mg (low concentration), 4mg (moderate concentration) and 28mg Ca (high concentration) as CaCl2. The optimum pH range of the nutrient solution was 6.0-7.0. Ten trays -were prepared for each treatment. The present study was carried out on the experimental farm of Kagoshima University during the cropping season from June to October in 2000 and 2001. The results in the 2000 cropping season were similar to those in 2001; therefore, only the data of the 2001 cropping season are presented in this report. 2.�˝ Experimental procedures

Behavior of Carbohydrates within Peanut Plant

Abstract To analyze the behavior of carbohydrates in the peanut plant (Arachis hypogea L.), changes in the sugar and starch contents were characterized in various parts of the plant throughout the growth stages and over the diurnal cycle. At the earlier growth stages, the contents of crude starch, fructose, and glucose in leaves, petioles, and stems remarkable decreased due to the rapid growth of the vegetative organs and formation of pods, while at the pod-enlarging stage, they remained at constantly high levels, suggesting that not all of the reserve pools of carbohydrates are utilized for seed formation. Compared with other sugars, a remarkably lower sucrose content remained in the leaves throughout the growth stages and over the diurnal cycles. However, the ratio of the content of sucrose to other sugars in each organ increased with the increase of the distance from leaves to roots. During the growth period and the diurnal cycle, the changes in the fructose content in leaves were similar to those of the sucrose content in stems. Furthermore, the fructose content in expanding leaves, fully expanded leaves, and petioles, respectively showed the most significant peak at 17:00 in the diurnal cycles. During constant darkness, the fructose content in expanding leaves and the sucrose content in stems continued to display the pattern of a diurnal cycle, while the fructose and glucose contents in fully expanded leaves decreased slightly. The predominant sugar in the gynophore sap was inositol, followed by fructose and glucose, while the sucrose content was lower. This composition of sugars in the sap was consistent with that of the leaves, but different from that of fruits in which sucrose was the main sugar. These results suggest that the exported form of photoassimilates from the leaves may be fructose, and not sucrose; that sucrose may be synthesized in the stems, roots, and pods; and that inositol may play an important role in the growth of the peanut plant.