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Water availability is a limiting factor to plant development and productivity. Many drought‐induced physiological processes that affect patterns of growth, biomass allocation, and ultimately, yield, are also regulated by the red/far‐red photoreceptor phytochromes (PHYs). However, as the mechanisms and responses to drought stress vary among plant developmental phases, it is reasonable to conjecture that PHY‐dependent morphophysiological responses to drought may be different according to the plant growth stage. In this study, we submitted tomato phyB1 mutant plants to water deficit in two distinct growth stages, during vegetative and flower‐bearing reproductive phases, comparing the morphophysiological development, fruit yield and quality to wild‐type (WT). In general, phyB1 plants overcome growth limitations imposed by water availability limitations during vegetative phase, being taller and leafier than WT. Restrictions to growth are less acute for both genotypes when water deficit occurs during reproductive phase compared to vegetative phase. phyB1 yield is lower when water is limited during reproductive phase, but its fruits accumulate more soluble solids, associated with better quality. These results highlight that drought‐induced modulations in tomato growth and yield are dependent upon PHYB1 regulation and the developmental phase when water deficit is applied. [ABSTRACT FROM AUTHOR]

Plant growth-promoting bacteria have several abilities to promote plant growth and development. One of these skills is the synthesis of indole-3-acetic acid (IAA), which mainly promotes root and shoot development. The bacteria Bacillus subtilis and Azospirillum brasilense have been widely used in agriculture with this function. However, little is known about whether the joint inoculation of these bacteria can reduce plant development by the excess of IAA produced as a result of the joint inoculation. The objective of the present study was to verify the effect of IAA on the inoculation of B. subtilis and A. brasilense in three tomato genotypes. The Micro-Tom genotype without mutation for IAA synthesis, Entire, has high sensitivity to IAA, and the diageotropic genotype (dgt) has low sensitivity to IAA. The results show that the plant parameter most sensitive to microbial inoculation is the number of roots. No treatment increased the shoot dry mass parameters for the Micro-Tom genotype and dgt, root dry mass for the Micro-Tom genotype, plant height for the Micro-Tom and Entire genotypes, root area and root volume for the genotype dgt. The Azm treatment reduced plant height compared to the control in the dgt, the BS + Azw and BS + Azm treatments in the Micro-Tom genotype and the Azw + Azm treatment in the dgt genotype reduced the plant diameter compared to the control. BS and BS + Azw reduced the number of roots in the Micro-Tom. The results strongly support that the mixture of B. subtilis and A. brasilense can reduce some parameters of plant development; however, this effect is possibly an interference in the mode of action of growth promotion of each isolate and is not related to an excess of IAA produced by the bacteria. [ABSTRACT FROM AUTHOR]

Photoreceptors are primarily known as key photomorphogenic modulators of various physiological events during plant development. Although there are different groups of photoreceptors, the phytochrome B (phyB) family mediates developmental responses in a wide range of plant species, from seed germination to flowering. In addition, these molecules also regulate abiotic stress acclimation responses, such as salinity, drought, low/high temperature, high light and heavy metals. The signalling pathways mediated by phyB could enhance plant resistance to environmental stresses, as phyB photoreceptors reduce leaf transpiration, increase the antioxidant system, enhance protective pigments and increase the expression of genes related to plant stress acclimation. Thus, the elucidation of positive or negative roles for phyB in these stress tolerance characteristics would provide essential knowledge for genetic engineering, improving plant growth and development in critical environments. In this review, we cover the main findings on how the phyB family works to modulate abiotic stress by discussing biochemical and molecular aspects of the underlying mechanisms operated by these photoreceptors. [ABSTRACT FROM AUTHOR]

It is well-documented that phytochromes can control plant growth and development from germination to flowering. Additionally, these photoreceptors have been shown to modulate both biotic and abiotic stress. This has led to a series of studies exploring the molecular and biochemical basis by which phytochromes modulate stresses, such as salinity, drought, high light or herbivory. Evidence for a role of phytrochromes in plant stress tolerance is explored and reviewed. [ABSTRACT FROM AUTHOR]

• There is a close interaction between Fe nutrition and light perception in plants. • The tomato response mechanisms to Fe deficiency is highly light-dependent. • hp-1 tomato mutant is more tolerant to Fe deficiency. • au tomato mutant tend to accumulate less nutrients. Iron (Fe) is a micronutrient for plant development, as constituent of several photosynthesis- and respiration-related proteins and enzymes. Consequently, Fe deficiency leads to chlorosis in leaves and plant growth impairment. It has become increasingly evident that light signals coordinate iron homeostasis in plants. To further address new insights into how light is a fundamental part of Fe deficiency responses, we employed Micro-Tom (wild type, WT) tomato (Solanum lycopersicum L.) plants and high-pigment 1 (hp1) and aurea (au) photomorphogenic mutants, which exhibit an excessive light response and low light perception, respectively. Plant growth, pigment contents, oxidative status, and nutrient profile were analyzed. The results revealed the influence of the different genotypes on Fe deficiency responses. WT and au exhibited plant growth reduction under Fe deficiency. WT, hp1 and au demonstrated that Fe availability and light perception play fundamental roles in chlorophyll and anthocyanin biosynthesis. Lipid peroxidation was not increased for any genotype under Fe deficiency, indicating that mutations in light perception and signaling differentially modulate H 2 O 2 production and scavenging under this condition. Additionally, macronutrients and micronutrients were taken up and distributed differently among the different plant genotypes, tissues and Fe conditions analyzed. In general, the au plants accumulated lower amounts of nutrients (Ca, S, P, Mg, B and Zn) than the WT and hp1 genotypes regardless of the Fe concentrations. Our data clearly indicates that light perception and signaling influence Fe-dependent morphophysiological responses in plants, suggesting possibilities for biotechnological improvement of crops grown under Fe shortage. [ABSTRACT FROM AUTHOR]

The low-auxin-sensitivity tomato mutant, dgt , despite displaying reduced plant growth, has been linked to greater resistance to N deficiency. This led us to test the role of auxin resistance of dgt in NH 4 + toxicity and N deficiency, compared to wild type tomato (cv. Micro-Tom, MT), grown in hydroponic media. A completely randomized design with three replications in a 2 × 4 factorial scheme was adopted, corresponding to the two tomato genotypes (MT and dgt), involving four nutritional treatments: NO 3 − (5 mM); NH 4 + (5 mM); NO 3 − (5 mM) plus exogenous auxin (10 μM IAA); and N omission. The results show that NH 4 + was toxic to MT but not to dgt. Under N deficiency, MT displayed a lower shoot NO 3 − content, a lower photosynthetic rate, and a decrease in both shoot and root dry weight. However, in dgt , no difference was observed in shoot NO 3 − content and photosynthetic rate between plants grown on NO 3 − or under N deficiency. In addition, dgt showed an increase in shoot dry weight under N deficiency. We highlight the role of auxin resistance in the adaptation of plants to NH 4 + toxicity and N deficiency. [ABSTRACT FROM AUTHOR]