Plant Biochemical Regulators and Agricultural Crops - American

Chapter 19

Plant Biochemical Regulators and Agricultural Crops 1,3

2

H. Yokoyama and H. Gausman

Downloaded by WEIZMANN INST OF SCIENCE on May 26, 2018 | https://pubs.acs.org Publication Date: August 13, 1996 | doi: 10.1021/bk-1996-0637.ch019

1

Fruit and Vegetable Chemistry Laboratory, Agricultural Research Service, U.S. Department of Agriculture, 263 South Chester Avenue, Pasadena, CA 91106 Agricultural Research Service, U.S. Department of Agriculture, Amarillo, TX 79109 2

New plant biochemical regulators (PBRs) were observed to have profound positive effects on crop performance. For the crops that were tested, the PBRs improved both crop yield and yield quality. Negative correlations between crop yield and crop quality were not observed. Early studies on bioregulation of plant responses by bioregulatory compounds have demonstrated the regulation of isoprenoid biosynthesis in fruits of Citrus spp. (7,2) and tomato (Lycopersicum esculatum) (3), in carotenogenic fungi (1,4), in cotton (Gossypium hirsutum) cotyledon (5), in rubber-producing desert shrub guayule (Parthenum argentenum) (6,7), and photosynthetic bacteria (8,9). Bioinduction of lycopene synthesis in lemon fruits by MPTA (N,N-diethylaminoethyl-4-methylphenylether) was shown to require nuclear gene transcription and translation of the poly A+ gene transcripts on 80S ribosomes (2). The mode of action of DCPTA (N,N-diethylaminoethyl-3,4-dichlorophenylether)- and MPTA-induced carotenoid accumulation in cotton cotyledons (5) involved the selective inhibition of zefa-carotene dehydrogenation and the inhibition of lycopene cyclase by MPTA. These observations indicate that the activities of bioregulatory agents on carotenoid biosynthesis involve (1) indirect general biosynthetic pathway induction effects that are mediated through nuclear gene expression, and (2) direct inhibitory effects on the cyclase enzymes involved in tetraterpenoid (carotenoid) biosynthesis. The inhibitory effects of MPTA and DCPTA on tetraterpenoid biosynthesis indicate that the individual bioregulatory agents may induce specific biological responses in crop plants. DCPTA treatments have induced significant enhancement of the biomass and phenology of cotton (10), increased root-shoot ratio of cotton seedlings (77) and radish (Raphanus sativus) (12), increased the seed yield and quality of soybean (Glycine max) (13). In the above studies, DCPTA was applied as either a seed treatment or as a foliar spray to early seedling plants just after they emerged from the seed. Studies (14) have shown that a i^C-labeled N,N-diethylaminoethyl analog of DCPTA, when applied to guayule leaves and stems, was completely catabolized within four days of application. No specific i^C-labeled catabolites were detected. However, 3

Current address: 975 Ellington Lane, Pasadena, CA 91105 This chapter not subject to U.S. copyright Published 1996 American Chemical Society

Takeoka et al.; Biotechnology for Improved Foods and Flavors ACS Symposium Series; American Chemical Society: Washington, DC, 1996.


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the stimulatory effect of DCPTA on rubber accumulation in guayule stem tissue is generally not observed until two to three months after treatment (7). These observations are indicative of the indirect role of DCPTA in rubber accumulation. Fungal studies (75), using the carotenogenic mold Phycomyces blakesleeanus, have indicated that DCPTA has an indirect role in the bioinduction of tetraterpenoids and a direct role in the inhibition of transformation of acyclic lycopene to bicyclicteta-carotene.In the mycelia cultured on GAY (glycine-asparagine-yeast) media containing DCPTA, the acyclic lycopene is bioinduced and is seen as the main pigment. However, when small pieces (1 mm2) of mycelia cultured on GAY media containing DCPTA were transferred to and cultured on G A Y media without the bioregulatory compound DCPTA, enhancement of bicyclicfota-carotenewas observed, and it accumulated as the main pigment in the mycelia instead of the acyclic lycopene. These results suggest that the enhancement of crop performance by bioregulatory compounds may involve secondary effector (promoter) compounds and that the putative effector(s) control long term crop performance. Studies (16) have shown that, as compared with controls, application of DCPTA to seedling spinach plants increased the total chloroplast volume per cell, or the chloroplast compartment size (CCS) of mature leaves. In DCPTA-treated leaves, coordinated increases in thylakoid development and stromal area per chloroplast were observed as compared with those of untreated leaves. In addition, starch grains of DCPTA-treated leaves were reduced in size as compared with controls. Extractable chlorophyll (Chi) per gram of fresh weight of leaf tissue and per unit leaf area were increased significantly in DCPTA-treated plants as compared to controls. Coordinated increases in Chi a and Chi b were observed in DCPTA-treated plants as compared with controls. However, statistically similar Chi a/b ratios for all DCPTA treatments suggested that Chi accumulation in DCPTA-treated spinach is regulated by the CCS and not by specific increases in either Chi a or Chi b synthesis. Electrophorectic analysis of thylakoid membrane proteins indicated that the light-harvesting chloroplast protein II (LHCPII) concentration per mg of total Chi was increased in thylakoids isolated from DCPTA-treated plants as compared with control preparations from untreated plants (16). Ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) activity in vitro in mature leaves of DCPTA-treated spinach plants was increased significantly. The enhanced biomass gain of mature DCPTA-treated spinach was due to a significant acceleration of relative growth rate and not to an extension (days) of exponential growth. In addition, the enhanced biomass gain observed in DCPTA-treated plants was manifested in all plant parts. Compared with controls, the accelerated leaf area development of DCPTA-treated plants would significantly increase light interception per plant during exponential plant growth, which in turn would help to increase photosynthetic productivity and subsequent crop growth rate (17). Promotive effects of DCPTA have been observed on the vegetative groweth rate of sugar beets (Beta vulgaris) (18), spinach (16), and Phalaenopsis (19). In this chapter we will present results of three new and improved bioregulatory compounds, or plant biochemical regulators (PBRs), on several agricultural crops. Bioregulation of Agricultural Crops Crop yield and crop quality are often determined by the same regulatory mechanisms that control crop growth rate and vegetative plant development (17,20,21). In PBR-treated tomato plants as shown in Table 1, harvestable crop yield is increased as much as 2.25 times that of the control (0.8 kg plant-1).


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Table 1. Effect of PBRs on Fruit Yield and Quality of Tomato (Lycopersicum esculatum cv. Pixie)

Treatment

Brix


PBR* U.M 1 1 2 2 3 3 4

Fruit

Carotenoids

mg (g fresh wt) 30 8.2±.04 186±7 3 7.9±.04 158±4 30 7.0±.03 160±8 3 7.2±.04 156±9 3 8.4±.04 191±8 0.3 7.3±.04 172±7 0 5.1±.07 78±8

_1

size %ripe vield kgfplant) total (plant)" g(fruit)- 1 total ripe 1.26 1.6 41 90 40 1.23 1.4 88 39 35 1.26 74 1.7 37 46 1.22 72 1.7 37 46 1.66 92 1.8 39 47 1.34 1.5 40 89 38 0.25 0.8 24 31 27 1

*1.FVCL-1 2.FVCL-8 3. FVCL-9 4. Control Foliar application of solutions containing 0.1% (w/v) Kinetic nonionic wetting agent at early seedling stage (3-4 leaf). Fruit harvested 3 months after planting. Results represent means of 6 replicate plants. Determination of Brix and carotenoid content made on fully mature fruits. Greenhouse grown in 2 gal pots. In each crop that was tested, in addition to tomato, PBR enhanced yield resulted from improved seedling vigor and leaf canopy development during exponential crop growth of treated as compared with untreated plants. In DCPTA-treated bush bean (Phaseolus vulgaris), eggplant (Solarium melongena), paprika pepper (Capsicum annum), and tomato enhanced yield was associated with acceleratyed development of secondary branches during exponential growth and with improved fruit set at crop maturity (3,18,22). Moreover, the harvestable yield of PBR-treated plants was associated with increased vegetative growth when compared to controls. Negative correlations between crop yield and crop quality were not observed. When compared with controls, the soluble solids content were increased at crop harvest. In addition, the carotenoid contents of treated tomato fruits were increased as compared with controls. FVCL-9 appears to be very effective at the lower concentration levels of 1 (3 |iM) and 0.1 (0.3 uM) ppm, indicative of its high biological activity. The sweetness and flavor intensity of ripe fruits were positively correlated with the total soluble solids content (23,24). However, negative correlations of total fruit yield with total soluble solids content of ripe fruits are often observed (24). That is, agricultural treatments (chemical, cultural, environmental) that tend to increase tomato fruit yields often produce mature fruits with a reduced total soluble solids content. This study shows the overall promotive effects of the new PBRs upon fruit yield and fruit quality of fresh market tomato. For example, both total soluble solids (degrees Brix) and ripe fruits harvested 60 days after seed planting were increased significantly for PBR-treated plants, including foliar applications of FVCL-1, FVCL-8 and FVCL-9, over those of their respective controls. The largest numerical increases in fruit ripening relative to the controls were observed in 3 u,M FVCL-9 treated plants. Increases, though at slightly



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lower levels, occurred also with FVCL-1 and FVCL8 treated plants. The red-ripe fruit yields of 3 pM FVCL-9 treated plants were six times those of the controls. Foliar application of the PBRs increased the total soluble solids and carotenoid contents of ripe tomato fruits. PBR treatment increased the biomass of spinach, Table 2. The largest increases (about two-fold) were observed with 3 pM FVCL-9 treated plants as compared with controls. The spinach leaves of the treated plants had a much deeper green coloration than leaves of the untreated plants. These observations were confirmed by the increased chlorophyll (Chi) content of PBR-treated plants over that of controls as shown in Table 2. There were parallel enhancement effects of FVCL-9 on total Chi accumulation and on biomass gains. Similar efects have been observed in DCPTA-treated blue spruce (Pices pungens) (25) and sugar beet (18). These results indicated that PBRs have an influence on the photosynthetic capacity of crop plants. Table 2. Effect of PBR on Spinach (Spinacea oleracea cv. New Zealand)

Treatment

Biomass

Total Chlorophvll

PBR* uM

dry wt gm

mg (g fresh wt)"

1 2 3 4

10.07±.31 10.21±.39 10.59±.43 5.76±.65

1.98±.ll 1.82±.12 1.69±.15 1.28±.17

30 30 3 0

1

*1. FVCL-1 2.FVCL-8 3. FVCL-9 4. Control Single foliar application of PBR solutions with 0.1% (w/v) Kinetic wetting agent at early seedling stage (2-3 true leaf). Harvested 60 days after planting. Greenhouse grown in 2 gal pots; 8 replicate plants. Table 3 shows that the new PBRs have profound effects on biomass and root formation in radish. Foliar treatment of radish resulted in greatly enhanced root and biomass development at crop harvest as compared with controls. FVCL-9 at both 3 pM and 0.3 pM levels was the most effect in increasing biomass about two-fold and promoting root formation almost three-fold, as compared with respective controls. The PBR effect on the biomass of the monocotyledenous com plant (Zea mays) are presented in Table 4. Foliar applications of the three PBRs, FVCL-1, FVCL-8, and FVCL-9, were made on corn seedlings, grown in pots under greenhouse conditions, at the early postemergence-growth stage. Thirty-five days later the plants were sacrificed for biomass determinations. As compared with the control (0 ppm treatment) 3 pM FVCL-1 gave the largest increase in biomass production, ranging in magnitude from 1.7 to 2.4-fold increases, the leaf blades of treated plants were larger with thiker culans than untreated plants, accounting for much of the biomass increases. These greenhouse results are important because com as a monocotyledenous plant was affected by PBRs as has been previously noted for dicotyledenous plants.


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Table 3. Effect of PBR on Radish (Raphanus sativus cv. Red Devil)

Treatment

Biomass

PBR* pM

wet wt (g)

1 1 2 2 3 3 4

55.4±3.3 57.7±4.7 59.0±4.6 54.0±3.5 72.9±2.9 70.2±2.6 37.7±2.8

30 3 30 3 3 0.3 0

Root wet wt (g) 25.3±1.8 25.2±2.3 23.9±1.5 16.5±1.3 41.3±4.0 40.4±2.8 14.6±1.2

*1.FVCL-1 2.FVCL-8 3. FVCL-9 4. Control Foliar application at early seedling stage (2-3 true leaf). Nonionic wetting agent used was Kinetic at 0.1% (w/v). All radishes harvested 32 days after planting; 6 replicate plants. Greenhouse grown in 2 gal pots.

Table 4. Effect of PBR on Biomass of Corn (Zea mays cv. Early Xtra Sweet)

Treatment PBR* 1 1 2 2 3 3 4

Biomass uM

dry wt g

30 3 30 3 3 0.3 0

57.9±3.4 72.5±2.3 52.6±2.5 53.4±1.5 52.6±2.5 53.5±1.5 30.1±3.4

*1.FVCL-1 2. FVCL-8 3. FVCL-9 4. Control Foliar application of PBR and control solutions with 0.1% (w/v) nonionic wetting agent Kinetic at early seedling stage (6-8 cm tall). Harvested 35 days after planting; 8 replicate plants. Greenhouse grown in 2 gal pots. Treatments with PBRs FVCL-1 and FVCL-8 increased Valencia orange (Citrus sinensis) fruit diameter significantly whereas DCPTA treatment effects were comparable to those of the controls (Table 5).


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Table 5. Comparison of PBR Effects on Orange (Citrus sinensis cv. Valencia) Fruit


Treatment Fruit Diam. Juice PBR* pM mm mlg1 2 3 4

75 75 75 0

65.4 a 65.2 a 64.1 b 63.9 b

1

0.53 a 0.53 a 0.49 b 0.49 b

Vitamin C mg(lOOml)fresh fruit wt 56.8 a 56.2 a 46.4 b 42.6 c

1

Serum Brix

Peel mm

Percent of Fruit Juice Peel+Pulp

14.8 a 14.6 a 12.3 ab 10.6 b

51.9 a 4.1b 51.8 a 4.2 b 4.7 ba 51.4 a 50.7 b 4.9 a

46.9 a 46.7 a 47.1b 47.4 b

*1. FVCL-1 2. FVCL-8 3. DCPTA (N,N-diethylaminoethyl-3,4-dichlorophenylether) 4. Control Foliar spray applied to entire tree shortly after fruit set (0.5-1.5 cm diameter fruit size). Higher concentrations (75 uM) were applied to compensate for the thicker layer of wax coating the leaves and young fruits of citrus trees. PBR and control solutions contained 0.1% (w/v) Kinetic nonionic wetting agent and were applied as a single foliar treatment during early fruit development. Fruits harvested at full maturity. Means associated with the same letter are not significantly different, according to Duncan's multiple range test (p

Plant Biochemical Regulators and Agricultural Crops - American

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