Evaluation of Low Pressure Fogging System for Improving Crop Yield of Tomato (Lycopersicon esculentum Mill.): Grown under Heat Stress Conditions

In Mediterranean regions, many tomato plants are grown throughout the hot summer period (May–September) in sheltered cultivation, mainly for plant protection reasons. Most of the shelters that are used are low cost net houses covered with 50 mesh insect proof net. In most cases these net houses have a flat roof and no ventilation or climate control measures. This insufficient ventilation during the hot summer leads to above optimal air temperatures and causes moderate heat stress inside the shelters, which leads to yield reduction. The aim of this study was to evaluate the ability of a simple and inexpensive low pressure fogging system installed in a naturally ventilated net house to lower temperatures and improve the yield during the summer. The study showed that in areas where relative air humidity (RH) during the daytime is less than 60%, tomato plants improved their performance when grown through the summer in net houses under moderate heat stress. Under fogging conditions pollen grain viability and fruit set were significantly improved. This improvement influenced the yield picked during September (104–136 DAP). However, total seasonal yield was not affected by the fogging treatment

Glyphosate-Induced Anther Indehiscence in Cotton Is Partially Temperature Dependent and Involves Cytoskeleton and Secondary Wall Modifications and Auxin Accumulation

Yield reduction caused by late application of glyphosate to glyphosate-resistant cotton (Gossypium hirsutum; GRC) expressing CP4 5-enol-pyruvylshikmate-3-P synthase under the cauliflower mosaic virus-35S promoter has been attributed to male sterility. This study was aimed to elucidate the factors and mechanisms involved in this phenomenon. Western and tissue-print blots demonstrated a reduced expression of the transgene in anthers of GRC compared to ovules of the same plants. Glyphosate application to GRC grown at a high temperature regime after the initiation of flower buds caused a complete loss of pollen viability and inhibition of anther dehiscence, while at a moderate temperature regime only 50% of the pollen grains were disrupted and anther dehiscence was normal. Glyphosate-damaged anthers exhibited a change in the deposition of the secondary cell wall thickenings (SWT) in the endothecium cells, from the normal longitudinal orientation to a transverse orientation, and hindered septum disintegration. These changes occurred only at the high temperature regime. The reorientation of SWT in GRC was accompanied by a similar change in microtubule orientation. A similar reorientation of microtubules was also observed in Arabidopsis (Arabidopsis thaliana) seedlings expressing green fluorescent protein tubulin (tubulin α 6) following glyphosate treatment. Glyphosate treatment induced the accumulation of high levels of indole-3-acetic acid in GRC anthers. Cotton plants treated with 2,4-dichlorophenoxyacetic acid had male sterile flowers, with SWT abnormalities in the endothecium layer similar to those observed in glyphosate-treated plants. Our data demonstrate that glyphosate inhibits anther dehiscence by inducing changes in the microtubule and cell wall organization in the endothecium cells, which are mediated by auxin

Differential Oxidative Metabolism and 5-Ketoclomazone Accumulation Are Involved in Echinochloa phyllopogon Resistance to Clomazone1[C][W][OA]

Echinochloa phyllopogon (late watergrass) is a major weed of California rice (Oryza sativa) that has evolved cytochrome P450-mediated metabolic resistance to different herbicides with multiple modes of action. E. phyllopogon populations from Sacramento Valley rice fields have also recently shown resistance to the herbicide clomazone. Clomazone is a proherbicide that must be metabolized to 5-ketoclomazone, which is the active compound that inhibits deoxyxylulose 5-phosphate synthase, a key enzyme of the nonmevalonate isoprenoid pathway. This study evaluated the differential clomazone metabolism within strains of the same species to investigate whether enhanced oxidative metabolism also confers clomazone resistance in E. phyllopogon. Using reverse-phase liquid chromatography-tandem mass spectrometry techniques in the multireaction monitoring mode, we elucidated that oxidative biotransformations are involved as a mechanism of clomazone resistance in this species. E. phyllopogon plants hydroxylated mostly the isoxazolidinone ring of clomazone, and clomazone hydroxylation activity was greater in resistant than in susceptible plants. The major clomazone metabolites resulted from monohydroxylation and dihydroxylation of the isoxazolidinone ring. Resistant plants accumulated 6- to 12-fold more of the monohydroxylated metabolite than susceptible plants, while susceptible plants accumulated 2.5-fold more of the phytotoxic metabolite of clomazone, 5-ketoclomazone. Our results demonstrate that oxidative metabolism endows multiple-herbicide-resistant E. phyllopogon with cross-resistance to clomazone through enhanced herbicide degradation and lower accumulation of the toxic metabolite in resistant versus susceptible plants

Phosphorous Nutritional Level, Carbohydrate Reserves and Flower Quality in Olives.

The olive tree is generally characterized by relatively low final fruit set consequential to a significant rate of undeveloped pistils, pistil abortion, and flower and fruitlet abscission. These processes are acknowledged to be governed by competition for resources between the developing vegetative and reproductive organs. To study the role of phosphorus (P) nutritional level on reproductive development, trees were grown under four levels of P for three years in large containers. Phosphorus nutritional level was positively related to rate of reproductive bud break, inflorescence weight, rate of hermaphrodite flowers, pistil weight, fruitlet persistence, fruit set and the consequential total number of fruits. The positive impact of P nutrition on the productivity parameters was not related to carbohydrate reserves or to carbohydrate transport to the developing inflorescence. Phosphorous deficient trees showed significant impairment of assimilation rate, and yet, carbohydrates were accumulated in inflorescences at levels comparable to or higher than trees receiving high P. In contrast to female reproductive organs, pollen viability was consistently higher in P deficient trees, possibly due to the enhanced carbohydrate availability. Overall, the positive effect of P on female reproductive development was found to be independent of the total carbohydrate availability. Hence, P is speculated to have a direct influence on reproductive processes

Integrating organic photovoltaics (OPVs) into greenhouses: electrical performance and lifetimes of OPVs

This paper presents the electrical performance of organic photovoltaic modules (OPVs) on top of a polyethylene covered greenhouse high tunnel in a Mediterranean climate. Modules from a previous study were kept on the tunnel and monitored together with new modules with improved connectors installed on the greenhouse roof and on frames adjacent to the greenhouse. Measured module power conversion efficiencies ranged from 1% to 3%. The typical combined output of the modules across the tunnel roof were 105Wh on a sunny day and 81Wh on a cloudy day. Module burn-in period was about 15 days, losing around 36% of its initial efficiency. Ts80 lifetimes ranged from 7 days to 94 days. Tunnel integration was shown to accelerate module degradation

Averages ± standard deviation of: phosphorus (P) concentration in irrigation solution, and corresponding P leaf concentration measured during the flowering periods, percentage of buds evolved into inflorescences, flowers to fruits, and total number of fruit per tree, all for each of the two years of study.

<p>Different letters indicate values with significant differences at <i>p</i><0.05 (6 repetition).</p

Pollen viability as affected by phosphorus levels (0.1, 1, 10 and 26 mg l^-1 P in irrigation for P1–P4 respectively).

<p>In 2012 (a) measured by Alexander reagent and in 2013 (b) by both Alexander reagent and fluorescein di-acetate (FDA) method (200–300 flowers per treatment). Different letters indicate significantly differences at p<0.05.</p

Assimilation rate (a, <i>A</i>_<i>n</i>) and stomatal conductance (b, <i>g</i>_<i>s</i>) of olive trees in response to four phosphorus (P) levels (0.1, 1, 10 and 26 mg l^-1 P in irrigation for P1–P4 respectively).

<p>Measurements were taken between 10:00–12:00 over three days in early May 2012. On each day, four trees per treatment were measured (n = 16). Different letters indicate significant differences at <i>p</i><0.05.</p

Pistil fresh weight as affected by P level.

<p>Measurements were taken proximate to full bloom, 30^th April 2012 (a) and 7^th May 2013 (b) as function of P level (0.1, 1, 10 and 26 mg l^-1 P in irrigation for P1–P4 respectively). Different letters indicate significant differences between treatments at <i>p</i><0.05.</p

Average concentrations of total soluble carbohydrates (SCH) and glucose (a) and mannitol, sucrose and fructose (b) in the developing inflorescences from emergence to full bloom (March-April 2012).

<p>Since phosphorus level had no effect on SCH all measurements were evaluated together (n = 16). Error bars indicate standard deviation.</p